2419 lines
88 KiB
C++
2419 lines
88 KiB
C++
//===- MemorySSA.cpp - Memory SSA Builder ---------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the MemorySSA class.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/MemorySSA.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/DenseMapInfo.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/Hashing.h"
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#include "llvm/ADT/None.h"
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#include "llvm/ADT/Optional.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/iterator.h"
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#include "llvm/ADT/iterator_range.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/IteratedDominanceFrontier.h"
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#include "llvm/Analysis/MemoryLocation.h"
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#include "llvm/Config/llvm-config.h"
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#include "llvm/IR/AssemblyAnnotationWriter.h"
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#include "llvm/IR/BasicBlock.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/Instruction.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/IR/Use.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/AtomicOrdering.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/FormattedStream.h"
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#include "llvm/Support/raw_ostream.h"
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#include <algorithm>
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#include <cassert>
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#include <iterator>
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#include <memory>
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#include <utility>
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using namespace llvm;
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#define DEBUG_TYPE "memoryssa"
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INITIALIZE_PASS_BEGIN(MemorySSAWrapperPass, "memoryssa", "Memory SSA", false,
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true)
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INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
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INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
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INITIALIZE_PASS_END(MemorySSAWrapperPass, "memoryssa", "Memory SSA", false,
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true)
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INITIALIZE_PASS_BEGIN(MemorySSAPrinterLegacyPass, "print-memoryssa",
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"Memory SSA Printer", false, false)
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INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)
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INITIALIZE_PASS_END(MemorySSAPrinterLegacyPass, "print-memoryssa",
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"Memory SSA Printer", false, false)
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static cl::opt<unsigned> MaxCheckLimit(
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"memssa-check-limit", cl::Hidden, cl::init(100),
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cl::desc("The maximum number of stores/phis MemorySSA"
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"will consider trying to walk past (default = 100)"));
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// Always verify MemorySSA if expensive checking is enabled.
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#ifdef EXPENSIVE_CHECKS
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bool llvm::VerifyMemorySSA = true;
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#else
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bool llvm::VerifyMemorySSA = false;
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#endif
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/// Enables memory ssa as a dependency for loop passes in legacy pass manager.
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cl::opt<bool> llvm::EnableMSSALoopDependency(
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"enable-mssa-loop-dependency", cl::Hidden, cl::init(false),
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cl::desc("Enable MemorySSA dependency for loop pass manager"));
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static cl::opt<bool, true>
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VerifyMemorySSAX("verify-memoryssa", cl::location(VerifyMemorySSA),
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cl::Hidden, cl::desc("Enable verification of MemorySSA."));
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namespace llvm {
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/// An assembly annotator class to print Memory SSA information in
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/// comments.
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class MemorySSAAnnotatedWriter : public AssemblyAnnotationWriter {
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friend class MemorySSA;
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const MemorySSA *MSSA;
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public:
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MemorySSAAnnotatedWriter(const MemorySSA *M) : MSSA(M) {}
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void emitBasicBlockStartAnnot(const BasicBlock *BB,
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formatted_raw_ostream &OS) override {
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if (MemoryAccess *MA = MSSA->getMemoryAccess(BB))
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OS << "; " << *MA << "\n";
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}
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void emitInstructionAnnot(const Instruction *I,
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formatted_raw_ostream &OS) override {
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if (MemoryAccess *MA = MSSA->getMemoryAccess(I))
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OS << "; " << *MA << "\n";
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}
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};
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} // end namespace llvm
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namespace {
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/// Our current alias analysis API differentiates heavily between calls and
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/// non-calls, and functions called on one usually assert on the other.
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/// This class encapsulates the distinction to simplify other code that wants
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/// "Memory affecting instructions and related data" to use as a key.
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/// For example, this class is used as a densemap key in the use optimizer.
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class MemoryLocOrCall {
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public:
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bool IsCall = false;
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MemoryLocOrCall(MemoryUseOrDef *MUD)
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: MemoryLocOrCall(MUD->getMemoryInst()) {}
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MemoryLocOrCall(const MemoryUseOrDef *MUD)
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: MemoryLocOrCall(MUD->getMemoryInst()) {}
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MemoryLocOrCall(Instruction *Inst) {
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if (auto *C = dyn_cast<CallBase>(Inst)) {
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IsCall = true;
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Call = C;
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} else {
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IsCall = false;
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// There is no such thing as a memorylocation for a fence inst, and it is
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// unique in that regard.
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if (!isa<FenceInst>(Inst))
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Loc = MemoryLocation::get(Inst);
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}
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}
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explicit MemoryLocOrCall(const MemoryLocation &Loc) : Loc(Loc) {}
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const CallBase *getCall() const {
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assert(IsCall);
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return Call;
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}
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MemoryLocation getLoc() const {
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assert(!IsCall);
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return Loc;
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}
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bool operator==(const MemoryLocOrCall &Other) const {
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if (IsCall != Other.IsCall)
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return false;
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if (!IsCall)
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return Loc == Other.Loc;
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if (Call->getCalledValue() != Other.Call->getCalledValue())
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return false;
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return Call->arg_size() == Other.Call->arg_size() &&
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std::equal(Call->arg_begin(), Call->arg_end(),
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Other.Call->arg_begin());
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}
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private:
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union {
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const CallBase *Call;
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MemoryLocation Loc;
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};
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};
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} // end anonymous namespace
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namespace llvm {
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template <> struct DenseMapInfo<MemoryLocOrCall> {
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static inline MemoryLocOrCall getEmptyKey() {
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return MemoryLocOrCall(DenseMapInfo<MemoryLocation>::getEmptyKey());
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}
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static inline MemoryLocOrCall getTombstoneKey() {
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return MemoryLocOrCall(DenseMapInfo<MemoryLocation>::getTombstoneKey());
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}
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static unsigned getHashValue(const MemoryLocOrCall &MLOC) {
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if (!MLOC.IsCall)
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return hash_combine(
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MLOC.IsCall,
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DenseMapInfo<MemoryLocation>::getHashValue(MLOC.getLoc()));
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hash_code hash =
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hash_combine(MLOC.IsCall, DenseMapInfo<const Value *>::getHashValue(
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MLOC.getCall()->getCalledValue()));
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for (const Value *Arg : MLOC.getCall()->args())
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hash = hash_combine(hash, DenseMapInfo<const Value *>::getHashValue(Arg));
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return hash;
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}
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static bool isEqual(const MemoryLocOrCall &LHS, const MemoryLocOrCall &RHS) {
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return LHS == RHS;
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}
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};
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} // end namespace llvm
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/// This does one-way checks to see if Use could theoretically be hoisted above
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/// MayClobber. This will not check the other way around.
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///
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/// This assumes that, for the purposes of MemorySSA, Use comes directly after
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/// MayClobber, with no potentially clobbering operations in between them.
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/// (Where potentially clobbering ops are memory barriers, aliased stores, etc.)
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static bool areLoadsReorderable(const LoadInst *Use,
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const LoadInst *MayClobber) {
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bool VolatileUse = Use->isVolatile();
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bool VolatileClobber = MayClobber->isVolatile();
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// Volatile operations may never be reordered with other volatile operations.
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if (VolatileUse && VolatileClobber)
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return false;
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// Otherwise, volatile doesn't matter here. From the language reference:
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// 'optimizers may change the order of volatile operations relative to
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// non-volatile operations.'"
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// If a load is seq_cst, it cannot be moved above other loads. If its ordering
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// is weaker, it can be moved above other loads. We just need to be sure that
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// MayClobber isn't an acquire load, because loads can't be moved above
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// acquire loads.
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//
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// Note that this explicitly *does* allow the free reordering of monotonic (or
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// weaker) loads of the same address.
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bool SeqCstUse = Use->getOrdering() == AtomicOrdering::SequentiallyConsistent;
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bool MayClobberIsAcquire = isAtLeastOrStrongerThan(MayClobber->getOrdering(),
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AtomicOrdering::Acquire);
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return !(SeqCstUse || MayClobberIsAcquire);
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}
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namespace {
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struct ClobberAlias {
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bool IsClobber;
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Optional<AliasResult> AR;
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};
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} // end anonymous namespace
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// Return a pair of {IsClobber (bool), AR (AliasResult)}. It relies on AR being
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// ignored if IsClobber = false.
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template <typename AliasAnalysisType>
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static ClobberAlias
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instructionClobbersQuery(const MemoryDef *MD, const MemoryLocation &UseLoc,
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const Instruction *UseInst, AliasAnalysisType &AA) {
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Instruction *DefInst = MD->getMemoryInst();
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assert(DefInst && "Defining instruction not actually an instruction");
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const auto *UseCall = dyn_cast<CallBase>(UseInst);
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Optional<AliasResult> AR;
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if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(DefInst)) {
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// These intrinsics will show up as affecting memory, but they are just
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// markers, mostly.
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//
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// FIXME: We probably don't actually want MemorySSA to model these at all
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// (including creating MemoryAccesses for them): we just end up inventing
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// clobbers where they don't really exist at all. Please see D43269 for
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// context.
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switch (II->getIntrinsicID()) {
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case Intrinsic::lifetime_start:
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if (UseCall)
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return {false, NoAlias};
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AR = AA.alias(MemoryLocation(II->getArgOperand(1)), UseLoc);
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return {AR != NoAlias, AR};
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case Intrinsic::lifetime_end:
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case Intrinsic::invariant_start:
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case Intrinsic::invariant_end:
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case Intrinsic::assume:
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return {false, NoAlias};
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default:
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break;
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}
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}
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if (UseCall) {
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ModRefInfo I = AA.getModRefInfo(DefInst, UseCall);
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AR = isMustSet(I) ? MustAlias : MayAlias;
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return {isModOrRefSet(I), AR};
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}
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if (auto *DefLoad = dyn_cast<LoadInst>(DefInst))
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if (auto *UseLoad = dyn_cast<LoadInst>(UseInst))
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return {!areLoadsReorderable(UseLoad, DefLoad), MayAlias};
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ModRefInfo I = AA.getModRefInfo(DefInst, UseLoc);
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AR = isMustSet(I) ? MustAlias : MayAlias;
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return {isModSet(I), AR};
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}
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template <typename AliasAnalysisType>
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static ClobberAlias instructionClobbersQuery(MemoryDef *MD,
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const MemoryUseOrDef *MU,
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const MemoryLocOrCall &UseMLOC,
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AliasAnalysisType &AA) {
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// FIXME: This is a temporary hack to allow a single instructionClobbersQuery
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// to exist while MemoryLocOrCall is pushed through places.
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if (UseMLOC.IsCall)
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return instructionClobbersQuery(MD, MemoryLocation(), MU->getMemoryInst(),
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AA);
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return instructionClobbersQuery(MD, UseMLOC.getLoc(), MU->getMemoryInst(),
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AA);
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}
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// Return true when MD may alias MU, return false otherwise.
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bool MemorySSAUtil::defClobbersUseOrDef(MemoryDef *MD, const MemoryUseOrDef *MU,
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AliasAnalysis &AA) {
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return instructionClobbersQuery(MD, MU, MemoryLocOrCall(MU), AA).IsClobber;
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}
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namespace {
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struct UpwardsMemoryQuery {
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// True if our original query started off as a call
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bool IsCall = false;
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// The pointer location we started the query with. This will be empty if
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// IsCall is true.
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MemoryLocation StartingLoc;
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// This is the instruction we were querying about.
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const Instruction *Inst = nullptr;
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// The MemoryAccess we actually got called with, used to test local domination
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const MemoryAccess *OriginalAccess = nullptr;
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Optional<AliasResult> AR = MayAlias;
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bool SkipSelfAccess = false;
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UpwardsMemoryQuery() = default;
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UpwardsMemoryQuery(const Instruction *Inst, const MemoryAccess *Access)
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: IsCall(isa<CallBase>(Inst)), Inst(Inst), OriginalAccess(Access) {
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if (!IsCall)
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StartingLoc = MemoryLocation::get(Inst);
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}
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};
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} // end anonymous namespace
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static bool lifetimeEndsAt(MemoryDef *MD, const MemoryLocation &Loc,
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BatchAAResults &AA) {
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Instruction *Inst = MD->getMemoryInst();
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if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
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switch (II->getIntrinsicID()) {
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case Intrinsic::lifetime_end:
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return AA.alias(MemoryLocation(II->getArgOperand(1)), Loc) == MustAlias;
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default:
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return false;
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}
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}
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return false;
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}
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template <typename AliasAnalysisType>
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static bool isUseTriviallyOptimizableToLiveOnEntry(AliasAnalysisType &AA,
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const Instruction *I) {
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// If the memory can't be changed, then loads of the memory can't be
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// clobbered.
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return isa<LoadInst>(I) && (I->getMetadata(LLVMContext::MD_invariant_load) ||
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AA.pointsToConstantMemory(MemoryLocation(
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cast<LoadInst>(I)->getPointerOperand())));
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}
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/// Verifies that `Start` is clobbered by `ClobberAt`, and that nothing
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/// inbetween `Start` and `ClobberAt` can clobbers `Start`.
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///
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/// This is meant to be as simple and self-contained as possible. Because it
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/// uses no cache, etc., it can be relatively expensive.
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///
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/// \param Start The MemoryAccess that we want to walk from.
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/// \param ClobberAt A clobber for Start.
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/// \param StartLoc The MemoryLocation for Start.
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/// \param MSSA The MemorySSA instance that Start and ClobberAt belong to.
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/// \param Query The UpwardsMemoryQuery we used for our search.
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/// \param AA The AliasAnalysis we used for our search.
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/// \param AllowImpreciseClobber Always false, unless we do relaxed verify.
