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llvm-mirror/lib/Analysis/ModuleSummaryAnalysis.cpp
Peter Collingbourne 724883c1d1 IR. Change strip* family of functions to not look through aliases. 
I noticed another instance of the issue where references to aliases were
being replaced with aliasees, this time in InstCombine. In the instance that
I saw it turned out to be only a QoI issue (a symbol ended up being missing
from the symbol table due to the last reference to the alias being removed,
preventing HWASAN from symbolizing a global reference), but it could easily
have manifested as incorrect behaviour.

Since this is the third such issue encountered (previously: D65118, D65314)
it seems to be time to address this common error/QoI issue once and for all
and make the strip* family of functions not look through aliases.

Includes a test for the specific issue that I saw, but no doubt there are
other similar bugs fixed here.

As with D65118 this has been tested to make sure that the optimization isn't
load bearing. I built Clang, Chromium for Linux, Android and Windows as well
as the test-suite and there were no size regressions.

Differential Revision: https://reviews.llvm.org/D66606

llvm-svn: 369697
2019-08-22 19:56:14 +00:00

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//===- ModuleSummaryAnalysis.cpp - Module summary index builder -----------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// 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/ArrayRef.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Analysis/BlockFrequencyInfo.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/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/ModuleSummaryIndex.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/Object/ModuleSymbolTable.h"
#include "llvm/Object/SymbolicFile.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "module-summary-analysis"
// Option to force edges cold which will block importing when the
// -import-cold-multiplier is set to 0. Useful for debugging.
FunctionSummary::ForceSummaryHotnessType ForceSummaryEdgesCold =
FunctionSummary::FSHT_None;
cl::opt<FunctionSummary::ForceSummaryHotnessType, true> FSEC(
"force-summary-edges-cold", cl::Hidden, cl::location(ForceSummaryEdgesCold),
cl::desc("Force all edges in the function summary to cold"),
cl::values(clEnumValN(FunctionSummary::FSHT_None, "none", "None."),
clEnumValN(FunctionSummary::FSHT_AllNonCritical,
"all-non-critical", "All non-critical edges."),
clEnumValN(FunctionSummary::FSHT_All, "all", "All edges.")));
cl::opt<std::string> ModuleSummaryDotFile(
"module-summary-dot-file", cl::init(""), cl::Hidden,
cl::value_desc("filename"),
cl::desc("File to emit dot graph of new summary into."));
// 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).
// Return true if any of the operands contains blockaddress. This is important
// to know when computing summary for global var, because if global variable
// references basic block address we can't import it separately from function
// containing that basic block. For simplicity we currently don't import such
// global vars at all. When importing function we aren't interested if any
// instruction in it takes an address of any basic block, because instruction
// can only take an address of basic block located in the same function.
static bool findRefEdges(ModuleSummaryIndex &Index, const User *CurUser,
SetVector<ValueInfo> &RefEdges,
SmallPtrSet<const User *, 8> &Visited) {
bool HasBlockAddress = false;
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)) {
HasBlockAddress = true;
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(Index.getOrInsertValueInfo(GV));
continue;
}
Worklist.push_back(Operand);
}
}
return HasBlockAddress;
}
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,
DominatorTree &DT) {
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, DT);
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, DT);
// 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 bool isNonVolatileLoad(const Instruction *I) {
if (const auto *LI = dyn_cast<LoadInst>(I))
return !LI->isVolatile();
return false;
}
static bool isNonVolatileStore(const Instruction *I) {
if (const auto *SI = dyn_cast<StoreInst>(I))
return !SI->isVolatile();
return false;
}
static void computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
const Function &F, BlockFrequencyInfo *BFI,
ProfileSummaryInfo *PSI, DominatorTree &DT,
bool HasLocalsInUsedOrAsm,
DenseSet<GlobalValue::GUID> &CantBePromoted,
bool IsThinLTO) {
// 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, LoadRefEdges, StoreRefEdges;
SetVector<GlobalValue::GUID> TypeTests;
SetVector<FunctionSummary::VFuncId> TypeTestAssumeVCalls,
TypeCheckedLoadVCalls;
SetVector<FunctionSummary::ConstVCall> TypeTestAssumeConstVCalls,
TypeCheckedLoadConstVCalls;
ICallPromotionAnalysis ICallAnalysis;
SmallPtrSet<const User *, 8> Visited;
// Add personality function, prefix data and prologue data to function's ref
// list.
