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[ThinLTO] Add call edges' relative block frequency to per-module summary. 

Summary:
This allows relative block frequency of call edges to be passed to the
thinlink stage where it will be used to compute synthetic entry counts
of functions.

Reviewers: tejohnson, pcc

Subscribers: mehdi_amini, llvm-commits, inglorion

Differential Revision: https://reviews.llvm.org/D42212

llvm-svn: 323349
This commit is contained in:
Easwaran Raman 2018-01-24 17:51:23 +00:00
parent 4bd8e5332f
commit 5f7aff9a0a
7 changed files with 119 additions and 27 deletions
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5
llvm/include/llvm/Bitcode/LLVMBitCodes.h
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@ -256,6 +256,11 @@ enum GlobalValueSummarySymtabCodes {
// strings in strtab.
// [n * name]
FS_CFI_FUNCTION_DECLS = 18,
// Per-module summary that also adds relative block frequency to callee info.
// PERMODULE_RELBF: [valueid, flags, instcount, numrefs,
// numrefs x valueid,
// n x (valueid, relblockfreq)]
FS_PERMODULE_RELBF = 19,
};
enum MetadataCodes {

21
llvm/include/llvm/IR/ModuleSummaryIndex.h
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@ -25,6 +25,7 @@
#include "llvm/ADT/StringRef.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/MathExtras.h"
#include <algorithm>
#include <array>
#include <cassert>
@ -54,14 +55,28 @@ struct CalleeInfo {
Hot = 3,
Critical = 4
};
HotnessType Hotness = HotnessType::Unknown;
CalleeInfo() = default;
explicit CalleeInfo(HotnessType Hotness) : Hotness(Hotness) {}
// The size of the bit-field might need to be adjusted if more values are
// added to HotnessType enum.
HotnessType Hotness : 3;
uint32_t RelBlockFreq : 29;
static constexpr uint64_t MaxRelBlockFreq = (1 << 29) - 1;
CalleeInfo() : Hotness(HotnessType::Unknown), RelBlockFreq(0) {}
explicit CalleeInfo(HotnessType Hotness, uint64_t RelBF)
: Hotness(Hotness), RelBlockFreq(RelBF) {}
void updateHotness(const HotnessType OtherHotness) {
Hotness = std::max(Hotness, OtherHotness);
}
// When there are multiple edges between the same (caller, callee) pair, the
// relative block frequencies are summed up.
void updateRelBlockFreq(uint64_t RBF) {
uint64_t Sum = SaturatingAdd<uint64_t>(RelBlockFreq, RBF);
Sum = std::min(Sum, uint64_t(MaxRelBlockFreq));
RelBlockFreq = static_cast<uint32_t>(Sum);
}
};
class GlobalValueSummary;

21
llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
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@ -273,9 +273,24 @@ computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
// 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[Index.getOrInsertValueInfo(
cast<GlobalValue>(CalledValue))]
.updateHotness(Hotness);
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) {
auto BBFreq = BFI->getBlockFreq(CI->getParent()).getFrequency();
// FIXME: This might need some scaling to prevent BBFreq values from
// being rounded down to 0.
auto EntryFreq = BFI->getEntryFreq();
// Block frequencies can be directly set for a block and so we need to
// handle the case of entry frequency being 0.
if (EntryFreq)
BBFreq /= EntryFreq;
else
BBFreq = 0;
ValueInfo.updateRelBlockFreq(BBFreq);
}
} else {
// Skip inline assembly calls.
if (CI && CI->isInlineAsm())