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template <typename AliasAnalysisType>
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LLVM_ATTRIBUTE_UNUSED static void
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checkClobberSanity(const MemoryAccess *Start, MemoryAccess *ClobberAt,
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const MemoryLocation &StartLoc, const MemorySSA &MSSA,
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const UpwardsMemoryQuery &Query, AliasAnalysisType &AA,
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bool AllowImpreciseClobber = false) {
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assert(MSSA.dominates(ClobberAt, Start) && "Clobber doesn't dominate start?");
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if (MSSA.isLiveOnEntryDef(Start)) {
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assert(MSSA.isLiveOnEntryDef(ClobberAt) &&
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"liveOnEntry must clobber itself");
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return;
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}
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bool FoundClobber = false;
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DenseSet<ConstMemoryAccessPair> VisitedPhis;
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SmallVector<ConstMemoryAccessPair, 8> Worklist;
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Worklist.emplace_back(Start, StartLoc);
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// Walk all paths from Start to ClobberAt, while looking for clobbers. If one
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// is found, complain.
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while (!Worklist.empty()) {
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auto MAP = Worklist.pop_back_val();
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// All we care about is that nothing from Start to ClobberAt clobbers Start.
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// We learn nothing from revisiting nodes.
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if (!VisitedPhis.insert(MAP).second)
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continue;
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for (const auto *MA : def_chain(MAP.first)) {
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if (MA == ClobberAt) {
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if (const auto *MD = dyn_cast<MemoryDef>(MA)) {
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// instructionClobbersQuery isn't essentially free, so don't use `|=`,
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// since it won't let us short-circuit.
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//
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// Also, note that this can't be hoisted out of the `Worklist` loop,
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// since MD may only act as a clobber for 1 of N MemoryLocations.
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FoundClobber = FoundClobber || MSSA.isLiveOnEntryDef(MD);
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if (!FoundClobber) {
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ClobberAlias CA =
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instructionClobbersQuery(MD, MAP.second, Query.Inst, AA);
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if (CA.IsClobber) {
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FoundClobber = true;
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// Not used: CA.AR;
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}
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}
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}
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break;
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}
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// We should never hit liveOnEntry, unless it's the clobber.
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assert(!MSSA.isLiveOnEntryDef(MA) && "Hit liveOnEntry before clobber?");
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if (const auto *MD = dyn_cast<MemoryDef>(MA)) {
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// If Start is a Def, skip self.
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if (MD == Start)
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continue;
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assert(!instructionClobbersQuery(MD, MAP.second, Query.Inst, AA)
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.IsClobber &&
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"Found clobber before reaching ClobberAt!");
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continue;
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}
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if (const auto *MU = dyn_cast<MemoryUse>(MA)) {
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(void)MU;
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assert (MU == Start &&
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"Can only find use in def chain if Start is a use");
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continue;
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}
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assert(isa<MemoryPhi>(MA));
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Worklist.append(
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upward_defs_begin({const_cast<MemoryAccess *>(MA), MAP.second}),
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upward_defs_end());
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}
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}
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// If the verify is done following an optimization, it's possible that
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// ClobberAt was a conservative clobbering, that we can now infer is not a
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// true clobbering access. Don't fail the verify if that's the case.
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// We do have accesses that claim they're optimized, but could be optimized
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// further. Updating all these can be expensive, so allow it for now (FIXME).
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if (AllowImpreciseClobber)
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return;
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// If ClobberAt is a MemoryPhi, we can assume something above it acted as a
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// clobber. Otherwise, `ClobberAt` should've acted as a clobber at some point.
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assert((isa<MemoryPhi>(ClobberAt) || FoundClobber) &&
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"ClobberAt never acted as a clobber");
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}
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namespace {
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/// Our algorithm for walking (and trying to optimize) clobbers, all wrapped up
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/// in one class.
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template <class AliasAnalysisType> class ClobberWalker {
|
|
/// Save a few bytes by using unsigned instead of size_t.
|
|
using ListIndex = unsigned;
|
|
|
|
/// Represents a span of contiguous MemoryDefs, potentially ending in a
|
|
/// MemoryPhi.
|
|
struct DefPath {
|
|
MemoryLocation Loc;
|
|
// Note that, because we always walk in reverse, Last will always dominate
|
|
// First. Also note that First and Last are inclusive.
|
|
MemoryAccess *First;
|
|
MemoryAccess *Last;
|
|
Optional<ListIndex> Previous;
|
|
|
|
DefPath(const MemoryLocation &Loc, MemoryAccess *First, MemoryAccess *Last,
|
|
Optional<ListIndex> Previous)
|
|
: Loc(Loc), First(First), Last(Last), Previous(Previous) {}
|
|
|
|
DefPath(const MemoryLocation &Loc, MemoryAccess *Init,
|
|
Optional<ListIndex> Previous)
|
|
: DefPath(Loc, Init, Init, Previous) {}
|
|
};
|
|
|
|
const MemorySSA &MSSA;
|
|
AliasAnalysisType &AA;
|
|
DominatorTree &DT;
|
|
UpwardsMemoryQuery *Query;
|
|
unsigned *UpwardWalkLimit;
|
|
|
|
// Phi optimization bookkeeping
|
|
SmallVector<DefPath, 32> Paths;
|
|
DenseSet<ConstMemoryAccessPair> VisitedPhis;
|
|
|
|
/// Find the nearest def or phi that `From` can legally be optimized to.
|
|
const MemoryAccess *getWalkTarget(const MemoryPhi *From) const {
|
|
assert(From->getNumOperands() && "Phi with no operands?");
|
|
|
|
BasicBlock *BB = From->getBlock();
|
|
MemoryAccess *Result = MSSA.getLiveOnEntryDef();
|
|
DomTreeNode *Node = DT.getNode(BB);
|
|
while ((Node = Node->getIDom())) {
|
|
auto *Defs = MSSA.getBlockDefs(Node->getBlock());
|
|
if (Defs)
|
|
return &*Defs->rbegin();
|
|
}
|
|
return Result;
|
|
}
|
|
|
|
/// Result of calling walkToPhiOrClobber.
|
|
struct UpwardsWalkResult {
|
|
/// The "Result" of the walk. Either a clobber, the last thing we walked, or
|
|
/// both. Include alias info when clobber found.
|
|
MemoryAccess *Result;
|
|
bool IsKnownClobber;
|
|
Optional<AliasResult> AR;
|
|
};
|
|
|
|
/// Walk to the next Phi or Clobber in the def chain starting at Desc.Last.
|
|
/// This will update Desc.Last as it walks. It will (optionally) also stop at
|
|
/// StopAt.
|
|
///
|
|
/// This does not test for whether StopAt is a clobber
|
|
UpwardsWalkResult
|
|
walkToPhiOrClobber(DefPath &Desc, const MemoryAccess *StopAt = nullptr,
|
|
const MemoryAccess *SkipStopAt = nullptr) const {
|
|
assert(!isa<MemoryUse>(Desc.Last) && "Uses don't exist in my world");
|
|
assert(UpwardWalkLimit && "Need a valid walk limit");
|
|
bool LimitAlreadyReached = false;
|
|
// (*UpwardWalkLimit) may be 0 here, due to the loop in tryOptimizePhi. Set
|
|
// it to 1. This will not do any alias() calls. It either returns in the
|
|
// first iteration in the loop below, or is set back to 0 if all def chains
|
|
// are free of MemoryDefs.
|
|
if (!*UpwardWalkLimit) {
|
|
*UpwardWalkLimit = 1;
|
|
LimitAlreadyReached = true;
|
|
}
|
|
|
|
for (MemoryAccess *Current : def_chain(Desc.Last)) {
|
|
Desc.Last = Current;
|
|
if (Current == StopAt || Current == SkipStopAt)
|
|
return {Current, false, MayAlias};
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|
|
|
if (auto *MD = dyn_cast<MemoryDef>(Current)) {
|
|
if (MSSA.isLiveOnEntryDef(MD))
|
|
return {MD, true, MustAlias};
|
|
|
|
if (!--*UpwardWalkLimit)
|
|
return {Current, true, MayAlias};
|
|
|
|
ClobberAlias CA =
|
|
instructionClobbersQuery(MD, Desc.Loc, Query->Inst, AA);
|
|
if (CA.IsClobber)
|
|
return {MD, true, CA.AR};
|
|
}
|
|
}
|
|
|
|
if (LimitAlreadyReached)
|
|
*UpwardWalkLimit = 0;
|
|
|
|
assert(isa<MemoryPhi>(Desc.Last) &&
|
|
"Ended at a non-clobber that's not a phi?");
|
|
return {Desc.Last, false, MayAlias};
|
|
}
|
|
|
|
void addSearches(MemoryPhi *Phi, SmallVectorImpl<ListIndex> &PausedSearches,
|
|
ListIndex PriorNode) {
|
|
auto UpwardDefs = make_range(upward_defs_begin({Phi, Paths[PriorNode].Loc}),
|
|
upward_defs_end());
|
|
for (const MemoryAccessPair &P : UpwardDefs) {
|
|
PausedSearches.push_back(Paths.size());
|
|
Paths.emplace_back(P.second, P.first, PriorNode);
|
|
}
|
|
}
|
|
|
|
/// Represents a search that terminated after finding a clobber. This clobber
|
|
/// may or may not be present in the path of defs from LastNode..SearchStart,
|
|
/// since it may have been retrieved from cache.
|
|
struct TerminatedPath {
|
|
MemoryAccess *Clobber;
|
|
ListIndex LastNode;
|
|
};
|
|
|
|
/// Get an access that keeps us from optimizing to the given phi.
|
|
///
|
|
/// PausedSearches is an array of indices into the Paths array. Its incoming
|
|
/// value is the indices of searches that stopped at the last phi optimization
|
|
/// target. It's left in an unspecified state.
|
|
///
|
|
/// If this returns None, NewPaused is a vector of searches that terminated
|
|
/// at StopWhere. Otherwise, NewPaused is left in an unspecified state.
|
|
Optional<TerminatedPath>
|
|
getBlockingAccess(const MemoryAccess *StopWhere,
|
|
SmallVectorImpl<ListIndex> &PausedSearches,
|
|
SmallVectorImpl<ListIndex> &NewPaused,
|
|
SmallVectorImpl<TerminatedPath> &Terminated) {
|
|
assert(!PausedSearches.empty() && "No searches to continue?");
|
|
|
|
// BFS vs DFS really doesn't make a difference here, so just do a DFS with
|
|
// PausedSearches as our stack.
|
|
while (!PausedSearches.empty()) {
|
|
ListIndex PathIndex = PausedSearches.pop_back_val();
|
|
DefPath &Node = Paths[PathIndex];
|
|
|
|
// If we've already visited this path with this MemoryLocation, we don't
|
|
// need to do so again.
|
|
//
|
|
// NOTE: That we just drop these paths on the ground makes caching
|
|
// behavior sporadic. e.g. given a diamond:
|
|
// A
|
|
// B C
|
|
// D
|
|
//
|
|
// ...If we walk D, B, A, C, we'll only cache the result of phi
|
|
// optimization for A, B, and D; C will be skipped because it dies here.
|
|
// This arguably isn't the worst thing ever, since:
|
|
// - We generally query things in a top-down order, so if we got below D
|
|
// without needing cache entries for {C, MemLoc}, then chances are
|
|
// that those cache entries would end up ultimately unused.
|
|
// - We still cache things for A, so C only needs to walk up a bit.
|
|
// If this behavior becomes problematic, we can fix without a ton of extra
|
|
// work.
|
|
if (!VisitedPhis.insert({Node.Last, Node.Loc}).second)
|
|
continue;
|
|
|
|
const MemoryAccess *SkipStopWhere = nullptr;
|
|
if (Query->SkipSelfAccess && Node.Loc == Query->StartingLoc) {
|
|
assert(isa<MemoryDef>(Query->OriginalAccess));
|
|
SkipStopWhere = Query->OriginalAccess;
|
|
}
|
|
|
|
UpwardsWalkResult Res = walkToPhiOrClobber(Node,
|
|
/*StopAt=*/StopWhere,
|
|
/*SkipStopAt=*/SkipStopWhere);
|
|
if (Res.IsKnownClobber) {
|
|
assert(Res.Result != StopWhere && Res.Result != SkipStopWhere);
|
|
|
|
// If this wasn't a cache hit, we hit a clobber when walking. That's a
|
|
// failure.
|
|
TerminatedPath Term{Res.Result, PathIndex};
|
|
if (!MSSA.dominates(Res.Result, StopWhere))
|
|
return Term;
|
|
|
|
// Otherwise, it's a valid thing to potentially optimize to.
|
|
Terminated.push_back(Term);
|
|
continue;
|
|
}
|
|
|
|
if (Res.Result == StopWhere || Res.Result == SkipStopWhere) {
|
|
// We've hit our target. Save this path off for if we want to continue
|
|
// walking. If we are in the mode of skipping the OriginalAccess, and
|
|
// we've reached back to the OriginalAccess, do not save path, we've
|
|
// just looped back to self.
