2923 lines
114 KiB
C++
2923 lines
114 KiB
C++
//===- RewriteStatepointsForGC.cpp - Make GC relocations explicit ---------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Rewrite an existing set of gc.statepoints such that they make potential
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// relocations performed by the garbage collector explicit in the IR.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Pass.h"
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#include "llvm/Analysis/CFG.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Analysis/TargetTransformInfo.h"
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#include "llvm/ADT/SetOperations.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/ADT/MapVector.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/CallSite.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/MDBuilder.h"
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#include "llvm/IR/Statepoint.h"
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#include "llvm/IR/Value.h"
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#include "llvm/IR/Verifier.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Cloning.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Transforms/Utils/PromoteMemToReg.h"
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#define DEBUG_TYPE "rewrite-statepoints-for-gc"
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using namespace llvm;
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// Print the liveset found at the insert location
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static cl::opt<bool> PrintLiveSet("spp-print-liveset", cl::Hidden,
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cl::init(false));
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static cl::opt<bool> PrintLiveSetSize("spp-print-liveset-size", cl::Hidden,
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cl::init(false));
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// Print out the base pointers for debugging
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static cl::opt<bool> PrintBasePointers("spp-print-base-pointers", cl::Hidden,
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cl::init(false));
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// Cost threshold measuring when it is profitable to rematerialize value instead
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// of relocating it
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static cl::opt<unsigned>
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RematerializationThreshold("spp-rematerialization-threshold", cl::Hidden,
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cl::init(6));
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#ifdef XDEBUG
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static bool ClobberNonLive = true;
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#else
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static bool ClobberNonLive = false;
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#endif
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static cl::opt<bool, true> ClobberNonLiveOverride("rs4gc-clobber-non-live",
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cl::location(ClobberNonLive),
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cl::Hidden);
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static cl::opt<bool> UseDeoptBundles("rs4gc-use-deopt-bundles", cl::Hidden,
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cl::init(false));
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static cl::opt<bool>
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AllowStatepointWithNoDeoptInfo("rs4gc-allow-statepoint-with-no-deopt-info",
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cl::Hidden, cl::init(true));
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namespace {
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struct RewriteStatepointsForGC : public ModulePass {
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static char ID; // Pass identification, replacement for typeid
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RewriteStatepointsForGC() : ModulePass(ID) {
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initializeRewriteStatepointsForGCPass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F);
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bool runOnModule(Module &M) override {
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bool Changed = false;
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for (Function &F : M)
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Changed |= runOnFunction(F);
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if (Changed) {
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// stripNonValidAttributes asserts that shouldRewriteStatepointsIn
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// returns true for at least one function in the module. Since at least
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// one function changed, we know that the precondition is satisfied.
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stripNonValidAttributes(M);
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}
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return Changed;
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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// We add and rewrite a bunch of instructions, but don't really do much
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// else. We could in theory preserve a lot more analyses here.
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AU.addRequired<DominatorTreeWrapperPass>();
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AU.addRequired<TargetTransformInfoWrapperPass>();
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}
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/// The IR fed into RewriteStatepointsForGC may have had attributes implying
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/// dereferenceability that are no longer valid/correct after
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/// RewriteStatepointsForGC has run. This is because semantically, after
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/// RewriteStatepointsForGC runs, all calls to gc.statepoint "free" the entire
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/// heap. stripNonValidAttributes (conservatively) restores correctness
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/// by erasing all attributes in the module that externally imply
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/// dereferenceability.
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/// Similar reasoning also applies to the noalias attributes. gc.statepoint
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/// can touch the entire heap including noalias objects.
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void stripNonValidAttributes(Module &M);
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// Helpers for stripNonValidAttributes
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void stripNonValidAttributesFromBody(Function &F);
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void stripNonValidAttributesFromPrototype(Function &F);
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};
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} // namespace
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char RewriteStatepointsForGC::ID = 0;
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ModulePass *llvm::createRewriteStatepointsForGCPass() {
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return new RewriteStatepointsForGC();
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}
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INITIALIZE_PASS_BEGIN(RewriteStatepointsForGC, "rewrite-statepoints-for-gc",
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"Make relocations explicit at statepoints", false, false)
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INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
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INITIALIZE_PASS_END(RewriteStatepointsForGC, "rewrite-statepoints-for-gc",
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"Make relocations explicit at statepoints", false, false)
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namespace {
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struct GCPtrLivenessData {
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/// Values defined in this block.
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DenseMap<BasicBlock *, DenseSet<Value *>> KillSet;
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/// Values used in this block (and thus live); does not included values
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/// killed within this block.
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DenseMap<BasicBlock *, DenseSet<Value *>> LiveSet;
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/// Values live into this basic block (i.e. used by any
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/// instruction in this basic block or ones reachable from here)
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DenseMap<BasicBlock *, DenseSet<Value *>> LiveIn;
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/// Values live out of this basic block (i.e. live into
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/// any successor block)
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DenseMap<BasicBlock *, DenseSet<Value *>> LiveOut;
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};
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// The type of the internal cache used inside the findBasePointers family
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// of functions. From the callers perspective, this is an opaque type and
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// should not be inspected.
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//
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// In the actual implementation this caches two relations:
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// - The base relation itself (i.e. this pointer is based on that one)
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// - The base defining value relation (i.e. before base_phi insertion)
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// Generally, after the execution of a full findBasePointer call, only the
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// base relation will remain. Internally, we add a mixture of the two
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// types, then update all the second type to the first type
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typedef DenseMap<Value *, Value *> DefiningValueMapTy;
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typedef DenseSet<Value *> StatepointLiveSetTy;
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typedef DenseMap<AssertingVH<Instruction>, AssertingVH<Value>>
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RematerializedValueMapTy;
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struct PartiallyConstructedSafepointRecord {
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/// The set of values known to be live across this safepoint
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StatepointLiveSetTy LiveSet;
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/// Mapping from live pointers to a base-defining-value
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DenseMap<Value *, Value *> PointerToBase;
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/// The *new* gc.statepoint instruction itself. This produces the token
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/// that normal path gc.relocates and the gc.result are tied to.
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Instruction *StatepointToken;
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/// Instruction to which exceptional gc relocates are attached
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/// Makes it easier to iterate through them during relocationViaAlloca.
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Instruction *UnwindToken;
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/// Record live values we are rematerialized instead of relocating.
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/// They are not included into 'LiveSet' field.
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/// Maps rematerialized copy to it's original value.
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RematerializedValueMapTy RematerializedValues;
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};
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}
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static ArrayRef<Use> GetDeoptBundleOperands(ImmutableCallSite CS) {
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assert(UseDeoptBundles && "Should not be called otherwise!");
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Optional<OperandBundleUse> DeoptBundle = CS.getOperandBundle("deopt");
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if (!DeoptBundle.hasValue()) {
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assert(AllowStatepointWithNoDeoptInfo &&
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"Found non-leaf call without deopt info!");
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return None;
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}
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return DeoptBundle.getValue().Inputs;
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}
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/// Compute the live-in set for every basic block in the function
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static void computeLiveInValues(DominatorTree &DT, Function &F,
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GCPtrLivenessData &Data);
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/// Given results from the dataflow liveness computation, find the set of live
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/// Values at a particular instruction.
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static void findLiveSetAtInst(Instruction *inst, GCPtrLivenessData &Data,
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StatepointLiveSetTy &out);
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// TODO: Once we can get to the GCStrategy, this becomes
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// Optional<bool> isGCManagedPointer(const Value *V) const override {
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static bool isGCPointerType(Type *T) {
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if (auto *PT = dyn_cast<PointerType>(T))
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// For the sake of this example GC, we arbitrarily pick addrspace(1) as our
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// GC managed heap. We know that a pointer into this heap needs to be
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// updated and that no other pointer does.
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return (1 == PT->getAddressSpace());
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return false;
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}
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// Return true if this type is one which a) is a gc pointer or contains a GC
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// pointer and b) is of a type this code expects to encounter as a live value.
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// (The insertion code will assert that a type which matches (a) and not (b)
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// is not encountered.)
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static bool isHandledGCPointerType(Type *T) {
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// We fully support gc pointers
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if (isGCPointerType(T))
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return true;
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// We partially support vectors of gc pointers. The code will assert if it
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// can't handle something.
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if (auto VT = dyn_cast<VectorType>(T))
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if (isGCPointerType(VT->getElementType()))
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return true;
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return false;
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}
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#ifndef NDEBUG
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/// Returns true if this type contains a gc pointer whether we know how to
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/// handle that type or not.
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static bool containsGCPtrType(Type *Ty) {
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if (isGCPointerType(Ty))
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return true;
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if (VectorType *VT = dyn_cast<VectorType>(Ty))
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return isGCPointerType(VT->getScalarType());
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if (ArrayType *AT = dyn_cast<ArrayType>(Ty))
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return containsGCPtrType(AT->getElementType());
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if (StructType *ST = dyn_cast<StructType>(Ty))
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return std::any_of(
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ST->subtypes().begin(), ST->subtypes().end(),
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[](Type *SubType) { return containsGCPtrType(SubType); });
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return false;
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}
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// Returns true if this is a type which a) is a gc pointer or contains a GC
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// pointer and b) is of a type which the code doesn't expect (i.e. first class
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// aggregates). Used to trip assertions.
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static bool isUnhandledGCPointerType(Type *Ty) {
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return containsGCPtrType(Ty) && !isHandledGCPointerType(Ty);
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}
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#endif
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static bool order_by_name(Value *a, Value *b) {
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if (a->hasName() && b->hasName()) {
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return -1 == a->getName().compare(b->getName());
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} else if (a->hasName() && !b->hasName()) {
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return true;
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} else if (!a->hasName() && b->hasName()) {
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return false;
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} else {
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// Better than nothing, but not stable
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return a < b;
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}
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}
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// Return the name of the value suffixed with the provided value, or if the
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// value didn't have a name, the default value specified.
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static std::string suffixed_name_or(Value *V, StringRef Suffix,
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StringRef DefaultName) {
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return V->hasName() ? (V->getName() + Suffix).str() : DefaultName.str();
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}
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// Conservatively identifies any definitions which might be live at the
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// given instruction. The analysis is performed immediately before the
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// given instruction. Values defined by that instruction are not considered
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// live. Values used by that instruction are considered live.
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static void analyzeParsePointLiveness(
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DominatorTree &DT, GCPtrLivenessData &OriginalLivenessData,
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const CallSite &CS, PartiallyConstructedSafepointRecord &result) {
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Instruction *inst = CS.getInstruction();
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StatepointLiveSetTy LiveSet;
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findLiveSetAtInst(inst, OriginalLivenessData, LiveSet);
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if (PrintLiveSet) {
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// Note: This output is used by several of the test cases
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// The order of elements in a set is not stable, put them in a vec and sort
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// by name
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SmallVector<Value *, 64> Temp;
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Temp.insert(Temp.end(), LiveSet.begin(), LiveSet.end());
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std::sort(Temp.begin(), Temp.end(), order_by_name);
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errs() << "Live Variables:\n";
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for (Value *V : Temp)
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dbgs() << " " << V->getName() << " " << *V << "\n";
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}
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if (PrintLiveSetSize) {
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errs() << "Safepoint For: " << CS.getCalledValue()->getName() << "\n";
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errs() << "Number live values: " << LiveSet.size() << "\n";
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}
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result.LiveSet = LiveSet;
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}
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static bool isKnownBaseResult(Value *V);
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namespace {
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/// A single base defining value - An immediate base defining value for an
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/// instruction 'Def' is an input to 'Def' whose base is also a base of 'Def'.
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/// For instructions which have multiple pointer [vector] inputs or that
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/// transition between vector and scalar types, there is no immediate base
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/// defining value. The 'base defining value' for 'Def' is the transitive
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/// closure of this relation stopping at the first instruction which has no
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/// immediate base defining value. The b.d.v. might itself be a base pointer,
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/// but it can also be an arbitrary derived pointer.
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struct BaseDefiningValueResult {
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/// Contains the value which is the base defining value.
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Value * const BDV;
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/// True if the base defining value is also known to be an actual base
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/// pointer.
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const bool IsKnownBase;
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BaseDefiningValueResult(Value *BDV, bool IsKnownBase)
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: BDV(BDV), IsKnownBase(IsKnownBase) {
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#ifndef NDEBUG
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// Check consistency between new and old means of checking whether a BDV is
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// a base.
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bool MustBeBase = isKnownBaseResult(BDV);
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assert(!MustBeBase || MustBeBase == IsKnownBase);
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#endif
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}
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};
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}
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static BaseDefiningValueResult findBaseDefiningValue(Value *I);
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/// Return a base defining value for the 'Index' element of the given vector
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/// instruction 'I'. If Index is null, returns a BDV for the entire vector
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/// 'I'. As an optimization, this method will try to determine when the
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/// element is known to already be a base pointer. If this can be established,
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/// the second value in the returned pair will be true. Note that either a
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/// vector or a pointer typed value can be returned. For the former, the
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/// vector returned is a BDV (and possibly a base) of the entire vector 'I'.
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/// If the later, the return pointer is a BDV (or possibly a base) for the
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/// particular element in 'I'.
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static BaseDefiningValueResult
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findBaseDefiningValueOfVector(Value *I) {
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assert(I->getType()->isVectorTy() &&
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cast<VectorType>(I->getType())->getElementType()->isPointerTy() &&
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"Illegal to ask for the base pointer of a non-pointer type");
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// Each case parallels findBaseDefiningValue below, see that code for
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// detailed motivation.
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if (isa<Argument>(I))
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// An incoming argument to the function is a base pointer
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return BaseDefiningValueResult(I, true);
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// We shouldn't see the address of a global as a vector value?
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assert(!isa<GlobalVariable>(I) &&
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"unexpected global variable found in base of vector");
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// inlining could possibly introduce phi node that contains
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// undef if callee has multiple returns
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if (isa<UndefValue>(I))
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// utterly meaningless, but useful for dealing with partially optimized
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// code.
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return BaseDefiningValueResult(I, true);
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// Due to inheritance, this must be _after_ the global variable and undef
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// checks
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if (Constant *Con = dyn_cast<Constant>(I)) {
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assert(!isa<GlobalVariable>(I) && !isa<UndefValue>(I) &&
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"order of checks wrong!");
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assert(Con->isNullValue() && "null is the only case which makes sense");
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return BaseDefiningValueResult(Con, true);
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}
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if (isa<LoadInst>(I))
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return BaseDefiningValueResult(I, true);
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if (isa<InsertElementInst>(I))
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// We don't know whether this vector contains entirely base pointers or
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// not. To be conservatively correct, we treat it as a BDV and will
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// duplicate code as needed to construct a parallel vector of bases.
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return BaseDefiningValueResult(I, false);
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if (isa<ShuffleVectorInst>(I))
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// We don't know whether this vector contains entirely base pointers or
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// not. To be conservatively correct, we treat it as a BDV and will
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// duplicate code as needed to construct a parallel vector of bases.
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// TODO: There a number of local optimizations which could be applied here
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// for particular sufflevector patterns.
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return BaseDefiningValueResult(I, false);
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// A PHI or Select is a base defining value. The outer findBasePointer
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// algorithm is responsible for constructing a base value for this BDV.
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assert((isa<SelectInst>(I) || isa<PHINode>(I)) &&
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"unknown vector instruction - no base found for vector element");
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return BaseDefiningValueResult(I, false);
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}
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/// Helper function for findBasePointer - Will return a value which either a)
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/// defines the base pointer for the input, b) blocks the simple search
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/// (i.e. a PHI or Select of two derived pointers), or c) involves a change
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/// from pointer to vector type or back.
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static BaseDefiningValueResult findBaseDefiningValue(Value *I) {
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if (I->getType()->isVectorTy())
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return findBaseDefiningValueOfVector(I);
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assert(I->getType()->isPointerTy() &&
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"Illegal to ask for the base pointer of a non-pointer type");
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if (isa<Argument>(I))
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// An incoming argument to the function is a base pointer
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// We should have never reached here if this argument isn't an gc value
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return BaseDefiningValueResult(I, true);
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if (isa<GlobalVariable>(I))
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// base case
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return BaseDefiningValueResult(I, true);
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// inlining could possibly introduce phi node that contains
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// undef if callee has multiple returns
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if (isa<UndefValue>(I))
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// utterly meaningless, but useful for dealing with
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// partially optimized code.
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return BaseDefiningValueResult(I, true);
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// Due to inheritance, this must be _after_ the global variable and undef
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// checks
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if (isa<Constant>(I)) {
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assert(!isa<GlobalVariable>(I) && !isa<UndefValue>(I) &&
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"order of checks wrong!");
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// Note: Finding a constant base for something marked for relocation
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// doesn't really make sense. The most likely case is either a) some
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// screwed up the address space usage or b) your validating against
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// compiled C++ code w/o the proper separation. The only real exception
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// is a null pointer. You could have generic code written to index of
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// off a potentially null value and have proven it null. We also use
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// null pointers in dead paths of relocation phis (which we might later
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// want to find a base pointer for).