23
llvm/lib/Bitcode/Reader/BitcodeReader.cpp
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@ -743,7 +743,8 @@ private:
std::vector<ValueInfo> makeRefList(ArrayRef<uint64_t> Record);
std::vector<FunctionSummary::EdgeTy> makeCallList(ArrayRef<uint64_t> Record,
bool IsOldProfileFormat,
bool HasProfile);
bool HasProfile,
bool HasRelBF);
Error parseEntireSummary(unsigned ID);
Error parseModuleStringTable();
@ -5047,12 +5048,15 @@ ModuleSummaryIndexBitcodeReader::makeRefList(ArrayRef<uint64_t> Record) {
return Ret;
}
std::vector<FunctionSummary::EdgeTy> ModuleSummaryIndexBitcodeReader::makeCallList(
ArrayRef<uint64_t> Record, bool IsOldProfileFormat, bool HasProfile) {
std::vector<FunctionSummary::EdgeTy>
ModuleSummaryIndexBitcodeReader::makeCallList(ArrayRef<uint64_t> Record,
bool IsOldProfileFormat,
bool HasProfile, bool HasRelBF) {
std::vector<FunctionSummary::EdgeTy> Ret;
Ret.reserve(Record.size());
for (unsigned I = 0, E = Record.size(); I != E; ++I) {
CalleeInfo::HotnessType Hotness = CalleeInfo::HotnessType::Unknown;
uint64_t RelBF = 0;
ValueInfo Callee = getValueInfoFromValueId(Record[I]).first;
if (IsOldProfileFormat) {
I += 1; // Skip old callsitecount field
@ -5060,7 +5064,9 @@ std::vector<FunctionSummary::EdgeTy> ModuleSummaryIndexBitcodeReader::makeCallLi
I += 1; // Skip old profilecount field
} else if (HasProfile)
Hotness = static_cast<CalleeInfo::HotnessType>(Record[++I]);
Ret.push_back(FunctionSummary::EdgeTy{Callee, CalleeInfo{Hotness}});
else if (HasRelBF)
RelBF = Record[++I];
Ret.push_back(FunctionSummary::EdgeTy{Callee, CalleeInfo(Hotness, RelBF)});
}
return Ret;
}
@ -5139,7 +5145,11 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
// FS_PERMODULE_PROFILE: [valueid, flags, instcount, fflags, numrefs,
// numrefs x valueid,
// n x (valueid, hotness)]
// FS_PERMODULE_RELBF: [valueid, flags, instcount, fflags, numrefs,
// numrefs x valueid,
// n x (valueid, relblockfreq)]
case bitc::FS_PERMODULE:
case bitc::FS_PERMODULE_RELBF:
case bitc::FS_PERMODULE_PROFILE: {
unsigned ValueID = Record[0];
uint64_t RawFlags = Record[1];
@ -5165,9 +5175,10 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
std::vector<ValueInfo> Refs = makeRefList(
ArrayRef<uint64_t>(Record).slice(RefListStartIndex, NumRefs));
bool HasProfile = (BitCode == bitc::FS_PERMODULE_PROFILE);
bool HasRelBF = (BitCode == bitc::FS_PERMODULE_RELBF);
std::vector<FunctionSummary::EdgeTy> Calls = makeCallList(
ArrayRef<uint64_t>(Record).slice(CallGraphEdgeStartIndex),
IsOldProfileFormat, HasProfile);
IsOldProfileFormat, HasProfile, HasRelBF);
auto FS = llvm::make_unique<FunctionSummary>(
Flags, InstCount, getDecodedFFlags(RawFunFlags), std::move(Refs),
std::move(Calls), std::move(PendingTypeTests),
@ -5259,7 +5270,7 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
bool HasProfile = (BitCode == bitc::FS_COMBINED_PROFILE);
std::vector<FunctionSummary::EdgeTy> Edges = makeCallList(
ArrayRef<uint64_t>(Record).slice(CallGraphEdgeStartIndex),
IsOldProfileFormat, HasProfile);
IsOldProfileFormat, HasProfile, false);
ValueInfo VI = getValueInfoFromValueId(ValueID).first;
auto FS = llvm::make_unique<FunctionSummary>(
Flags, InstCount, getDecodedFFlags(RawFunFlags), std::move(Refs),

