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llvm-mirror/lib/Analysis/ModuleSummaryAnalysis.cpp
Hiroshi Yamauchi 9896d761e8 [ThinLTO] Compute the basic block count across modules. 
Summary:
Count the per-module number of basic blocks when the module summary is computed
and sum them up during Thin LTO indexing.

This is used to estimate the working set size under the partial sample PGO.

This is split off of D79831.

Reviewers: davidxl, espindola

Subscribers: emaste, inglorion, hiraditya, MaskRay, steven_wu, dexonsmith, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80403
2020-05-28 10:33:05 -07:00

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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/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/InitializePasses.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;
const auto *CB = dyn_cast<CallBase>(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 (!(CB && CB->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.CB.arg_begin() + 1, Call.CB.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);
const auto *CB = dyn_cast<CallBase>(&I);
if (!CB)
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 = CB->getCalledOperand();
auto *CalledFunction = CB->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(*CB, 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));
}
}
Index.addBlockCount(F.size());
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),
F.hasFnAttribute(Attribute::AlwaysInline)};
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();
bool Constant = V.isConstant();
GlobalVarSummary::GVarFlags VarFlags(CanBeInternalized,
Constant ? false : CanBeInternalized,
Constant, V.getVCallVisibility());
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,
F->hasFnAttribute(Attribute::AlwaysInline)},
/*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, cast<GlobalVariable>(GV)->isConstant(),
GlobalObject::VCallVisibilityPublic),
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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