findRefEdges(Index, &F, RefEdges, Visited);
std::vector<const Instruction *> NonVolatileLoads;
std::vector<const Instruction *> NonVolatileStores;
bool HasInlineAsmMaybeReferencingInternal = false;
for (const BasicBlock &BB : F)
for (const Instruction &I : BB) {
if (isa<DbgInfoIntrinsic>(I))
continue;
++NumInsts;
// Regular LTO module doesn't participate in ThinLTO import,
// so no reference from it can be read/writeonly, since this
// would require importing variable as local copy
if (IsThinLTO) {
if (isNonVolatileLoad(&I)) {
// Postpone processing of non-volatile load instructions
// See comments below
Visited.insert(&I);
NonVolatileLoads.push_back(&I);
continue;
} else if (isNonVolatileStore(&I)) {
Visited.insert(&I);
NonVolatileStores.push_back(&I);
// All references from second operand of store (destination address)
// can be considered write-only if they're not referenced by any
// non-store instruction. References from first operand of store
// (stored value) can't be treated either as read- or as write-only
// so we add them to RefEdges as we do with all other instructions
// except non-volatile load.
Value *Stored = I.getOperand(0);
if (auto *GV = dyn_cast<GlobalValue>(Stored))
// findRefEdges will try to examine GV operands, so instead
// of calling it we should add GV to RefEdges directly.
RefEdges.insert(Index.getOrInsertValueInfo(GV));
else if (auto *U = dyn_cast<User>(Stored))
findRefEdges(Index, U, RefEdges, Visited);
continue;
}
}
findRefEdges(Index, &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 (HasLocalsInUsedOrAsm && CI && CI->isInlineAsm())
HasInlineAsmMaybeReferencingInternal = true;
auto *CalledValue = CS.getCalledValue();
auto *CalledFunction = CS.getCalledFunction();
if (CalledValue && !CalledFunction) {
CalledValue = CalledValue->stripPointerCasts();
// Stripping pointer casts can reveal a called function.
CalledFunction = dyn_cast<Function>(CalledValue);
}
// 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, DT);
continue;
}
// We should have named any anonymous globals
assert(CalledFunction->hasName());
auto ScaledCount = PSI->getProfileCount(&I, BFI);
auto Hotness = ScaledCount ? getHotness(ScaledCount.getValue(), PSI)
: CalleeInfo::HotnessType::Unknown;
if (ForceSummaryEdgesCold != FunctionSummary::FSHT_None)
Hotness = CalleeInfo::HotnessType::Cold;
// 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.
auto &ValueInfo = CallGraphEdges[Index.getOrInsertValueInfo(
cast<GlobalValue>(CalledValue))];
ValueInfo.updateHotness(Hotness);
// Add the relative block frequency to CalleeInfo if there is no profile
// information.
if (BFI != nullptr && Hotness == CalleeInfo::HotnessType::Unknown) {
uint64_t BBFreq = BFI->getBlockFreq(&BB).getFrequency();
uint64_t EntryFreq = BFI->getEntryFreq();
ValueInfo.updateRelBlockFreq(BBFreq, EntryFreq);
}
} else {
// Skip inline assembly calls.
if (CI && CI->isInlineAsm())
continue;
// Skip direct calls.
if (!CalledValue || isa<Constant>(CalledValue))
continue;
// Check if the instruction has a callees metadata. If so, add callees
// to CallGraphEdges to reflect the references from the metadata, and
// to enable importing for subsequent indirect call promotion and
// inlining.