|
|
if (Res.Result != SkipStopWhere)
|
|
NewPaused.push_back(PathIndex);
|
|
continue;
|
|
}
|
|
|
|
assert(!MSSA.isLiveOnEntryDef(Res.Result) && "liveOnEntry is a clobber");
|
|
addSearches(cast<MemoryPhi>(Res.Result), PausedSearches, PathIndex);
|
|
}
|
|
|
|
return None;
|
|
}
|
|
|
|
template <typename T, typename Walker>
|
|
struct generic_def_path_iterator
|
|
: public iterator_facade_base<generic_def_path_iterator<T, Walker>,
|
|
std::forward_iterator_tag, T *> {
|
|
generic_def_path_iterator() {}
|
|
generic_def_path_iterator(Walker *W, ListIndex N) : W(W), N(N) {}
|
|
|
|
T &operator*() const { return curNode(); }
|
|
|
|
generic_def_path_iterator &operator++() {
|
|
N = curNode().Previous;
|
|
return *this;
|
|
}
|
|
|
|
bool operator==(const generic_def_path_iterator &O) const {
|
|
if (N.hasValue() != O.N.hasValue())
|
|
return false;
|
|
return !N.hasValue() || *N == *O.N;
|
|
}
|
|
|
|
private:
|
|
T &curNode() const { return W->Paths[*N]; }
|
|
|
|
Walker *W = nullptr;
|
|
Optional<ListIndex> N = None;
|
|
};
|
|
|
|
using def_path_iterator = generic_def_path_iterator<DefPath, ClobberWalker>;
|
|
using const_def_path_iterator =
|
|
generic_def_path_iterator<const DefPath, const ClobberWalker>;
|
|
|
|
iterator_range<def_path_iterator> def_path(ListIndex From) {
|
|
return make_range(def_path_iterator(this, From), def_path_iterator());
|
|
}
|
|
|
|
iterator_range<const_def_path_iterator> const_def_path(ListIndex From) const {
|
|
return make_range(const_def_path_iterator(this, From),
|
|
const_def_path_iterator());
|
|
}
|
|
|
|
struct OptznResult {
|
|
/// The path that contains our result.
|
|
TerminatedPath PrimaryClobber;
|
|
/// The paths that we can legally cache back from, but that aren't
|
|
/// necessarily the result of the Phi optimization.
|
|
SmallVector<TerminatedPath, 4> OtherClobbers;
|
|
};
|
|
|
|
ListIndex defPathIndex(const DefPath &N) const {
|
|
// The assert looks nicer if we don't need to do &N
|
|
const DefPath *NP = &N;
|
|
assert(!Paths.empty() && NP >= &Paths.front() && NP <= &Paths.back() &&
|
|
"Out of bounds DefPath!");
|
|
return NP - &Paths.front();
|
|
}
|
|
|
|
/// Try to optimize a phi as best as we can. Returns a SmallVector of Paths
|
|
/// that act as legal clobbers. Note that this won't return *all* clobbers.
|
|
///
|
|
/// Phi optimization algorithm tl;dr:
|
|
/// - Find the earliest def/phi, A, we can optimize to
|
|
/// - Find if all paths from the starting memory access ultimately reach A
|
|
/// - If not, optimization isn't possible.
|
|
/// - Otherwise, walk from A to another clobber or phi, A'.
|
|
/// - If A' is a def, we're done.
|
|
/// - If A' is a phi, try to optimize it.
|
|
///
|
|
/// A path is a series of {MemoryAccess, MemoryLocation} pairs. A path
|
|
/// terminates when a MemoryAccess that clobbers said MemoryLocation is found.
|
|
OptznResult tryOptimizePhi(MemoryPhi *Phi, MemoryAccess *Start,
|
|
const MemoryLocation &Loc) {
|
|
assert(Paths.empty() && VisitedPhis.empty() &&
|
|
"Reset the optimization state.");
|
|
|
|
Paths.emplace_back(Loc, Start, Phi, None);
|
|
// Stores how many "valid" optimization nodes we had prior to calling
|
|
// addSearches/getBlockingAccess. Necessary for caching if we had a blocker.
|
|
auto PriorPathsSize = Paths.size();
|
|
|
|
SmallVector<ListIndex, 16> PausedSearches;
|
|
SmallVector<ListIndex, 8> NewPaused;
|
|
SmallVector<TerminatedPath, 4> TerminatedPaths;
|
|
|
|
addSearches(Phi, PausedSearches, 0);
|
|
|
|
// Moves the TerminatedPath with the "most dominated" Clobber to the end of
|
|
// Paths.
|
|
auto MoveDominatedPathToEnd = [&](SmallVectorImpl<TerminatedPath> &Paths) {
|
|
assert(!Paths.empty() && "Need a path to move");
|
|
auto Dom = Paths.begin();
|
|
for (auto I = std::next(Dom), E = Paths.end(); I != E; ++I)
|
|
if (!MSSA.dominates(I->Clobber, Dom->Clobber))
|
|
Dom = I;
|
|
auto Last = Paths.end() - 1;
|
|
if (Last != Dom)
|
|
std::iter_swap(Last, Dom);
|
|
};
|
|
|
|
MemoryPhi *Current = Phi;
|
|
while (true) {
|
|
assert(!MSSA.isLiveOnEntryDef(Current) &&
|
|
"liveOnEntry wasn't treated as a clobber?");
|
|
|
|
const auto *Target = getWalkTarget(Current);
|
|
// If a TerminatedPath doesn't dominate Target, then it wasn't a legal
|
|
// optimization for the prior phi.
|
|
assert(all_of(TerminatedPaths, [&](const TerminatedPath &P) {
|
|
return MSSA.dominates(P.Clobber, Target);
|
|
}));
|
|
|
|
// FIXME: This is broken, because the Blocker may be reported to be
|
|
// liveOnEntry, and we'll happily wait for that to disappear (read: never)
|
|
// For the moment, this is fine, since we do nothing with blocker info.
|
|
if (Optional<TerminatedPath> Blocker = getBlockingAccess(
|
|
Target, PausedSearches, NewPaused, TerminatedPaths)) {
|
|
|
|
// Find the node we started at. We can't search based on N->Last, since
|
|
// we may have gone around a loop with a different MemoryLocation.
|
|
auto Iter = find_if(def_path(Blocker->LastNode), [&](const DefPath &N) {
|
|
return defPathIndex(N) < PriorPathsSize;
|
|
});
|
|
assert(Iter != def_path_iterator());
|
|
|
|
DefPath &CurNode = *Iter;
|
|
assert(CurNode.Last == Current);
|
|
|
|
// Two things:
|
|
// A. We can't reliably cache all of NewPaused back. Consider a case
|
|
// where we have two paths in NewPaused; one of which can't optimize
|
|
// above this phi, whereas the other can. If we cache the second path
|
|
// back, we'll end up with suboptimal cache entries. We can handle
|
|
// cases like this a bit better when we either try to find all
|
|
// clobbers that block phi optimization, or when our cache starts
|
|
// supporting unfinished searches.
|
|
// B. We can't reliably cache TerminatedPaths back here without doing
|
|
// extra checks; consider a case like:
|
|
// T
|
|
// / \
|
|
// D C
|
|
// \ /
|
|
// S
|
|
// Where T is our target, C is a node with a clobber on it, D is a
|
|
// diamond (with a clobber *only* on the left or right node, N), and
|
|
// S is our start. Say we walk to D, through the node opposite N
|
|
// (read: ignoring the clobber), and see a cache entry in the top
|
|
// node of D. That cache entry gets put into TerminatedPaths. We then
|
|
// walk up to C (N is later in our worklist), find the clobber, and
|
|
// quit. If we append TerminatedPaths to OtherClobbers, we'll cache
|
|
// the bottom part of D to the cached clobber, ignoring the clobber
|
|
// in N. Again, this problem goes away if we start tracking all
|
|
// blockers for a given phi optimization.
|
|
TerminatedPath Result{CurNode.Last, defPathIndex(CurNode)};
|
|
return {Result, {}};
|
|
}
|
|
|
|
// If there's nothing left to search, then all paths led to valid clobbers
|
|
// that we got from our cache; pick the nearest to the start, and allow
|
|
// the rest to be cached back.
|
|
if (NewPaused.empty()) {
|
|
MoveDominatedPathToEnd(TerminatedPaths);
|
|
TerminatedPath Result = TerminatedPaths.pop_back_val();
|
|
return {Result, std::move(TerminatedPaths)};
|
|
}
|
|
|
|
MemoryAccess *DefChainEnd = nullptr;
|
|
SmallVector<TerminatedPath, 4> Clobbers;
|
|
for (ListIndex Paused : NewPaused) {
|
|
UpwardsWalkResult WR = walkToPhiOrClobber(Paths[Paused]);
|
|
if (WR.IsKnownClobber)
|
|
Clobbers.push_back({WR.Result, Paused});
|
|
else
|
|
// Micro-opt: If we hit the end of the chain, save it.
|
|
DefChainEnd = WR.Result;
|
|
}
|
|
|
|
if (!TerminatedPaths.empty()) {
|
|
// If we couldn't find the dominating phi/liveOnEntry in the above loop,
|
|
// do it now.
|
|
if (!DefChainEnd)
|
|
for (auto *MA : def_chain(const_cast<MemoryAccess *>(Target)))
|
|
DefChainEnd = MA;
|
|
|
|
// If any of the terminated paths don't dominate the phi we'll try to
|
|
// optimize, we need to figure out what they are and quit.
|
|
const BasicBlock *ChainBB = DefChainEnd->getBlock();
|
|
for (const TerminatedPath &TP : TerminatedPaths) {
|
|
// Because we know that DefChainEnd is as "high" as we can go, we
|
|
// don't need local dominance checks; BB dominance is sufficient.
|
|
if (DT.dominates(ChainBB, TP.Clobber->getBlock()))
|
|
Clobbers.push_back(TP);
|
|
}
|
|
}
|
|
|
|
// If we have clobbers in the def chain, find the one closest to Current
|
|
// and quit.
|
|
if (!Clobbers.empty()) {
|
|
MoveDominatedPathToEnd(Clobbers);
|
|
TerminatedPath Result = Clobbers.pop_back_val();
|
|
return {Result, std::move(Clobbers)};
|
|
}
|
|
|
|
assert(all_of(NewPaused,
|
|
[&](ListIndex I) { return Paths[I].Last == DefChainEnd; }));
|
|
|
|
// Because liveOnEntry is a clobber, this must be a phi.
|
|
auto *DefChainPhi = cast<MemoryPhi>(DefChainEnd);
|
|
|
|
PriorPathsSize = Paths.size();
|
|
PausedSearches.clear();
|
|
for (ListIndex I : NewPaused)
|
|
addSearches(DefChainPhi, PausedSearches, I);
|
|
NewPaused.clear();
|
|
|
|
Current = DefChainPhi;
|
|
}
|
|
}
|
|
|
|
void verifyOptResult(const OptznResult &R) const {
|
|
assert(all_of(R.OtherClobbers, [&](const TerminatedPath &P) {
|
|
return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber);
|
|
}));
|
|
}
|
|
|
|
void resetPhiOptznState() {
|
|
Paths.clear();
|
|
VisitedPhis.clear();
|
|
}
|
|
|
|
public:
|
|
ClobberWalker(const MemorySSA &MSSA, AliasAnalysisType &AA, DominatorTree &DT)
|
|
: MSSA(MSSA), AA(AA), DT(DT) {}
|
|
|
|
AliasAnalysisType *getAA() { return &AA; }
|
|
/// Finds the nearest clobber for the given query, optimizing phis if
|
|
/// possible.
|
|
MemoryAccess *findClobber(MemoryAccess *Start, UpwardsMemoryQuery &Q,
|
|
unsigned &UpWalkLimit) {
|
|
Query = &Q;
|
|
UpwardWalkLimit = &UpWalkLimit;
|
|
// Starting limit must be > 0.
|
|
if (!UpWalkLimit)
|
|
UpWalkLimit++;
|
|
|
|
MemoryAccess *Current = Start;
|
|
// This walker pretends uses don't exist. If we're handed one, silently grab
|
|
// its def. (This has the nice side-effect of ensuring we never cache uses)
|
|
if (auto *MU = dyn_cast<MemoryUse>(Start))
|
|
Current = MU->getDefiningAccess();
|
|
|
|
DefPath FirstDesc(Q.StartingLoc, Current, Current, None);
|
|
// Fast path for the overly-common case (no crazy phi optimization
|
|
// necessary)
|
|
UpwardsWalkResult WalkResult = walkToPhiOrClobber(FirstDesc);
|
|
MemoryAccess *Result;
|
|
if (WalkResult.IsKnownClobber) {
|
|
Result = WalkResult.Result;
|
|
Q.AR = WalkResult.AR;
|
|
} else {
|
|
OptznResult OptRes = tryOptimizePhi(cast<MemoryPhi>(FirstDesc.Last),
|
|
Current, Q.StartingLoc);
|
|
verifyOptResult(OptRes);
|
|
resetPhiOptznState();
|
|
Result = OptRes.PrimaryClobber.Clobber;
|
|
}
|
|
|
|
#ifdef EXPENSIVE_CHECKS
|
|
if (!Q.SkipSelfAccess && *UpwardWalkLimit > 0)
|
|
checkClobberSanity(Current, Result, Q.StartingLoc, MSSA, Q, AA);
|
|
#endif
|
|
return Result;
|
|
}
|
|
};
|
|
|
|
struct RenamePassData {
|
|
DomTreeNode *DTN;
|
|
DomTreeNode::const_iterator ChildIt;
|
|
MemoryAccess *IncomingVal;
|
|
|
|
RenamePassData(DomTreeNode *D, DomTreeNode::const_iterator It,
|
|
MemoryAccess *M)
|
|
: DTN(D), ChildIt(It), IncomingVal(M) {}
|
|
|
|
void swap(RenamePassData &RHS) {
|
|
std::swap(DTN, RHS.DTN);
|
|
std::swap(ChildIt, RHS.ChildIt);
|
|
std::swap(IncomingVal, RHS.IncomingVal);
|
|
}
|
|
};
|
|
|
|
} // end anonymous namespace
|
|
|
|
namespace llvm {
|
|
|
|
template <class AliasAnalysisType> class MemorySSA::ClobberWalkerBase {
|
|
ClobberWalker<AliasAnalysisType> Walker;
|
|
MemorySSA *MSSA;
|
|
|
|
public:
|
|
ClobberWalkerBase(MemorySSA *M, AliasAnalysisType *A, DominatorTree *D)
|
|
: Walker(*M, *A, *D), MSSA(M) {}
|
|
|
|
MemoryAccess *getClobberingMemoryAccessBase(MemoryAccess *,
|
|
const MemoryLocation &,
|
|
unsigned &);
|
|
// Third argument (bool), defines whether the clobber search should skip the
|
|
// original queried access. If true, there will be a follow-up query searching
|
|
// for a clobber access past "self". Note that the Optimized access is not
|
|
// updated if a new clobber is found by this SkipSelf search. If this
|
|
// additional query becomes heavily used we may decide to cache the result.
