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llvm-project/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp

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//===- ModuleSummaryAnalysis.cpp - Module summary index builder -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass builds a ModuleSummaryIndex object for the module, to be written
// to bitcode or LLVM assembly.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/ModuleSummaryAnalysis.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/IndirectCallPromotionAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TypeMetadataUtils.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/ValueSymbolTable.h"
#include "llvm/Object/IRObjectFile.h"
#include "llvm/Pass.h"
using namespace llvm;
#define DEBUG_TYPE "module-summary-analysis"
// Walk through the operands of a given User via worklist iteration and populate
// the set of GlobalValue references encountered. Invoked either on an
// Instruction or a GlobalVariable (which walks its initializer).
static void findRefEdges(const User *CurUser, SetVector<ValueInfo> &RefEdges,
SmallPtrSet<const User *, 8> &Visited) {
SmallVector<const User *, 32> Worklist;
Worklist.push_back(CurUser);
while (!Worklist.empty()) {
const User *U = Worklist.pop_back_val();
if (!Visited.insert(U).second)
continue;
ImmutableCallSite CS(U);
for (const auto &OI : U->operands()) {
const User *Operand = dyn_cast<User>(OI);
if (!Operand)
continue;
if (isa<BlockAddress>(Operand))
continue;
if (auto *GV = dyn_cast<GlobalValue>(Operand)) {
// We have a reference to a global value. This should be added to
// the reference set unless it is a callee. Callees are handled
// specially by WriteFunction and are added to a separate list.
if (!(CS && CS.isCallee(&OI)))
RefEdges.insert(GV);
continue;
}
Worklist.push_back(Operand);
}
}
}
static CalleeInfo::HotnessType getHotness(uint64_t ProfileCount,
ProfileSummaryInfo *PSI) {
if (!PSI)
return CalleeInfo::HotnessType::Unknown;
if (PSI->isHotCount(ProfileCount))
return CalleeInfo::HotnessType::Hot;
if (PSI->isColdCount(ProfileCount))
return CalleeInfo::HotnessType::Cold;
return CalleeInfo::HotnessType::None;
}
static bool isNonRenamableLocal(const GlobalValue &GV) {
return GV.hasSection() && GV.hasLocalLinkage();
}
/// Determine whether this call has all constant integer arguments (excluding
/// "this") and summarize it to VCalls or ConstVCalls as appropriate.
static void addVCallToSet(DevirtCallSite Call, GlobalValue::GUID Guid,
SetVector<FunctionSummary::VFuncId> &VCalls,
SetVector<FunctionSummary::ConstVCall> &ConstVCalls) {
std::vector<uint64_t> Args;
// Start from the second argument to skip the "this" pointer.
for (auto &Arg : make_range(Call.CS.arg_begin() + 1, Call.CS.arg_end())) {
auto *CI = dyn_cast<ConstantInt>(Arg);
if (!CI || CI->getBitWidth() > 64) {
VCalls.insert({Guid, Call.Offset});
return;
}
Args.push_back(CI->getZExtValue());
}
ConstVCalls.insert({{Guid, Call.Offset}, std::move(Args)});
}
/// If this intrinsic call requires that we add information to the function
/// summary, do so via the non-constant reference arguments.
static void addIntrinsicToSummary(
const CallInst *CI, SetVector<GlobalValue::GUID> &TypeTests,
SetVector<FunctionSummary::VFuncId> &TypeTestAssumeVCalls,
SetVector<FunctionSummary::VFuncId> &TypeCheckedLoadVCalls,
SetVector<FunctionSummary::ConstVCall> &TypeTestAssumeConstVCalls,
SetVector<FunctionSummary::ConstVCall> &TypeCheckedLoadConstVCalls) {
switch (CI->getCalledFunction()->getIntrinsicID()) {
case Intrinsic::type_test: {
auto *TypeMDVal = cast<MetadataAsValue>(CI->getArgOperand(1));
auto *TypeId = dyn_cast<MDString>(TypeMDVal->getMetadata());
if (!TypeId)
break;
GlobalValue::GUID Guid = GlobalValue::getGUID(TypeId->getString());
// Produce a summary from type.test intrinsics. We only summarize type.test
// intrinsics that are used other than by an llvm.assume intrinsic.