if (auto *MD = I.getMetadata(LLVMContext::MD_callees)) {
for (auto &Op : MD->operands()) {
Function *Callee = mdconst::extract_or_null<Function>(Op);
if (Callee)
CallGraphEdges[Index.getOrInsertValueInfo(Callee)];
}
}
uint32_t NumVals, NumCandidates;
uint64_t TotalCount;
auto CandidateProfileData =
ICallAnalysis.getPromotionCandidatesForInstruction(
&I, NumVals, TotalCount, NumCandidates);
for (auto &Candidate : CandidateProfileData)
CallGraphEdges[Index.getOrInsertValueInfo(Candidate.Value)]
.updateHotness(getHotness(Candidate.Count, PSI));
}
}
std::vector<ValueInfo> Refs;
if (IsThinLTO) {
auto AddRefEdges = [&](const std::vector<const Instruction *> &Instrs,
SetVector<ValueInfo> &Edges,
SmallPtrSet<const User *, 8> &Cache) {
for (const auto *I : Instrs) {
Cache.erase(I);
findRefEdges(Index, I, Edges, Cache);
}
};
// By now we processed all instructions in a function, except
// non-volatile loads and non-volatile value stores. Let's find
// ref edges for both of instruction sets
AddRefEdges(NonVolatileLoads, LoadRefEdges, Visited);
// We can add some values to the Visited set when processing load
// instructions which are also used by stores in NonVolatileStores.
// For example this can happen if we have following code:
//
// store %Derived* @foo, %Derived** bitcast (%Base** @bar to %Derived**)
// %42 = load %Derived*, %Derived** bitcast (%Base** @bar to %Derived**)
//
// After processing loads we'll add bitcast to the Visited set, and if
// we use the same set while processing stores, we'll never see store
// to @bar and @bar will be mistakenly treated as readonly.
SmallPtrSet<const llvm::User *, 8> StoreCache;
AddRefEdges(NonVolatileStores, StoreRefEdges, StoreCache);
// If both load and store instruction reference the same variable
// we won't be able to optimize it. Add all such reference edges
// to RefEdges set.
for (auto &VI : StoreRefEdges)
if (LoadRefEdges.remove(VI))
RefEdges.insert(VI);
unsigned RefCnt = RefEdges.size();
// All new reference edges inserted in two loops below are either
// read or write only. They will be grouped in the end of RefEdges
// vector, so we can use a single integer value to identify them.
for (auto &VI : LoadRefEdges)
RefEdges.insert(VI);
unsigned FirstWORef = RefEdges.size();
for (auto &VI : StoreRefEdges)
RefEdges.insert(VI);
Refs = RefEdges.takeVector();
for (; RefCnt < FirstWORef; ++RefCnt)
Refs[RefCnt].setReadOnly();
for (; RefCnt < Refs.size(); ++RefCnt)
Refs[RefCnt].setWriteOnly();
} else {
Refs = RefEdges.takeVector();
}
// 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[Index.getOrInsertValueInfo(I)].updateHotness(
ForceSummaryEdgesCold == FunctionSummary::FSHT_All
? CalleeInfo::HotnessType::Cold
: CalleeInfo::HotnessType::Critical);
bool NonRenamableLocal = isNonRenamableLocal(F);
bool NotEligibleForImport =
NonRenamableLocal || HasInlineAsmMaybeReferencingInternal;
GlobalValueSummary::GVFlags Flags(F.getLinkage(), NotEligibleForImport,
/* Live = */ false, F.isDSOLocal(),
F.hasLinkOnceODRLinkage() && F.hasGlobalUnnamedAddr());
FunctionSummary::FFlags FunFlags{
F.hasFnAttribute(Attribute::ReadNone),
F.hasFnAttribute(Attribute::ReadOnly),
F.hasFnAttribute(Attribute::NoRecurse), F.returnDoesNotAlias(),
// FIXME: refactor this to use the same code that inliner is using.
// Don't try to import functions with noinline attribute.