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assert(isa<ConstantPointerNull>(I) &&
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"null is the only case which makes sense");
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return BaseDefiningValueResult(I, true);
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}
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if (CastInst *CI = dyn_cast<CastInst>(I)) {
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Value *Def = CI->stripPointerCasts();
|
|
// If we find a cast instruction here, it means we've found a cast which is
|
|
// not simply a pointer cast (i.e. an inttoptr). We don't know how to
|
|
// handle int->ptr conversion.
|
|
assert(!isa<CastInst>(Def) && "shouldn't find another cast here");
|
|
return findBaseDefiningValue(Def);
|
|
}
|
|
|
|
if (isa<LoadInst>(I))
|
|
// The value loaded is an gc base itself
|
|
return BaseDefiningValueResult(I, true);
|
|
|
|
|
|
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I))
|
|
// The base of this GEP is the base
|
|
return findBaseDefiningValue(GEP->getPointerOperand());
|
|
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
|
|
switch (II->getIntrinsicID()) {
|
|
case Intrinsic::experimental_gc_result_ptr:
|
|
default:
|
|
// fall through to general call handling
|
|
break;
|
|
case Intrinsic::experimental_gc_statepoint:
|
|
case Intrinsic::experimental_gc_result_float:
|
|
case Intrinsic::experimental_gc_result_int:
|
|
llvm_unreachable("these don't produce pointers");
|
|
case Intrinsic::experimental_gc_relocate: {
|
|
// Rerunning safepoint insertion after safepoints are already
|
|
// inserted is not supported. It could probably be made to work,
|
|
// but why are you doing this? There's no good reason.
|
|
llvm_unreachable("repeat safepoint insertion is not supported");
|
|
}
|
|
case Intrinsic::gcroot:
|
|
// Currently, this mechanism hasn't been extended to work with gcroot.
|
|
// There's no reason it couldn't be, but I haven't thought about the
|
|
// implications much.
|
|
llvm_unreachable(
|
|
"interaction with the gcroot mechanism is not supported");
|
|
}
|
|
}
|
|
// We assume that functions in the source language only return base
|
|
// pointers. This should probably be generalized via attributes to support
|
|
// both source language and internal functions.
|
|
if (isa<CallInst>(I) || isa<InvokeInst>(I))
|
|
return BaseDefiningValueResult(I, true);
|
|
|
|
// I have absolutely no idea how to implement this part yet. It's not
|
|
// necessarily hard, I just haven't really looked at it yet.
|
|
assert(!isa<LandingPadInst>(I) && "Landing Pad is unimplemented");
|
|
|
|
if (isa<AtomicCmpXchgInst>(I))
|
|
// A CAS is effectively a atomic store and load combined under a
|
|
// predicate. From the perspective of base pointers, we just treat it
|
|
// like a load.
|
|
return BaseDefiningValueResult(I, true);
|
|
|
|
assert(!isa<AtomicRMWInst>(I) && "Xchg handled above, all others are "
|
|
"binary ops which don't apply to pointers");
|
|
|
|
// The aggregate ops. Aggregates can either be in the heap or on the
|
|
// stack, but in either case, this is simply a field load. As a result,
|
|
// this is a defining definition of the base just like a load is.
|
|
if (isa<ExtractValueInst>(I))
|
|
return BaseDefiningValueResult(I, true);
|
|
|
|
// We should never see an insert vector since that would require we be
|
|
// tracing back a struct value not a pointer value.
|
|
assert(!isa<InsertValueInst>(I) &&
|
|
"Base pointer for a struct is meaningless");
|
|
|
|
// An extractelement produces a base result exactly when it's input does.
|
|
// We may need to insert a parallel instruction to extract the appropriate
|
|
// element out of the base vector corresponding to the input. Given this,
|
|
// it's analogous to the phi and select case even though it's not a merge.
|
|
if (isa<ExtractElementInst>(I))
|
|
// Note: There a lot of obvious peephole cases here. This are deliberately
|
|
// handled after the main base pointer inference algorithm to make writing
|
|
// test cases to exercise that code easier.
|
|
return BaseDefiningValueResult(I, false);
|
|
|
|
// The last two cases here don't return a base pointer. Instead, they
|
|
// return a value which dynamically selects from among several base
|
|
// derived pointers (each with it's own base potentially). It's the job of
|
|
// the caller to resolve these.
|
|
assert((isa<SelectInst>(I) || isa<PHINode>(I)) &&
|
|
"missing instruction case in findBaseDefiningValing");
|
|
return BaseDefiningValueResult(I, false);
|
|
}
|
|
|
|
/// Returns the base defining value for this value.
|
|
static Value *findBaseDefiningValueCached(Value *I, DefiningValueMapTy &Cache) {
|
|
Value *&Cached = Cache[I];
|
|
if (!Cached) {
|
|
Cached = findBaseDefiningValue(I).BDV;
|
|
DEBUG(dbgs() << "fBDV-cached: " << I->getName() << " -> "
|
|
<< Cached->getName() << "\n");
|
|
}
|
|
assert(Cache[I] != nullptr);
|
|
return Cached;
|
|
}
|
|
|
|
/// Return a base pointer for this value if known. Otherwise, return it's
|
|
/// base defining value.
|
|
static Value *findBaseOrBDV(Value *I, DefiningValueMapTy &Cache) {
|
|
Value *Def = findBaseDefiningValueCached(I, Cache);
|
|
auto Found = Cache.find(Def);
|
|
if (Found != Cache.end()) {
|
|
// Either a base-of relation, or a self reference. Caller must check.
|
|
return Found->second;
|
|
}
|
|
// Only a BDV available
|
|
return Def;
|
|
}
|
|
|
|
/// Given the result of a call to findBaseDefiningValue, or findBaseOrBDV,
|
|
/// is it known to be a base pointer? Or do we need to continue searching.
|
|
static bool isKnownBaseResult(Value *V) {
|
|
if (!isa<PHINode>(V) && !isa<SelectInst>(V) &&
|
|
!isa<ExtractElementInst>(V) && !isa<InsertElementInst>(V) &&
|
|
!isa<ShuffleVectorInst>(V)) {
|
|
// no recursion possible
|
|
return true;
|
|
}
|
|
if (isa<Instruction>(V) &&
|
|
cast<Instruction>(V)->getMetadata("is_base_value")) {
|
|
// This is a previously inserted base phi or select. We know
|
|
// that this is a base value.
|
|
return true;
|
|
}
|
|
|
|
// We need to keep searching
|
|
return false;
|
|
}
|
|
|
|
namespace {
|
|
/// Models the state of a single base defining value in the findBasePointer
|
|
/// algorithm for determining where a new instruction is needed to propagate
|
|
/// the base of this BDV.
|
|
class BDVState {
|
|
public:
|
|
enum Status { Unknown, Base, Conflict };
|
|
|
|
BDVState(Status s, Value *b = nullptr) : status(s), base(b) {
|
|
assert(status != Base || b);
|
|
}
|
|
explicit BDVState(Value *b) : status(Base), base(b) {}
|
|
BDVState() : status(Unknown), base(nullptr) {}
|
|
|
|
Status getStatus() const { return status; }
|
|
Value *getBase() const { return base; }
|
|
|
|
bool isBase() const { return getStatus() == Base; }
|
|
bool isUnknown() const { return getStatus() == Unknown; }
|
|
bool isConflict() const { return getStatus() == Conflict; }
|
|
|
|
bool operator==(const BDVState &other) const {
|
|
return base == other.base && status == other.status;
|
|
}
|
|
|
|
bool operator!=(const BDVState &other) const { return !(*this == other); }
|
|
|
|
LLVM_DUMP_METHOD
|
|
void dump() const { print(dbgs()); dbgs() << '\n'; }
|
|
|
|
void print(raw_ostream &OS) const {
|
|
switch (status) {
|
|
case Unknown:
|
|
OS << "U";
|
|
break;
|
|
case Base:
|
|
OS << "B";
|
|
break;
|
|
case Conflict:
|
|
OS << "C";
|
|
break;
|
|
};
|
|
OS << " (" << base << " - "
|
|
<< (base ? base->getName() : "nullptr") << "): ";
|
|
}
|
|
|
|
private:
|
|
Status status;
|
|
Value *base; // non null only if status == base
|
|
};
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
static raw_ostream &operator<<(raw_ostream &OS, const BDVState &State) {
|
|
State.print(OS);
|
|
return OS;
|
|
}
|
|
#endif
|
|
|
|
namespace {
|
|
// Values of type BDVState form a lattice, and this is a helper
|
|
// class that implementes the meet operation. The meat of the meet
|
|
// operation is implemented in MeetBDVStates::pureMeet
|
|
class MeetBDVStates {
|
|
public:
|
|
/// Initializes the currentResult to the TOP state so that if can be met with
|
|
/// any other state to produce that state.
|
|
MeetBDVStates() {}
|
|
|
|
// Destructively meet the current result with the given BDVState
|
|
void meetWith(BDVState otherState) {
|
|
currentResult = meet(otherState, currentResult);
|
|
}
|
|
|
|
BDVState getResult() const { return currentResult; }
|
|
|
|
private:
|
|
BDVState currentResult;
|
|
|
|
/// Perform a meet operation on two elements of the BDVState lattice.
|
|
static BDVState meet(BDVState LHS, BDVState RHS) {
|
|
assert((pureMeet(LHS, RHS) == pureMeet(RHS, LHS)) &&
|
|
"math is wrong: meet does not commute!");
|
|
BDVState Result = pureMeet(LHS, RHS);
|
|
DEBUG(dbgs() << "meet of " << LHS << " with " << RHS
|
|
<< " produced " << Result << "\n");
|
|
return Result;
|
|
}
|
|
|
|
static BDVState pureMeet(const BDVState &stateA, const BDVState &stateB) {
|
|
switch (stateA.getStatus()) {
|
|
case BDVState::Unknown:
|
|
return stateB;
|
|
|
|
case BDVState::Base:
|
|
assert(stateA.getBase() && "can't be null");
|
|
if (stateB.isUnknown())
|
|
return stateA;
|
|
|
|
if (stateB.isBase()) {
|
|
if (stateA.getBase() == stateB.getBase()) {
|
|
assert(stateA == stateB && "equality broken!");
|
|
return stateA;
|
|
}
|
|
return BDVState(BDVState::Conflict);
|
|
}
|
|
assert(stateB.isConflict() && "only three states!");
|
|
return BDVState(BDVState::Conflict);
|
|
|
|
case BDVState::Conflict:
|
|
return stateA;
|
|
}
|
|
llvm_unreachable("only three states!");
|
|
}
|
|
};
|
|
}
|
|
|
|
|
|
/// For a given value or instruction, figure out what base ptr it's derived
|
|
/// from. For gc objects, this is simply itself. On success, returns a value
|
|
/// which is the base pointer. (This is reliable and can be used for
|
|
/// relocation.) On failure, returns nullptr.
|
|
static Value *findBasePointer(Value *I, DefiningValueMapTy &cache) {
|
|
Value *def = findBaseOrBDV(I, cache);
|
|
|
|
if (isKnownBaseResult(def)) {
|
|
return def;
|
|
}
|
|
|
|
// Here's the rough algorithm:
|
|
// - For every SSA value, construct a mapping to either an actual base
|
|
// pointer or a PHI which obscures the base pointer.
|
|
// - Construct a mapping from PHI to unknown TOP state. Use an
|
|
// optimistic algorithm to propagate base pointer information. Lattice
|
|
// looks like:
|
|
// UNKNOWN
|
|
// b1 b2 b3 b4
|
|
// CONFLICT
|
|
// When algorithm terminates, all PHIs will either have a single concrete
|
|
// base or be in a conflict state.
|
|
// - For every conflict, insert a dummy PHI node without arguments. Add
|
|
// these to the base[Instruction] = BasePtr mapping. For every
|
|
// non-conflict, add the actual base.
|
|
// - For every conflict, add arguments for the base[a] of each input
|
|
// arguments.
|
|
//
|
|
// Note: A simpler form of this would be to add the conflict form of all
|
|
// PHIs without running the optimistic algorithm. This would be
|
|
// analogous to pessimistic data flow and would likely lead to an
|
|
// overall worse solution.
|
|
|
|
#ifndef NDEBUG
|
|
auto isExpectedBDVType = [](Value *BDV) {
|
|
return isa<PHINode>(BDV) || isa<SelectInst>(BDV) ||
|
|
isa<ExtractElementInst>(BDV) || isa<InsertElementInst>(BDV);
|
|
};
|
|
#endif
|
|
|
|
// Once populated, will contain a mapping from each potentially non-base BDV
|
|
// to a lattice value (described above) which corresponds to that BDV.
|
|
// We use the order of insertion (DFS over the def/use graph) to provide a
|
|
// stable deterministic ordering for visiting DenseMaps (which are unordered)
|
|
// below. This is important for deterministic compilation.
|
|
MapVector<Value *, BDVState> States;
|
|
|
|
// Recursively fill in all base defining values reachable from the initial
|
|
// one for which we don't already know a definite base value for
|
|
/* scope */ {
|
|
SmallVector<Value*, 16> Worklist;
|
|
Worklist.push_back(def);
|
|
States.insert(std::make_pair(def, BDVState()));
|
|
while (!Worklist.empty()) {
|
|
Value *Current = Worklist.pop_back_val();
|
|
assert(!isKnownBaseResult(Current) && "why did it get added?");
|
|
|
|
auto visitIncomingValue = [&](Value *InVal) {
|
|
Value *Base = findBaseOrBDV(InVal, cache);
|
|
if (isKnownBaseResult(Base))
|
|
// Known bases won't need new instructions introduced and can be
|
|
// ignored safely
|
|
return;
|
|
assert(isExpectedBDVType(Base) && "the only non-base values "
|
|
"we see should be base defining values");
|
|
if (States.insert(std::make_pair(Base, BDVState())).second)
|
|
Worklist.push_back(Base);
|
|
};
|
|
if (PHINode *Phi = dyn_cast<PHINode>(Current)) {
|
|
for (Value *InVal : Phi->incoming_values())
|
|
visitIncomingValue(InVal);
|
|
} else if (SelectInst *Sel = dyn_cast<SelectInst>(Current)) {
|
|
visitIncomingValue(Sel->getTrueValue());
|
|
visitIncomingValue(Sel->getFalseValue());
|
|
} else if (auto *EE = dyn_cast<ExtractElementInst>(Current)) {
|
|
visitIncomingValue(EE->getVectorOperand());
|
|
} else if (auto *IE = dyn_cast<InsertElementInst>(Current)) {
|
|
visitIncomingValue(IE->getOperand(0)); // vector operand
|
|
visitIncomingValue(IE->getOperand(1)); // scalar operand
|
|
} else {
|
|
// There is one known class of instructions we know we don't handle.
|
|
assert(isa<ShuffleVectorInst>(Current));
|
|
llvm_unreachable("unimplemented instruction case");
|
|
}
|
|
}
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
DEBUG(dbgs() << "States after initialization:\n");
|
|
for (auto Pair : States) {
|
|
DEBUG(dbgs() << " " << Pair.second << " for " << *Pair.first << "\n");
|
|
}
|
|
#endif
|
|
|
|
// Return a phi state for a base defining value. We'll generate a new
|
|
// base state for known bases and expect to find a cached state otherwise.
|
|
auto getStateForBDV = [&](Value *baseValue) {
|
|
if (isKnownBaseResult(baseValue))
|
|
return BDVState(baseValue);
|
|
auto I = States.find(baseValue);
|
|
assert(I != States.end() && "lookup failed!");
|
|
return I->second;
|
|
};
|
|
|
|
bool progress = true;
|
|
while (progress) {
|
|
#ifndef NDEBUG
|
|
const size_t oldSize = States.size();
|
|
#endif
|
|
progress = false;
|
|
// We're only changing values in this loop, thus safe to keep iterators.
|
|
// Since this is computing a fixed point, the order of visit does not
|
|
// effect the result. TODO: We could use a worklist here and make this run
|
|
// much faster.
|
|
for (auto Pair : States) {
|
|
Value *BDV = Pair.first;
|
|
assert(!isKnownBaseResult(BDV) && "why did it get added?");
|
|
|
|
// Given an input value for the current instruction, return a BDVState
|
|
// instance which represents the BDV of that value.