// Intrinsics that are assumed are relevant only to the devirtualization
// pass, not the type test lowering pass.
bool HasNonAssumeUses = llvm::any_of(CI->uses(), [](const Use &CIU) {
auto *AssumeCI = dyn_cast<CallInst>(CIU.getUser());
if (!AssumeCI)
return true;
Function *F = AssumeCI->getCalledFunction();
return !F || F->getIntrinsicID() != Intrinsic::assume;
});
if (HasNonAssumeUses)
TypeTests.insert(Guid);
SmallVector<DevirtCallSite, 4> DevirtCalls;
SmallVector<CallInst *, 4> Assumes;
findDevirtualizableCallsForTypeTest(DevirtCalls, Assumes, CI);
for (auto &Call : DevirtCalls)
addVCallToSet(Call, Guid, TypeTestAssumeVCalls,
TypeTestAssumeConstVCalls);
break;
}
case Intrinsic::type_checked_load: {
auto *TypeMDVal = cast<MetadataAsValue>(CI->getArgOperand(2));
auto *TypeId = dyn_cast<MDString>(TypeMDVal->getMetadata());
if (!TypeId)
break;
GlobalValue::GUID Guid = GlobalValue::getGUID(TypeId->getString());
SmallVector<DevirtCallSite, 4> DevirtCalls;
SmallVector<Instruction *, 4> LoadedPtrs;
SmallVector<Instruction *, 4> Preds;
bool HasNonCallUses = false;
findDevirtualizableCallsForTypeCheckedLoad(DevirtCalls, LoadedPtrs, Preds,
HasNonCallUses, CI);
// Any non-call uses of the result of llvm.type.checked.load will
// prevent us from optimizing away the llvm.type.test.
if (HasNonCallUses)
TypeTests.insert(Guid);
for (auto &Call : DevirtCalls)
addVCallToSet(Call, Guid, TypeCheckedLoadVCalls,
TypeCheckedLoadConstVCalls);
break;
}
default:
break;
}
}
static void
computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
const Function &F, BlockFrequencyInfo *BFI,
ProfileSummaryInfo *PSI, bool HasLocalsInUsed,
DenseSet<GlobalValue::GUID> &CantBePromoted) {
// Summary not currently supported for anonymous functions, they should
// have been named.
assert(F.hasName());
unsigned NumInsts = 0;
// Map from callee ValueId to profile count. Used to accumulate profile
// counts for all static calls to a given callee.
MapVector<ValueInfo, CalleeInfo> CallGraphEdges;
SetVector<ValueInfo> RefEdges;
SetVector<GlobalValue::GUID> TypeTests;
SetVector<FunctionSummary::VFuncId> TypeTestAssumeVCalls,
TypeCheckedLoadVCalls;
SetVector<FunctionSummary::ConstVCall> TypeTestAssumeConstVCalls,
TypeCheckedLoadConstVCalls;
ICallPromotionAnalysis ICallAnalysis;
bool HasInlineAsmMaybeReferencingInternal = false;
SmallPtrSet<const User *, 8> Visited;
for (const BasicBlock &BB : F)
for (const Instruction &I : BB) {
if (isa<DbgInfoIntrinsic>(I))
continue;
++NumInsts;
findRefEdges(&I, RefEdges, Visited);
auto CS = ImmutableCallSite(&I);
if (!CS)
continue;
const auto *CI = dyn_cast<CallInst>(&I);
// Since we don't know exactly which local values are referenced in inline
// assembly, conservatively mark the function as possibly referencing
// a local value from inline assembly to ensure we don't export a
// reference (which would require renaming and promotion of the
// referenced value).
if (HasLocalsInUsed && CI && CI->isInlineAsm())
HasInlineAsmMaybeReferencingInternal = true;
auto *CalledValue = CS.getCalledValue();
auto *CalledFunction = CS.getCalledFunction();
// Check if this is an alias to a function. If so, get the
// called aliasee for the checks below.
if (auto *GA = dyn_cast<GlobalAlias>(CalledValue)) {
assert(!CalledFunction && "Expected null called function in callsite for alias");
CalledFunction = dyn_cast<Function>(GA->getBaseObject());
}
// Check if this is a direct call to a known function or a known
// intrinsic, or an indirect call with profile data.