F.getAttributes().hasFnAttribute(Attribute::NoInline)};
auto FuncSummary = std::make_unique<FunctionSummary>(
Flags, NumInsts, FunFlags, /*EntryCount=*/0, std::move(Refs),
CallGraphEdges.takeVector(), TypeTests.takeVector(),
TypeTestAssumeVCalls.takeVector(), TypeCheckedLoadVCalls.takeVector(),
TypeTestAssumeConstVCalls.takeVector(),
TypeCheckedLoadConstVCalls.takeVector());
if (NonRenamableLocal)
CantBePromoted.insert(F.getGUID());
Index.addGlobalValueSummary(F, std::move(FuncSummary));
}
/// Find function pointers referenced within the given vtable initializer
/// (or subset of an initializer) \p I. The starting offset of \p I within
/// the vtable initializer is \p StartingOffset. Any discovered function
/// pointers are added to \p VTableFuncs along with their cumulative offset
/// within the initializer.
static void findFuncPointers(const Constant *I, uint64_t StartingOffset,
const Module &M, ModuleSummaryIndex &Index,
VTableFuncList &VTableFuncs) {
// First check if this is a function pointer.
if (I->getType()->isPointerTy()) {
auto Fn = dyn_cast<Function>(I->stripPointerCasts());
// We can disregard __cxa_pure_virtual as a possible call target, as
// calls to pure virtuals are UB.
if (Fn && Fn->getName() != "__cxa_pure_virtual")
VTableFuncs.push_back({Index.getOrInsertValueInfo(Fn), StartingOffset});
return;
}
// Walk through the elements in the constant struct or array and recursively
// look for virtual function pointers.
const DataLayout &DL = M.getDataLayout();
if (auto *C = dyn_cast<ConstantStruct>(I)) {
StructType *STy = dyn_cast<StructType>(C->getType());
assert(STy);
const StructLayout *SL = DL.getStructLayout(C->getType());
for (StructType::element_iterator EB = STy->element_begin(), EI = EB,
EE = STy->element_end();
EI != EE; ++EI) {
auto Offset = SL->getElementOffset(EI - EB);
unsigned Op = SL->getElementContainingOffset(Offset);
findFuncPointers(cast<Constant>(I->getOperand(Op)),
StartingOffset + Offset, M, Index, VTableFuncs);
}
} else if (auto *C = dyn_cast<ConstantArray>(I)) {
ArrayType *ATy = C->getType();
Type *EltTy = ATy->getElementType();
uint64_t EltSize = DL.getTypeAllocSize(EltTy);
for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) {
findFuncPointers(cast<Constant>(I->getOperand(i)),
StartingOffset + i * EltSize, M, Index, VTableFuncs);
}
}
}
// Identify the function pointers referenced by vtable definition \p V.
static void computeVTableFuncs(ModuleSummaryIndex &Index,
const GlobalVariable &V, const Module &M,
VTableFuncList &VTableFuncs) {
if (!V.isConstant())
return;
findFuncPointers(V.getInitializer(), /*StartingOffset=*/0, M, Index,
VTableFuncs);
#ifndef NDEBUG
// Validate that the VTableFuncs list is ordered by offset.
uint64_t PrevOffset = 0;
for (auto &P : VTableFuncs) {
// The findVFuncPointers traversal should have encountered the
// functions in offset order. We need to use ">=" since PrevOffset
// starts at 0.
assert(P.VTableOffset >= PrevOffset);
PrevOffset = P.VTableOffset;
}
#endif
}
/// Record vtable definition \p V for each type metadata it references.
