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 | |
9 | #include "llvm/Transforms/Instrumentation/LowerAllowCheckPass.h" |
10 | |
11 | #include "llvm/ADT/SmallVector.h" |
12 | #include "llvm/ADT/Statistic.h" |
13 | #include "llvm/ADT/StringRef.h" |
14 | #include "llvm/Analysis/OptimizationRemarkEmitter.h" |
15 | #include "llvm/Analysis/ProfileSummaryInfo.h" |
16 | #include "llvm/IR/Constant.h" |
17 | #include "llvm/IR/Constants.h" |
18 | #include "llvm/IR/DiagnosticInfo.h" |
19 | #include "llvm/IR/Instructions.h" |
20 | #include "llvm/IR/IntrinsicInst.h" |
21 | #include "llvm/IR/Intrinsics.h" |
22 | #include "llvm/IR/Metadata.h" |
23 | #include "llvm/Support/RandomNumberGenerator.h" |
24 | #include <memory> |
25 | #include <random> |
26 | |
27 | using namespace llvm; |
28 | |
29 | #define DEBUG_TYPE "lower-allow-check" |
30 | |
31 | static cl::opt<int> |
32 | HotPercentileCutoff("lower-allow-check-percentile-cutoff-hot" , |
33 | cl::desc("Hot percentile cuttoff." )); |
34 | |
35 | static 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 | |
40 | STATISTIC(NumChecksTotal, "Number of checks" ); |
41 | STATISTIC(NumChecksRemoved, "Number of removed checks" ); |
42 | |
43 | struct { |
44 | ore::NV ; |
45 | ore::NV ; |
46 | ore::NV ; |
47 | explicit (IntrinsicInst *II) |
48 | : Kind("Kind" , II->getArgOperand(i: 0)), |
49 | F("Function" , II->getParent()->getParent()), |
50 | BB("Block" , II->getParent()->getName()) {} |
51 | }; |
52 | |
53 | static void (IntrinsicInst *II, OptimizationRemarkEmitter &ORE, |
54 | bool Removed) { |
55 | if (Removed) { |
56 | ORE.emit(RemarkBuilder: [&]() { |
57 | RemarkInfo Info(II); |
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(RemarkBuilder: [&]() { |
64 | RemarkInfo Info(II); |
65 | return OptimizationRemarkMissed(DEBUG_TYPE, "Allowed" , II) |
66 | << "Allowed check: Kind=" << Info.Kind << " F=" << Info.F |
67 | << " BB=" << Info.BB; |
68 | }); |
69 | } |
70 | } |
71 | |
72 | static bool (Function &F, const BlockFrequencyInfo &BFI, |
73 | const ProfileSummaryInfo *PSI, |
74 | OptimizationRemarkEmitter &ORE) { |
75 | SmallVector<std::pair<IntrinsicInst *, bool>, 16> ReplaceWithValue; |
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(Name: 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>(Val: &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: &BB).value_or(u: 0); |
101 | IsHot = PSI->isHotCountNthPercentile(PercentileCutoff: HotPercentileCutoff, C: Count); |
102 | } |
103 | |
104 | bool ToRemove = ShouldRemove(IsHot); |
105 | ReplaceWithValue.push_back(Elt: { |
106 | II, |
107 | ToRemove, |
108 | }); |
109 | if (ToRemove) |
110 | ++NumChecksRemoved; |
111 | emitRemark(II, ORE, Removed: ToRemove); |
112 | break; |
113 | } |
114 | default: |
115 | break; |
116 | } |
117 | } |
118 | } |
119 | |
120 | for (auto [I, V] : ReplaceWithValue) { |
121 | I->replaceAllUsesWith(V: ConstantInt::getBool(Ty: I->getType(), V: !V)); |
122 | I->eraseFromParent(); |
123 | } |
124 | |
125 | return !ReplaceWithValue.empty(); |
126 | } |
127 | |
128 | PreservedAnalyses LowerAllowCheckPass::run(Function &F, |
129 | FunctionAnalysisManager &AM) { |
130 | if (F.isDeclaration()) |
131 | return PreservedAnalyses::all(); |
132 | auto &MAMProxy = AM.getResult<ModuleAnalysisManagerFunctionProxy>(IR&: F); |
133 | ProfileSummaryInfo *PSI = |
134 | MAMProxy.getCachedResult<ProfileSummaryAnalysis>(IR&: *F.getParent()); |
135 | BlockFrequencyInfo &BFI = AM.getResult<BlockFrequencyAnalysis>(IR&: F); |
136 | OptimizationRemarkEmitter &ORE = |
137 | AM.getResult<OptimizationRemarkEmitterAnalysis>(IR&: F); |
138 | |
139 | return removeUbsanTraps(F, BFI, PSI, ORE) ? PreservedAnalyses::none() |
140 | : PreservedAnalyses::all(); |
141 | } |
142 | |
143 | bool LowerAllowCheckPass::IsRequested() { |
144 | return RandomRate.getNumOccurrences() || |
145 | HotPercentileCutoff.getNumOccurrences(); |
146 | } |
147 | |