if (CalledFunction) {
if (CI && CalledFunction->isIntrinsic()) {
addIntrinsicToSummary(
CI, TypeTests, TypeTestAssumeVCalls, TypeCheckedLoadVCalls,
TypeTestAssumeConstVCalls, TypeCheckedLoadConstVCalls);
continue;
}
// We should have named any anonymous globals
assert(CalledFunction->hasName());
auto ScaledCount = ProfileSummaryInfo::getProfileCount(&I, BFI);
auto Hotness = ScaledCount ? getHotness(ScaledCount.getValue(), PSI)
: CalleeInfo::HotnessType::Unknown;
// Use the original CalledValue, in case it was an alias. We want
// to record the call edge to the alias in that case. Eventually
// an alias summary will be created to associate the alias and
// aliasee.
CallGraphEdges[cast<GlobalValue>(CalledValue)].updateHotness(Hotness);
} else {
// Skip inline assembly calls.
if (CI && CI->isInlineAsm())
continue;
// Skip direct calls.
if (!CS.getCalledValue() || isa<Constant>(CS.getCalledValue()))
continue;
uint32_t NumVals, NumCandidates;
uint64_t TotalCount;
auto CandidateProfileData =
ICallAnalysis.getPromotionCandidatesForInstruction(
&I, NumVals, TotalCount, NumCandidates);
for (auto &Candidate : CandidateProfileData)
CallGraphEdges[Candidate.Value].updateHotness(
getHotness(Candidate.Count, PSI));
}
}
// Explicit add hot edges to enforce importing for designated GUIDs for
// sample PGO, to enable the same inlines as the profiled optimized binary.
for (auto &I : F.getImportGUIDs())
CallGraphEdges[I].updateHotness(CalleeInfo::HotnessType::Hot);
bool NonRenamableLocal = isNonRenamableLocal(F);
bool NotEligibleForImport =
NonRenamableLocal || HasInlineAsmMaybeReferencingInternal ||
// Inliner doesn't handle variadic functions.
// FIXME: refactor this to use the same code that inliner is using.
F.isVarArg();
GlobalValueSummary::GVFlags Flags(F.getLinkage(), NotEligibleForImport,
/* LiveRoot = */ false);
auto FuncSummary = llvm::make_unique<FunctionSummary>(
Flags, NumInsts, RefEdges.takeVector(), CallGraphEdges.takeVector(),
TypeTests.takeVector(), TypeTestAssumeVCalls.takeVector(),
TypeCheckedLoadVCalls.takeVector(),
TypeTestAssumeConstVCalls.takeVector(),
TypeCheckedLoadConstVCalls.takeVector());
if (NonRenamableLocal)
CantBePromoted.insert(F.getGUID());
Index.addGlobalValueSummary(F.getName(), std::move(FuncSummary));
}
static void
computeVariableSummary(ModuleSummaryIndex &Index, const GlobalVariable &V,
DenseSet<GlobalValue::GUID> &CantBePromoted) {
SetVector<ValueInfo> RefEdges;
SmallPtrSet<const User *, 8> Visited;
findRefEdges(&V, RefEdges, Visited);
bool NonRenamableLocal = isNonRenamableLocal(V);
GlobalValueSummary::GVFlags Flags(V.getLinkage(), NonRenamableLocal,
/* LiveRoot = */ false);
auto GVarSummary =
llvm::make_unique<GlobalVarSummary>(Flags, RefEdges.takeVector());
if (NonRenamableLocal)
CantBePromoted.insert(V.getGUID());
Index.addGlobalValueSummary(V.getName(), std::move(GVarSummary));
}
static void
computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
DenseSet<GlobalValue::GUID> &CantBePromoted) {
bool NonRenamableLocal = isNonRenamableLocal(A);
GlobalValueSummary::GVFlags Flags(A.getLinkage(), NonRenamableLocal,
/* LiveRoot = */ false);
auto AS = llvm::make_unique<AliasSummary>(Flags, ArrayRef<ValueInfo>{});
auto *Aliasee = A.getBaseObject();
auto *AliaseeSummary = Index.getGlobalValueSummary(*Aliasee);
assert(AliaseeSummary && "Alias expects aliasee summary to be parsed");
AS->setAliasee(AliaseeSummary);
if (NonRenamableLocal)
CantBePromoted.insert(A.getGUID());
Index.addGlobalValueSummary(A.getName(), std::move(AS));
}
// Set LiveRoot flag on entries matching the given value name.