|
|
// Walker instantiations will decide how to set the SkipSelf bool.
|
|
MemoryAccess *getClobberingMemoryAccessBase(MemoryAccess *, unsigned &, bool);
|
|
};
|
|
|
|
/// A MemorySSAWalker that does AA walks to disambiguate accesses. It no
|
|
/// longer does caching on its own, but the name has been retained for the
|
|
/// moment.
|
|
template <class AliasAnalysisType>
|
|
class MemorySSA::CachingWalker final : public MemorySSAWalker {
|
|
ClobberWalkerBase<AliasAnalysisType> *Walker;
|
|
|
|
public:
|
|
CachingWalker(MemorySSA *M, ClobberWalkerBase<AliasAnalysisType> *W)
|
|
: MemorySSAWalker(M), Walker(W) {}
|
|
~CachingWalker() override = default;
|
|
|
|
using MemorySSAWalker::getClobberingMemoryAccess;
|
|
|
|
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA, unsigned &UWL) {
|
|
return Walker->getClobberingMemoryAccessBase(MA, UWL, false);
|
|
}
|
|
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA,
|
|
const MemoryLocation &Loc,
|
|
unsigned &UWL) {
|
|
return Walker->getClobberingMemoryAccessBase(MA, Loc, UWL);
|
|
}
|
|
|
|
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA) override {
|
|
unsigned UpwardWalkLimit = MaxCheckLimit;
|
|
return getClobberingMemoryAccess(MA, UpwardWalkLimit);
|
|
}
|
|
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA,
|
|
const MemoryLocation &Loc) override {
|
|
unsigned UpwardWalkLimit = MaxCheckLimit;
|
|
return getClobberingMemoryAccess(MA, Loc, UpwardWalkLimit);
|
|
}
|
|
|
|
void invalidateInfo(MemoryAccess *MA) override {
|
|
if (auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
|
|
MUD->resetOptimized();
|
|
}
|
|
};
|
|
|
|
template <class AliasAnalysisType>
|
|
class MemorySSA::SkipSelfWalker final : public MemorySSAWalker {
|
|
ClobberWalkerBase<AliasAnalysisType> *Walker;
|
|
|
|
public:
|
|
SkipSelfWalker(MemorySSA *M, ClobberWalkerBase<AliasAnalysisType> *W)
|
|
: MemorySSAWalker(M), Walker(W) {}
|
|
~SkipSelfWalker() override = default;
|
|
|
|
using MemorySSAWalker::getClobberingMemoryAccess;
|
|
|
|
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA, unsigned &UWL) {
|
|
return Walker->getClobberingMemoryAccessBase(MA, UWL, true);
|
|
}
|
|
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA,
|
|
const MemoryLocation &Loc,
|
|
unsigned &UWL) {
|
|
return Walker->getClobberingMemoryAccessBase(MA, Loc, UWL);
|
|
}
|
|
|
|
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA) override {
|
|
unsigned UpwardWalkLimit = MaxCheckLimit;
|
|
return getClobberingMemoryAccess(MA, UpwardWalkLimit);
|
|
}
|
|
MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA,
|
|
const MemoryLocation &Loc) override {
|
|
unsigned UpwardWalkLimit = MaxCheckLimit;
|
|
return getClobberingMemoryAccess(MA, Loc, UpwardWalkLimit);
|
|
}
|
|
|
|
void invalidateInfo(MemoryAccess *MA) override {
|
|
if (auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
|
|
MUD->resetOptimized();
|
|
}
|
|
};
|
|
|
|
} // end namespace llvm
|
|
|
|
void MemorySSA::renameSuccessorPhis(BasicBlock *BB, MemoryAccess *IncomingVal,
|
|
bool RenameAllUses) {
|
|
// Pass through values to our successors
|
|
for (const BasicBlock *S : successors(BB)) {
|
|
auto It = PerBlockAccesses.find(S);
|
|
// Rename the phi nodes in our successor block
|
|
if (It == PerBlockAccesses.end() || !isa<MemoryPhi>(It->second->front()))
|
|
continue;
|
|
AccessList *Accesses = It->second.get();
|
|
auto *Phi = cast<MemoryPhi>(&Accesses->front());
|
|
if (RenameAllUses) {
|
|
int PhiIndex = Phi->getBasicBlockIndex(BB);
|
|
assert(PhiIndex != -1 && "Incomplete phi during partial rename");
|
|
Phi->setIncomingValue(PhiIndex, IncomingVal);
|
|
} else
|
|
Phi->addIncoming(IncomingVal, BB);
|
|
}
|
|
}
|
|
|
|
/// Rename a single basic block into MemorySSA form.
|
|
/// Uses the standard SSA renaming algorithm.
|
|
/// \returns The new incoming value.
|
|
MemoryAccess *MemorySSA::renameBlock(BasicBlock *BB, MemoryAccess *IncomingVal,
|
|
bool RenameAllUses) {
|
|
auto It = PerBlockAccesses.find(BB);
|
|
// Skip most processing if the list is empty.
|
|
if (It != PerBlockAccesses.end()) {
|
|
AccessList *Accesses = It->second.get();
|
|
for (MemoryAccess &L : *Accesses) {
|
|
if (MemoryUseOrDef *MUD = dyn_cast<MemoryUseOrDef>(&L)) {
|
|
if (MUD->getDefiningAccess() == nullptr || RenameAllUses)
|
|
MUD->setDefiningAccess(IncomingVal);
|
|
if (isa<MemoryDef>(&L))
|
|
IncomingVal = &L;
|
|
} else {
|
|
IncomingVal = &L;
|
|
}
|
|
}
|
|
}
|
|
return IncomingVal;
|
|
}
|
|
|
|
/// This is the standard SSA renaming algorithm.
|
|
///
|
|
/// We walk the dominator tree in preorder, renaming accesses, and then filling
|
|
/// in phi nodes in our successors.
|
|
void MemorySSA::renamePass(DomTreeNode *Root, MemoryAccess *IncomingVal,
|
|
SmallPtrSetImpl<BasicBlock *> &Visited,
|
|
bool SkipVisited, bool RenameAllUses) {
|
|
assert(Root && "Trying to rename accesses in an unreachable block");
|
|
|
|
SmallVector<RenamePassData, 32> WorkStack;
|
|
// Skip everything if we already renamed this block and we are skipping.
|
|
// Note: You can't sink this into the if, because we need it to occur
|
|
// regardless of whether we skip blocks or not.
|
|
bool AlreadyVisited = !Visited.insert(Root->getBlock()).second;
|
|
if (SkipVisited && AlreadyVisited)
|
|
return;
|
|
|
|
IncomingVal = renameBlock(Root->getBlock(), IncomingVal, RenameAllUses);
|
|
renameSuccessorPhis(Root->getBlock(), IncomingVal, RenameAllUses);
|
|
WorkStack.push_back({Root, Root->begin(), IncomingVal});
|
|
|
|
while (!WorkStack.empty()) {
|
|
DomTreeNode *Node = WorkStack.back().DTN;
|
|
DomTreeNode::const_iterator ChildIt = WorkStack.back().ChildIt;
|
|
IncomingVal = WorkStack.back().IncomingVal;
|
|
|
|
if (ChildIt == Node->end()) {
|
|
WorkStack.pop_back();
|
|
} else {
|
|
DomTreeNode *Child = *ChildIt;
|
|
++WorkStack.back().ChildIt;
|
|
BasicBlock *BB = Child->getBlock();
|
|
// Note: You can't sink this into the if, because we need it to occur
|
|
// regardless of whether we skip blocks or not.
|
|
AlreadyVisited = !Visited.insert(BB).second;
|
|
if (SkipVisited && AlreadyVisited) {
|
|
// We already visited this during our renaming, which can happen when
|
|
// being asked to rename multiple blocks. Figure out the incoming val,
|
|
// which is the last def.
|
|
// Incoming value can only change if there is a block def, and in that
|
|
// case, it's the last block def in the list.
|
|
if (auto *BlockDefs = getWritableBlockDefs(BB))
|
|
IncomingVal = &*BlockDefs->rbegin();
|
|
} else
|
|
IncomingVal = renameBlock(BB, IncomingVal, RenameAllUses);
|
|
renameSuccessorPhis(BB, IncomingVal, RenameAllUses);
|
|
WorkStack.push_back({Child, Child->begin(), IncomingVal});
|
|
}
|
|
}
|
|
}
|
|
|
|
/// This handles unreachable block accesses by deleting phi nodes in
|
|
/// unreachable blocks, and marking all other unreachable MemoryAccess's as
|
|
/// being uses of the live on entry definition.
|
|
void MemorySSA::markUnreachableAsLiveOnEntry(BasicBlock *BB) {
|
|
assert(!DT->isReachableFromEntry(BB) &&
|
|
"Reachable block found while handling unreachable blocks");
|
|
|
|
// Make sure phi nodes in our reachable successors end up with a
|
|
// LiveOnEntryDef for our incoming edge, even though our block is forward
|
|
// unreachable. We could just disconnect these blocks from the CFG fully,
|
|
// but we do not right now.
|
|
for (const BasicBlock *S : successors(BB)) {
|
|
if (!DT->isReachableFromEntry(S))
|
|
continue;
|
|
auto It = PerBlockAccesses.find(S);
|
|
// Rename the phi nodes in our successor block
|
|
if (It == PerBlockAccesses.end() || !isa<MemoryPhi>(It->second->front()))
|
|
continue;
|
|
AccessList *Accesses = It->second.get();
|
|
auto *Phi = cast<MemoryPhi>(&Accesses->front());
|
|
Phi->addIncoming(LiveOnEntryDef.get(), BB);
|
|
}
|
|
|
|
auto It = PerBlockAccesses.find(BB);
|
|
if (It == PerBlockAccesses.end())
|
|
return;
|
|
|
|
auto &Accesses = It->second;
|
|
for (auto AI = Accesses->begin(), AE = Accesses->end(); AI != AE;) {
|
|
auto Next = std::next(AI);
|
|
// If we have a phi, just remove it. We are going to replace all
|
|
// users with live on entry.
|
|
if (auto *UseOrDef = dyn_cast<MemoryUseOrDef>(AI))
|
|
UseOrDef->setDefiningAccess(LiveOnEntryDef.get());
|
|
else
|
|
Accesses->erase(AI);
|
|
AI = Next;
|
|
}
|
|
}
|
|
|
|
MemorySSA::MemorySSA(Function &Func, AliasAnalysis *AA, DominatorTree *DT)
|
|
: AA(nullptr), DT(DT), F(Func), LiveOnEntryDef(nullptr), Walker(nullptr),
|
|
SkipWalker(nullptr), NextID(0) {
|
|
// Build MemorySSA using a batch alias analysis. This reuses the internal
|
|
// state that AA collects during an alias()/getModRefInfo() call. This is
|
|
// safe because there are no CFG changes while building MemorySSA and can
|
|
// significantly reduce the time spent by the compiler in AA, because we will
|
|
// make queries about all the instructions in the Function.
|
|
BatchAAResults BatchAA(*AA);
|
|
buildMemorySSA(BatchAA);
|
|
// Intentionally leave AA to nullptr while building so we don't accidently
|
|
// use non-batch AliasAnalysis.
|
|
this->AA = AA;
|
|
// Also create the walker here.
|
|
getWalker();
|
|
}
|
|
|
|
MemorySSA::~MemorySSA() {
|
|
// Drop all our references
|
|
for (const auto &Pair : PerBlockAccesses)
|
|
for (MemoryAccess &MA : *Pair.second)
|
|
MA.dropAllReferences();
|
|
}
|
|
|
|
MemorySSA::AccessList *MemorySSA::getOrCreateAccessList(const BasicBlock *BB) {
|
|
auto Res = PerBlockAccesses.insert(std::make_pair(BB, nullptr));
|
|
|
|
if (Res.second)
|
|
Res.first->second = llvm::make_unique<AccessList>();
|
|
return Res.first->second.get();
|
|
}
|
|
|
|
MemorySSA::DefsList *MemorySSA::getOrCreateDefsList(const BasicBlock *BB) {
|
|
auto Res = PerBlockDefs.insert(std::make_pair(BB, nullptr));
|
|
|
|
if (Res.second)
|
|
Res.first->second = llvm::make_unique<DefsList>();
|
|
return Res.first->second.get();
|
|
}
|
|
|
|
namespace llvm {
|
|
|
|
/// This class is a batch walker of all MemoryUse's in the program, and points
|
|
/// their defining access at the thing that actually clobbers them. Because it
|
|
/// is a batch walker that touches everything, it does not operate like the
|
|
/// other walkers. This walker is basically performing a top-down SSA renaming
|
|
/// pass, where the version stack is used as the cache. This enables it to be
|
|
/// significantly more time and memory efficient than using the regular walker,
|
|
/// which is walking bottom-up.