|
|
auto getStateForInput = [&](Value *V) mutable {
|
|
Value *BDV = findBaseOrBDV(V, cache);
|
|
return getStateForBDV(BDV);
|
|
};
|
|
|
|
MeetBDVStates calculateMeet;
|
|
if (SelectInst *select = dyn_cast<SelectInst>(BDV)) {
|
|
calculateMeet.meetWith(getStateForInput(select->getTrueValue()));
|
|
calculateMeet.meetWith(getStateForInput(select->getFalseValue()));
|
|
} else if (PHINode *Phi = dyn_cast<PHINode>(BDV)) {
|
|
for (Value *Val : Phi->incoming_values())
|
|
calculateMeet.meetWith(getStateForInput(Val));
|
|
} else if (auto *EE = dyn_cast<ExtractElementInst>(BDV)) {
|
|
// The 'meet' for an extractelement is slightly trivial, but it's still
|
|
// useful in that it drives us to conflict if our input is.
|
|
calculateMeet.meetWith(getStateForInput(EE->getVectorOperand()));
|
|
} else {
|
|
// Given there's a inherent type mismatch between the operands, will
|
|
// *always* produce Conflict.
|
|
auto *IE = cast<InsertElementInst>(BDV);
|
|
calculateMeet.meetWith(getStateForInput(IE->getOperand(0)));
|
|
calculateMeet.meetWith(getStateForInput(IE->getOperand(1)));
|
|
}
|
|
|
|
BDVState oldState = States[BDV];
|
|
BDVState newState = calculateMeet.getResult();
|
|
if (oldState != newState) {
|
|
progress = true;
|
|
States[BDV] = newState;
|
|
}
|
|
}
|
|
|
|
assert(oldSize == States.size() &&
|
|
"fixed point shouldn't be adding any new nodes to state");
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
DEBUG(dbgs() << "States after meet iteration:\n");
|
|
for (auto Pair : States) {
|
|
DEBUG(dbgs() << " " << Pair.second << " for " << *Pair.first << "\n");
|
|
}
|
|
#endif
|
|
|
|
// Insert Phis for all conflicts
|
|
// TODO: adjust naming patterns to avoid this order of iteration dependency
|
|
for (auto Pair : States) {
|
|
Instruction *I = cast<Instruction>(Pair.first);
|
|
BDVState State = Pair.second;
|
|
assert(!isKnownBaseResult(I) && "why did it get added?");
|
|
assert(!State.isUnknown() && "Optimistic algorithm didn't complete!");
|
|
|
|
// extractelement instructions are a bit special in that we may need to
|
|
// insert an extract even when we know an exact base for the instruction.
|
|
// The problem is that we need to convert from a vector base to a scalar
|
|
// base for the particular indice we're interested in.
|
|
if (State.isBase() && isa<ExtractElementInst>(I) &&
|
|
isa<VectorType>(State.getBase()->getType())) {
|
|
auto *EE = cast<ExtractElementInst>(I);
|
|
// TODO: In many cases, the new instruction is just EE itself. We should
|
|
// exploit this, but can't do it here since it would break the invariant
|
|
// about the BDV not being known to be a base.
|
|
auto *BaseInst = ExtractElementInst::Create(State.getBase(),
|
|
EE->getIndexOperand(),
|
|
"base_ee", EE);
|
|
BaseInst->setMetadata("is_base_value", MDNode::get(I->getContext(), {}));
|
|
States[I] = BDVState(BDVState::Base, BaseInst);
|
|
}
|
|
|
|
// Since we're joining a vector and scalar base, they can never be the
|
|
// same. As a result, we should always see insert element having reached
|
|
// the conflict state.
|
|
if (isa<InsertElementInst>(I)) {
|
|
assert(State.isConflict());
|
|
}
|
|
|
|
if (!State.isConflict())
|
|
continue;
|
|
|
|
/// Create and insert a new instruction which will represent the base of
|
|
/// the given instruction 'I'.
|
|
auto MakeBaseInstPlaceholder = [](Instruction *I) -> Instruction* {
|
|
if (isa<PHINode>(I)) {
|
|
BasicBlock *BB = I->getParent();
|
|
int NumPreds = std::distance(pred_begin(BB), pred_end(BB));
|
|
assert(NumPreds > 0 && "how did we reach here");
|
|
std::string Name = suffixed_name_or(I, ".base", "base_phi");
|
|
return PHINode::Create(I->getType(), NumPreds, Name, I);
|
|
} else if (SelectInst *Sel = dyn_cast<SelectInst>(I)) {
|
|
// The undef will be replaced later
|
|
UndefValue *Undef = UndefValue::get(Sel->getType());
|
|
std::string Name = suffixed_name_or(I, ".base", "base_select");
|
|
return SelectInst::Create(Sel->getCondition(), Undef,
|
|
Undef, Name, Sel);
|
|
} else if (auto *EE = dyn_cast<ExtractElementInst>(I)) {
|
|
UndefValue *Undef = UndefValue::get(EE->getVectorOperand()->getType());
|
|
std::string Name = suffixed_name_or(I, ".base", "base_ee");
|
|
return ExtractElementInst::Create(Undef, EE->getIndexOperand(), Name,
|
|
EE);
|
|
} else {
|
|
auto *IE = cast<InsertElementInst>(I);
|
|
UndefValue *VecUndef = UndefValue::get(IE->getOperand(0)->getType());
|
|
UndefValue *ScalarUndef = UndefValue::get(IE->getOperand(1)->getType());
|
|
std::string Name = suffixed_name_or(I, ".base", "base_ie");
|
|
return InsertElementInst::Create(VecUndef, ScalarUndef,
|
|
IE->getOperand(2), Name, IE);
|
|
}
|
|
|
|
};
|
|
Instruction *BaseInst = MakeBaseInstPlaceholder(I);
|
|
// Add metadata marking this as a base value
|
|
BaseInst->setMetadata("is_base_value", MDNode::get(I->getContext(), {}));
|
|
States[I] = BDVState(BDVState::Conflict, BaseInst);
|
|
}
|
|
|
|
// Returns a instruction which produces the base pointer for a given
|
|
// instruction. The instruction is assumed to be an input to one of the BDVs
|
|
// seen in the inference algorithm above. As such, we must either already
|
|
// know it's base defining value is a base, or have inserted a new
|
|
// instruction to propagate the base of it's BDV and have entered that newly
|
|
// introduced instruction into the state table. In either case, we are
|
|
// assured to be able to determine an instruction which produces it's base
|
|
// pointer.
|
|
auto getBaseForInput = [&](Value *Input, Instruction *InsertPt) {
|
|
Value *BDV = findBaseOrBDV(Input, cache);
|
|
Value *Base = nullptr;
|
|
if (isKnownBaseResult(BDV)) {
|
|
Base = BDV;
|
|
} else {
|
|
// Either conflict or base.
|
|
assert(States.count(BDV));
|
|
Base = States[BDV].getBase();
|
|
}
|
|
assert(Base && "can't be null");
|
|
// The cast is needed since base traversal may strip away bitcasts
|
|
if (Base->getType() != Input->getType() &&
|
|
InsertPt) {
|
|
Base = new BitCastInst(Base, Input->getType(), "cast",
|
|
InsertPt);
|
|
}
|
|
return Base;
|
|
};
|
|
|
|
// Fixup all the inputs of the new PHIs. Visit order needs to be
|
|
// deterministic and predictable because we're naming newly created
|
|
// instructions.
|
|
for (auto Pair : States) {
|
|
Instruction *BDV = cast<Instruction>(Pair.first);
|
|
BDVState State = Pair.second;
|
|
|
|
assert(!isKnownBaseResult(BDV) && "why did it get added?");
|
|
assert(!State.isUnknown() && "Optimistic algorithm didn't complete!");
|
|
if (!State.isConflict())
|
|
continue;
|
|
|
|
if (PHINode *basephi = dyn_cast<PHINode>(State.getBase())) {
|
|
PHINode *phi = cast<PHINode>(BDV);
|
|
unsigned NumPHIValues = phi->getNumIncomingValues();
|
|
for (unsigned i = 0; i < NumPHIValues; i++) {
|
|
Value *InVal = phi->getIncomingValue(i);
|
|
BasicBlock *InBB = phi->getIncomingBlock(i);
|
|
|
|
// If we've already seen InBB, add the same incoming value
|
|
// we added for it earlier. The IR verifier requires phi
|
|
// nodes with multiple entries from the same basic block
|
|
// to have the same incoming value for each of those
|
|
// entries. If we don't do this check here and basephi
|
|
// has a different type than base, we'll end up adding two
|
|
// bitcasts (and hence two distinct values) as incoming
|
|
// values for the same basic block.
|
|
|
|
int blockIndex = basephi->getBasicBlockIndex(InBB);
|
|
if (blockIndex != -1) {
|
|
Value *oldBase = basephi->getIncomingValue(blockIndex);
|
|
basephi->addIncoming(oldBase, InBB);
|
|
|
|
#ifndef NDEBUG
|
|
Value *Base = getBaseForInput(InVal, nullptr);
|
|
// In essence this assert states: the only way two
|
|
// values incoming from the same basic block may be
|
|
// different is by being different bitcasts of the same
|
|
// value. A cleanup that remains TODO is changing
|
|
// findBaseOrBDV to return an llvm::Value of the correct
|
|
// type (and still remain pure). This will remove the
|
|
// need to add bitcasts.
|
|
assert(Base->stripPointerCasts() == oldBase->stripPointerCasts() &&
|
|
"sanity -- findBaseOrBDV should be pure!");
|
|
#endif
|
|
continue;
|
|
}
|
|
|
|
// Find the instruction which produces the base for each input. We may
|
|
// need to insert a bitcast in the incoming block.
|
|
// TODO: Need to split critical edges if insertion is needed
|
|
Value *Base = getBaseForInput(InVal, InBB->getTerminator());
|
|
basephi->addIncoming(Base, InBB);
|
|
}
|
|
assert(basephi->getNumIncomingValues() == NumPHIValues);
|
|
} else if (SelectInst *BaseSel = dyn_cast<SelectInst>(State.getBase())) {
|
|
SelectInst *Sel = cast<SelectInst>(BDV);
|
|
// Operand 1 & 2 are true, false path respectively. TODO: refactor to
|
|
// something more safe and less hacky.
|
|
for (int i = 1; i <= 2; i++) {
|
|
Value *InVal = Sel->getOperand(i);
|
|
// Find the instruction which produces the base for each input. We may
|
|
// need to insert a bitcast.
|
|
Value *Base = getBaseForInput(InVal, BaseSel);
|
|
BaseSel->setOperand(i, Base);
|
|
}
|
|
} else if (auto *BaseEE = dyn_cast<ExtractElementInst>(State.getBase())) {
|
|
Value *InVal = cast<ExtractElementInst>(BDV)->getVectorOperand();
|
|
// Find the instruction which produces the base for each input. We may
|
|
// need to insert a bitcast.
|
|
Value *Base = getBaseForInput(InVal, BaseEE);
|
|
BaseEE->setOperand(0, Base);
|
|
} else {
|
|
auto *BaseIE = cast<InsertElementInst>(State.getBase());
|
|
auto *BdvIE = cast<InsertElementInst>(BDV);
|
|
auto UpdateOperand = [&](int OperandIdx) {
|
|
Value *InVal = BdvIE->getOperand(OperandIdx);
|
|
Value *Base = getBaseForInput(InVal, BaseIE);
|
|
BaseIE->setOperand(OperandIdx, Base);
|
|
};
|
|
UpdateOperand(0); // vector operand
|
|
UpdateOperand(1); // scalar operand
|
|
}
|
|
|
|
}
|
|
|
|
// Now that we're done with the algorithm, see if we can optimize the
|
|
// results slightly by reducing the number of new instructions needed.
|
|
// Arguably, this should be integrated into the algorithm above, but
|
|
// doing as a post process step is easier to reason about for the moment.
|
|
DenseMap<Value *, Value *> ReverseMap;
|
|
SmallPtrSet<Instruction *, 16> NewInsts;
|
|
SmallSetVector<AssertingVH<Instruction>, 16> Worklist;
|
|
// Note: We need to visit the states in a deterministic order. We uses the
|
|
// Keys we sorted above for this purpose. Note that we are papering over a
|
|
// bigger problem with the algorithm above - it's visit order is not
|
|
// deterministic. A larger change is needed to fix this.
|
|
for (auto Pair : States) {
|
|
auto *BDV = Pair.first;
|
|
auto State = Pair.second;
|
|
Value *Base = State.getBase();
|
|
assert(BDV && Base);
|
|
assert(!isKnownBaseResult(BDV) && "why did it get added?");
|
|
assert(isKnownBaseResult(Base) &&
|
|
"must be something we 'know' is a base pointer");
|
|
if (!State.isConflict())
|
|
continue;
|
|
|
|
ReverseMap[Base] = BDV;
|
|
if (auto *BaseI = dyn_cast<Instruction>(Base)) {
|
|
NewInsts.insert(BaseI);
|
|
Worklist.insert(BaseI);
|
|
}
|
|
}
|
|
auto ReplaceBaseInstWith = [&](Value *BDV, Instruction *BaseI,
|
|
Value *Replacement) {
|
|
// Add users which are new instructions (excluding self references)
|
|
for (User *U : BaseI->users())
|
|
if (auto *UI = dyn_cast<Instruction>(U))
|
|
if (NewInsts.count(UI) && UI != BaseI)
|
|
Worklist.insert(UI);
|
|
// Then do the actual replacement
|
|
NewInsts.erase(BaseI);
|
|
ReverseMap.erase(BaseI);
|
|
BaseI->replaceAllUsesWith(Replacement);
|
|
BaseI->eraseFromParent();
|
|
assert(States.count(BDV));
|
|
assert(States[BDV].isConflict() && States[BDV].getBase() == BaseI);
|
|
States[BDV] = BDVState(BDVState::Conflict, Replacement);
|
|
};
|
|
const DataLayout &DL = cast<Instruction>(def)->getModule()->getDataLayout();
|
|
while (!Worklist.empty()) {
|
|
Instruction *BaseI = Worklist.pop_back_val();
|
|
assert(NewInsts.count(BaseI));
|
|
Value *Bdv = ReverseMap[BaseI];
|
|
if (auto *BdvI = dyn_cast<Instruction>(Bdv))
|
|
if (BaseI->isIdenticalTo(BdvI)) {
|
|
DEBUG(dbgs() << "Identical Base: " << *BaseI << "\n");
|
|
ReplaceBaseInstWith(Bdv, BaseI, Bdv);
|
|
continue;
|
|
}
|
|
if (Value *V = SimplifyInstruction(BaseI, DL)) {
|
|
DEBUG(dbgs() << "Base " << *BaseI << " simplified to " << *V << "\n");
|
|
ReplaceBaseInstWith(Bdv, BaseI, V);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
// Cache all of our results so we can cheaply reuse them
|
|
// NOTE: This is actually two caches: one of the base defining value
|
|
// relation and one of the base pointer relation! FIXME
|
|
for (auto Pair : States) {
|
|
auto *BDV = Pair.first;
|
|
Value *base = Pair.second.getBase();
|
|
assert(BDV && base);
|
|
|
|
std::string fromstr = cache.count(BDV) ? cache[BDV]->getName() : "none";
|
|
DEBUG(dbgs() << "Updating base value cache"
|
|
<< " for: " << BDV->getName()
|
|
<< " from: " << fromstr
|
|
<< " to: " << base->getName() << "\n");
|
|
|
|
if (cache.count(BDV)) {
|
|
// Once we transition from the BDV relation being store in the cache to
|
|
// the base relation being stored, it must be stable
|
|
assert((!isKnownBaseResult(cache[BDV]) || cache[BDV] == base) &&
|
|
"base relation should be stable");
|
|
}
|
|
cache[BDV] = base;
|
|
}
|
|
assert(cache.find(def) != cache.end());
|
|
return cache[def];
|
|
}
|
|
|
|
// For a set of live pointers (base and/or derived), identify the base
|
|
// pointer of the object which they are derived from. This routine will
|
|
// mutate the IR graph as needed to make the 'base' pointer live at the
|
|
// definition site of 'derived'. This ensures that any use of 'derived' can
|
|
// also use 'base'. This may involve the insertion of a number of
|
|
// additional PHI nodes.
|
|
//
|
|
// preconditions: live is a set of pointer type Values
|
|
//
|
|
// side effects: may insert PHI nodes into the existing CFG, will preserve
|
|
// CFG, will not remove or mutate any existing nodes
|
|
//
|
|
// post condition: PointerToBase contains one (derived, base) pair for every
|
|
// pointer in live. Note that derived can be equal to base if the original
|
|
// pointer was a base pointer.
