LLVM 17.0.0git
SummaryBasedOptimizations.cpp
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1//==-SummaryBasedOptimizations.cpp - Optimizations based on ThinLTO summary-==//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements optimizations that are based on the module summaries.
10// These optimizations are performed during the thinlink phase of the
11// compilation.
12//
13//===----------------------------------------------------------------------===//
14
19
20using namespace llvm;
21
23 "thinlto-synthesize-entry-counts", cl::init(false), cl::Hidden,
24 cl::desc("Synthesize entry counts based on the summary"));
25
26namespace llvm {
28}
29
31 auto Root = Index.calculateCallGraphRoot();
32 // Root is a fake node. All its successors are the actual roots of the
33 // callgraph.
34 // FIXME: This initializes the entry counts of only the root nodes. This makes
35 // sense when compiling a binary with ThinLTO, but for libraries any of the
36 // non-root nodes could be called from outside.
37 for (auto &C : Root.calls()) {
38 auto &V = C.first;
39 for (auto &GVS : V.getSummaryList()) {
40 auto S = GVS.get()->getBaseObject();
41 auto *F = cast<FunctionSummary>(S);
42 F->setEntryCount(InitialSyntheticCount);
43 }
44 }
45}
46
49 return;
50
53 auto GetCallSiteRelFreq = [](FunctionSummary::EdgeTy &Edge) {
54 return Scaled64(Edge.second.RelBlockFreq, -CalleeInfo::ScaleShift);
55 };
56 auto GetEntryCount = [](ValueInfo V) {
57 if (V.getSummaryList().size()) {
58 auto S = V.getSummaryList().front()->getBaseObject();
59 auto *F = cast<FunctionSummary>(S);
60 return F->entryCount();
61 } else {
62 return UINT64_C(0);
63 }
64 };
65 auto AddToEntryCount = [](ValueInfo V, Scaled64 New) {
66 if (!V.getSummaryList().size())
67 return;
68 for (auto &GVS : V.getSummaryList()) {
69 auto S = GVS.get()->getBaseObject();
70 auto *F = cast<FunctionSummary>(S);
71 F->setEntryCount(
72 SaturatingAdd(F->entryCount(), New.template toInt<uint64_t>()));
73 }
74 };
75
76 auto GetProfileCount = [&](ValueInfo V, FunctionSummary::EdgeTy &Edge) {
77 auto RelFreq = GetCallSiteRelFreq(Edge);
78 Scaled64 EC(GetEntryCount(V), 0);
79 return RelFreq * EC;
80 };
81 // After initializing the counts in initializeCounts above, the counts have to
82 // be propagated across the combined callgraph.
83 // SyntheticCountsUtils::propagate takes care of this propagation on any
84 // callgraph that specialized GraphTraits.
86 AddToEntryCount);
87 Index.setHasSyntheticEntryCounts();
88}
#define F(x, y, z)
Definition: MD5.cpp:55
ModuleSummaryIndex.h This file contains the declarations the classes that hold the module index and s...
static void initializeCounts(ModuleSummaryIndex &Index)
static cl::opt< bool > ThinLTOSynthesizeEntryCounts("thinlto-synthesize-entry-counts", cl::init(false), cl::Hidden, cl::desc("Synthesize entry counts based on the summary"))
ScaledNumber< uint64_t > Scaled64
std::pair< ValueInfo, CalleeInfo > EdgeTy
<CalleeValueInfo, CalleeInfo> call edge pair.
Class to hold module path string table and global value map, and encapsulate methods for operating on...
static void propagate(const CallGraphType &CG, GetProfCountTy GetProfCount, AddCountTy AddCount)
Propgate synthetic entry counts on a callgraph CG.
@ C
The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:445
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
void computeSyntheticCounts(ModuleSummaryIndex &Index)
Compute synthetic function entry counts.
cl::opt< int > InitialSyntheticCount
std::enable_if_t< std::is_unsigned< T >::value, T > SaturatingAdd(T X, T Y, bool *ResultOverflowed=nullptr)
Add two unsigned integers, X and Y, of type T.
Definition: MathExtras.h:569
static constexpr int32_t ScaleShift
Struct that holds a reference to a particular GUID in a global value summary.
ArrayRef< std::unique_ptr< GlobalValueSummary > > getSummaryList() const