|
|
class MemorySSA::OptimizeUses {
|
|
public:
|
|
OptimizeUses(MemorySSA *MSSA, CachingWalker<BatchAAResults> *Walker,
|
|
BatchAAResults *BAA, DominatorTree *DT)
|
|
: MSSA(MSSA), Walker(Walker), AA(BAA), DT(DT) {}
|
|
|
|
void optimizeUses();
|
|
|
|
private:
|
|
/// This represents where a given memorylocation is in the stack.
|
|
struct MemlocStackInfo {
|
|
// This essentially is keeping track of versions of the stack. Whenever
|
|
// the stack changes due to pushes or pops, these versions increase.
|
|
unsigned long StackEpoch;
|
|
unsigned long PopEpoch;
|
|
// This is the lower bound of places on the stack to check. It is equal to
|
|
// the place the last stack walk ended.
|
|
// Note: Correctness depends on this being initialized to 0, which densemap
|
|
// does
|
|
unsigned long LowerBound;
|
|
const BasicBlock *LowerBoundBlock;
|
|
// This is where the last walk for this memory location ended.
|
|
unsigned long LastKill;
|
|
bool LastKillValid;
|
|
Optional<AliasResult> AR;
|
|
};
|
|
|
|
void optimizeUsesInBlock(const BasicBlock *, unsigned long &, unsigned long &,
|
|
SmallVectorImpl<MemoryAccess *> &,
|
|
DenseMap<MemoryLocOrCall, MemlocStackInfo> &);
|
|
|
|
MemorySSA *MSSA;
|
|
CachingWalker<BatchAAResults> *Walker;
|
|
BatchAAResults *AA;
|
|
DominatorTree *DT;
|
|
};
|
|
|
|
} // end namespace llvm
|
|
|
|
/// Optimize the uses in a given block This is basically the SSA renaming
|
|
/// algorithm, with one caveat: We are able to use a single stack for all
|
|
/// MemoryUses. This is because the set of *possible* reaching MemoryDefs is
|
|
/// the same for every MemoryUse. The *actual* clobbering MemoryDef is just
|
|
/// going to be some position in that stack of possible ones.
|
|
///
|
|
/// We track the stack positions that each MemoryLocation needs
|
|
/// to check, and last ended at. This is because we only want to check the
|
|
/// things that changed since last time. The same MemoryLocation should
|
|
/// get clobbered by the same store (getModRefInfo does not use invariantness or
|
|
/// things like this, and if they start, we can modify MemoryLocOrCall to
|
|
/// include relevant data)
|
|
void MemorySSA::OptimizeUses::optimizeUsesInBlock(
|
|
const BasicBlock *BB, unsigned long &StackEpoch, unsigned long &PopEpoch,
|
|
SmallVectorImpl<MemoryAccess *> &VersionStack,
|
|
DenseMap<MemoryLocOrCall, MemlocStackInfo> &LocStackInfo) {
|
|
|
|
/// If no accesses, nothing to do.
|
|
MemorySSA::AccessList *Accesses = MSSA->getWritableBlockAccesses(BB);
|
|
if (Accesses == nullptr)
|
|
return;
|
|
|
|
// Pop everything that doesn't dominate the current block off the stack,
|
|
// increment the PopEpoch to account for this.
|
|
while (true) {
|
|
assert(
|
|
!VersionStack.empty() &&
|
|
"Version stack should have liveOnEntry sentinel dominating everything");
|
|
BasicBlock *BackBlock = VersionStack.back()->getBlock();
|
|
if (DT->dominates(BackBlock, BB))
|
|
break;
|
|
while (VersionStack.back()->getBlock() == BackBlock)
|
|
VersionStack.pop_back();
|
|
++PopEpoch;
|
|
}
|
|
|
|
for (MemoryAccess &MA : *Accesses) {
|
|
auto *MU = dyn_cast<MemoryUse>(&MA);
|
|
if (!MU) {
|
|
VersionStack.push_back(&MA);
|
|
++StackEpoch;
|
|
continue;
|
|
}
|
|
|
|
if (isUseTriviallyOptimizableToLiveOnEntry(*AA, MU->getMemoryInst())) {
|
|
MU->setDefiningAccess(MSSA->getLiveOnEntryDef(), true, None);
|
|
continue;
|
|
}
|
|
|
|
MemoryLocOrCall UseMLOC(MU);
|
|
auto &LocInfo = LocStackInfo[UseMLOC];
|
|
// If the pop epoch changed, it means we've removed stuff from top of
|
|
// stack due to changing blocks. We may have to reset the lower bound or
|
|
// last kill info.
|
|
if (LocInfo.PopEpoch != PopEpoch) {
|
|
LocInfo.PopEpoch = PopEpoch;
|
|
LocInfo.StackEpoch = StackEpoch;
|
|
// If the lower bound was in something that no longer dominates us, we
|
|
// have to reset it.
|
|
// We can't simply track stack size, because the stack may have had
|
|
// pushes/pops in the meantime.
|
|
// XXX: This is non-optimal, but only is slower cases with heavily
|
|
// branching dominator trees. To get the optimal number of queries would
|
|
// be to make lowerbound and lastkill a per-loc stack, and pop it until
|
|
// the top of that stack dominates us. This does not seem worth it ATM.
|
|
// A much cheaper optimization would be to always explore the deepest
|
|
// branch of the dominator tree first. This will guarantee this resets on
|
|
// the smallest set of blocks.
|
|
if (LocInfo.LowerBoundBlock && LocInfo.LowerBoundBlock != BB &&
|
|
!DT->dominates(LocInfo.LowerBoundBlock, BB)) {
|
|
// Reset the lower bound of things to check.
|
|
// TODO: Some day we should be able to reset to last kill, rather than
|
|
// 0.
|
|
LocInfo.LowerBound = 0;
|
|
LocInfo.LowerBoundBlock = VersionStack[0]->getBlock();
|
|
LocInfo.LastKillValid = false;
|
|
}
|
|
} else if (LocInfo.StackEpoch != StackEpoch) {
|
|
// If all that has changed is the StackEpoch, we only have to check the
|
|
// new things on the stack, because we've checked everything before. In
|
|
// this case, the lower bound of things to check remains the same.
|
|
LocInfo.PopEpoch = PopEpoch;
|
|
LocInfo.StackEpoch = StackEpoch;
|
|
}
|
|
if (!LocInfo.LastKillValid) {
|
|
LocInfo.LastKill = VersionStack.size() - 1;
|
|
LocInfo.LastKillValid = true;
|
|
LocInfo.AR = MayAlias;
|
|
}
|
|
|
|
// At this point, we should have corrected last kill and LowerBound to be
|
|
// in bounds.
|
|
assert(LocInfo.LowerBound < VersionStack.size() &&
|
|
"Lower bound out of range");
|
|
assert(LocInfo.LastKill < VersionStack.size() &&
|
|
"Last kill info out of range");
|
|
// In any case, the new upper bound is the top of the stack.
|
|
unsigned long UpperBound = VersionStack.size() - 1;
|
|
|
|
if (UpperBound - LocInfo.LowerBound > MaxCheckLimit) {
|
|
LLVM_DEBUG(dbgs() << "MemorySSA skipping optimization of " << *MU << " ("
|
|
<< *(MU->getMemoryInst()) << ")"
|
|
<< " because there are "
|
|
<< UpperBound - LocInfo.LowerBound
|
|
<< " stores to disambiguate\n");
|
|
// Because we did not walk, LastKill is no longer valid, as this may
|
|
// have been a kill.
|
|
LocInfo.LastKillValid = false;
|
|
continue;
|
|
}
|
|
bool FoundClobberResult = false;
|
|
unsigned UpwardWalkLimit = MaxCheckLimit;
|
|
while (UpperBound > LocInfo.LowerBound) {
|
|
if (isa<MemoryPhi>(VersionStack[UpperBound])) {
|
|
// For phis, use the walker, see where we ended up, go there
|
|
MemoryAccess *Result =
|
|
Walker->getClobberingMemoryAccess(MU, UpwardWalkLimit);
|
|
// We are guaranteed to find it or something is wrong
|
|
while (VersionStack[UpperBound] != Result) {
|
|
assert(UpperBound != 0);
|
|
--UpperBound;
|
|
}
|
|
FoundClobberResult = true;
|
|
break;
|
|
}
|
|
|
|
MemoryDef *MD = cast<MemoryDef>(VersionStack[UpperBound]);
|
|
// If the lifetime of the pointer ends at this instruction, it's live on
|
|
// entry.
|
|
if (!UseMLOC.IsCall && lifetimeEndsAt(MD, UseMLOC.getLoc(), *AA)) {
|
|
// Reset UpperBound to liveOnEntryDef's place in the stack
|
|
UpperBound = 0;
|
|
FoundClobberResult = true;
|
|
LocInfo.AR = MustAlias;
|
|
break;
|
|
}
|
|
ClobberAlias CA = instructionClobbersQuery(MD, MU, UseMLOC, *AA);
|
|
if (CA.IsClobber) {
|
|
FoundClobberResult = true;
|
|
LocInfo.AR = CA.AR;
|
|
break;
|
|
}
|
|
--UpperBound;
|
|
}
|
|
|
|
// Note: Phis always have AliasResult AR set to MayAlias ATM.
|
|
|
|
// At the end of this loop, UpperBound is either a clobber, or lower bound
|
|
// PHI walking may cause it to be < LowerBound, and in fact, < LastKill.
|
|
if (FoundClobberResult || UpperBound < LocInfo.LastKill) {
|
|
// We were last killed now by where we got to
|
|
if (MSSA->isLiveOnEntryDef(VersionStack[UpperBound]))
|
|
LocInfo.AR = None;
|
|
MU->setDefiningAccess(VersionStack[UpperBound], true, LocInfo.AR);
|
|
LocInfo.LastKill = UpperBound;
|
|
} else {
|
|
// Otherwise, we checked all the new ones, and now we know we can get to
|
|
// LastKill.
|
|
MU->setDefiningAccess(VersionStack[LocInfo.LastKill], true, LocInfo.AR);
|
|
}
|
|
LocInfo.LowerBound = VersionStack.size() - 1;
|
|
LocInfo.LowerBoundBlock = BB;
|
|
}
|
|
}
|
|
|
|
/// Optimize uses to point to their actual clobbering definitions.
|
|
void MemorySSA::OptimizeUses::optimizeUses() {
|
|
SmallVector<MemoryAccess *, 16> VersionStack;
|
|
DenseMap<MemoryLocOrCall, MemlocStackInfo> LocStackInfo;
|
|
VersionStack.push_back(MSSA->getLiveOnEntryDef());
|
|
|
|
unsigned long StackEpoch = 1;
|
|
unsigned long PopEpoch = 1;
|
|
// We perform a non-recursive top-down dominator tree walk.
|
|
for (const auto *DomNode : depth_first(DT->getRootNode()))
|
|
optimizeUsesInBlock(DomNode->getBlock(), StackEpoch, PopEpoch, VersionStack,
|
|
LocStackInfo);
|
|
}
|
|
|
|
void MemorySSA::placePHINodes(
|
|
const SmallPtrSetImpl<BasicBlock *> &DefiningBlocks) {
|
|
// Determine where our MemoryPhi's should go
|
|
ForwardIDFCalculator IDFs(*DT);
|
|
IDFs.setDefiningBlocks(DefiningBlocks);
|
|
SmallVector<BasicBlock *, 32> IDFBlocks;
|
|
IDFs.calculate(IDFBlocks);
|
|
|
|
// Now place MemoryPhi nodes.
|
|
for (auto &BB : IDFBlocks)
|
|
createMemoryPhi(BB);
|
|
}
|
|
|
|
void MemorySSA::buildMemorySSA(BatchAAResults &BAA) {
|
|
// We create an access to represent "live on entry", for things like
|
|
// arguments or users of globals, where the memory they use is defined before
|
|
// the beginning of the function. We do not actually insert it into the IR.
|
|
// We do not define a live on exit for the immediate uses, and thus our
|
|
// semantics do *not* imply that something with no immediate uses can simply
|
|
// be removed.
|
|
BasicBlock &StartingPoint = F.getEntryBlock();
|
|
LiveOnEntryDef.reset(new MemoryDef(F.getContext(), nullptr, nullptr,
|
|
&StartingPoint, NextID++));
|
|
|
|
// We maintain lists of memory accesses per-block, trading memory for time. We
|
|
// could just look up the memory access for every possible instruction in the
|
|
// stream.
|
|
SmallPtrSet<BasicBlock *, 32> DefiningBlocks;
|
|
// Go through each block, figure out where defs occur, and chain together all
|
|
// the accesses.
|
|
for (BasicBlock &B : F) {
|
|
bool InsertIntoDef = false;
|
|
AccessList *Accesses = nullptr;
|
|
DefsList *Defs = nullptr;
|
|
for (Instruction &I : B) {
|
|
MemoryUseOrDef *MUD = createNewAccess(&I, &BAA);
|
|
if (!MUD)
|
|
continue;
|
|
|
|
if (!Accesses)
|
|
Accesses = getOrCreateAccessList(&B);
|
|
Accesses->push_back(MUD);
|
|
if (isa<MemoryDef>(MUD)) {
|
|
InsertIntoDef = true;
|
|
if (!Defs)
|
|
Defs = getOrCreateDefsList(&B);
|
|
Defs->push_back(*MUD);
|
|
}
|
|
}
|
|
if (InsertIntoDef)
|
|
DefiningBlocks.insert(&B);
|
|
}
|
|
placePHINodes(DefiningBlocks);
|
|
|
|
// Now do regular SSA renaming on the MemoryDef/MemoryUse. Visited will get
|
|
// filled in with all blocks.