|
|
static void
|
|
findBasePointers(const StatepointLiveSetTy &live,
|
|
DenseMap<Value *, Value *> &PointerToBase,
|
|
DominatorTree *DT, DefiningValueMapTy &DVCache) {
|
|
// For the naming of values inserted to be deterministic - which makes for
|
|
// much cleaner and more stable tests - we need to assign an order to the
|
|
// live values. DenseSets do not provide a deterministic order across runs.
|
|
SmallVector<Value *, 64> Temp;
|
|
Temp.insert(Temp.end(), live.begin(), live.end());
|
|
std::sort(Temp.begin(), Temp.end(), order_by_name);
|
|
for (Value *ptr : Temp) {
|
|
Value *base = findBasePointer(ptr, DVCache);
|
|
assert(base && "failed to find base pointer");
|
|
PointerToBase[ptr] = base;
|
|
assert((!isa<Instruction>(base) || !isa<Instruction>(ptr) ||
|
|
DT->dominates(cast<Instruction>(base)->getParent(),
|
|
cast<Instruction>(ptr)->getParent())) &&
|
|
"The base we found better dominate the derived pointer");
|
|
|
|
// If you see this trip and like to live really dangerously, the code should
|
|
// be correct, just with idioms the verifier can't handle. You can try
|
|
// disabling the verifier at your own substantial risk.
|
|
assert(!isa<ConstantPointerNull>(base) &&
|
|
"the relocation code needs adjustment to handle the relocation of "
|
|
"a null pointer constant without causing false positives in the "
|
|
"safepoint ir verifier.");
|
|
}
|
|
}
|
|
|
|
/// Find the required based pointers (and adjust the live set) for the given
|
|
/// parse point.
|
|
static void findBasePointers(DominatorTree &DT, DefiningValueMapTy &DVCache,
|
|
const CallSite &CS,
|
|
PartiallyConstructedSafepointRecord &result) {
|
|
DenseMap<Value *, Value *> PointerToBase;
|
|
findBasePointers(result.LiveSet, PointerToBase, &DT, DVCache);
|
|
|
|
if (PrintBasePointers) {
|
|
// Note: Need to print these in a stable order since this is checked in
|
|
// some tests.
|
|
errs() << "Base Pairs (w/o Relocation):\n";
|
|
SmallVector<Value *, 64> Temp;
|
|
Temp.reserve(PointerToBase.size());
|
|
for (auto Pair : PointerToBase) {
|
|
Temp.push_back(Pair.first);
|
|
}
|
|
std::sort(Temp.begin(), Temp.end(), order_by_name);
|
|
for (Value *Ptr : Temp) {
|
|
Value *Base = PointerToBase[Ptr];
|
|
errs() << " derived %" << Ptr->getName() << " base %" << Base->getName()
|
|
<< "\n";
|
|
}
|
|
}
|
|
|
|
result.PointerToBase = PointerToBase;
|
|
}
|
|
|
|
/// Given an updated version of the dataflow liveness results, update the
|
|
/// liveset and base pointer maps for the call site CS.
|
|
static void recomputeLiveInValues(GCPtrLivenessData &RevisedLivenessData,
|
|
const CallSite &CS,
|
|
PartiallyConstructedSafepointRecord &result);
|
|
|
|
static void recomputeLiveInValues(
|
|
Function &F, DominatorTree &DT, Pass *P, ArrayRef<CallSite> toUpdate,
|
|
MutableArrayRef<struct PartiallyConstructedSafepointRecord> records) {
|
|
// TODO-PERF: reuse the original liveness, then simply run the dataflow
|
|
// again. The old values are still live and will help it stabilize quickly.
|
|
GCPtrLivenessData RevisedLivenessData;
|
|
computeLiveInValues(DT, F, RevisedLivenessData);
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
const CallSite &CS = toUpdate[i];
|
|
recomputeLiveInValues(RevisedLivenessData, CS, info);
|
|
}
|
|
}
|
|
|
|
// When inserting gc.relocate and gc.result calls, we need to ensure there are
|
|
// no uses of the original value / return value between the gc.statepoint and
|
|
// the gc.relocate / gc.result call. One case which can arise is a phi node
|
|
// starting one of the successor blocks. We also need to be able to insert the
|
|
// gc.relocates only on the path which goes through the statepoint. We might
|
|
// need to split an edge to make this possible.
|
|
static BasicBlock *
|
|
normalizeForInvokeSafepoint(BasicBlock *BB, BasicBlock *InvokeParent,
|
|
DominatorTree &DT) {
|
|
BasicBlock *Ret = BB;
|
|
if (!BB->getUniquePredecessor())
|
|
Ret = SplitBlockPredecessors(BB, InvokeParent, "", &DT);
|
|
|
|
// Now that 'Ret' has unique predecessor we can safely remove all phi nodes
|
|
// from it
|
|
FoldSingleEntryPHINodes(Ret);
|
|
assert(!isa<PHINode>(Ret->begin()) &&
|
|
"All PHI nodes should have been removed!");
|
|
|
|
// At this point, we can safely insert a gc.relocate or gc.result as the first
|
|
// instruction in Ret if needed.
|
|
return Ret;
|
|
}
|
|
|
|
// Create new attribute set containing only attributes which can be transferred
|
|
// from original call to the safepoint.
|
|
static AttributeSet legalizeCallAttributes(AttributeSet AS) {
|
|
AttributeSet Ret;
|
|
|
|
for (unsigned Slot = 0; Slot < AS.getNumSlots(); Slot++) {
|
|
unsigned Index = AS.getSlotIndex(Slot);
|
|
|
|
if (Index == AttributeSet::ReturnIndex ||
|
|
Index == AttributeSet::FunctionIndex) {
|
|
|
|
for (Attribute Attr : make_range(AS.begin(Slot), AS.end(Slot))) {
|
|
|
|
// Do not allow certain attributes - just skip them
|
|
// Safepoint can not be read only or read none.
|
|
if (Attr.hasAttribute(Attribute::ReadNone) ||
|
|
Attr.hasAttribute(Attribute::ReadOnly))
|
|
continue;
|
|
|
|
// These attributes control the generation of the gc.statepoint call /
|
|
// invoke itself; and once the gc.statepoint is in place, they're of no
|
|
// use.
|
|
if (Attr.hasAttribute("statepoint-num-patch-bytes") ||
|
|
Attr.hasAttribute("statepoint-id"))
|
|
continue;
|
|
|
|
Ret = Ret.addAttributes(
|
|
AS.getContext(), Index,
|
|
AttributeSet::get(AS.getContext(), Index, AttrBuilder(Attr)));
|
|
}
|
|
}
|
|
|
|
// Just skip parameter attributes for now
|
|
}
|
|
|
|
return Ret;
|
|
}
|
|
|
|
/// Helper function to place all gc relocates necessary for the given
|
|
/// statepoint.
|
|
/// Inputs:
|
|
/// liveVariables - list of variables to be relocated.
|
|
/// liveStart - index of the first live variable.
|
|
/// basePtrs - base pointers.
|
|
/// statepointToken - statepoint instruction to which relocates should be
|
|
/// bound.
|
|
/// Builder - Llvm IR builder to be used to construct new calls.
|
|
static void CreateGCRelocates(ArrayRef<Value *> LiveVariables,
|
|
const int LiveStart,
|
|
ArrayRef<Value *> BasePtrs,
|
|
Instruction *StatepointToken,
|
|
IRBuilder<> Builder) {
|
|
if (LiveVariables.empty())
|
|
return;
|
|
|
|
auto FindIndex = [](ArrayRef<Value *> LiveVec, Value *Val) {
|
|
auto ValIt = std::find(LiveVec.begin(), LiveVec.end(), Val);
|
|
assert(ValIt != LiveVec.end() && "Val not found in LiveVec!");
|
|
size_t Index = std::distance(LiveVec.begin(), ValIt);
|
|
assert(Index < LiveVec.size() && "Bug in std::find?");
|
|
return Index;
|
|
};
|
|
|
|
// All gc_relocate are set to i8 addrspace(1)* type. We originally generated
|
|
// unique declarations for each pointer type, but this proved problematic
|
|
// because the intrinsic mangling code is incomplete and fragile. Since
|
|
// we're moving towards a single unified pointer type anyways, we can just
|
|
// cast everything to an i8* of the right address space. A bitcast is added
|
|
// later to convert gc_relocate to the actual value's type.
|
|
Module *M = StatepointToken->getModule();
|
|
auto AS = cast<PointerType>(LiveVariables[0]->getType())->getAddressSpace();
|
|
Type *Types[] = {Type::getInt8PtrTy(M->getContext(), AS)};
|
|
Value *GCRelocateDecl =
|
|
Intrinsic::getDeclaration(M, Intrinsic::experimental_gc_relocate, Types);
|
|
|
|
for (unsigned i = 0; i < LiveVariables.size(); i++) {
|
|
// Generate the gc.relocate call and save the result
|
|
Value *BaseIdx =
|
|
Builder.getInt32(LiveStart + FindIndex(LiveVariables, BasePtrs[i]));
|
|
Value *LiveIdx = Builder.getInt32(LiveStart + i);
|
|
|
|
// only specify a debug name if we can give a useful one
|
|
CallInst *Reloc = Builder.CreateCall(
|
|
GCRelocateDecl, {StatepointToken, BaseIdx, LiveIdx},
|
|
suffixed_name_or(LiveVariables[i], ".relocated", ""));
|
|
// Trick CodeGen into thinking there are lots of free registers at this
|
|
// fake call.
|
|
Reloc->setCallingConv(CallingConv::Cold);
|
|
}
|
|
}
|
|
|
|
namespace {
|
|
|
|
/// This struct is used to defer RAUWs and `eraseFromParent` s. Using this
|
|
/// avoids having to worry about keeping around dangling pointers to Values.
|
|
class DeferredReplacement {
|
|
AssertingVH<Instruction> Old;
|
|
AssertingVH<Instruction> New;
|
|
|
|
public:
|
|
explicit DeferredReplacement(Instruction *Old, Instruction *New) :
|
|
Old(Old), New(New) {
|
|
assert(Old != New && "Not allowed!");
|
|
}
|
|
|
|
/// Does the task represented by this instance.
|
|
void doReplacement() {
|
|
Instruction *OldI = Old;
|
|
Instruction *NewI = New;
|
|
|
|
assert(OldI != NewI && "Disallowed at construction?!");
|
|
|
|
Old = nullptr;
|
|
New = nullptr;
|
|
|
|
if (NewI)
|
|
OldI->replaceAllUsesWith(NewI);
|
|
OldI->eraseFromParent();
|
|
}
|
|
};
|
|
}
|
|
|
|
static void
|
|
makeStatepointExplicitImpl(const CallSite CS, /* to replace */
|
|
const SmallVectorImpl<Value *> &BasePtrs,
|
|
const SmallVectorImpl<Value *> &LiveVariables,
|
|
PartiallyConstructedSafepointRecord &Result,
|
|
std::vector<DeferredReplacement> &Replacements) {
|
|
assert(BasePtrs.size() == LiveVariables.size());
|
|
assert((UseDeoptBundles || isStatepoint(CS)) &&
|
|
"This method expects to be rewriting a statepoint");
|
|
|
|
// Then go ahead and use the builder do actually do the inserts. We insert
|
|
// immediately before the previous instruction under the assumption that all
|
|
// arguments will be available here. We can't insert afterwards since we may
|
|
// be replacing a terminator.
|
|
Instruction *InsertBefore = CS.getInstruction();
|
|
IRBuilder<> Builder(InsertBefore);
|
|
|
|
ArrayRef<Value *> GCArgs(LiveVariables);
|
|
uint64_t StatepointID = 0xABCDEF00;
|
|
uint32_t NumPatchBytes = 0;
|
|
uint32_t Flags = uint32_t(StatepointFlags::None);
|
|
|
|
ArrayRef<Use> CallArgs;
|
|
ArrayRef<Use> DeoptArgs;
|
|
ArrayRef<Use> TransitionArgs;
|
|
|
|
Value *CallTarget = nullptr;
|
|
|
|
if (UseDeoptBundles) {
|
|
CallArgs = {CS.arg_begin(), CS.arg_end()};
|
|
DeoptArgs = GetDeoptBundleOperands(CS);
|
|
// TODO: we don't fill in TransitionArgs or Flags in this branch, but we
|
|
// could have an operand bundle for that too.
|
|
AttributeSet OriginalAttrs = CS.getAttributes();
|
|
|
|
Attribute AttrID = OriginalAttrs.getAttribute(AttributeSet::FunctionIndex,
|
|
"statepoint-id");
|
|
if (AttrID.isStringAttribute())
|
|
AttrID.getValueAsString().getAsInteger(10, StatepointID);
|
|
|
|
Attribute AttrNumPatchBytes = OriginalAttrs.getAttribute(
|
|
AttributeSet::FunctionIndex, "statepoint-num-patch-bytes");
|
|
if (AttrNumPatchBytes.isStringAttribute())
|
|
AttrNumPatchBytes.getValueAsString().getAsInteger(10, NumPatchBytes);
|
|
|
|
CallTarget = CS.getCalledValue();
|
|
} else {
|
|
// This branch will be gone soon, and we will soon only support the
|
|
// UseDeoptBundles == true configuration.
|
|
Statepoint OldSP(CS);
|
|
StatepointID = OldSP.getID();
|
|
NumPatchBytes = OldSP.getNumPatchBytes();
|
|
Flags = OldSP.getFlags();
|
|
|
|
CallArgs = {OldSP.arg_begin(), OldSP.arg_end()};
|
|
DeoptArgs = {OldSP.vm_state_begin(), OldSP.vm_state_end()};
|
|
TransitionArgs = {OldSP.gc_transition_args_begin(),
|
|
OldSP.gc_transition_args_end()};
|
|
CallTarget = OldSP.getCalledValue();
|
|
}
|
|
|
|
// Create the statepoint given all the arguments
|
|
Instruction *Token = nullptr;
|
|
AttributeSet ReturnAttrs;
|
|
if (CS.isCall()) {
|
|
CallInst *ToReplace = cast<CallInst>(CS.getInstruction());
|
|
CallInst *Call = Builder.CreateGCStatepointCall(
|
|
StatepointID, NumPatchBytes, CallTarget, Flags, CallArgs,
|
|
TransitionArgs, DeoptArgs, GCArgs, "safepoint_token");
|
|
|
|
Call->setTailCall(ToReplace->isTailCall());
|
|
Call->setCallingConv(ToReplace->getCallingConv());
|
|
|
|
// Currently we will fail on parameter attributes and on certain
|
|
// function attributes.
|
|
AttributeSet NewAttrs = legalizeCallAttributes(ToReplace->getAttributes());
|
|
// In case if we can handle this set of attributes - set up function attrs
|
|
// directly on statepoint and return attrs later for gc_result intrinsic.
|
|
Call->setAttributes(NewAttrs.getFnAttributes());
|
|
ReturnAttrs = NewAttrs.getRetAttributes();
|
|
|
|
Token = Call;
|
|
|
|
// Put the following gc_result and gc_relocate calls immediately after the
|
|
// the old call (which we're about to delete)
|
|
assert(ToReplace->getNextNode() && "Not a terminator, must have next!");
|
|
Builder.SetInsertPoint(ToReplace->getNextNode());
|
|
Builder.SetCurrentDebugLocation(ToReplace->getNextNode()->getDebugLoc());
|
|
} else {
|
|
InvokeInst *ToReplace = cast<InvokeInst>(CS.getInstruction());
|
|
|
|
// Insert the new invoke into the old block. We'll remove the old one in a
|
|
// moment at which point this will become the new terminator for the
|
|
// original block.
|
|
InvokeInst *Invoke = Builder.CreateGCStatepointInvoke(
|
|
StatepointID, NumPatchBytes, CallTarget, ToReplace->getNormalDest(),
|
|
ToReplace->getUnwindDest(), Flags, CallArgs, TransitionArgs, DeoptArgs,
|
|
GCArgs, "statepoint_token");
|
|
|
|
Invoke->setCallingConv(ToReplace->getCallingConv());
|
|
|
|
// Currently we will fail on parameter attributes and on certain
|
|
// function attributes.
|
|
AttributeSet NewAttrs = legalizeCallAttributes(ToReplace->getAttributes());
|
|
// In case if we can handle this set of attributes - set up function attrs
|
|
// directly on statepoint and return attrs later for gc_result intrinsic.
|
|
Invoke->setAttributes(NewAttrs.getFnAttributes());
|
|
ReturnAttrs = NewAttrs.getRetAttributes();
|
|
|
|
Token = Invoke;
|
|
|
|
// Generate gc relocates in exceptional path
|
|
BasicBlock *UnwindBlock = ToReplace->getUnwindDest();
|
|
assert(!isa<PHINode>(UnwindBlock->begin()) &&
|
|
UnwindBlock->getUniquePredecessor() &&
|
|
"can't safely insert in this block!");
|
|
|
|
Builder.SetInsertPoint(&*UnwindBlock->getFirstInsertionPt());
|
|
Builder.SetCurrentDebugLocation(ToReplace->getDebugLoc());
|
|
|
|
// Extract second element from landingpad return value. We will attach
|
|
// exceptional gc relocates to it.