40
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
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@ -86,6 +86,9 @@ static cl::opt<unsigned>
cl::desc("Number of metadatas above which we emit an index "
"to enable lazy-loading"));
cl::opt<bool> WriteRelBFToSummary(
"write-relbf-to-summary", cl::Hidden, cl::init(false),
cl::desc("Write relative block frequency to function summary "));
namespace {
/// These are manifest constants used by the bitcode writer. They do not need to
@ -3378,11 +3381,15 @@ void ModuleBitcodeWriterBase::writePerModuleFunctionSummaryRecord(
NameVals.push_back(getValueId(ECI.first));
if (HasProfileData)
NameVals.push_back(static_cast<uint8_t>(ECI.second.Hotness));
else if (WriteRelBFToSummary)
NameVals.push_back(ECI.second.RelBlockFreq);
}
unsigned FSAbbrev = (HasProfileData ? FSCallsProfileAbbrev : FSCallsAbbrev);
unsigned Code =
(HasProfileData ? bitc::FS_PERMODULE_PROFILE : bitc::FS_PERMODULE);
(HasProfileData ? bitc::FS_PERMODULE_PROFILE
: (WriteRelBFToSummary ? bitc::FS_PERMODULE_RELBF
: bitc::FS_PERMODULE));
// Emit the finished record.
Stream.EmitRecord(Code, NameVals, FSAbbrev);
@ -3448,21 +3455,8 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
ArrayRef<uint64_t>{GVI.second, GVI.first});
}
// Abbrev for FS_PERMODULE.
auto Abbv = std::make_shared<BitCodeAbbrev>();
Abbv->Add(BitCodeAbbrevOp(bitc::FS_PERMODULE));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8)); // valueid
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // flags
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8)); // instcount
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // fflags
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // numrefs
// numrefs x valueid, n x (valueid)
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
unsigned FSCallsAbbrev = Stream.EmitAbbrev(std::move(Abbv));
// Abbrev for FS_PERMODULE_PROFILE.
Abbv = std::make_shared<BitCodeAbbrev>();
auto Abbv = std::make_shared<BitCodeAbbrev>();
Abbv->Add(BitCodeAbbrevOp(bitc::FS_PERMODULE_PROFILE));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8)); // valueid
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // flags
@ -3474,6 +3468,22 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
unsigned FSCallsProfileAbbrev = Stream.EmitAbbrev(std::move(Abbv));
// Abbrev for FS_PERMODULE or FS_PERMODULE_RELBF.
Abbv = std::make_shared<BitCodeAbbrev>();
if (WriteRelBFToSummary)
Abbv->Add(BitCodeAbbrevOp(bitc::FS_PERMODULE_RELBF));
else
Abbv->Add(BitCodeAbbrevOp(bitc::FS_PERMODULE));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8)); // valueid
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // flags
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8)); // instcount
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // fflags
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // numrefs
// numrefs x valueid, n x (valueid [, rel_block_freq])
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
unsigned FSCallsAbbrev = Stream.EmitAbbrev(std::move(Abbv));
// Abbrev for FS_PERMODULE_GLOBALVAR_INIT_REFS.
Abbv = std::make_shared<BitCodeAbbrev>();
Abbv->Add(BitCodeAbbrevOp(bitc::FS_PERMODULE_GLOBALVAR_INIT_REFS));

35
llvm/test/Bitcode/thinlto-function-summary-callgraph-relbf.ll Normal file
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@ -0,0 +1,35 @@
; Test to check the callgraph in summary
; RUN: opt -write-relbf-to-summary -module-summary %s -o %t.o
; RUN: llvm-bcanalyzer -dump %t.o | FileCheck %s
; CHECK: <SOURCE_FILENAME
; CHECK-NEXT: <GLOBALVAR
; CHECK-NEXT: <FUNCTION
; "func"
; CHECK-NEXT: <FUNCTION op0=17 op1=4
; CHECK: <GLOBALVAL_SUMMARY_BLOCK
; CHECK-NEXT: <VERSION
; See if the call to func is registered.
; CHECK-NEXT: <PERMODULE_RELBF {{.*}} op4=1 {{.*}} op7=1
; CHECK-NEXT: </GLOBALVAL_SUMMARY_BLOCK>
; CHECK: <STRTAB_BLOCK
; CHECK-NEXT: blob data = 'undefinedglobmainfunc{{.*}}'
; ModuleID = 'thinlto-function-summary-callgraph.ll'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; Function Attrs: nounwind uwtable
define i32 @main() #0 {
entry:
call void (...) @func()
%u = load i32, i32* @undefinedglob
ret i32 %u
}
declare void @func(...) #1
@undefinedglob = external global i32
; OLD: Index {{.*}} contains 1 nodes (1 functions, 0 alias, 0 globals) and 1 edges (0 refs and 1 calls)

1
llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
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@ -306,6 +306,7 @@ static const char *GetCodeName(unsigned CodeID, unsigned BlockID,
return nullptr;
STRINGIFY_CODE(FS, PERMODULE)
STRINGIFY_CODE(FS, PERMODULE_PROFILE)
STRINGIFY_CODE(FS, PERMODULE_RELBF)
STRINGIFY_CODE(FS, PERMODULE_GLOBALVAR_INIT_REFS)
STRINGIFY_CODE(FS, COMBINED)
STRINGIFY_CODE(FS, COMBINED_PROFILE)