|
|
SmallPtrSet<BasicBlock *, 16> Visited;
|
|
renamePass(DT->getRootNode(), LiveOnEntryDef.get(), Visited);
|
|
|
|
ClobberWalkerBase<BatchAAResults> WalkerBase(this, &BAA, DT);
|
|
CachingWalker<BatchAAResults> WalkerLocal(this, &WalkerBase);
|
|
OptimizeUses(this, &WalkerLocal, &BAA, DT).optimizeUses();
|
|
|
|
// Mark the uses in unreachable blocks as live on entry, so that they go
|
|
// somewhere.
|
|
for (auto &BB : F)
|
|
if (!Visited.count(&BB))
|
|
markUnreachableAsLiveOnEntry(&BB);
|
|
}
|
|
|
|
MemorySSAWalker *MemorySSA::getWalker() { return getWalkerImpl(); }
|
|
|
|
MemorySSA::CachingWalker<AliasAnalysis> *MemorySSA::getWalkerImpl() {
|
|
if (Walker)
|
|
return Walker.get();
|
|
|
|
if (!WalkerBase)
|
|
WalkerBase =
|
|
llvm::make_unique<ClobberWalkerBase<AliasAnalysis>>(this, AA, DT);
|
|
|
|
Walker =
|
|
llvm::make_unique<CachingWalker<AliasAnalysis>>(this, WalkerBase.get());
|
|
return Walker.get();
|
|
}
|
|
|
|
MemorySSAWalker *MemorySSA::getSkipSelfWalker() {
|
|
if (SkipWalker)
|
|
return SkipWalker.get();
|
|
|
|
if (!WalkerBase)
|
|
WalkerBase =
|
|
llvm::make_unique<ClobberWalkerBase<AliasAnalysis>>(this, AA, DT);
|
|
|
|
SkipWalker =
|
|
llvm::make_unique<SkipSelfWalker<AliasAnalysis>>(this, WalkerBase.get());
|
|
return SkipWalker.get();
|
|
}
|
|
|
|
|
|
// This is a helper function used by the creation routines. It places NewAccess
|
|
// into the access and defs lists for a given basic block, at the given
|
|
// insertion point.
|
|
void MemorySSA::insertIntoListsForBlock(MemoryAccess *NewAccess,
|
|
const BasicBlock *BB,
|
|
InsertionPlace Point) {
|
|
auto *Accesses = getOrCreateAccessList(BB);
|
|
if (Point == Beginning) {
|
|
// If it's a phi node, it goes first, otherwise, it goes after any phi
|
|
// nodes.
|
|
if (isa<MemoryPhi>(NewAccess)) {
|
|
Accesses->push_front(NewAccess);
|
|
auto *Defs = getOrCreateDefsList(BB);
|
|
Defs->push_front(*NewAccess);
|
|
} else {
|
|
auto AI = find_if_not(
|
|
*Accesses, [](const MemoryAccess &MA) { return isa<MemoryPhi>(MA); });
|
|
Accesses->insert(AI, NewAccess);
|
|
if (!isa<MemoryUse>(NewAccess)) {
|
|
auto *Defs = getOrCreateDefsList(BB);
|
|
auto DI = find_if_not(
|
|
*Defs, [](const MemoryAccess &MA) { return isa<MemoryPhi>(MA); });
|
|
Defs->insert(DI, *NewAccess);
|
|
}
|
|
}
|
|
} else {
|
|
Accesses->push_back(NewAccess);
|
|
if (!isa<MemoryUse>(NewAccess)) {
|
|
auto *Defs = getOrCreateDefsList(BB);
|
|
Defs->push_back(*NewAccess);
|
|
}
|
|
}
|
|
BlockNumberingValid.erase(BB);
|
|
}
|
|
|
|
void MemorySSA::insertIntoListsBefore(MemoryAccess *What, const BasicBlock *BB,
|
|
AccessList::iterator InsertPt) {
|
|
auto *Accesses = getWritableBlockAccesses(BB);
|
|
bool WasEnd = InsertPt == Accesses->end();
|
|
Accesses->insert(AccessList::iterator(InsertPt), What);
|
|
if (!isa<MemoryUse>(What)) {
|
|
auto *Defs = getOrCreateDefsList(BB);
|
|
// If we got asked to insert at the end, we have an easy job, just shove it
|
|
// at the end. If we got asked to insert before an existing def, we also get
|
|
// an iterator. If we got asked to insert before a use, we have to hunt for
|
|
// the next def.
|
|
if (WasEnd) {
|
|
Defs->push_back(*What);
|
|
} else if (isa<MemoryDef>(InsertPt)) {
|
|
Defs->insert(InsertPt->getDefsIterator(), *What);
|
|
} else {
|
|
while (InsertPt != Accesses->end() && !isa<MemoryDef>(InsertPt))
|
|
++InsertPt;
|
|
// Either we found a def, or we are inserting at the end
|
|
if (InsertPt == Accesses->end())
|
|
Defs->push_back(*What);
|
|
else
|
|
Defs->insert(InsertPt->getDefsIterator(), *What);
|
|
}
|
|
}
|
|
BlockNumberingValid.erase(BB);
|
|
}
|
|
|
|
void MemorySSA::prepareForMoveTo(MemoryAccess *What, BasicBlock *BB) {
|
|
// Keep it in the lookup tables, remove from the lists
|
|
removeFromLists(What, false);
|
|
|
|
// Note that moving should implicitly invalidate the optimized state of a
|
|
// MemoryUse (and Phis can't be optimized). However, it doesn't do so for a
|
|
// MemoryDef.
|
|
if (auto *MD = dyn_cast<MemoryDef>(What))
|
|
MD->resetOptimized();
|
|
What->setBlock(BB);
|
|
}
|
|
|
|
// Move What before Where in the IR. The end result is that What will belong to
|
|
// the right lists and have the right Block set, but will not otherwise be
|
|
// correct. It will not have the right defining access, and if it is a def,
|
|
// things below it will not properly be updated.
|
|
void MemorySSA::moveTo(MemoryUseOrDef *What, BasicBlock *BB,
|
|
AccessList::iterator Where) {
|
|
prepareForMoveTo(What, BB);
|
|
insertIntoListsBefore(What, BB, Where);
|
|
}
|
|
|
|
void MemorySSA::moveTo(MemoryAccess *What, BasicBlock *BB,
|
|
InsertionPlace Point) {
|
|
if (isa<MemoryPhi>(What)) {
|
|
assert(Point == Beginning &&
|
|
"Can only move a Phi at the beginning of the block");
|
|
// Update lookup table entry
|
|
ValueToMemoryAccess.erase(What->getBlock());
|
|
bool Inserted = ValueToMemoryAccess.insert({BB, What}).second;
|
|
(void)Inserted;
|
|
assert(Inserted && "Cannot move a Phi to a block that already has one");
|
|
}
|
|
|
|
prepareForMoveTo(What, BB);
|
|
insertIntoListsForBlock(What, BB, Point);
|
|
}
|
|
|
|
MemoryPhi *MemorySSA::createMemoryPhi(BasicBlock *BB) {
|
|
assert(!getMemoryAccess(BB) && "MemoryPhi already exists for this BB");
|
|
MemoryPhi *Phi = new MemoryPhi(BB->getContext(), BB, NextID++);
|
|
// Phi's always are placed at the front of the block.
|
|
insertIntoListsForBlock(Phi, BB, Beginning);
|
|
ValueToMemoryAccess[BB] = Phi;
|
|
return Phi;
|
|
}
|
|
|
|
MemoryUseOrDef *MemorySSA::createDefinedAccess(Instruction *I,
|
|
MemoryAccess *Definition,
|
|
const MemoryUseOrDef *Template) {
|
|
assert(!isa<PHINode>(I) && "Cannot create a defined access for a PHI");
|
|
MemoryUseOrDef *NewAccess = createNewAccess(I, AA, Template);
|
|
assert(
|
|
NewAccess != nullptr &&
|
|
"Tried to create a memory access for a non-memory touching instruction");
|
|
NewAccess->setDefiningAccess(Definition);
|
|
return NewAccess;
|
|
}
|
|
|
|
// Return true if the instruction has ordering constraints.
|
|
// Note specifically that this only considers stores and loads
|
|
// because others are still considered ModRef by getModRefInfo.
|
|
static inline bool isOrdered(const Instruction *I) {
|
|
if (auto *SI = dyn_cast<StoreInst>(I)) {
|
|
if (!SI->isUnordered())
|
|
return true;
|
|
} else if (auto *LI = dyn_cast<LoadInst>(I)) {
|
|
if (!LI->isUnordered())
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// Helper function to create new memory accesses
|
|
template <typename AliasAnalysisType>
|
|
MemoryUseOrDef *MemorySSA::createNewAccess(Instruction *I,
|
|
AliasAnalysisType *AAP,
|
|
const MemoryUseOrDef *Template) {
|
|
// The assume intrinsic has a control dependency which we model by claiming
|
|
// that it writes arbitrarily. Ignore that fake memory dependency here.
|
|
// FIXME: Replace this special casing with a more accurate modelling of
|
|
// assume's control dependency.
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
|
|
if (II->getIntrinsicID() == Intrinsic::assume)
|
|
return nullptr;
|
|
|
|
bool Def, Use;
|
|
if (Template) {
|
|
Def = dyn_cast_or_null<MemoryDef>(Template) != nullptr;
|
|
Use = dyn_cast_or_null<MemoryUse>(Template) != nullptr;
|
|
#if !defined(NDEBUG)
|
|
ModRefInfo ModRef = AAP->getModRefInfo(I, None);
|
|
bool DefCheck, UseCheck;
|
|
DefCheck = isModSet(ModRef) || isOrdered(I);
|
|
UseCheck = isRefSet(ModRef);
|
|
assert(Def == DefCheck && (Def || Use == UseCheck) && "Invalid template");
|
|
#endif
|
|
} else {
|
|
// Find out what affect this instruction has on memory.
|
|
ModRefInfo ModRef = AAP->getModRefInfo(I, None);
|
|
// The isOrdered check is used to ensure that volatiles end up as defs
|
|
// (atomics end up as ModRef right now anyway). Until we separate the
|
|
// ordering chain from the memory chain, this enables people to see at least
|
|
// some relative ordering to volatiles. Note that getClobberingMemoryAccess
|
|
// will still give an answer that bypasses other volatile loads. TODO:
|
|
// Separate memory aliasing and ordering into two different chains so that
|
|
// we can precisely represent both "what memory will this read/write/is
|
|
// clobbered by" and "what instructions can I move this past".
|
|
Def = isModSet(ModRef) || isOrdered(I);
|
|
Use = isRefSet(ModRef);
|
|
}
|
|
|
|
// It's possible for an instruction to not modify memory at all. During
|
|
// construction, we ignore them.
|
|
if (!Def && !Use)
|
|
return nullptr;
|
|
|
|
MemoryUseOrDef *MUD;
|
|
if (Def)
|
|
MUD = new MemoryDef(I->getContext(), nullptr, I, I->getParent(), NextID++);
|
|
else
|
|
MUD = new MemoryUse(I->getContext(), nullptr, I, I->getParent());
|
|
ValueToMemoryAccess[I] = MUD;
|
|
return MUD;
|
|
}
|
|
|
|
/// Returns true if \p Replacer dominates \p Replacee .
|
|
bool MemorySSA::dominatesUse(const MemoryAccess *Replacer,
|
|
const MemoryAccess *Replacee) const {
|
|
if (isa<MemoryUseOrDef>(Replacee))
|
|
return DT->dominates(Replacer->getBlock(), Replacee->getBlock());
|
|
const auto *MP = cast<MemoryPhi>(Replacee);
|
|
// For a phi node, the use occurs in the predecessor block of the phi node.
|
|
// Since we may occur multiple times in the phi node, we have to check each
|
|
// operand to ensure Replacer dominates each operand where Replacee occurs.
|
|
for (const Use &Arg : MP->operands()) {
|
|
if (Arg.get() != Replacee &&
|
|
!DT->dominates(Replacer->getBlock(), MP->getIncomingBlock(Arg)))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// Properly remove \p MA from all of MemorySSA's lookup tables.
|
|
void MemorySSA::removeFromLookups(MemoryAccess *MA) {
|
|
assert(MA->use_empty() &&
|
|
"Trying to remove memory access that still has uses");
|
|
BlockNumbering.erase(MA);
|
|
if (auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
|
|
MUD->setDefiningAccess(nullptr);
|
|
// Invalidate our walker's cache if necessary
|
|
if (!isa<MemoryUse>(MA))
|
|
getWalker()->invalidateInfo(MA);
|
|
|
|
Value *MemoryInst;
|
|
if (const auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
|
|
MemoryInst = MUD->getMemoryInst();
|
|
else
|
|
MemoryInst = MA->getBlock();
|
|
|
|
auto VMA = ValueToMemoryAccess.find(MemoryInst);
|
|
if (VMA->second == MA)
|
|
ValueToMemoryAccess.erase(VMA);
|
|
}
|
|
|
|
/// Properly remove \p MA from all of MemorySSA's lists.
|
|
///
|
|
/// Because of the way the intrusive list and use lists work, it is important to
|
|
/// do removal in the right order.
|
|
/// ShouldDelete defaults to true, and will cause the memory access to also be
|
|
/// deleted, not just removed.
|
|
void MemorySSA::removeFromLists(MemoryAccess *MA, bool ShouldDelete) {
|
|
BasicBlock *BB = MA->getBlock();
|
|
// The access list owns the reference, so we erase it from the non-owning list
|
|
// first.