|
|
Instruction *ExceptionalToken =
|
|
cast<Instruction>(Builder.CreateExtractValue(
|
|
UnwindBlock->getLandingPadInst(), 1, "relocate_token"));
|
|
Result.UnwindToken = ExceptionalToken;
|
|
|
|
const unsigned LiveStartIdx = Statepoint(Token).gcArgsStartIdx();
|
|
CreateGCRelocates(LiveVariables, LiveStartIdx, BasePtrs, ExceptionalToken,
|
|
Builder);
|
|
|
|
// Generate gc relocates and returns for normal block
|
|
BasicBlock *NormalDest = ToReplace->getNormalDest();
|
|
assert(!isa<PHINode>(NormalDest->begin()) &&
|
|
NormalDest->getUniquePredecessor() &&
|
|
"can't safely insert in this block!");
|
|
|
|
Builder.SetInsertPoint(&*NormalDest->getFirstInsertionPt());
|
|
|
|
// gc relocates will be generated later as if it were regular call
|
|
// statepoint
|
|
}
|
|
assert(Token && "Should be set in one of the above branches!");
|
|
|
|
if (UseDeoptBundles) {
|
|
Token->setName("statepoint_token");
|
|
if (!CS.getType()->isVoidTy() && !CS.getInstruction()->use_empty()) {
|
|
StringRef Name =
|
|
CS.getInstruction()->hasName() ? CS.getInstruction()->getName() : "";
|
|
CallInst *GCResult = Builder.CreateGCResult(Token, CS.getType(), Name);
|
|
GCResult->setAttributes(CS.getAttributes().getRetAttributes());
|
|
|
|
// We cannot RAUW or delete CS.getInstruction() because it could be in the
|
|
// live set of some other safepoint, in which case that safepoint's
|
|
// PartiallyConstructedSafepointRecord will hold a raw pointer to this
|
|
// llvm::Instruction. Instead, we defer the replacement and deletion to
|
|
// after the live sets have been made explicit in the IR, and we no longer
|
|
// have raw pointers to worry about.
|
|
Replacements.emplace_back(CS.getInstruction(), GCResult);
|
|
} else {
|
|
Replacements.emplace_back(CS.getInstruction(), nullptr);
|
|
}
|
|
} else {
|
|
assert(!CS.getInstruction()->hasNUsesOrMore(2) &&
|
|
"only valid use before rewrite is gc.result");
|
|
assert(!CS.getInstruction()->hasOneUse() ||
|
|
isGCResult(cast<Instruction>(*CS.getInstruction()->user_begin())));
|
|
|
|
// Take the name of the original statepoint token if there was one.
|
|
Token->takeName(CS.getInstruction());
|
|
|
|
// Update the gc.result of the original statepoint (if any) to use the newly
|
|
// inserted statepoint. This is safe to do here since the token can't be
|
|
// considered a live reference.
|
|
CS.getInstruction()->replaceAllUsesWith(Token);
|
|
CS.getInstruction()->eraseFromParent();
|
|
}
|
|
|
|
Result.StatepointToken = Token;
|
|
|
|
// Second, create a gc.relocate for every live variable
|
|
const unsigned LiveStartIdx = Statepoint(Token).gcArgsStartIdx();
|
|
CreateGCRelocates(LiveVariables, LiveStartIdx, BasePtrs, Token, Builder);
|
|
}
|
|
|
|
namespace {
|
|
struct NameOrdering {
|
|
Value *Base;
|
|
Value *Derived;
|
|
|
|
bool operator()(NameOrdering const &a, NameOrdering const &b) {
|
|
return -1 == a.Derived->getName().compare(b.Derived->getName());
|
|
}
|
|
};
|
|
}
|
|
|
|
static void StabilizeOrder(SmallVectorImpl<Value *> &BaseVec,
|
|
SmallVectorImpl<Value *> &LiveVec) {
|
|
assert(BaseVec.size() == LiveVec.size());
|
|
|
|
SmallVector<NameOrdering, 64> Temp;
|
|
for (size_t i = 0; i < BaseVec.size(); i++) {
|
|
NameOrdering v;
|
|
v.Base = BaseVec[i];
|
|
v.Derived = LiveVec[i];
|
|
Temp.push_back(v);
|
|
}
|
|
|
|
std::sort(Temp.begin(), Temp.end(), NameOrdering());
|
|
for (size_t i = 0; i < BaseVec.size(); i++) {
|
|
BaseVec[i] = Temp[i].Base;
|
|
LiveVec[i] = Temp[i].Derived;
|
|
}
|
|
}
|
|
|
|
// Replace an existing gc.statepoint with a new one and a set of gc.relocates
|
|
// which make the relocations happening at this safepoint explicit.
|
|
//
|
|
// WARNING: Does not do any fixup to adjust users of the original live
|
|
// values. That's the callers responsibility.
|
|
static void
|
|
makeStatepointExplicit(DominatorTree &DT, const CallSite &CS,
|
|
PartiallyConstructedSafepointRecord &Result,
|
|
std::vector<DeferredReplacement> &Replacements) {
|
|
const auto &LiveSet = Result.LiveSet;
|
|
const auto &PointerToBase = Result.PointerToBase;
|
|
|
|
// Convert to vector for efficient cross referencing.
|
|
SmallVector<Value *, 64> BaseVec, LiveVec;
|
|
LiveVec.reserve(LiveSet.size());
|
|
BaseVec.reserve(LiveSet.size());
|
|
for (Value *L : LiveSet) {
|
|
LiveVec.push_back(L);
|
|
assert(PointerToBase.count(L));
|
|
Value *Base = PointerToBase.find(L)->second;
|
|
BaseVec.push_back(Base);
|
|
}
|
|
assert(LiveVec.size() == BaseVec.size());
|
|
|
|
// To make the output IR slightly more stable (for use in diffs), ensure a
|
|
// fixed order of the values in the safepoint (by sorting the value name).
|
|
// The order is otherwise meaningless.
|
|
StabilizeOrder(BaseVec, LiveVec);
|
|
|
|
// Do the actual rewriting and delete the old statepoint
|
|
makeStatepointExplicitImpl(CS, BaseVec, LiveVec, Result, Replacements);
|
|
}
|
|
|
|
// Helper function for the relocationViaAlloca.
|
|
//
|
|
// It receives iterator to the statepoint gc relocates and emits a store to the
|
|
// assigned location (via allocaMap) for the each one of them. It adds the
|
|
// visited values into the visitedLiveValues set, which we will later use them
|
|
// for sanity checking.
|
|
static void
|
|
insertRelocationStores(iterator_range<Value::user_iterator> GCRelocs,
|
|
DenseMap<Value *, Value *> &AllocaMap,
|
|
DenseSet<Value *> &VisitedLiveValues) {
|
|
|
|
for (User *U : GCRelocs) {
|
|
if (!isa<IntrinsicInst>(U))
|
|
continue;
|
|
|
|
IntrinsicInst *RelocatedValue = cast<IntrinsicInst>(U);
|
|
|
|
// We only care about relocates
|
|
if (RelocatedValue->getIntrinsicID() !=
|
|
Intrinsic::experimental_gc_relocate) {
|
|
continue;
|
|
}
|
|
|
|
GCRelocateOperands RelocateOperands(RelocatedValue);
|
|
Value *OriginalValue =
|
|
const_cast<Value *>(RelocateOperands.getDerivedPtr());
|
|
assert(AllocaMap.count(OriginalValue));
|
|
Value *Alloca = AllocaMap[OriginalValue];
|
|
|
|
// Emit store into the related alloca
|
|
// All gc_relocates are i8 addrspace(1)* typed, and it must be bitcasted to
|
|
// the correct type according to alloca.
|
|
assert(RelocatedValue->getNextNode() &&
|
|
"Should always have one since it's not a terminator");
|
|
IRBuilder<> Builder(RelocatedValue->getNextNode());
|
|
Value *CastedRelocatedValue =
|
|
Builder.CreateBitCast(RelocatedValue,
|
|
cast<AllocaInst>(Alloca)->getAllocatedType(),
|
|
suffixed_name_or(RelocatedValue, ".casted", ""));
|
|
|
|
StoreInst *Store = new StoreInst(CastedRelocatedValue, Alloca);
|
|
Store->insertAfter(cast<Instruction>(CastedRelocatedValue));
|
|
|
|
#ifndef NDEBUG
|
|
VisitedLiveValues.insert(OriginalValue);
|
|
#endif
|
|
}
|
|
}
|
|
|
|
// Helper function for the "relocationViaAlloca". Similar to the
|
|
// "insertRelocationStores" but works for rematerialized values.
|
|
static void
|
|
insertRematerializationStores(
|
|
RematerializedValueMapTy RematerializedValues,
|
|
DenseMap<Value *, Value *> &AllocaMap,
|
|
DenseSet<Value *> &VisitedLiveValues) {
|
|
|
|
for (auto RematerializedValuePair: RematerializedValues) {
|
|
Instruction *RematerializedValue = RematerializedValuePair.first;
|
|
Value *OriginalValue = RematerializedValuePair.second;
|
|
|
|
assert(AllocaMap.count(OriginalValue) &&
|
|
"Can not find alloca for rematerialized value");
|
|
Value *Alloca = AllocaMap[OriginalValue];
|
|
|
|
StoreInst *Store = new StoreInst(RematerializedValue, Alloca);
|
|
Store->insertAfter(RematerializedValue);
|
|
|
|
#ifndef NDEBUG
|
|
VisitedLiveValues.insert(OriginalValue);
|
|
#endif
|
|
}
|
|
}
|
|
|
|
/// Do all the relocation update via allocas and mem2reg
|
|
static void relocationViaAlloca(
|
|
Function &F, DominatorTree &DT, ArrayRef<Value *> Live,
|
|
ArrayRef<PartiallyConstructedSafepointRecord> Records) {
|
|
#ifndef NDEBUG
|
|
// record initial number of (static) allocas; we'll check we have the same
|
|
// number when we get done.
|
|
int InitialAllocaNum = 0;
|
|
for (auto I = F.getEntryBlock().begin(), E = F.getEntryBlock().end(); I != E;
|
|
I++)
|
|
if (isa<AllocaInst>(*I))
|
|
InitialAllocaNum++;
|
|
#endif
|
|
|
|
// TODO-PERF: change data structures, reserve
|
|
DenseMap<Value *, Value *> AllocaMap;
|
|
SmallVector<AllocaInst *, 200> PromotableAllocas;
|
|
// Used later to chack that we have enough allocas to store all values
|
|
std::size_t NumRematerializedValues = 0;
|
|
PromotableAllocas.reserve(Live.size());
|
|
|
|
// Emit alloca for "LiveValue" and record it in "allocaMap" and
|
|
// "PromotableAllocas"
|
|
auto emitAllocaFor = [&](Value *LiveValue) {
|
|
AllocaInst *Alloca = new AllocaInst(LiveValue->getType(), "",
|
|
F.getEntryBlock().getFirstNonPHI());
|
|
AllocaMap[LiveValue] = Alloca;
|
|
PromotableAllocas.push_back(Alloca);
|
|
};
|
|
|
|
// Emit alloca for each live gc pointer
|
|
for (Value *V : Live)
|
|
emitAllocaFor(V);
|
|
|
|
// Emit allocas for rematerialized values
|
|
for (const auto &Info : Records)
|
|
for (auto RematerializedValuePair : Info.RematerializedValues) {
|
|
Value *OriginalValue = RematerializedValuePair.second;
|
|
if (AllocaMap.count(OriginalValue) != 0)
|
|
continue;
|
|
|
|
emitAllocaFor(OriginalValue);
|
|
++NumRematerializedValues;
|
|
}
|
|
|
|
// The next two loops are part of the same conceptual operation. We need to
|
|
// insert a store to the alloca after the original def and at each
|
|
// redefinition. We need to insert a load before each use. These are split
|
|
// into distinct loops for performance reasons.
|
|
|
|
// Update gc pointer after each statepoint: either store a relocated value or
|
|
// null (if no relocated value was found for this gc pointer and it is not a
|
|
// gc_result). This must happen before we update the statepoint with load of
|
|
// alloca otherwise we lose the link between statepoint and old def.
|
|
for (const auto &Info : Records) {
|
|
Value *Statepoint = Info.StatepointToken;
|
|
|
|
// This will be used for consistency check
|
|
DenseSet<Value *> VisitedLiveValues;
|
|
|
|
// Insert stores for normal statepoint gc relocates
|
|
insertRelocationStores(Statepoint->users(), AllocaMap, VisitedLiveValues);
|
|
|
|
// In case if it was invoke statepoint
|
|
// we will insert stores for exceptional path gc relocates.
|
|
if (isa<InvokeInst>(Statepoint)) {
|
|
insertRelocationStores(Info.UnwindToken->users(), AllocaMap,
|
|
VisitedLiveValues);
|
|
}
|
|
|
|
// Do similar thing with rematerialized values
|
|
insertRematerializationStores(Info.RematerializedValues, AllocaMap,
|
|
VisitedLiveValues);
|
|
|
|
if (ClobberNonLive) {
|
|
// As a debugging aid, pretend that an unrelocated pointer becomes null at
|
|
// the gc.statepoint. This will turn some subtle GC problems into
|
|
// slightly easier to debug SEGVs. Note that on large IR files with
|
|
// lots of gc.statepoints this is extremely costly both memory and time
|
|
// wise.
|
|
SmallVector<AllocaInst *, 64> ToClobber;
|
|
for (auto Pair : AllocaMap) {
|
|
Value *Def = Pair.first;
|
|
AllocaInst *Alloca = cast<AllocaInst>(Pair.second);
|
|
|
|
// This value was relocated
|
|
if (VisitedLiveValues.count(Def)) {
|
|
continue;
|
|
}
|
|
ToClobber.push_back(Alloca);
|
|
}
|
|
|
|
auto InsertClobbersAt = [&](Instruction *IP) {
|
|
for (auto *AI : ToClobber) {
|
|
auto AIType = cast<PointerType>(AI->getType());
|
|
auto PT = cast<PointerType>(AIType->getElementType());
|
|
Constant *CPN = ConstantPointerNull::get(PT);
|
|
StoreInst *Store = new StoreInst(CPN, AI);
|
|
Store->insertBefore(IP);
|
|
}
|
|
};
|
|
|
|
// Insert the clobbering stores. These may get intermixed with the
|
|
// gc.results and gc.relocates, but that's fine.
|
|
if (auto II = dyn_cast<InvokeInst>(Statepoint)) {
|
|
InsertClobbersAt(&*II->getNormalDest()->getFirstInsertionPt());
|
|
InsertClobbersAt(&*II->getUnwindDest()->getFirstInsertionPt());
|
|
} else {
|
|
InsertClobbersAt(cast<Instruction>(Statepoint)->getNextNode());
|
|
}
|
|
}
|
|
}
|
|
|
|
// Update use with load allocas and add store for gc_relocated.
|
|
for (auto Pair : AllocaMap) {
|
|
Value *Def = Pair.first;
|
|
Value *Alloca = Pair.second;
|
|
|
|
// We pre-record the uses of allocas so that we dont have to worry about
|
|
// later update that changes the user information..
|
|
|
|
SmallVector<Instruction *, 20> Uses;
|
|
// PERF: trade a linear scan for repeated reallocation
|
|
Uses.reserve(std::distance(Def->user_begin(), Def->user_end()));
|
|
for (User *U : Def->users()) {
|
|
if (!isa<ConstantExpr>(U)) {
|
|
// If the def has a ConstantExpr use, then the def is either a
|
|
// ConstantExpr use itself or null. In either case
|
|
// (recursively in the first, directly in the second), the oop
|
|
// it is ultimately dependent on is null and this particular
|
|
// use does not need to be fixed up.