static void
recordTypeIdCompatibleVtableReferences(ModuleSummaryIndex &Index,
const GlobalVariable &V,
SmallVectorImpl<MDNode *> &Types) {
for (MDNode *Type : Types) {
auto TypeID = Type->getOperand(1).get();
uint64_t Offset =
cast<ConstantInt>(
cast<ConstantAsMetadata>(Type->getOperand(0))->getValue())
->getZExtValue();
if (auto *TypeId = dyn_cast<MDString>(TypeID))
Index.getOrInsertTypeIdCompatibleVtableSummary(TypeId->getString())
.push_back({Offset, Index.getOrInsertValueInfo(&V)});
}
}
static void computeVariableSummary(ModuleSummaryIndex &Index,
const GlobalVariable &V,
DenseSet<GlobalValue::GUID> &CantBePromoted,
const Module &M,
SmallVectorImpl<MDNode *> &Types) {
SetVector<ValueInfo> RefEdges;
SmallPtrSet<const User *, 8> Visited;
bool HasBlockAddress = findRefEdges(Index, &V, RefEdges, Visited);
bool NonRenamableLocal = isNonRenamableLocal(V);
GlobalValueSummary::GVFlags Flags(V.getLinkage(), NonRenamableLocal,
/* Live = */ false, V.isDSOLocal(),
V.hasLinkOnceODRLinkage() && V.hasGlobalUnnamedAddr());
VTableFuncList VTableFuncs;
// If splitting is not enabled, then we compute the summary information
// necessary for index-based whole program devirtualization.
if (!Index.enableSplitLTOUnit()) {
Types.clear();
V.getMetadata(LLVMContext::MD_type, Types);
if (!Types.empty()) {
// Identify the function pointers referenced by this vtable definition.
computeVTableFuncs(Index, V, M, VTableFuncs);
// Record this vtable definition for each type metadata it references.
recordTypeIdCompatibleVtableReferences(Index, V, Types);
}
}
// Don't mark variables we won't be able to internalize as read/write-only.
bool CanBeInternalized =
!V.hasComdat() && !V.hasAppendingLinkage() && !V.isInterposable() &&
!V.hasAvailableExternallyLinkage() && !V.hasDLLExportStorageClass();
GlobalVarSummary::GVarFlags VarFlags(CanBeInternalized, CanBeInternalized);
auto GVarSummary = std::make_unique<GlobalVarSummary>(Flags, VarFlags,
RefEdges.takeVector());
if (NonRenamableLocal)
CantBePromoted.insert(V.getGUID());
if (HasBlockAddress)
GVarSummary->setNotEligibleToImport();
if (!VTableFuncs.empty())
GVarSummary->setVTableFuncs(VTableFuncs);
Index.addGlobalValueSummary(V, 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,
/* Live = */ false, A.isDSOLocal(),
A.hasLinkOnceODRLinkage() && A.hasGlobalUnnamedAddr());
auto AS = std::make_unique<AliasSummary>(Flags);
auto *Aliasee = A.getBaseObject();
auto AliaseeVI = Index.getValueInfo(Aliasee->getGUID());
assert(AliaseeVI && "Alias expects aliasee summary to be available");
assert(AliaseeVI.getSummaryList().size() == 1 &&
"Expected a single entry per aliasee in per-module index");
AS->setAliasee(AliaseeVI, AliaseeVI.getSummaryList()[0].get());
if (NonRenamableLocal)
CantBePromoted.insert(A.getGUID());
Index.addGlobalValueSummary(A, std::move(AS));
}
// Set LiveRoot flag on entries matching the given value name.
static void setLiveRoot(ModuleSummaryIndex &Index, StringRef Name) {
if (ValueInfo VI = Index.getValueInfo(GlobalValue::getGUID(Name)))
for (auto &Summary : VI.getSummaryList())
Summary->setLive(true);
}
ModuleSummaryIndex llvm::buildModuleSummaryIndex(
const Module &M,
std::function<BlockFrequencyInfo *(const Function &F)> GetBFICallback,
ProfileSummaryInfo *PSI) {
assert(PSI);
bool EnableSplitLTOUnit = false;
if (auto *MD = mdconst::extract_or_null<ConstantInt>(
M.getModuleFlag("EnableSplitLTOUnit")))
EnableSplitLTOUnit = MD->getZExtValue();
ModuleSummaryIndex Index(/*HaveGVs=*/true, EnableSplitLTOUnit);
// 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());
}
}
bool HasLocalInlineAsmSymbol = false;
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, [&](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;
HasLocalInlineAsmSymbol = true;
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,
/* Live = */ true,
/* Local */ GV->isDSOLocal(),
GV->hasLinkOnceODRLinkage() && GV->hasGlobalUnnamedAddr());
CantBePromoted.insert(GV->getGUID());
// Create the appropriate summary type.