|
|
if (!isa<MemoryUse>(MA)) {
|
|
auto DefsIt = PerBlockDefs.find(BB);
|
|
std::unique_ptr<DefsList> &Defs = DefsIt->second;
|
|
Defs->remove(*MA);
|
|
if (Defs->empty())
|
|
PerBlockDefs.erase(DefsIt);
|
|
}
|
|
|
|
// The erase call here will delete it. If we don't want it deleted, we call
|
|
// remove instead.
|
|
auto AccessIt = PerBlockAccesses.find(BB);
|
|
std::unique_ptr<AccessList> &Accesses = AccessIt->second;
|
|
if (ShouldDelete)
|
|
Accesses->erase(MA);
|
|
else
|
|
Accesses->remove(MA);
|
|
|
|
if (Accesses->empty()) {
|
|
PerBlockAccesses.erase(AccessIt);
|
|
BlockNumberingValid.erase(BB);
|
|
}
|
|
}
|
|
|
|
void MemorySSA::print(raw_ostream &OS) const {
|
|
MemorySSAAnnotatedWriter Writer(this);
|
|
F.print(OS, &Writer);
|
|
}
|
|
|
|
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
|
|
LLVM_DUMP_METHOD void MemorySSA::dump() const { print(dbgs()); }
|
|
#endif
|
|
|
|
void MemorySSA::verifyMemorySSA() const {
|
|
verifyDefUses(F);
|
|
verifyDomination(F);
|
|
verifyOrdering(F);
|
|
verifyDominationNumbers(F);
|
|
// Previously, the verification used to also verify that the clobberingAccess
|
|
// cached by MemorySSA is the same as the clobberingAccess found at a later
|
|
// query to AA. This does not hold true in general due to the current fragility
|
|
// of BasicAA which has arbitrary caps on the things it analyzes before giving
|
|
// up. As a result, transformations that are correct, will lead to BasicAA
|
|
// returning different Alias answers before and after that transformation.
|
|
// Invalidating MemorySSA is not an option, as the results in BasicAA can be so
|
|
// random, in the worst case we'd need to rebuild MemorySSA from scratch after
|
|
// every transformation, which defeats the purpose of using it. For such an
|
|
// example, see test4 added in D51960.
|
|
}
|
|
|
|
/// Verify that all of the blocks we believe to have valid domination numbers
|
|
/// actually have valid domination numbers.
|
|
void MemorySSA::verifyDominationNumbers(const Function &F) const {
|
|
#ifndef NDEBUG
|
|
if (BlockNumberingValid.empty())
|
|
return;
|
|
|
|
SmallPtrSet<const BasicBlock *, 16> ValidBlocks = BlockNumberingValid;
|
|
for (const BasicBlock &BB : F) {
|
|
if (!ValidBlocks.count(&BB))
|
|
continue;
|
|
|
|
ValidBlocks.erase(&BB);
|
|
|
|
const AccessList *Accesses = getBlockAccesses(&BB);
|
|
// It's correct to say an empty block has valid numbering.
|
|
if (!Accesses)
|
|
continue;
|
|
|
|
// Block numbering starts at 1.
|
|
unsigned long LastNumber = 0;
|
|
for (const MemoryAccess &MA : *Accesses) {
|
|
auto ThisNumberIter = BlockNumbering.find(&MA);
|
|
assert(ThisNumberIter != BlockNumbering.end() &&
|
|
"MemoryAccess has no domination number in a valid block!");
|
|
|
|
unsigned long ThisNumber = ThisNumberIter->second;
|
|
assert(ThisNumber > LastNumber &&
|
|
"Domination numbers should be strictly increasing!");
|
|
LastNumber = ThisNumber;
|
|
}
|
|
}
|
|
|
|
assert(ValidBlocks.empty() &&
|
|
"All valid BasicBlocks should exist in F -- dangling pointers?");
|
|
#endif
|
|
}
|
|
|
|
/// Verify that the order and existence of MemoryAccesses matches the
|
|
/// order and existence of memory affecting instructions.
|
|
void MemorySSA::verifyOrdering(Function &F) const {
|
|
#ifndef NDEBUG
|
|
// Walk all the blocks, comparing what the lookups think and what the access
|
|
// lists think, as well as the order in the blocks vs the order in the access
|
|
// lists.
|
|
SmallVector<MemoryAccess *, 32> ActualAccesses;
|
|
SmallVector<MemoryAccess *, 32> ActualDefs;
|
|
for (BasicBlock &B : F) {
|
|
const AccessList *AL = getBlockAccesses(&B);
|
|
const auto *DL = getBlockDefs(&B);
|
|
MemoryAccess *Phi = getMemoryAccess(&B);
|
|
if (Phi) {
|
|
ActualAccesses.push_back(Phi);
|
|
ActualDefs.push_back(Phi);
|
|
}
|
|
|
|
for (Instruction &I : B) {
|
|
MemoryAccess *MA = getMemoryAccess(&I);
|
|
assert((!MA || (AL && (isa<MemoryUse>(MA) || DL))) &&
|
|
"We have memory affecting instructions "
|
|
"in this block but they are not in the "
|
|
"access list or defs list");
|
|
if (MA) {
|
|
ActualAccesses.push_back(MA);
|
|
if (isa<MemoryDef>(MA))
|
|
ActualDefs.push_back(MA);
|
|
}
|
|
}
|
|
// Either we hit the assert, really have no accesses, or we have both
|
|
// accesses and an access list.
|
|
// Same with defs.
|
|
if (!AL && !DL)
|
|
continue;
|
|
assert(AL->size() == ActualAccesses.size() &&
|
|
"We don't have the same number of accesses in the block as on the "
|
|
"access list");
|
|
assert((DL || ActualDefs.size() == 0) &&
|
|
"Either we should have a defs list, or we should have no defs");
|
|
assert((!DL || DL->size() == ActualDefs.size()) &&
|
|
"We don't have the same number of defs in the block as on the "
|
|
"def list");
|
|
auto ALI = AL->begin();
|
|
auto AAI = ActualAccesses.begin();
|
|
while (ALI != AL->end() && AAI != ActualAccesses.end()) {
|
|
assert(&*ALI == *AAI && "Not the same accesses in the same order");
|
|
++ALI;
|
|
++AAI;
|
|
}
|
|
ActualAccesses.clear();
|
|
if (DL) {
|
|
auto DLI = DL->begin();
|
|
auto ADI = ActualDefs.begin();
|
|
while (DLI != DL->end() && ADI != ActualDefs.end()) {
|
|
assert(&*DLI == *ADI && "Not the same defs in the same order");
|
|
++DLI;
|
|
++ADI;
|
|
}
|
|
}
|
|
ActualDefs.clear();
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/// Verify the domination properties of MemorySSA by checking that each
|
|
/// definition dominates all of its uses.
|
|
void MemorySSA::verifyDomination(Function &F) const {
|
|
#ifndef NDEBUG
|
|
for (BasicBlock &B : F) {
|
|
// Phi nodes are attached to basic blocks
|
|
if (MemoryPhi *MP = getMemoryAccess(&B))
|
|
for (const Use &U : MP->uses())
|
|
assert(dominates(MP, U) && "Memory PHI does not dominate it's uses");
|
|
|
|
for (Instruction &I : B) {
|
|
MemoryAccess *MD = dyn_cast_or_null<MemoryDef>(getMemoryAccess(&I));
|
|
if (!MD)
|
|
continue;
|
|
|
|
for (const Use &U : MD->uses())
|
|
assert(dominates(MD, U) && "Memory Def does not dominate it's uses");
|
|
}
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/// Verify the def-use lists in MemorySSA, by verifying that \p Use
|
|
/// appears in the use list of \p Def.
|
|
void MemorySSA::verifyUseInDefs(MemoryAccess *Def, MemoryAccess *Use) const {
|
|
#ifndef NDEBUG
|
|
// The live on entry use may cause us to get a NULL def here
|
|
if (!Def)
|
|
assert(isLiveOnEntryDef(Use) &&
|
|
"Null def but use not point to live on entry def");
|
|
else
|
|
assert(is_contained(Def->users(), Use) &&
|
|
"Did not find use in def's use list");
|
|
#endif
|
|
}
|
|
|
|
/// Verify the immediate use information, by walking all the memory
|
|
/// accesses and verifying that, for each use, it appears in the
|
|
/// appropriate def's use list
|
|
void MemorySSA::verifyDefUses(Function &F) const {
|
|
#ifndef NDEBUG
|
|
for (BasicBlock &B : F) {
|
|
// Phi nodes are attached to basic blocks
|
|
if (MemoryPhi *Phi = getMemoryAccess(&B)) {
|
|
assert(Phi->getNumOperands() == static_cast<unsigned>(std::distance(
|
|
pred_begin(&B), pred_end(&B))) &&
|
|
"Incomplete MemoryPhi Node");
|
|
for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I) {
|
|
verifyUseInDefs(Phi->getIncomingValue(I), Phi);
|
|
assert(find(predecessors(&B), Phi->getIncomingBlock(I)) !=
|
|
pred_end(&B) &&
|
|
"Incoming phi block not a block predecessor");
|
|
}
|
|
}
|
|
|
|
for (Instruction &I : B) {
|
|
if (MemoryUseOrDef *MA = getMemoryAccess(&I)) {
|
|
verifyUseInDefs(MA->getDefiningAccess(), MA);
|
|
}
|
|
}
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/// Perform a local numbering on blocks so that instruction ordering can be
|
|
/// determined in constant time.
|
|
/// TODO: We currently just number in order. If we numbered by N, we could
|
|
/// allow at least N-1 sequences of insertBefore or insertAfter (and at least
|
|
/// log2(N) sequences of mixed before and after) without needing to invalidate
|
|
/// the numbering.
|
|
void MemorySSA::renumberBlock(const BasicBlock *B) const {
|
|
// The pre-increment ensures the numbers really start at 1.
|
|
unsigned long CurrentNumber = 0;
|
|
const AccessList *AL = getBlockAccesses(B);
|
|
assert(AL != nullptr && "Asking to renumber an empty block");
|
|
for (const auto &I : *AL)
|
|
BlockNumbering[&I] = ++CurrentNumber;
|
|
BlockNumberingValid.insert(B);
|
|
}
|
|
|
|
/// Determine, for two memory accesses in the same block,
|
|
/// whether \p Dominator dominates \p Dominatee.
|
|
/// \returns True if \p Dominator dominates \p Dominatee.
|
|
bool MemorySSA::locallyDominates(const MemoryAccess *Dominator,
|
|
const MemoryAccess *Dominatee) const {
|
|
const BasicBlock *DominatorBlock = Dominator->getBlock();
|
|
|
|
assert((DominatorBlock == Dominatee->getBlock()) &&
|
|
"Asking for local domination when accesses are in different blocks!");
|
|
// A node dominates itself.
|
|
if (Dominatee == Dominator)
|
|
return true;
|
|
|
|
// When Dominatee is defined on function entry, it is not dominated by another
|
|
// memory access.
|
|
if (isLiveOnEntryDef(Dominatee))
|
|
return false;
|
|
|
|
// When Dominator is defined on function entry, it dominates the other memory
|
|
// access.
|
|
if (isLiveOnEntryDef(Dominator))
|
|
return true;
|
|
|
|
if (!BlockNumberingValid.count(DominatorBlock))
|
|
renumberBlock(DominatorBlock);
|
|
|
|
unsigned long DominatorNum = BlockNumbering.lookup(Dominator);
|
|
// All numbers start with 1
|
|
assert(DominatorNum != 0 && "Block was not numbered properly");
|
|
unsigned long DominateeNum = BlockNumbering.lookup(Dominatee);
|
|
assert(DominateeNum != 0 && "Block was not numbered properly");
|
|
return DominatorNum < DominateeNum;
|
|
}
|
|
|
|
bool MemorySSA::dominates(const MemoryAccess *Dominator,
|
|
const MemoryAccess *Dominatee) const {
|
|
if (Dominator == Dominatee)
|
|
return true;
|
|
|
|
if (isLiveOnEntryDef(Dominatee))
|
|
return false;
|
|
|
|
if (Dominator->getBlock() != Dominatee->getBlock())
|
|
return DT->dominates(Dominator->getBlock(), Dominatee->getBlock());
|
|
return locallyDominates(Dominator, Dominatee);
|
|
}
|
|
|
|
bool MemorySSA::dominates(const MemoryAccess *Dominator,
|
|
const Use &Dominatee) const {
|
|
if (MemoryPhi *MP = dyn_cast<MemoryPhi>(Dominatee.getUser())) {
|
|
BasicBlock *UseBB = MP->getIncomingBlock(Dominatee);
|
|
// The def must dominate the incoming block of the phi.
|
|
if (UseBB != Dominator->getBlock())
|
|
return DT->dominates(Dominator->getBlock(), UseBB);
|
|
// If the UseBB and the DefBB are the same, compare locally.
|
|
return locallyDominates(Dominator, cast<MemoryAccess>(Dominatee));
|
|
}
|
|
// If it's not a PHI node use, the normal dominates can already handle it.