|
|
Uses.push_back(cast<Instruction>(U));
|
|
}
|
|
}
|
|
|
|
std::sort(Uses.begin(), Uses.end());
|
|
auto Last = std::unique(Uses.begin(), Uses.end());
|
|
Uses.erase(Last, Uses.end());
|
|
|
|
for (Instruction *Use : Uses) {
|
|
if (isa<PHINode>(Use)) {
|
|
PHINode *Phi = cast<PHINode>(Use);
|
|
for (unsigned i = 0; i < Phi->getNumIncomingValues(); i++) {
|
|
if (Def == Phi->getIncomingValue(i)) {
|
|
LoadInst *Load = new LoadInst(
|
|
Alloca, "", Phi->getIncomingBlock(i)->getTerminator());
|
|
Phi->setIncomingValue(i, Load);
|
|
}
|
|
}
|
|
} else {
|
|
LoadInst *Load = new LoadInst(Alloca, "", Use);
|
|
Use->replaceUsesOfWith(Def, Load);
|
|
}
|
|
}
|
|
|
|
// Emit store for the initial gc value. Store must be inserted after load,
|
|
// otherwise store will be in alloca's use list and an extra load will be
|
|
// inserted before it.
|
|
StoreInst *Store = new StoreInst(Def, Alloca);
|
|
if (Instruction *Inst = dyn_cast<Instruction>(Def)) {
|
|
if (InvokeInst *Invoke = dyn_cast<InvokeInst>(Inst)) {
|
|
// InvokeInst is a TerminatorInst so the store need to be inserted
|
|
// into its normal destination block.
|
|
BasicBlock *NormalDest = Invoke->getNormalDest();
|
|
Store->insertBefore(NormalDest->getFirstNonPHI());
|
|
} else {
|
|
assert(!Inst->isTerminator() &&
|
|
"The only TerminatorInst that can produce a value is "
|
|
"InvokeInst which is handled above.");
|
|
Store->insertAfter(Inst);
|
|
}
|
|
} else {
|
|
assert(isa<Argument>(Def));
|
|
Store->insertAfter(cast<Instruction>(Alloca));
|
|
}
|
|
}
|
|
|
|
assert(PromotableAllocas.size() == Live.size() + NumRematerializedValues &&
|
|
"we must have the same allocas with lives");
|
|
if (!PromotableAllocas.empty()) {
|
|
// Apply mem2reg to promote alloca to SSA
|
|
PromoteMemToReg(PromotableAllocas, DT);
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
for (auto &I : F.getEntryBlock())
|
|
if (isa<AllocaInst>(I))
|
|
InitialAllocaNum--;
|
|
assert(InitialAllocaNum == 0 && "We must not introduce any extra allocas");
|
|
#endif
|
|
}
|
|
|
|
/// Implement a unique function which doesn't require we sort the input
|
|
/// vector. Doing so has the effect of changing the output of a couple of
|
|
/// tests in ways which make them less useful in testing fused safepoints.
|
|
template <typename T> static void unique_unsorted(SmallVectorImpl<T> &Vec) {
|
|
SmallSet<T, 8> Seen;
|
|
Vec.erase(std::remove_if(Vec.begin(), Vec.end(), [&](const T &V) {
|
|
return !Seen.insert(V).second;
|
|
}), Vec.end());
|
|
}
|
|
|
|
/// Insert holders so that each Value is obviously live through the entire
|
|
/// lifetime of the call.
|
|
static void insertUseHolderAfter(CallSite &CS, const ArrayRef<Value *> Values,
|
|
SmallVectorImpl<CallInst *> &Holders) {
|
|
if (Values.empty())
|
|
// No values to hold live, might as well not insert the empty holder
|
|
return;
|
|
|
|
Module *M = CS.getInstruction()->getParent()->getParent()->getParent();
|
|
// Use a dummy vararg function to actually hold the values live
|
|
Function *Func = cast<Function>(M->getOrInsertFunction(
|
|
"__tmp_use", FunctionType::get(Type::getVoidTy(M->getContext()), true)));
|
|
if (CS.isCall()) {
|
|
// For call safepoints insert dummy calls right after safepoint
|
|
Holders.push_back(CallInst::Create(Func, Values, "",
|
|
&*++CS.getInstruction()->getIterator()));
|
|
return;
|
|
}
|
|
// For invoke safepooints insert dummy calls both in normal and
|
|
// exceptional destination blocks
|
|
auto *II = cast<InvokeInst>(CS.getInstruction());
|
|
Holders.push_back(CallInst::Create(
|
|
Func, Values, "", &*II->getNormalDest()->getFirstInsertionPt()));
|
|
Holders.push_back(CallInst::Create(
|
|
Func, Values, "", &*II->getUnwindDest()->getFirstInsertionPt()));
|
|
}
|
|
|
|
static void findLiveReferences(
|
|
Function &F, DominatorTree &DT, Pass *P, ArrayRef<CallSite> toUpdate,
|
|
MutableArrayRef<struct PartiallyConstructedSafepointRecord> records) {
|
|
GCPtrLivenessData OriginalLivenessData;
|
|
computeLiveInValues(DT, F, OriginalLivenessData);
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
const CallSite &CS = toUpdate[i];
|
|
analyzeParsePointLiveness(DT, OriginalLivenessData, CS, info);
|
|
}
|
|
}
|
|
|
|
/// Remove any vector of pointers from the live set by scalarizing them over the
|
|
/// statepoint instruction. Adds the scalarized pieces to the live set. It
|
|
/// would be preferable to include the vector in the statepoint itself, but
|
|
/// the lowering code currently does not handle that. Extending it would be
|
|
/// slightly non-trivial since it requires a format change. Given how rare
|
|
/// such cases are (for the moment?) scalarizing is an acceptable compromise.
|
|
static void splitVectorValues(Instruction *StatepointInst,
|
|
StatepointLiveSetTy &LiveSet,
|
|
DenseMap<Value *, Value *>& PointerToBase,
|
|
DominatorTree &DT) {
|
|
SmallVector<Value *, 16> ToSplit;
|
|
for (Value *V : LiveSet)
|
|
if (isa<VectorType>(V->getType()))
|
|
ToSplit.push_back(V);
|
|
|
|
if (ToSplit.empty())
|
|
return;
|
|
|
|
DenseMap<Value *, SmallVector<Value *, 16>> ElementMapping;
|
|
|
|
Function &F = *(StatepointInst->getParent()->getParent());
|
|
|
|
DenseMap<Value *, AllocaInst *> AllocaMap;
|
|
// First is normal return, second is exceptional return (invoke only)
|
|
DenseMap<Value *, std::pair<Value *, Value *>> Replacements;
|
|
for (Value *V : ToSplit) {
|
|
AllocaInst *Alloca =
|
|
new AllocaInst(V->getType(), "", F.getEntryBlock().getFirstNonPHI());
|
|
AllocaMap[V] = Alloca;
|
|
|
|
VectorType *VT = cast<VectorType>(V->getType());
|
|
IRBuilder<> Builder(StatepointInst);
|
|
SmallVector<Value *, 16> Elements;
|
|
for (unsigned i = 0; i < VT->getNumElements(); i++)
|
|
Elements.push_back(Builder.CreateExtractElement(V, Builder.getInt32(i)));
|
|
ElementMapping[V] = Elements;
|
|
|
|
auto InsertVectorReform = [&](Instruction *IP) {
|
|
Builder.SetInsertPoint(IP);
|
|
Builder.SetCurrentDebugLocation(IP->getDebugLoc());
|
|
Value *ResultVec = UndefValue::get(VT);
|
|
for (unsigned i = 0; i < VT->getNumElements(); i++)
|
|
ResultVec = Builder.CreateInsertElement(ResultVec, Elements[i],
|
|
Builder.getInt32(i));
|
|
return ResultVec;
|
|
};
|
|
|
|
if (isa<CallInst>(StatepointInst)) {
|
|
BasicBlock::iterator Next(StatepointInst);
|
|
Next++;
|
|
Instruction *IP = &*(Next);
|
|
Replacements[V].first = InsertVectorReform(IP);
|
|
Replacements[V].second = nullptr;
|
|
} else {
|
|
InvokeInst *Invoke = cast<InvokeInst>(StatepointInst);
|
|
// We've already normalized - check that we don't have shared destination
|
|
// blocks
|
|
BasicBlock *NormalDest = Invoke->getNormalDest();
|
|
assert(!isa<PHINode>(NormalDest->begin()));
|
|
BasicBlock *UnwindDest = Invoke->getUnwindDest();
|
|
assert(!isa<PHINode>(UnwindDest->begin()));
|
|
// Insert insert element sequences in both successors
|
|
Instruction *IP = &*(NormalDest->getFirstInsertionPt());
|
|
Replacements[V].first = InsertVectorReform(IP);
|
|
IP = &*(UnwindDest->getFirstInsertionPt());
|
|
Replacements[V].second = InsertVectorReform(IP);
|
|
}
|
|
}
|
|
|
|
for (Value *V : ToSplit) {
|
|
AllocaInst *Alloca = AllocaMap[V];
|
|
|
|
// Capture all users before we start mutating use lists
|
|
SmallVector<Instruction *, 16> Users;
|
|
for (User *U : V->users())
|
|
Users.push_back(cast<Instruction>(U));
|
|
|
|
for (Instruction *I : Users) {
|
|
if (auto Phi = dyn_cast<PHINode>(I)) {
|
|
for (unsigned i = 0; i < Phi->getNumIncomingValues(); i++)
|
|
if (V == Phi->getIncomingValue(i)) {
|
|
LoadInst *Load = new LoadInst(
|
|
Alloca, "", Phi->getIncomingBlock(i)->getTerminator());
|
|
Phi->setIncomingValue(i, Load);
|
|
}
|
|
} else {
|
|
LoadInst *Load = new LoadInst(Alloca, "", I);
|
|
I->replaceUsesOfWith(V, Load);
|
|
}
|
|
}
|
|
|
|
// Store the original value and the replacement value into the alloca
|
|
StoreInst *Store = new StoreInst(V, Alloca);
|
|
if (auto I = dyn_cast<Instruction>(V))
|
|
Store->insertAfter(I);
|
|
else
|
|
Store->insertAfter(Alloca);
|
|
|
|
// Normal return for invoke, or call return
|
|
Instruction *Replacement = cast<Instruction>(Replacements[V].first);
|
|
(new StoreInst(Replacement, Alloca))->insertAfter(Replacement);
|
|
// Unwind return for invoke only
|
|
Replacement = cast_or_null<Instruction>(Replacements[V].second);
|
|
if (Replacement)
|
|
(new StoreInst(Replacement, Alloca))->insertAfter(Replacement);
|
|
}
|
|
|
|
// apply mem2reg to promote alloca to SSA
|
|
SmallVector<AllocaInst *, 16> Allocas;
|
|
for (Value *V : ToSplit)
|
|
Allocas.push_back(AllocaMap[V]);
|
|
PromoteMemToReg(Allocas, DT);
|
|
|
|
// Update our tracking of live pointers and base mappings to account for the
|
|
// changes we just made.
|
|
for (Value *V : ToSplit) {
|
|
auto &Elements = ElementMapping[V];
|
|
|
|
LiveSet.erase(V);
|
|
LiveSet.insert(Elements.begin(), Elements.end());
|
|
// We need to update the base mapping as well.
|
|
assert(PointerToBase.count(V));
|
|
Value *OldBase = PointerToBase[V];
|
|
auto &BaseElements = ElementMapping[OldBase];
|
|
PointerToBase.erase(V);
|
|
assert(Elements.size() == BaseElements.size());
|
|
for (unsigned i = 0; i < Elements.size(); i++) {
|
|
Value *Elem = Elements[i];
|
|
PointerToBase[Elem] = BaseElements[i];
|
|
}
|
|
}
|
|
}
|
|
|
|
// Helper function for the "rematerializeLiveValues". It walks use chain
|
|
// starting from the "CurrentValue" until it meets "BaseValue". Only "simple"
|
|
// values are visited (currently it is GEP's and casts). Returns true if it
|
|
// successfully reached "BaseValue" and false otherwise.
|
|
// Fills "ChainToBase" array with all visited values. "BaseValue" is not
|
|
// recorded.
|
|
static bool findRematerializableChainToBasePointer(
|
|
SmallVectorImpl<Instruction*> &ChainToBase,
|
|
Value *CurrentValue, Value *BaseValue) {
|
|
|
|
// We have found a base value
|
|
if (CurrentValue == BaseValue) {
|
|
return true;
|
|
}
|
|
|
|
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurrentValue)) {
|
|
ChainToBase.push_back(GEP);
|
|
return findRematerializableChainToBasePointer(ChainToBase,
|
|
GEP->getPointerOperand(),
|
|
BaseValue);
|
|
}
|
|
|
|
if (CastInst *CI = dyn_cast<CastInst>(CurrentValue)) {
|
|
Value *Def = CI->stripPointerCasts();
|
|
|
|
// This two checks are basically similar. First one is here for the
|
|
// consistency with findBasePointers logic.
|
|
assert(!isa<CastInst>(Def) && "not a pointer cast found");
|
|
if (!CI->isNoopCast(CI->getModule()->getDataLayout()))
|
|
return false;
|
|
|
|
ChainToBase.push_back(CI);
|
|
return findRematerializableChainToBasePointer(ChainToBase, Def, BaseValue);
|
|
}
|
|
|
|
// Not supported instruction in the chain
|
|
return false;
|
|
}
|
|
|
|
// Helper function for the "rematerializeLiveValues". Compute cost of the use
|
|
// chain we are going to rematerialize.
|
|
static unsigned
|
|
chainToBasePointerCost(SmallVectorImpl<Instruction*> &Chain,
|
|
TargetTransformInfo &TTI) {
|
|
unsigned Cost = 0;
|
|
|
|
for (Instruction *Instr : Chain) {
|
|
if (CastInst *CI = dyn_cast<CastInst>(Instr)) {
|
|
assert(CI->isNoopCast(CI->getModule()->getDataLayout()) &&
|
|
"non noop cast is found during rematerialization");
|
|
|
|
Type *SrcTy = CI->getOperand(0)->getType();
|
|
Cost += TTI.getCastInstrCost(CI->getOpcode(), CI->getType(), SrcTy);
|
|
|
|
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Instr)) {
|
|
// Cost of the address calculation
|
|
Type *ValTy = GEP->getPointerOperandType()->getPointerElementType();
|
|
Cost += TTI.getAddressComputationCost(ValTy);
|
|
|
|
// And cost of the GEP itself
|
|
// TODO: Use TTI->getGEPCost here (it exists, but appears to be not
|
|
// allowed for the external usage)
|
|
if (!GEP->hasAllConstantIndices())
|
|
Cost += 2;
|
|
|
|
} else {
|
|
llvm_unreachable("unsupported instruciton type during rematerialization");
|
|
}
|
|
}
|
|
|
|
return Cost;
|
|
}
|
|
|
|
// From the statepoint live set pick values that are cheaper to recompute then
|
|
// to relocate. Remove this values from the live set, rematerialize them after
|
|
// statepoint and record them in "Info" structure. Note that similar to
|
|
// relocated values we don't do any user adjustments here.
|
|
static void rematerializeLiveValues(CallSite CS,
|
|
PartiallyConstructedSafepointRecord &Info,
|
|
TargetTransformInfo &TTI) {
|
|
const unsigned int ChainLengthThreshold = 10;
|
|
|
|
// Record values we are going to delete from this statepoint live set.
|
|
// We can not di this in following loop due to iterator invalidation.
|
|
SmallVector<Value *, 32> LiveValuesToBeDeleted;
|
|
|
|
for (Value *LiveValue: Info.LiveSet) {
|
|
// For each live pointer find it's defining chain
|
|
SmallVector<Instruction *, 3> ChainToBase;
|
|
assert(Info.PointerToBase.count(LiveValue));
|
|
bool FoundChain =
|
|
findRematerializableChainToBasePointer(ChainToBase,
|
|
LiveValue,
|
|
Info.PointerToBase[LiveValue]);
|
|
// Nothing to do, or chain is too long
|
|
if (!FoundChain ||
|
|
ChainToBase.size() == 0 ||
|
|
ChainToBase.size() > ChainLengthThreshold)
|
|
continue;
|
|
|
|
// Compute cost of this chain
|
|
unsigned Cost = chainToBasePointerCost(ChainToBase, TTI);
|
|
// TODO: We can also account for cases when we will be able to remove some
|
|
// of the rematerialized values by later optimization passes. I.e if
|
|
// we rematerialized several intersecting chains. Or if original values
|
|
// don't have any uses besides this statepoint.
|
|
|
|
// For invokes we need to rematerialize each chain twice - for normal and
|
|
// for unwind basic blocks. Model this by multiplying cost by two.
|
|
if (CS.isInvoke()) {
|
|
Cost *= 2;
|
|
}
|
|
// If it's too expensive - skip it
|
|
if (Cost >= RematerializationThreshold)
|
|
continue;
|
|
|
|
// Remove value from the live set
|
|
LiveValuesToBeDeleted.push_back(LiveValue);
|
|
|
|
// Clone instructions and record them inside "Info" structure
|
|
|
|
// Walk backwards to visit top-most instructions first
|
|
std::reverse(ChainToBase.begin(), ChainToBase.end());
|
|
|
|
// Utility function which clones all instructions from "ChainToBase"
|
|
// and inserts them before "InsertBefore". Returns rematerialized value
|
|
// which should be used after statepoint.