static void setLiveRoot(ModuleSummaryIndex &Index, StringRef Name) {
auto SummaryList =
Index.findGlobalValueSummaryList(GlobalValue::getGUID(Name));
if (SummaryList == Index.end())
return;
for (auto &Summary : SummaryList->second)
Summary->setLiveRoot();
}
ModuleSummaryIndex llvm::buildModuleSummaryIndex(
const Module &M,
std::function<BlockFrequencyInfo *(const Function &F)> GetBFICallback,
ProfileSummaryInfo *PSI) {
ModuleSummaryIndex Index;
// Identify the local values in the llvm.used and llvm.compiler.used sets,
// which should not be exported as they would then require renaming and
// promotion, but we may have opaque uses e.g. in inline asm. We collect them
// here because we use this information to mark functions containing inline
// assembly calls as not importable.
SmallPtrSet<GlobalValue *, 8> LocalsUsed;
SmallPtrSet<GlobalValue *, 8> Used;
// First collect those in the llvm.used set.
collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
// Next collect those in the llvm.compiler.used set.
collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ true);
DenseSet<GlobalValue::GUID> CantBePromoted;
for (auto *V : Used) {
if (V->hasLocalLinkage()) {
LocalsUsed.insert(V);
CantBePromoted.insert(V->getGUID());
}
}
// Compute summaries for all functions defined in module, and save in the
// index.
for (auto &F : M) {
if (F.isDeclaration())
continue;
BlockFrequencyInfo *BFI = nullptr;
std::unique_ptr<BlockFrequencyInfo> BFIPtr;
if (GetBFICallback)
BFI = GetBFICallback(F);
else if (F.getEntryCount().hasValue()) {
LoopInfo LI{DominatorTree(const_cast<Function &>(F))};
BranchProbabilityInfo BPI{F, LI};
BFIPtr = llvm::make_unique<BlockFrequencyInfo>(F, BPI, LI);
BFI = BFIPtr.get();
}
computeFunctionSummary(Index, M, F, BFI, PSI, !LocalsUsed.empty(),
CantBePromoted);
}
// Compute summaries for all variables defined in module, and save in the
// index.
for (const GlobalVariable &G : M.globals()) {
if (G.isDeclaration())
continue;
computeVariableSummary(Index, G, CantBePromoted);
}
// Compute summaries for all aliases defined in module, and save in the
// index.
for (const GlobalAlias &A : M.aliases())
computeAliasSummary(Index, A, CantBePromoted);
for (auto *V : LocalsUsed) {
auto *Summary = Index.getGlobalValueSummary(*V);
assert(Summary && "Missing summary for global value");
Summary->setNotEligibleToImport();
}
// The linker doesn't know about these LLVM produced values, so we need
// to flag them as live in the index to ensure index-based dead value
// analysis treats them as live roots of the analysis.
setLiveRoot(Index, "llvm.used");
setLiveRoot(Index, "llvm.compiler.used");
setLiveRoot(Index, "llvm.global_ctors");
setLiveRoot(Index, "llvm.global_dtors");
setLiveRoot(Index, "llvm.global.annotations");
if (!M.getModuleInlineAsm().empty()) {
// Collect the local values defined by module level asm, and set up
// summaries for these symbols so that they can be marked as NoRename,
// to prevent export of any use of them in regular IR that would require
// renaming within the module level asm. Note we don't need to create a
// summary for weak or global defs, as they don't need to be flagged as
// NoRename, and defs in module level asm can't be imported anyway.
// Also, any values used but not defined within module level asm should
// be listed on the llvm.used or llvm.compiler.used global and marked as
// referenced from there.
