b45994b843
Summary: Instead of using two separate callbacks to return the entry count and the relative block frequency, use a single callback to return callsite count. This would allow better supporting hybrid mode in the future as the count of callsite need not always be derived from entry count (as in sample PGO). Reviewers: davidxl Subscribers: mehdi_amini, steven_wu, dexonsmith, dang, llvm-commits Differential Revision: https://reviews.llvm.org/D56464 llvm-svn: 350755
87 lines
3.1 KiB
C++
87 lines
3.1 KiB
C++
//==-SummaryBasedOptimizations.cpp - Optimizations based on ThinLTO summary-==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements optimizations that are based on the module summaries.
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// These optimizations are performed during the thinlink phase of the
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// compilation.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/LTO/SummaryBasedOptimizations.h"
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#include "llvm/Analysis/SyntheticCountsUtils.h"
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#include "llvm/IR/ModuleSummaryIndex.h"
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using namespace llvm;
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cl::opt<bool> ThinLTOSynthesizeEntryCounts(
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"thinlto-synthesize-entry-counts", cl::init(false), cl::Hidden,
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cl::desc("Synthesize entry counts based on the summary"));
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extern cl::opt<int> InitialSyntheticCount;
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static void initializeCounts(ModuleSummaryIndex &Index) {
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auto Root = Index.calculateCallGraphRoot();
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// Root is a fake node. All its successors are the actual roots of the
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// callgraph.
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// FIXME: This initializes the entry counts of only the root nodes. This makes
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// sense when compiling a binary with ThinLTO, but for libraries any of the
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// non-root nodes could be called from outside.
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for (auto &C : Root.calls()) {
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auto &V = C.first;
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for (auto &GVS : V.getSummaryList()) {
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auto S = GVS.get()->getBaseObject();
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auto *F = cast<FunctionSummary>(S);
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F->setEntryCount(InitialSyntheticCount);
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}
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}
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}
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void llvm::computeSyntheticCounts(ModuleSummaryIndex &Index) {
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if (!ThinLTOSynthesizeEntryCounts)
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return;
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using Scaled64 = ScaledNumber<uint64_t>;
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initializeCounts(Index);
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auto GetCallSiteRelFreq = [](FunctionSummary::EdgeTy &Edge) {
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return Scaled64(Edge.second.RelBlockFreq, -CalleeInfo::ScaleShift);
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};
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auto GetEntryCount = [](ValueInfo V) {
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if (V.getSummaryList().size()) {
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auto S = V.getSummaryList().front().get()->getBaseObject();
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auto *F = cast<FunctionSummary>(S);
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return F->entryCount();
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} else {
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return UINT64_C(0);
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}
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};
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auto AddToEntryCount = [](ValueInfo V, Scaled64 New) {
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if (!V.getSummaryList().size())
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return;
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for (auto &GVS : V.getSummaryList()) {
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auto S = GVS.get()->getBaseObject();
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auto *F = cast<FunctionSummary>(S);
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F->setEntryCount(
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SaturatingAdd(F->entryCount(), New.template toInt<uint64_t>()));
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}
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};
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auto GetProfileCount = [&](ValueInfo V, FunctionSummary::EdgeTy &Edge) {
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auto RelFreq = GetCallSiteRelFreq(Edge);
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Scaled64 EC(GetEntryCount(V), 0);
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return RelFreq * EC;
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};
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// After initializing the counts in initializeCounts above, the counts have to
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// be propagated across the combined callgraph.
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// SyntheticCountsUtils::propagate takes care of this propagation on any
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// callgraph that specialized GraphTraits.
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SyntheticCountsUtils<ModuleSummaryIndex *>::propagate(&Index, GetProfileCount,
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AddToEntryCount);
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Index.setHasSyntheticEntryCounts();
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}
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