|
|
auto rematerializeChain = [&ChainToBase](Instruction *InsertBefore) {
|
|
Instruction *LastClonedValue = nullptr;
|
|
Instruction *LastValue = nullptr;
|
|
for (Instruction *Instr: ChainToBase) {
|
|
// Only GEP's and casts are suported as we need to be careful to not
|
|
// introduce any new uses of pointers not in the liveset.
|
|
// Note that it's fine to introduce new uses of pointers which were
|
|
// otherwise not used after this statepoint.
|
|
assert(isa<GetElementPtrInst>(Instr) || isa<CastInst>(Instr));
|
|
|
|
Instruction *ClonedValue = Instr->clone();
|
|
ClonedValue->insertBefore(InsertBefore);
|
|
ClonedValue->setName(Instr->getName() + ".remat");
|
|
|
|
// If it is not first instruction in the chain then it uses previously
|
|
// cloned value. We should update it to use cloned value.
|
|
if (LastClonedValue) {
|
|
assert(LastValue);
|
|
ClonedValue->replaceUsesOfWith(LastValue, LastClonedValue);
|
|
#ifndef NDEBUG
|
|
// Assert that cloned instruction does not use any instructions from
|
|
// this chain other than LastClonedValue
|
|
for (auto OpValue : ClonedValue->operand_values()) {
|
|
assert(std::find(ChainToBase.begin(), ChainToBase.end(), OpValue) ==
|
|
ChainToBase.end() &&
|
|
"incorrect use in rematerialization chain");
|
|
}
|
|
#endif
|
|
}
|
|
|
|
LastClonedValue = ClonedValue;
|
|
LastValue = Instr;
|
|
}
|
|
assert(LastClonedValue);
|
|
return LastClonedValue;
|
|
};
|
|
|
|
// Different cases for calls and invokes. For invokes we need to clone
|
|
// instructions both on normal and unwind path.
|
|
if (CS.isCall()) {
|
|
Instruction *InsertBefore = CS.getInstruction()->getNextNode();
|
|
assert(InsertBefore);
|
|
Instruction *RematerializedValue = rematerializeChain(InsertBefore);
|
|
Info.RematerializedValues[RematerializedValue] = LiveValue;
|
|
} else {
|
|
InvokeInst *Invoke = cast<InvokeInst>(CS.getInstruction());
|
|
|
|
Instruction *NormalInsertBefore =
|
|
&*Invoke->getNormalDest()->getFirstInsertionPt();
|
|
Instruction *UnwindInsertBefore =
|
|
&*Invoke->getUnwindDest()->getFirstInsertionPt();
|
|
|
|
Instruction *NormalRematerializedValue =
|
|
rematerializeChain(NormalInsertBefore);
|
|
Instruction *UnwindRematerializedValue =
|
|
rematerializeChain(UnwindInsertBefore);
|
|
|
|
Info.RematerializedValues[NormalRematerializedValue] = LiveValue;
|
|
Info.RematerializedValues[UnwindRematerializedValue] = LiveValue;
|
|
}
|
|
}
|
|
|
|
// Remove rematerializaed values from the live set
|
|
for (auto LiveValue: LiveValuesToBeDeleted) {
|
|
Info.LiveSet.erase(LiveValue);
|
|
}
|
|
}
|
|
|
|
static bool insertParsePoints(Function &F, DominatorTree &DT, Pass *P,
|
|
SmallVectorImpl<CallSite> &ToUpdate) {
|
|
#ifndef NDEBUG
|
|
// sanity check the input
|
|
std::set<CallSite> Uniqued;
|
|
Uniqued.insert(ToUpdate.begin(), ToUpdate.end());
|
|
assert(Uniqued.size() == ToUpdate.size() && "no duplicates please!");
|
|
|
|
for (CallSite CS : ToUpdate) {
|
|
assert(CS.getInstruction()->getParent()->getParent() == &F);
|
|
assert((UseDeoptBundles || isStatepoint(CS)) &&
|
|
"expected to already be a deopt statepoint");
|
|
}
|
|
#endif
|
|
|
|
// When inserting gc.relocates for invokes, we need to be able to insert at
|
|
// the top of the successor blocks. See the comment on
|
|
// normalForInvokeSafepoint on exactly what is needed. Note that this step
|
|
// may restructure the CFG.
|
|
for (CallSite CS : ToUpdate) {
|
|
if (!CS.isInvoke())
|
|
continue;
|
|
auto *II = cast<InvokeInst>(CS.getInstruction());
|
|
normalizeForInvokeSafepoint(II->getNormalDest(), II->getParent(), DT);
|
|
normalizeForInvokeSafepoint(II->getUnwindDest(), II->getParent(), DT);
|
|
}
|
|
|
|
// A list of dummy calls added to the IR to keep various values obviously
|
|
// live in the IR. We'll remove all of these when done.
|
|
SmallVector<CallInst *, 64> Holders;
|
|
|
|
// Insert a dummy call with all of the arguments to the vm_state we'll need
|
|
// for the actual safepoint insertion. This ensures reference arguments in
|
|
// the deopt argument list are considered live through the safepoint (and
|
|
// thus makes sure they get relocated.)
|
|
for (CallSite CS : ToUpdate) {
|
|
SmallVector<Value *, 64> DeoptValues;
|
|
|
|
iterator_range<const Use *> DeoptStateRange =
|
|
UseDeoptBundles
|
|
? iterator_range<const Use *>(GetDeoptBundleOperands(CS))
|
|
: iterator_range<const Use *>(Statepoint(CS).vm_state_args());
|
|
|
|
for (Value *Arg : DeoptStateRange) {
|
|
assert(!isUnhandledGCPointerType(Arg->getType()) &&
|
|
"support for FCA unimplemented");
|
|
if (isHandledGCPointerType(Arg->getType()))
|
|
DeoptValues.push_back(Arg);
|
|
}
|
|
|
|
insertUseHolderAfter(CS, DeoptValues, Holders);
|
|
}
|
|
|
|
SmallVector<PartiallyConstructedSafepointRecord, 64> Records(ToUpdate.size());
|
|
|
|
// A) Identify all gc pointers which are statically live at the given call
|
|
// site.
|
|
findLiveReferences(F, DT, P, ToUpdate, Records);
|
|
|
|
// B) Find the base pointers for each live pointer
|
|
/* scope for caching */ {
|
|
// Cache the 'defining value' relation used in the computation and
|
|
// insertion of base phis and selects. This ensures that we don't insert
|
|
// large numbers of duplicate base_phis.
|
|
DefiningValueMapTy DVCache;
|
|
|
|
for (size_t i = 0; i < Records.size(); i++) {
|
|
PartiallyConstructedSafepointRecord &info = Records[i];
|
|
findBasePointers(DT, DVCache, ToUpdate[i], info);
|
|
}
|
|
} // end of cache scope
|
|
|
|
// The base phi insertion logic (for any safepoint) may have inserted new
|
|
// instructions which are now live at some safepoint. The simplest such
|
|
// example is:
|
|
// loop:
|
|
// phi a <-- will be a new base_phi here
|
|
// safepoint 1 <-- that needs to be live here
|
|
// gep a + 1
|
|
// safepoint 2
|
|
// br loop
|
|
// We insert some dummy calls after each safepoint to definitely hold live
|
|
// the base pointers which were identified for that safepoint. We'll then
|
|
// ask liveness for _every_ base inserted to see what is now live. Then we
|
|
// remove the dummy calls.
|
|
Holders.reserve(Holders.size() + Records.size());
|
|
for (size_t i = 0; i < Records.size(); i++) {
|
|
PartiallyConstructedSafepointRecord &Info = Records[i];
|
|
|
|
SmallVector<Value *, 128> Bases;
|
|
for (auto Pair : Info.PointerToBase)
|
|
Bases.push_back(Pair.second);
|
|
|
|
insertUseHolderAfter(ToUpdate[i], Bases, Holders);
|
|
}
|
|
|
|
// By selecting base pointers, we've effectively inserted new uses. Thus, we
|
|
// need to rerun liveness. We may *also* have inserted new defs, but that's
|
|
// not the key issue.
|
|
recomputeLiveInValues(F, DT, P, ToUpdate, Records);
|
|
|
|
if (PrintBasePointers) {
|
|
for (auto &Info : Records) {
|
|
errs() << "Base Pairs: (w/Relocation)\n";
|
|
for (auto Pair : Info.PointerToBase)
|
|
errs() << " derived %" << Pair.first->getName() << " base %"
|
|
<< Pair.second->getName() << "\n";
|
|
}
|
|
}
|
|
|
|
for (CallInst *CI : Holders)
|
|
CI->eraseFromParent();
|
|
|
|
Holders.clear();
|
|
|
|
// Do a limited scalarization of any live at safepoint vector values which
|
|
// contain pointers. This enables this pass to run after vectorization at
|
|
// the cost of some possible performance loss. TODO: it would be nice to
|
|
// natively support vectors all the way through the backend so we don't need
|
|
// to scalarize here.
|
|
for (size_t i = 0; i < Records.size(); i++) {
|
|
PartiallyConstructedSafepointRecord &Info = Records[i];
|
|
Instruction *Statepoint = ToUpdate[i].getInstruction();
|
|
splitVectorValues(cast<Instruction>(Statepoint), Info.LiveSet,
|
|
Info.PointerToBase, DT);
|
|
}
|
|
|
|
// In order to reduce live set of statepoint we might choose to rematerialize
|
|
// some values instead of relocating them. This is purely an optimization and
|
|
// does not influence correctness.
|
|
TargetTransformInfo &TTI =
|
|
P->getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
|
|
|
|
for (size_t i = 0; i < Records.size(); i++)
|
|
rematerializeLiveValues(ToUpdate[i], Records[i], TTI);
|
|
|
|
// We need this to safely RAUW and delete call or invoke return values that
|
|
// may themselves be live over a statepoint. For details, please see usage in
|
|
// makeStatepointExplicitImpl.
|
|
std::vector<DeferredReplacement> Replacements;
|
|
|
|
// Now run through and replace the existing statepoints with new ones with
|
|
// the live variables listed. We do not yet update uses of the values being
|
|
// relocated. We have references to live variables that need to
|
|
// survive to the last iteration of this loop. (By construction, the
|
|
// previous statepoint can not be a live variable, thus we can and remove
|
|
// the old statepoint calls as we go.)
|
|
for (size_t i = 0; i < Records.size(); i++)
|
|
makeStatepointExplicit(DT, ToUpdate[i], Records[i], Replacements);
|
|
|
|
ToUpdate.clear(); // prevent accident use of invalid CallSites
|
|
|
|
for (auto &PR : Replacements)
|
|
PR.doReplacement();
|
|
|
|
Replacements.clear();
|
|
|
|
for (auto &Info : Records) {
|
|
// These live sets may contain state Value pointers, since we replaced calls
|
|
// with operand bundles with calls wrapped in gc.statepoint, and some of
|
|
// those calls may have been def'ing live gc pointers. Clear these out to
|
|
// avoid accidentally using them.
|
|
//
|
|
// TODO: We should create a separate data structure that does not contain
|
|
// these live sets, and migrate to using that data structure from this point
|
|
// onward.
|
|
Info.LiveSet.clear();
|
|
Info.PointerToBase.clear();
|
|
}
|
|
|
|
// Do all the fixups of the original live variables to their relocated selves
|
|
SmallVector<Value *, 128> Live;
|
|
for (size_t i = 0; i < Records.size(); i++) {
|
|
PartiallyConstructedSafepointRecord &Info = Records[i];
|
|
|
|
// We can't simply save the live set from the original insertion. One of
|
|
// the live values might be the result of a call which needs a safepoint.
|
|
// That Value* no longer exists and we need to use the new gc_result.
|
|
// Thankfully, the live set is embedded in the statepoint (and updated), so
|
|
// we just grab that.
|
|
Statepoint Statepoint(Info.StatepointToken);
|
|
Live.insert(Live.end(), Statepoint.gc_args_begin(),
|
|
Statepoint.gc_args_end());
|
|
#ifndef NDEBUG
|
|
// Do some basic sanity checks on our liveness results before performing
|
|
// relocation. Relocation can and will turn mistakes in liveness results
|
|
// into non-sensical code which is must harder to debug.
|
|
// TODO: It would be nice to test consistency as well
|
|
assert(DT.isReachableFromEntry(Info.StatepointToken->getParent()) &&
|
|
"statepoint must be reachable or liveness is meaningless");
|
|
for (Value *V : Statepoint.gc_args()) {
|
|
if (!isa<Instruction>(V))
|
|
// Non-instruction values trivial dominate all possible uses
|
|
continue;
|
|
auto *LiveInst = cast<Instruction>(V);
|
|
assert(DT.isReachableFromEntry(LiveInst->getParent()) &&
|
|
"unreachable values should never be live");
|
|
assert(DT.dominates(LiveInst, Info.StatepointToken) &&
|
|
"basic SSA liveness expectation violated by liveness analysis");
|
|
}
|
|
#endif
|
|
}
|
|
unique_unsorted(Live);
|
|
|
|
#ifndef NDEBUG
|
|
// sanity check
|
|
for (auto *Ptr : Live)
|
|
assert(isGCPointerType(Ptr->getType()) && "must be a gc pointer type");
|
|
#endif
|
|
|
|
relocationViaAlloca(F, DT, Live, Records);
|
|
return !Records.empty();
|
|
}
|
|
|
|
// Handles both return values and arguments for Functions and CallSites.
|
|
template <typename AttrHolder>
|
|
static void RemoveNonValidAttrAtIndex(LLVMContext &Ctx, AttrHolder &AH,
|
|
unsigned Index) {
|
|
AttrBuilder R;
|
|
if (AH.getDereferenceableBytes(Index))
|
|
R.addAttribute(Attribute::get(Ctx, Attribute::Dereferenceable,
|
|
AH.getDereferenceableBytes(Index)));
|
|
if (AH.getDereferenceableOrNullBytes(Index))
|
|
R.addAttribute(Attribute::get(Ctx, Attribute::DereferenceableOrNull,
|
|
AH.getDereferenceableOrNullBytes(Index)));
|
|
if (AH.doesNotAlias(Index))
|
|
R.addAttribute(Attribute::NoAlias);
|
|
|
|
if (!R.empty())
|
|
AH.setAttributes(AH.getAttributes().removeAttributes(
|
|
Ctx, Index, AttributeSet::get(Ctx, Index, R)));
|
|
}
|
|
|
|
void
|
|
RewriteStatepointsForGC::stripNonValidAttributesFromPrototype(Function &F) {
|
|
LLVMContext &Ctx = F.getContext();
|
|
|
|
for (Argument &A : F.args())
|
|
if (isa<PointerType>(A.getType()))
|
|
RemoveNonValidAttrAtIndex(Ctx, F, A.getArgNo() + 1);
|
|
|
|
if (isa<PointerType>(F.getReturnType()))
|
|
RemoveNonValidAttrAtIndex(Ctx, F, AttributeSet::ReturnIndex);
|
|
}
|
|
|
|
void RewriteStatepointsForGC::stripNonValidAttributesFromBody(Function &F) {
|
|
if (F.empty())
|
|
return;
|
|
|
|
LLVMContext &Ctx = F.getContext();
|
|
MDBuilder Builder(Ctx);
|
|
|
|
for (Instruction &I : instructions(F)) {
|
|
if (const MDNode *MD = I.getMetadata(LLVMContext::MD_tbaa)) {
|
|
assert(MD->getNumOperands() < 5 && "unrecognized metadata shape!");
|
|
bool IsImmutableTBAA =
|
|
MD->getNumOperands() == 4 &&
|
|
mdconst::extract<ConstantInt>(MD->getOperand(3))->getValue() == 1;
|
|
|
|
if (!IsImmutableTBAA)
|
|
continue; // no work to do, MD_tbaa is already marked mutable
|
|
|
|
MDNode *Base = cast<MDNode>(MD->getOperand(0));
|
|
MDNode *Access = cast<MDNode>(MD->getOperand(1));
|
|
uint64_t Offset =
|
|
mdconst::extract<ConstantInt>(MD->getOperand(2))->getZExtValue();
|
|
|
|
MDNode *MutableTBAA =
|
|
Builder.createTBAAStructTagNode(Base, Access, Offset);
|
|
I.setMetadata(LLVMContext::MD_tbaa, MutableTBAA);
|
|
}
|
|
|
|
if (CallSite CS = CallSite(&I)) {
|
|
for (int i = 0, e = CS.arg_size(); i != e; i++)
|
|
if (isa<PointerType>(CS.getArgument(i)->getType()))
|
|
RemoveNonValidAttrAtIndex(Ctx, CS, i + 1);
|
|
if (isa<PointerType>(CS.getType()))
|
|
RemoveNonValidAttrAtIndex(Ctx, CS, AttributeSet::ReturnIndex);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Returns true if this function should be rewritten by this pass. The main
|
|
/// point of this function is as an extension point for custom logic.