ModuleSymbolTable::CollectAsmSymbols(
M, [&M, &Index, &CantBePromoted](StringRef Name,
object::BasicSymbolRef::Flags Flags) {
// Symbols not marked as Weak or Global are local definitions.
if (Flags & (object::BasicSymbolRef::SF_Weak |
object::BasicSymbolRef::SF_Global))
return;
GlobalValue *GV = M.getNamedValue(Name);
if (!GV)
return;
assert(GV->isDeclaration() && "Def in module asm already has definition");
GlobalValueSummary::GVFlags GVFlags(GlobalValue::InternalLinkage,
/* NotEligibleToImport */ true,
/* LiveRoot */ true);
CantBePromoted.insert(GlobalValue::getGUID(Name));
// Create the appropriate summary type.
if (isa<Function>(GV)) {
std::unique_ptr<FunctionSummary> Summary =
llvm::make_unique<FunctionSummary>(
GVFlags, 0, ArrayRef<ValueInfo>{},
ArrayRef<FunctionSummary::EdgeTy>{},
ArrayRef<GlobalValue::GUID>{},
ArrayRef<FunctionSummary::VFuncId>{},
ArrayRef<FunctionSummary::VFuncId>{},
ArrayRef<FunctionSummary::ConstVCall>{},
ArrayRef<FunctionSummary::ConstVCall>{});
Index.addGlobalValueSummary(Name, std::move(Summary));
} else {
std::unique_ptr<GlobalVarSummary> Summary =
llvm::make_unique<GlobalVarSummary>(GVFlags,
ArrayRef<ValueInfo>{});
Index.addGlobalValueSummary(Name, std::move(Summary));
}
});
}
for (auto &GlobalList : Index) {
assert(GlobalList.second.size() == 1 &&
"Expected module's index to have one summary per GUID");
auto &Summary = GlobalList.second[0];
bool AllRefsCanBeExternallyReferenced =
llvm::all_of(Summary->refs(), [&](const ValueInfo &VI) {
// If a global value definition references an unnamed global,
// be conservative. They're valid IR so we don't want to crash
// when we encounter any of them but they're infrequent enough
// that we don't bother optimizing them.
if (!VI.getValue()->hasName())
return false;
return !CantBePromoted.count(VI.getValue()->getGUID());
});
if (!AllRefsCanBeExternallyReferenced) {
Summary->setNotEligibleToImport();
continue;
}
if (auto *FuncSummary = dyn_cast<FunctionSummary>(Summary.get())) {
bool AllCallsCanBeExternallyReferenced = llvm::all_of(
FuncSummary->calls(), [&](const FunctionSummary::EdgeTy &Edge) {
auto GUID = Edge.first.isGUID() ? Edge.first.getGUID()
: Edge.first.getValue()->getGUID();
return !CantBePromoted.count(GUID);
});
if (!AllCallsCanBeExternallyReferenced)
Summary->setNotEligibleToImport();
}
}
return Index;
}
AnalysisKey ModuleSummaryIndexAnalysis::Key;
ModuleSummaryIndex
ModuleSummaryIndexAnalysis::run(Module &M, ModuleAnalysisManager &AM) {
ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
auto &FAM = AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
return buildModuleSummaryIndex(
M,
[&FAM](const Function &F) {
return &FAM.getResult<BlockFrequencyAnalysis>(
*const_cast<Function *>(&F));
},
&PSI);
}
char ModuleSummaryIndexWrapperPass::ID = 0;
INITIALIZE_PASS_BEGIN(ModuleSummaryIndexWrapperPass, "module-summary-analysis",
"Module Summary Analysis", false, true)
INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
INITIALIZE_PASS_END(ModuleSummaryIndexWrapperPass, "module-summary-analysis",
"Module Summary Analysis", false, true)
ModulePass *llvm::createModuleSummaryIndexWrapperPass() {
return new ModuleSummaryIndexWrapperPass();
}
ModuleSummaryIndexWrapperPass::ModuleSummaryIndexWrapperPass()
: ModulePass(ID) {
initializeModuleSummaryIndexWrapperPassPass(*PassRegistry::getPassRegistry());
}
bool ModuleSummaryIndexWrapperPass::runOnModule(Module &M) {
auto &PSI = *getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
Index = buildModuleSummaryIndex(
M,
[this](const Function &F) {
return &(this->getAnalysis<BlockFrequencyInfoWrapperPass>(
*const_cast<Function *>(&F))
.getBFI());
},
&PSI);
return false;
}
bool ModuleSummaryIndexWrapperPass::doFinalization(Module &M) {
Index.reset();
return false;
}
void ModuleSummaryIndexWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<BlockFrequencyInfoWrapperPass>();
AU.addRequired<ProfileSummaryInfoWrapperPass>();
}
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