if (Function *F = dyn_cast<Function>(GV)) {
std::unique_ptr<FunctionSummary> Summary =
std::make_unique<FunctionSummary>(
GVFlags, /*InstCount=*/0,
FunctionSummary::FFlags{
F->hasFnAttribute(Attribute::ReadNone),
F->hasFnAttribute(Attribute::ReadOnly),
F->hasFnAttribute(Attribute::NoRecurse),
F->returnDoesNotAlias(),
/* NoInline = */ false},
/*EntryCount=*/0, ArrayRef<ValueInfo>{},
ArrayRef<FunctionSummary::EdgeTy>{},
ArrayRef<GlobalValue::GUID>{},
ArrayRef<FunctionSummary::VFuncId>{},
ArrayRef<FunctionSummary::VFuncId>{},
ArrayRef<FunctionSummary::ConstVCall>{},
ArrayRef<FunctionSummary::ConstVCall>{});
Index.addGlobalValueSummary(*GV, std::move(Summary));
} else {
std::unique_ptr<GlobalVarSummary> Summary =
std::make_unique<GlobalVarSummary>(
GVFlags, GlobalVarSummary::GVarFlags(false, false),
ArrayRef<ValueInfo>{});
Index.addGlobalValueSummary(*GV, std::move(Summary));
}
});
}
bool IsThinLTO = true;
if (auto *MD =
mdconst::extract_or_null<ConstantInt>(M.getModuleFlag("ThinLTO")))
IsThinLTO = MD->getZExtValue();
// Compute summaries for all functions defined in module, and save in the
// index.
for (auto &F : M) {
if (F.isDeclaration())
continue;
DominatorTree DT(const_cast<Function &>(F));
BlockFrequencyInfo *BFI = nullptr;
std::unique_ptr<BlockFrequencyInfo> BFIPtr;
if (GetBFICallback)
BFI = GetBFICallback(F);
else if (F.hasProfileData()) {
LoopInfo LI{DT};
BranchProbabilityInfo BPI{F, LI};
BFIPtr = std::make_unique<BlockFrequencyInfo>(F, BPI, LI);
BFI = BFIPtr.get();
}
computeFunctionSummary(Index, M, F, BFI, PSI, DT,
!LocalsUsed.empty() || HasLocalInlineAsmSymbol,
CantBePromoted, IsThinLTO);
}
// Compute summaries for all variables defined in module, and save in the
// index.
SmallVector<MDNode *, 2> Types;
for (const GlobalVariable &G : M.globals()) {
if (G.isDeclaration())
continue;
computeVariableSummary(Index, G, CantBePromoted, M, Types);
}
// 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");
for (auto &GlobalList : Index) {
// Ignore entries for references that are undefined in the current module.
if (GlobalList.second.SummaryList.empty())
continue;
assert(GlobalList.second.SummaryList.size() == 1 &&
"Expected module's index to have one summary per GUID");
auto &Summary = GlobalList.second.SummaryList[0];
if (!IsThinLTO) {
Summary->setNotEligibleToImport();
continue;
}
bool AllRefsCanBeExternallyReferenced =
llvm::all_of(Summary->refs(), [&](const ValueInfo &VI) {
return !CantBePromoted.count(VI.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) {
return !CantBePromoted.count(Edge.first.getGUID());
});
if (!AllCallsCanBeExternallyReferenced)
Summary->setNotEligibleToImport();
}
}
if (!ModuleSummaryDotFile.empty()) {
std::error_code EC;
raw_fd_ostream OSDot(ModuleSummaryDotFile, EC, sys::fs::OpenFlags::OF_None);
if (EC)
report_fatal_error(Twine("Failed to open dot file ") +
ModuleSummaryDotFile + ": " + EC.message() + "\n");
Index.exportToDot(OSDot);
}
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.emplace(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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