|
|
static bool shouldRewriteStatepointsIn(Function &F) {
|
|
// TODO: This should check the GCStrategy
|
|
if (F.hasGC()) {
|
|
const char *FunctionGCName = F.getGC();
|
|
const StringRef StatepointExampleName("statepoint-example");
|
|
const StringRef CoreCLRName("coreclr");
|
|
return (StatepointExampleName == FunctionGCName) ||
|
|
(CoreCLRName == FunctionGCName);
|
|
} else
|
|
return false;
|
|
}
|
|
|
|
void RewriteStatepointsForGC::stripNonValidAttributes(Module &M) {
|
|
#ifndef NDEBUG
|
|
assert(std::any_of(M.begin(), M.end(), shouldRewriteStatepointsIn) &&
|
|
"precondition!");
|
|
#endif
|
|
|
|
for (Function &F : M)
|
|
stripNonValidAttributesFromPrototype(F);
|
|
|
|
for (Function &F : M)
|
|
stripNonValidAttributesFromBody(F);
|
|
}
|
|
|
|
bool RewriteStatepointsForGC::runOnFunction(Function &F) {
|
|
// Nothing to do for declarations.
|
|
if (F.isDeclaration() || F.empty())
|
|
return false;
|
|
|
|
// Policy choice says not to rewrite - the most common reason is that we're
|
|
// compiling code without a GCStrategy.
|
|
if (!shouldRewriteStatepointsIn(F))
|
|
return false;
|
|
|
|
DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
|
|
|
|
auto NeedsRewrite = [](Instruction &I) {
|
|
if (UseDeoptBundles) {
|
|
if (ImmutableCallSite CS = ImmutableCallSite(&I))
|
|
return !callsGCLeafFunction(CS);
|
|
return false;
|
|
}
|
|
|
|
return isStatepoint(I);
|
|
};
|
|
|
|
// Gather all the statepoints which need rewritten. Be careful to only
|
|
// consider those in reachable code since we need to ask dominance queries
|
|
// when rewriting. We'll delete the unreachable ones in a moment.
|
|
SmallVector<CallSite, 64> ParsePointNeeded;
|
|
bool HasUnreachableStatepoint = false;
|
|
for (Instruction &I : instructions(F)) {
|
|
// TODO: only the ones with the flag set!
|
|
if (NeedsRewrite(I)) {
|
|
if (DT.isReachableFromEntry(I.getParent()))
|
|
ParsePointNeeded.push_back(CallSite(&I));
|
|
else
|
|
HasUnreachableStatepoint = true;
|
|
}
|
|
}
|
|
|
|
bool MadeChange = false;
|
|
|
|
// Delete any unreachable statepoints so that we don't have unrewritten
|
|
// statepoints surviving this pass. This makes testing easier and the
|
|
// resulting IR less confusing to human readers. Rather than be fancy, we
|
|
// just reuse a utility function which removes the unreachable blocks.
|
|
if (HasUnreachableStatepoint)
|
|
MadeChange |= removeUnreachableBlocks(F);
|
|
|
|
// Return early if no work to do.
|
|
if (ParsePointNeeded.empty())
|
|
return MadeChange;
|
|
|
|
// As a prepass, go ahead and aggressively destroy single entry phi nodes.
|
|
// These are created by LCSSA. They have the effect of increasing the size
|
|
// of liveness sets for no good reason. It may be harder to do this post
|
|
// insertion since relocations and base phis can confuse things.
|
|
for (BasicBlock &BB : F)
|
|
if (BB.getUniquePredecessor()) {
|
|
MadeChange = true;
|
|
FoldSingleEntryPHINodes(&BB);
|
|
}
|
|
|
|
// Before we start introducing relocations, we want to tweak the IR a bit to
|
|
// avoid unfortunate code generation effects. The main example is that we
|
|
// want to try to make sure the comparison feeding a branch is after any
|
|
// safepoints. Otherwise, we end up with a comparison of pre-relocation
|
|
// values feeding a branch after relocation. This is semantically correct,
|
|
// but results in extra register pressure since both the pre-relocation and
|
|
// post-relocation copies must be available in registers. For code without
|
|
// relocations this is handled elsewhere, but teaching the scheduler to
|
|
// reverse the transform we're about to do would be slightly complex.
|
|
// Note: This may extend the live range of the inputs to the icmp and thus
|
|
// increase the liveset of any statepoint we move over. This is profitable
|
|
// as long as all statepoints are in rare blocks. If we had in-register
|
|
// lowering for live values this would be a much safer transform.
|
|
auto getConditionInst = [](TerminatorInst *TI) -> Instruction* {
|
|
if (auto *BI = dyn_cast<BranchInst>(TI))
|
|
if (BI->isConditional())
|
|
return dyn_cast<Instruction>(BI->getCondition());
|
|
// TODO: Extend this to handle switches
|
|
return nullptr;
|
|
};
|
|
for (BasicBlock &BB : F) {
|
|
TerminatorInst *TI = BB.getTerminator();
|
|
if (auto *Cond = getConditionInst(TI))
|
|
// TODO: Handle more than just ICmps here. We should be able to move
|
|
// most instructions without side effects or memory access.
|
|
if (isa<ICmpInst>(Cond) && Cond->hasOneUse()) {
|
|
MadeChange = true;
|
|
Cond->moveBefore(TI);
|
|
}
|
|
}
|
|
|
|
MadeChange |= insertParsePoints(F, DT, this, ParsePointNeeded);
|
|
return MadeChange;
|
|
}
|
|
|
|
// liveness computation via standard dataflow
|
|
// -------------------------------------------------------------------
|
|
|
|
// TODO: Consider using bitvectors for liveness, the set of potentially
|
|
// interesting values should be small and easy to pre-compute.
|
|
|
|
/// Compute the live-in set for the location rbegin starting from
|
|
/// the live-out set of the basic block
|
|
static void computeLiveInValues(BasicBlock::reverse_iterator rbegin,
|
|
BasicBlock::reverse_iterator rend,
|
|
DenseSet<Value *> &LiveTmp) {
|
|
|
|
for (BasicBlock::reverse_iterator ritr = rbegin; ritr != rend; ritr++) {
|
|
Instruction *I = &*ritr;
|
|
|
|
// KILL/Def - Remove this definition from LiveIn
|
|
LiveTmp.erase(I);
|
|
|
|
// Don't consider *uses* in PHI nodes, we handle their contribution to
|
|
// predecessor blocks when we seed the LiveOut sets
|
|
if (isa<PHINode>(I))
|
|
continue;
|
|
|
|
// USE - Add to the LiveIn set for this instruction
|
|
for (Value *V : I->operands()) {
|
|
assert(!isUnhandledGCPointerType(V->getType()) &&
|
|
"support for FCA unimplemented");
|
|
if (isHandledGCPointerType(V->getType()) && !isa<Constant>(V)) {
|
|
// The choice to exclude all things constant here is slightly subtle.
|
|
// There are two independent reasons:
|
|
// - We assume that things which are constant (from LLVM's definition)
|
|
// do not move at runtime. For example, the address of a global
|
|
// variable is fixed, even though it's contents may not be.
|
|
// - Second, we can't disallow arbitrary inttoptr constants even
|
|
// if the language frontend does. Optimization passes are free to
|
|
// locally exploit facts without respect to global reachability. This
|
|
// can create sections of code which are dynamically unreachable and
|
|
// contain just about anything. (see constants.ll in tests)
|
|
LiveTmp.insert(V);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
static void computeLiveOutSeed(BasicBlock *BB, DenseSet<Value *> &LiveTmp) {
|
|
|
|
for (BasicBlock *Succ : successors(BB)) {
|
|
const BasicBlock::iterator E(Succ->getFirstNonPHI());
|
|
for (BasicBlock::iterator I = Succ->begin(); I != E; I++) {
|
|
PHINode *Phi = cast<PHINode>(&*I);
|
|
Value *V = Phi->getIncomingValueForBlock(BB);
|
|
assert(!isUnhandledGCPointerType(V->getType()) &&
|
|
"support for FCA unimplemented");
|
|
if (isHandledGCPointerType(V->getType()) && !isa<Constant>(V)) {
|
|
LiveTmp.insert(V);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
static DenseSet<Value *> computeKillSet(BasicBlock *BB) {
|
|
DenseSet<Value *> KillSet;
|
|
for (Instruction &I : *BB)
|
|
if (isHandledGCPointerType(I.getType()))
|
|
KillSet.insert(&I);
|
|
return KillSet;
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
/// Check that the items in 'Live' dominate 'TI'. This is used as a basic
|
|
/// sanity check for the liveness computation.
|
|
static void checkBasicSSA(DominatorTree &DT, DenseSet<Value *> &Live,
|
|
TerminatorInst *TI, bool TermOkay = false) {
|
|
for (Value *V : Live) {
|
|
if (auto *I = dyn_cast<Instruction>(V)) {
|
|
// The terminator can be a member of the LiveOut set. LLVM's definition
|
|
// of instruction dominance states that V does not dominate itself. As
|
|
// such, we need to special case this to allow it.
|
|
if (TermOkay && TI == I)
|
|
continue;
|
|
assert(DT.dominates(I, TI) &&
|
|
"basic SSA liveness expectation violated by liveness analysis");
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Check that all the liveness sets used during the computation of liveness
|
|
/// obey basic SSA properties. This is useful for finding cases where we miss
|
|
/// a def.
|
|
static void checkBasicSSA(DominatorTree &DT, GCPtrLivenessData &Data,
|
|
BasicBlock &BB) {
|
|
checkBasicSSA(DT, Data.LiveSet[&BB], BB.getTerminator());
|
|
checkBasicSSA(DT, Data.LiveOut[&BB], BB.getTerminator(), true);
|
|
checkBasicSSA(DT, Data.LiveIn[&BB], BB.getTerminator());
|
|
}
|
|
#endif
|
|
|
|
static void computeLiveInValues(DominatorTree &DT, Function &F,
|
|
GCPtrLivenessData &Data) {
|
|
|
|
SmallSetVector<BasicBlock *, 200> Worklist;
|
|
auto AddPredsToWorklist = [&](BasicBlock *BB) {
|
|
// We use a SetVector so that we don't have duplicates in the worklist.
|
|
Worklist.insert(pred_begin(BB), pred_end(BB));
|
|
};
|
|
auto NextItem = [&]() {
|
|
BasicBlock *BB = Worklist.back();
|
|
Worklist.pop_back();
|
|
return BB;
|
|
};
|
|
|
|
// Seed the liveness for each individual block
|
|
for (BasicBlock &BB : F) {
|
|
Data.KillSet[&BB] = computeKillSet(&BB);
|
|
Data.LiveSet[&BB].clear();
|
|
computeLiveInValues(BB.rbegin(), BB.rend(), Data.LiveSet[&BB]);
|
|
|
|
#ifndef NDEBUG
|
|
for (Value *Kill : Data.KillSet[&BB])
|
|
assert(!Data.LiveSet[&BB].count(Kill) && "live set contains kill");
|
|
#endif
|
|
|
|
Data.LiveOut[&BB] = DenseSet<Value *>();
|
|
computeLiveOutSeed(&BB, Data.LiveOut[&BB]);
|
|
Data.LiveIn[&BB] = Data.LiveSet[&BB];
|
|
set_union(Data.LiveIn[&BB], Data.LiveOut[&BB]);
|
|
set_subtract(Data.LiveIn[&BB], Data.KillSet[&BB]);
|
|
if (!Data.LiveIn[&BB].empty())
|
|
AddPredsToWorklist(&BB);
|
|
}
|
|
|
|
// Propagate that liveness until stable
|
|
while (!Worklist.empty()) {
|
|
BasicBlock *BB = NextItem();
|
|
|
|
// Compute our new liveout set, then exit early if it hasn't changed
|
|
// despite the contribution of our successor.
|
|
DenseSet<Value *> LiveOut = Data.LiveOut[BB];
|
|
const auto OldLiveOutSize = LiveOut.size();
|
|
for (BasicBlock *Succ : successors(BB)) {
|
|
assert(Data.LiveIn.count(Succ));
|
|
set_union(LiveOut, Data.LiveIn[Succ]);
|
|
}
|
|
// assert OutLiveOut is a subset of LiveOut
|
|
if (OldLiveOutSize == LiveOut.size()) {
|
|
// If the sets are the same size, then we didn't actually add anything
|
|
// when unioning our successors LiveIn Thus, the LiveIn of this block
|
|
// hasn't changed.
|
|
continue;
|
|
}
|
|
Data.LiveOut[BB] = LiveOut;
|
|
|
|
// Apply the effects of this basic block
|
|
DenseSet<Value *> LiveTmp = LiveOut;
|
|
set_union(LiveTmp, Data.LiveSet[BB]);
|
|
set_subtract(LiveTmp, Data.KillSet[BB]);
|
|
|
|
assert(Data.LiveIn.count(BB));
|
|
const DenseSet<Value *> &OldLiveIn = Data.LiveIn[BB];
|
|
// assert: OldLiveIn is a subset of LiveTmp
|
|
if (OldLiveIn.size() != LiveTmp.size()) {
|
|
Data.LiveIn[BB] = LiveTmp;
|
|
AddPredsToWorklist(BB);
|
|
}
|
|
} // while( !worklist.empty() )
|
|
|
|
#ifndef NDEBUG
|
|
// Sanity check our output against SSA properties. This helps catch any
|
|
// missing kills during the above iteration.
|
|
for (BasicBlock &BB : F) {
|
|
checkBasicSSA(DT, Data, BB);
|
|
}
|
|
#endif
|
|
}
|
|
|
|
static void findLiveSetAtInst(Instruction *Inst, GCPtrLivenessData &Data,
|
|
StatepointLiveSetTy &Out) {
|
|
|
|
BasicBlock *BB = Inst->getParent();
|
|
|
|
// Note: The copy is intentional and required
|
|
assert(Data.LiveOut.count(BB));
|
|
DenseSet<Value *> LiveOut = Data.LiveOut[BB];
|
|
|
|
// We want to handle the statepoint itself oddly. It's
|
|
// call result is not live (normal), nor are it's arguments
|
|
// (unless they're used again later). This adjustment is
|
|
// specifically what we need to relocate
|
|
BasicBlock::reverse_iterator rend(Inst->getIterator());
|
|
computeLiveInValues(BB->rbegin(), rend, LiveOut);
|
|
LiveOut.erase(Inst);
|
|
Out.insert(LiveOut.begin(), LiveOut.end());
|
|
}
|
|
|
|
static void recomputeLiveInValues(GCPtrLivenessData &RevisedLivenessData,
|
|
const CallSite &CS,
|
|
PartiallyConstructedSafepointRecord &Info) {
|
|
Instruction *Inst = CS.getInstruction();
|
|
StatepointLiveSetTy Updated;
|
|
findLiveSetAtInst(Inst, RevisedLivenessData, Updated);
|
|
|
|
#ifndef NDEBUG
|
|
DenseSet<Value *> Bases;
|
|
for (auto KVPair : Info.PointerToBase) {
|
|
Bases.insert(KVPair.second);
|
|
}
|
|
#endif
|
|
// We may have base pointers which are now live that weren't before. We need
|
|
// to update the PointerToBase structure to reflect this.
|
|
for (auto V : Updated)
|
|
if (!Info.PointerToBase.count(V)) {
|
|
assert(Bases.count(V) && "can't find base for unexpected live value");
|
|
Info.PointerToBase[V] = V;
|
|
continue;
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
for (auto V : Updated) {
|
|
assert(Info.PointerToBase.count(V) &&
|
|
"must be able to find base for live value");
|
|
}
|
|
#endif
|
|
|
|
// Remove any stale base mappings - this can happen since our liveness is
|
|
// more precise then the one inherent in the base pointer analysis
|
|
DenseSet<Value *> ToErase;
|
|
for (auto KVPair : Info.PointerToBase)
|
|
if (!Updated.count(KVPair.first))
|
|
ToErase.insert(KVPair.first);
|
|
for (auto V : ToErase)
|
|
Info.PointerToBase.erase(V);
|
|
|
|
#ifndef NDEBUG
|
|
for (auto KVPair : Info.PointerToBase)
|
|
assert(Updated.count(KVPair.first) && "record for non-live value");
|
|
#endif
|
|
|
|
Info.LiveSet = Updated;
|
|
}
|