|
|
return dominates(Dominator, cast<MemoryAccess>(Dominatee.getUser()));
|
|
}
|
|
|
|
const static char LiveOnEntryStr[] = "liveOnEntry";
|
|
|
|
void MemoryAccess::print(raw_ostream &OS) const {
|
|
switch (getValueID()) {
|
|
case MemoryPhiVal: return static_cast<const MemoryPhi *>(this)->print(OS);
|
|
case MemoryDefVal: return static_cast<const MemoryDef *>(this)->print(OS);
|
|
case MemoryUseVal: return static_cast<const MemoryUse *>(this)->print(OS);
|
|
}
|
|
llvm_unreachable("invalid value id");
|
|
}
|
|
|
|
void MemoryDef::print(raw_ostream &OS) const {
|
|
MemoryAccess *UO = getDefiningAccess();
|
|
|
|
auto printID = [&OS](MemoryAccess *A) {
|
|
if (A && A->getID())
|
|
OS << A->getID();
|
|
else
|
|
OS << LiveOnEntryStr;
|
|
};
|
|
|
|
OS << getID() << " = MemoryDef(";
|
|
printID(UO);
|
|
OS << ")";
|
|
|
|
if (isOptimized()) {
|
|
OS << "->";
|
|
printID(getOptimized());
|
|
|
|
if (Optional<AliasResult> AR = getOptimizedAccessType())
|
|
OS << " " << *AR;
|
|
}
|
|
}
|
|
|
|
void MemoryPhi::print(raw_ostream &OS) const {
|
|
bool First = true;
|
|
OS << getID() << " = MemoryPhi(";
|
|
for (const auto &Op : operands()) {
|
|
BasicBlock *BB = getIncomingBlock(Op);
|
|
MemoryAccess *MA = cast<MemoryAccess>(Op);
|
|
if (!First)
|
|
OS << ',';
|
|
else
|
|
First = false;
|
|
|
|
OS << '{';
|
|
if (BB->hasName())
|
|
OS << BB->getName();
|
|
else
|
|
BB->printAsOperand(OS, false);
|
|
OS << ',';
|
|
if (unsigned ID = MA->getID())
|
|
OS << ID;
|
|
else
|
|
OS << LiveOnEntryStr;
|
|
OS << '}';
|
|
}
|
|
OS << ')';
|
|
}
|
|
|
|
void MemoryUse::print(raw_ostream &OS) const {
|
|
MemoryAccess *UO = getDefiningAccess();
|
|
OS << "MemoryUse(";
|
|
if (UO && UO->getID())
|
|
OS << UO->getID();
|
|
else
|
|
OS << LiveOnEntryStr;
|
|
OS << ')';
|
|
|
|
if (Optional<AliasResult> AR = getOptimizedAccessType())
|
|
OS << " " << *AR;
|
|
}
|
|
|
|
void MemoryAccess::dump() const {
|
|
// Cannot completely remove virtual function even in release mode.
|
|
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
|
|
print(dbgs());
|
|
dbgs() << "\n";
|
|
#endif
|
|
}
|
|
|
|
char MemorySSAPrinterLegacyPass::ID = 0;
|
|
|
|
MemorySSAPrinterLegacyPass::MemorySSAPrinterLegacyPass() : FunctionPass(ID) {
|
|
initializeMemorySSAPrinterLegacyPassPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
void MemorySSAPrinterLegacyPass::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.setPreservesAll();
|
|
AU.addRequired<MemorySSAWrapperPass>();
|
|
}
|
|
|
|
bool MemorySSAPrinterLegacyPass::runOnFunction(Function &F) {
|
|
auto &MSSA = getAnalysis<MemorySSAWrapperPass>().getMSSA();
|
|
MSSA.print(dbgs());
|
|
if (VerifyMemorySSA)
|
|
MSSA.verifyMemorySSA();
|
|
return false;
|
|
}
|
|
|
|
AnalysisKey MemorySSAAnalysis::Key;
|
|
|
|
MemorySSAAnalysis::Result MemorySSAAnalysis::run(Function &F,
|
|
FunctionAnalysisManager &AM) {
|
|
auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
|
|
auto &AA = AM.getResult<AAManager>(F);
|
|
return MemorySSAAnalysis::Result(llvm::make_unique<MemorySSA>(F, &AA, &DT));
|
|
}
|
|
|
|
bool MemorySSAAnalysis::Result::invalidate(
|
|
Function &F, const PreservedAnalyses &PA,
|
|
FunctionAnalysisManager::Invalidator &Inv) {
|
|
auto PAC = PA.getChecker<MemorySSAAnalysis>();
|
|
return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>()) ||
|
|
Inv.invalidate<AAManager>(F, PA) ||
|
|
Inv.invalidate<DominatorTreeAnalysis>(F, PA);
|
|
}
|
|
|
|
PreservedAnalyses MemorySSAPrinterPass::run(Function &F,
|
|
FunctionAnalysisManager &AM) {
|
|
OS << "MemorySSA for function: " << F.getName() << "\n";
|
|
AM.getResult<MemorySSAAnalysis>(F).getMSSA().print(OS);
|
|
|
|
return PreservedAnalyses::all();
|
|
}
|
|
|
|
PreservedAnalyses MemorySSAVerifierPass::run(Function &F,
|
|
FunctionAnalysisManager &AM) {
|
|
AM.getResult<MemorySSAAnalysis>(F).getMSSA().verifyMemorySSA();
|
|
|
|
return PreservedAnalyses::all();
|
|
}
|
|
|
|
char MemorySSAWrapperPass::ID = 0;
|
|
|
|
MemorySSAWrapperPass::MemorySSAWrapperPass() : FunctionPass(ID) {
|
|
initializeMemorySSAWrapperPassPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
void MemorySSAWrapperPass::releaseMemory() { MSSA.reset(); }
|
|
|
|
void MemorySSAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.setPreservesAll();
|
|
AU.addRequiredTransitive<DominatorTreeWrapperPass>();
|
|
AU.addRequiredTransitive<AAResultsWrapperPass>();
|
|
}
|
|
|
|
bool MemorySSAWrapperPass::runOnFunction(Function &F) {
|
|
auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
|
|
auto &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
|
|
MSSA.reset(new MemorySSA(F, &AA, &DT));
|
|
return false;
|
|
}
|
|
|
|
void MemorySSAWrapperPass::verifyAnalysis() const { MSSA->verifyMemorySSA(); }
|
|
|
|
void MemorySSAWrapperPass::print(raw_ostream &OS, const Module *M) const {
|
|
MSSA->print(OS);
|
|
}
|
|
|
|
MemorySSAWalker::MemorySSAWalker(MemorySSA *M) : MSSA(M) {}
|
|
|
|
/// Walk the use-def chains starting at \p StartingAccess and find
|
|
/// the MemoryAccess that actually clobbers Loc.
|
|
///
|
|
/// \returns our clobbering memory access
|
|
template <typename AliasAnalysisType>
|
|
MemoryAccess *
|
|
MemorySSA::ClobberWalkerBase<AliasAnalysisType>::getClobberingMemoryAccessBase(
|
|
MemoryAccess *StartingAccess, const MemoryLocation &Loc,
|
|
unsigned &UpwardWalkLimit) {
|
|
if (isa<MemoryPhi>(StartingAccess))
|
|
return StartingAccess;
|
|
|
|
auto *StartingUseOrDef = cast<MemoryUseOrDef>(StartingAccess);
|
|
if (MSSA->isLiveOnEntryDef(StartingUseOrDef))
|
|
return StartingUseOrDef;
|
|
|
|
Instruction *I = StartingUseOrDef->getMemoryInst();
|
|
|
|
// Conservatively, fences are always clobbers, so don't perform the walk if we
|
|
// hit a fence.
|
|
if (!isa<CallBase>(I) && I->isFenceLike())
|
|
return StartingUseOrDef;
|
|
|
|
UpwardsMemoryQuery Q;
|
|
Q.OriginalAccess = StartingUseOrDef;
|
|
Q.StartingLoc = Loc;
|
|
Q.Inst = I;
|
|
Q.IsCall = false;
|
|
|
|
// Unlike the other function, do not walk to the def of a def, because we are
|
|
// handed something we already believe is the clobbering access.
|
|
// We never set SkipSelf to true in Q in this method.
|
|
MemoryAccess *DefiningAccess = isa<MemoryUse>(StartingUseOrDef)
|
|
? StartingUseOrDef->getDefiningAccess()
|
|
: StartingUseOrDef;
|
|
|
|
MemoryAccess *Clobber =
|
|
Walker.findClobber(DefiningAccess, Q, UpwardWalkLimit);
|
|
LLVM_DEBUG(dbgs() << "Starting Memory SSA clobber for " << *I << " is ");
|
|
LLVM_DEBUG(dbgs() << *StartingUseOrDef << "\n");
|
|
LLVM_DEBUG(dbgs() << "Final Memory SSA clobber for " << *I << " is ");
|
|
LLVM_DEBUG(dbgs() << *Clobber << "\n");
|
|
return Clobber;
|
|
}
|
|
|
|
template <typename AliasAnalysisType>
|
|
MemoryAccess *
|
|
MemorySSA::ClobberWalkerBase<AliasAnalysisType>::getClobberingMemoryAccessBase(
|
|
MemoryAccess *MA, unsigned &UpwardWalkLimit, bool SkipSelf) {
|
|
auto *StartingAccess = dyn_cast<MemoryUseOrDef>(MA);
|
|
// If this is a MemoryPhi, we can't do anything.
|
|
if (!StartingAccess)
|
|
return MA;
|
|
|
|
bool IsOptimized = false;
|
|
|
|
// If this is an already optimized use or def, return the optimized result.
|
|
// Note: Currently, we store the optimized def result in a separate field,
|
|
// since we can't use the defining access.
|
|
if (StartingAccess->isOptimized()) {
|
|
if (!SkipSelf || !isa<MemoryDef>(StartingAccess))
|
|
return StartingAccess->getOptimized();
|
|
IsOptimized = true;
|
|
}
|
|
|
|
const Instruction *I = StartingAccess->getMemoryInst();
|
|
// We can't sanely do anything with a fence, since they conservatively clobber
|
|
// all memory, and have no locations to get pointers from to try to
|
|
// disambiguate.
|
|
if (!isa<CallBase>(I) && I->isFenceLike())
|
|
return StartingAccess;
|
|
|
|
UpwardsMemoryQuery Q(I, StartingAccess);
|
|
|
|
if (isUseTriviallyOptimizableToLiveOnEntry(*Walker.getAA(), I)) {
|
|
MemoryAccess *LiveOnEntry = MSSA->getLiveOnEntryDef();
|
|
StartingAccess->setOptimized(LiveOnEntry);
|
|
StartingAccess->setOptimizedAccessType(None);
|
|
return LiveOnEntry;
|
|
}
|
|
|
|
MemoryAccess *OptimizedAccess;
|
|
if (!IsOptimized) {
|
|
// Start with the thing we already think clobbers this location
|
|
MemoryAccess *DefiningAccess = StartingAccess->getDefiningAccess();
|
|
|
|
// At this point, DefiningAccess may be the live on entry def.
|
|
// If it is, we will not get a better result.
|
|
if (MSSA->isLiveOnEntryDef(DefiningAccess)) {
|
|
StartingAccess->setOptimized(DefiningAccess);
|
|
StartingAccess->setOptimizedAccessType(None);
|
|
return DefiningAccess;
|
|
}
|
|
|
|
OptimizedAccess = Walker.findClobber(DefiningAccess, Q, UpwardWalkLimit);
|
|
StartingAccess->setOptimized(OptimizedAccess);
|
|
if (MSSA->isLiveOnEntryDef(OptimizedAccess))
|
|
StartingAccess->setOptimizedAccessType(None);
|
|
else if (Q.AR == MustAlias)
|
|
StartingAccess->setOptimizedAccessType(MustAlias);
|
|
} else
|
|
OptimizedAccess = StartingAccess->getOptimized();
|
|
|
|
LLVM_DEBUG(dbgs() << "Starting Memory SSA clobber for " << *I << " is ");
|
|
LLVM_DEBUG(dbgs() << *StartingAccess << "\n");
|
|
LLVM_DEBUG(dbgs() << "Optimized Memory SSA clobber for " << *I << " is ");
|
|
LLVM_DEBUG(dbgs() << *OptimizedAccess << "\n");
|
|
|
|
MemoryAccess *Result;
|
|
if (SkipSelf && isa<MemoryPhi>(OptimizedAccess) &&
|
|
isa<MemoryDef>(StartingAccess) && UpwardWalkLimit) {
|
|
assert(isa<MemoryDef>(Q.OriginalAccess));
|
|
Q.SkipSelfAccess = true;
|
|
Result = Walker.findClobber(OptimizedAccess, Q, UpwardWalkLimit);
|
|
} else
|
|
Result = OptimizedAccess;
|
|
|
|
LLVM_DEBUG(dbgs() << "Result Memory SSA clobber [SkipSelf = " << SkipSelf);
|
|
LLVM_DEBUG(dbgs() << "] for " << *I << " is " << *Result << "\n");
|
|
|
|
return Result;
|
|
}
|
|
|
|
MemoryAccess *
|
|
DoNothingMemorySSAWalker::getClobberingMemoryAccess(MemoryAccess *MA) {
|
|
if (auto *Use = dyn_cast<MemoryUseOrDef>(MA))
|
|
return Use->getDefiningAccess();
|
|
return MA;
|
|
}
|
|
|
|
MemoryAccess *DoNothingMemorySSAWalker::getClobberingMemoryAccess(
|
|
MemoryAccess *StartingAccess, const MemoryLocation &) {
|
|
if (auto *Use = dyn_cast<MemoryUseOrDef>(StartingAccess))
|
|
return Use->getDefiningAccess();
|
|
return StartingAccess;
|
|
}
|
|
|
|
void MemoryPhi::deleteMe(DerivedUser *Self) {
|
|
delete static_cast<MemoryPhi *>(Self);
|
|
}
|
|
|
|
void MemoryDef::deleteMe(DerivedUser *Self) {
|
|
delete static_cast<MemoryDef *>(Self);
|
|
}
|
|
|
|
void MemoryUse::deleteMe(DerivedUser *Self) {
|
|
delete static_cast<MemoryUse *>(Self);
|
|
}
|