LLVM 19.0.0git
LowerAllowCheckPass.cpp
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1//===- LowerAllowCheckPass.cpp ----------------------------------*- C++ -*-===//
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
10
12#include "llvm/ADT/Statistic.h"
13#include "llvm/ADT/StringRef.h"
16#include "llvm/IR/Constant.h"
17#include "llvm/IR/Constants.h"
21#include "llvm/IR/Intrinsics.h"
22#include "llvm/IR/Metadata.h"
24#include <memory>
25#include <random>
26
27using namespace llvm;
28
29#define DEBUG_TYPE "lower-allow-check"
30
31static cl::opt<int>
32 HotPercentileCutoff("lower-allow-check-percentile-cutoff-hot",
33 cl::desc("Hot percentile cuttoff."));
34
35static cl::opt<float>
36 RandomRate("lower-allow-check-random-rate",
37 cl::desc("Probability value in the range [0.0, 1.0] of "
38 "unconditional pseudo-random checks."));
39
40STATISTIC(NumChecksTotal, "Number of checks");
41STATISTIC(NumChecksRemoved, "Number of removed checks");
42
43struct RemarkInfo {
48 : Kind("Kind", II->getArgOperand(0)),
49 F("Function", II->getParent()->getParent()),
50 BB("Block", II->getParent()->getName()) {}
51};
52
54 bool Removed) {
55 if (Removed) {
56 ORE.emit([&]() {
58 return OptimizationRemark(DEBUG_TYPE, "Removed", II)
59 << "Removed check: Kind=" << Info.Kind << " F=" << Info.F
60 << " BB=" << Info.BB;
61 });
62 } else {
63 ORE.emit([&]() {
65 return OptimizationRemarkMissed(DEBUG_TYPE, "Allowed", II)
66 << "Allowed check: Kind=" << Info.Kind << " F=" << Info.F
67 << " BB=" << Info.BB;
68 });
69 }
70}
71
73 const ProfileSummaryInfo *PSI,
76 std::unique_ptr<RandomNumberGenerator> Rng;
77
78 auto ShouldRemove = [&](bool IsHot) {
79 if (!RandomRate.getNumOccurrences())
80 return IsHot;
81 if (!Rng)
82 Rng = F.getParent()->createRNG(F.getName());
83 std::bernoulli_distribution D(RandomRate);
84 return !D(*Rng);
85 };
86
87 for (BasicBlock &BB : F) {
88 for (Instruction &I : BB) {
89 IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
90 if (!II)
91 continue;
92 auto ID = II->getIntrinsicID();
93 switch (ID) {
94 case Intrinsic::allow_ubsan_check:
95 case Intrinsic::allow_runtime_check: {
96 ++NumChecksTotal;
97
98 bool IsHot = false;
99 if (PSI) {
100 uint64_t Count = BFI.getBlockProfileCount(&BB).value_or(0);
101 IsHot = PSI->isHotCountNthPercentile(HotPercentileCutoff, Count);
102 }
103
104 bool ToRemove = ShouldRemove(IsHot);
105 ReplaceWithValue.push_back({
106 II,
107 ToRemove,
108 });
109 if (ToRemove)
110 ++NumChecksRemoved;
111 emitRemark(II, ORE, ToRemove);
112 break;
113 }
114 default:
115 break;
116 }
117 }
118 }
119
120 for (auto [I, V] : ReplaceWithValue) {
121 I->replaceAllUsesWith(ConstantInt::getBool(I->getType(), !V));
122 I->eraseFromParent();
123 }
124
125 return !ReplaceWithValue.empty();
126}
127
130 if (F.isDeclaration())
131 return PreservedAnalyses::all();
132 auto &MAMProxy = AM.getResult<ModuleAnalysisManagerFunctionProxy>(F);
133 ProfileSummaryInfo *PSI =
134 MAMProxy.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
138
139 return removeUbsanTraps(F, BFI, PSI, ORE) ? PreservedAnalyses::none()
141}
142
144 return RandomRate.getNumOccurrences() ||
145 HotPercentileCutoff.getNumOccurrences();
146}
ReachingDefAnalysis InstSet & ToRemove
static const Function * getParent(const Value *V)
static GCRegistry::Add< StatepointGC > D("statepoint-example", "an example strategy for statepoint")
Analysis containing CSE Info
Definition: CSEInfo.cpp:27
This file contains the declarations for the subclasses of Constant, which represent the different fla...
static bool removeUbsanTraps(Function &F, const BlockFrequencyInfo &BFI, const ProfileSummaryInfo *PSI, OptimizationRemarkEmitter &ORE)
static cl::opt< int > HotPercentileCutoff("lower-allow-check-percentile-cutoff-hot", cl::desc("Hot percentile cuttoff."))
static cl::opt< float > RandomRate("lower-allow-check-random-rate", cl::desc("Probability value in the range [0.0, 1.0] of " "unconditional pseudo-random checks."))
static void emitRemark(IntrinsicInst *II, OptimizationRemarkEmitter &ORE, bool Removed)
#define DEBUG_TYPE
This file provides the interface for the pass responsible for removing expensive ubsan checks.
#define F(x, y, z)
Definition: MD5.cpp:55
#define I(x, y, z)
Definition: MD5.cpp:58
This file contains the declarations for metadata subclasses.
uint64_t IntrinsicInst * II
static StringRef getName(Value *V)
This file defines the SmallVector class.
This file defines the 'Statistic' class, which is designed to be an easy way to expose various metric...
#define STATISTIC(VARNAME, DESC)
Definition: Statistic.h:167
A container for analyses that lazily runs them and caches their results.
Definition: PassManager.h:321
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:473
LLVM Basic Block Representation.
Definition: BasicBlock.h:60
Analysis pass which computes BlockFrequencyInfo.
BlockFrequencyInfo pass uses BlockFrequencyInfoImpl implementation to estimate IR basic block frequen...
static ConstantInt * getBool(LLVMContext &Context, bool V)
Definition: Constants.cpp:864
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:48
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
The optimization diagnostic interface.
void emit(DiagnosticInfoOptimizationBase &OptDiag)
Output the remark via the diagnostic handler and to the optimization record file.
Diagnostic information for missed-optimization remarks.
Diagnostic information for applied optimization remarks.
An analysis over an "inner" IR unit that provides access to an analysis manager over a "outer" IR uni...
Definition: PassManager.h:756
A set of analyses that are preserved following a run of a transformation pass.
Definition: Analysis.h:109
static PreservedAnalyses none()
Convenience factory function for the empty preserved set.
Definition: Analysis.h:112
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: Analysis.h:115
An analysis pass based on the new PM to deliver ProfileSummaryInfo.
Analysis providing profile information.
bool isHotCountNthPercentile(int PercentileCutoff, uint64_t C) const
Returns true if count C is considered hot with regard to a given hot percentile cutoff value.
bool empty() const
Definition: SmallVector.h:94
void push_back(const T &Elt)
Definition: SmallVector.h:426
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1209
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
RemarkInfo(IntrinsicInst *II)
Used in the streaming interface as the general argument type.