1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
|
//===- PGOCtxProfFlattening.cpp - Contextual Instr. Flattening ------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Flattens the contextual profile and lowers it to MD_prof.
// This should happen after all IPO (which is assumed to have maintained the
// contextual profile) happened. Flattening consists of summing the values at
// the same index of the counters belonging to all the contexts of a function.
// The lowering consists of materializing the counter values to function
// entrypoint counts and branch probabilities.
//
// This pass also removes contextual instrumentation, which has been kept around
// to facilitate its functionality.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Instrumentation/PGOCtxProfFlattening.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/CtxProfAnalysis.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/IR/Analysis.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/ProfileSummary.h"
#include "llvm/ProfileData/ProfileCommon.h"
#include "llvm/Transforms/Instrumentation/PGOInstrumentation.h"
#include "llvm/Transforms/Scalar/DCE.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
using namespace llvm;
#define DEBUG_TYPE "ctx_prof_flatten"
namespace {
/// Assign branch weights and function entry count. Also update the PSI
/// builder.
void assignProfileData(Function &F, ArrayRef<uint64_t> RawCounters) {
assert(!RawCounters.empty());
ProfileAnnotator PA(F, RawCounters);
F.setEntryCount(RawCounters[0]);
SmallVector<uint64_t, 2> ProfileHolder;
for (auto &BB : F) {
for (auto &I : BB)
if (auto *SI = dyn_cast<SelectInst>(&I)) {
uint64_t TrueCount, FalseCount = 0;
if (!PA.getSelectInstrProfile(*SI, TrueCount, FalseCount))
continue;
setProfMetadata(F.getParent(), SI, {TrueCount, FalseCount},
std::max(TrueCount, FalseCount));
}
if (succ_size(&BB) < 2)
continue;
uint64_t MaxCount = 0;
if (!PA.getOutgoingBranchWeights(BB, ProfileHolder, MaxCount))
continue;
assert(MaxCount > 0);
setProfMetadata(F.getParent(), BB.getTerminator(), ProfileHolder, MaxCount);
}
}
[[maybe_unused]] bool areAllBBsReachable(const Function &F,
FunctionAnalysisManager &FAM) {
auto &DT = FAM.getResult<DominatorTreeAnalysis>(const_cast<Function &>(F));
return llvm::all_of(
F, [&](const BasicBlock &BB) { return DT.isReachableFromEntry(&BB); });
}
void clearColdFunctionProfile(Function &F) {
for (auto &BB : F)
BB.getTerminator()->setMetadata(LLVMContext::MD_prof, nullptr);
F.setEntryCount(0U);
}
void removeInstrumentation(Function &F) {
for (auto &BB : F)
for (auto &I : llvm::make_early_inc_range(BB))
if (isa<InstrProfCntrInstBase>(I))
I.eraseFromParent();
}
void annotateIndirectCall(
Module &M, CallBase &CB,
const DenseMap<uint32_t, FlatIndirectTargets> &FlatProf,
const InstrProfCallsite &Ins) {
auto Idx = Ins.getIndex()->getZExtValue();
auto FIt = FlatProf.find(Idx);
if (FIt == FlatProf.end())
return;
const auto &Targets = FIt->second;
SmallVector<InstrProfValueData, 2> Data;
uint64_t Sum = 0;
for (auto &[Guid, Count] : Targets) {
Data.push_back({/*.Value=*/Guid, /*.Count=*/Count});
Sum += Count;
}
llvm::sort(Data,
[](const InstrProfValueData &A, const InstrProfValueData &B) {
return A.Count > B.Count;
});
llvm::annotateValueSite(M, CB, Data, Sum,
InstrProfValueKind::IPVK_IndirectCallTarget,
Data.size());
LLVM_DEBUG(dbgs() << "[ctxprof] flat indirect call prof: " << CB
<< CB.getMetadata(LLVMContext::MD_prof) << "\n");
}
// We normally return a "Changed" bool, but the calling pass' run assumes
// something will change - some profile will be added - so this won't add much
// by returning false when applicable.
void annotateIndirectCalls(Module &M, const CtxProfAnalysis::Result &CtxProf) {
const auto FlatIndCalls = CtxProf.flattenVirtCalls();
for (auto &F : M) {
if (F.isDeclaration())
continue;
auto FlatProfIter = FlatIndCalls.find(AssignGUIDPass::getGUID(F));
if (FlatProfIter == FlatIndCalls.end())
continue;
const auto &FlatProf = FlatProfIter->second;
for (auto &BB : F) {
for (auto &I : BB) {
auto *CB = dyn_cast<CallBase>(&I);
if (!CB || !CB->isIndirectCall())
continue;
if (auto *Ins = CtxProfAnalysis::getCallsiteInstrumentation(*CB))
annotateIndirectCall(M, *CB, FlatProf, *Ins);
}
}
}
}
} // namespace
PreservedAnalyses PGOCtxProfFlatteningPass::run(Module &M,
ModuleAnalysisManager &MAM) {
// Ensure in all cases the instrumentation is removed: if this module had no
// roots, the contextual profile would evaluate to false, but there would
// still be instrumentation.
// Note: in such cases we leave as-is any other profile info (if present -
// e.g. synthetic weights, etc) because it wouldn't interfere with the
// contextual - based one (which would be in other modules)
auto OnExit = llvm::make_scope_exit([&]() {
if (IsPreThinlink)
return;
for (auto &F : M)
removeInstrumentation(F);
});
auto &CtxProf = MAM.getResult<CtxProfAnalysis>(M);
// post-thinlink, we only reprocess for the module(s) containing the
// contextual tree. For everything else, OnExit will just clean the
// instrumentation.
if (!IsPreThinlink && !CtxProf.isInSpecializedModule())
return PreservedAnalyses::none();
if (IsPreThinlink)
annotateIndirectCalls(M, CtxProf);
const auto FlattenedProfile = CtxProf.flatten();
for (auto &F : M) {
if (F.isDeclaration())
continue;
assert(areAllBBsReachable(
F, MAM.getResult<FunctionAnalysisManagerModuleProxy>(M)
.getManager()) &&
"Function has unreacheable basic blocks. The expectation was that "
"DCE was run before.");
auto It = FlattenedProfile.find(AssignGUIDPass::getGUID(F));
// If this function didn't appear in the contextual profile, it's cold.
if (It == FlattenedProfile.end())
clearColdFunctionProfile(F);
else
assignProfileData(F, It->second);
}
InstrProfSummaryBuilder PB(ProfileSummaryBuilder::DefaultCutoffs);
// use here the flat profiles just so the importer doesn't complain about
// how different the PSIs are between the module with the roots and the
// various modules it imports.
for (auto &C : FlattenedProfile) {
PB.addEntryCount(C.second[0]);
for (auto V : llvm::drop_begin(C.second))
PB.addInternalCount(V);
}
M.setProfileSummary(PB.getSummary()->getMD(M.getContext()),
ProfileSummary::Kind::PSK_Instr);
PreservedAnalyses PA;
PA.abandon<ProfileSummaryAnalysis>();
MAM.invalidate(M, PA);
auto &PSI = MAM.getResult<ProfileSummaryAnalysis>(M);
PSI.refresh(PB.getSummary());
return PreservedAnalyses::none();
}
|
