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[ubsan] Parse and use <cutoffs[0,1,2]=70000;cutoffs[5,6,8]=90000> in LowerAllowCheckPass (#124211)

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This adds and utilizes a cutoffs parameter for LowerAllowCheckPass, via the Options parameter (introduced in https://github.com/llvm/llvm-project/pull/122994).

Future work will connect -fsanitize-skip-hot-cutoff (introduced patch in https://github.com/llvm/llvm-project/pull/121619) in the clang frontend to the cutoffs parameter used here.
This commit is contained in:
Thurston Dang
2025-01-27 20:08:53 -08:00
committed by GitHub
parent 5ab43c3e7d
commit fa9ac62d02
4 changed files with 121 additions and 15 deletions
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4
llvm/include/llvm/Transforms/Instrumentation/LowerAllowCheckPass.h
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@@ -25,7 +25,7 @@ namespace llvm {
class LowerAllowCheckPass : public PassInfoMixin<LowerAllowCheckPass> {
public:
struct Options {
std::vector<unsigned int> placeholder; // TODO: cutoffs
std::vector<unsigned int> cutoffs;
};
explicit LowerAllowCheckPass(LowerAllowCheckPass::Options Opts)
@@ -33,6 +33,8 @@ public:
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
static bool IsRequested();
void printPipeline(raw_ostream &OS,
function_ref<StringRef(StringRef)> MapClassName2PassName);
private:
LowerAllowCheckPass::Options Opts;

62
llvm/lib/Passes/PassBuilder.cpp
View File

@@ -828,11 +828,65 @@ parseLowerAllowCheckPassOptions(StringRef Params) {
StringRef ParamName;
std::tie(ParamName, Params) = Params.split(';');
return make_error<StringError>(
formatv("invalid LowerAllowCheck pass parameter '{0}' ", ParamName)
.str(),
inconvertibleErrorCode());
// Format is <cutoffs[1,2,3]=70000;cutoffs[5,6,8]=90000>
//
// Parsing allows duplicate indices (last one takes precedence).
// It would technically be in spec to specify
// cutoffs[0]=70000,cutoffs[1]=90000,cutoffs[0]=80000,...
if (ParamName.starts_with("cutoffs[")) {
StringRef IndicesStr;
StringRef CutoffStr;
std::tie(IndicesStr, CutoffStr) = ParamName.split("]=");
// cutoffs[1,2,3
// 70000
int cutoff;
if (CutoffStr.getAsInteger(0, cutoff))
return make_error<StringError>(
formatv("invalid LowerAllowCheck pass cutoffs parameter '{0}' "
"({1})",
CutoffStr, Params)
.str(),
inconvertibleErrorCode());
if (!IndicesStr.consume_front("cutoffs[") || IndicesStr == "")
return make_error<StringError>(
formatv("invalid LowerAllowCheck pass index parameter '{0}' "
"({1})",
IndicesStr, CutoffStr)
.str(),
inconvertibleErrorCode());
while (IndicesStr != "") {
StringRef firstIndexStr;
std::tie(firstIndexStr, IndicesStr) = IndicesStr.split('|');
unsigned int index;
if (firstIndexStr.getAsInteger(0, index))
return make_error<StringError>(
formatv("invalid LowerAllowCheck pass index parameter '{0}' "
"({1}) {2}",
firstIndexStr, IndicesStr)
.str(),
inconvertibleErrorCode());
// In the common case (sequentially increasing indices), we will issue
// O(n) resize requests. We assume the underlying data structure has
// O(1) runtime for each added element.
if (index >= Result.cutoffs.size())
Result.cutoffs.resize(index + 1, 0);
Result.cutoffs[index] = cutoff;
}
} else {
return make_error<StringError>(
formatv("invalid LowerAllowCheck pass parameter '{0}' ", ParamName)
.str(),
inconvertibleErrorCode());
}
}
return Result;
}

62
llvm/lib/Transforms/Instrumentation/LowerAllowCheckPass.cpp
View File

@@ -20,6 +20,7 @@
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/RandomNumberGenerator.h"
#include <memory>
#include <random>
@@ -71,7 +72,8 @@ static void emitRemark(IntrinsicInst *II, OptimizationRemarkEmitter &ORE,
static bool removeUbsanTraps(Function &F, const BlockFrequencyInfo &BFI,
const ProfileSummaryInfo *PSI,
OptimizationRemarkEmitter &ORE) {
OptimizationRemarkEmitter &ORE,
const std::vector<unsigned int> &cutoffs) {
SmallVector<std::pair<IntrinsicInst *, bool>, 16> ReplaceWithValue;
std::unique_ptr<RandomNumberGenerator> Rng;
@@ -81,10 +83,22 @@ static bool removeUbsanTraps(Function &F, const BlockFrequencyInfo &BFI,
return *Rng;
};
auto ShouldRemoveHot = [&](const BasicBlock &BB) {
return HotPercentileCutoff.getNumOccurrences() && PSI &&
PSI->isHotCountNthPercentile(
HotPercentileCutoff, BFI.getBlockProfileCount(&BB).value_or(0));
auto GetCutoff = [&](const IntrinsicInst *II) -> unsigned {
if (HotPercentileCutoff.getNumOccurrences())
return HotPercentileCutoff;
else if (II->getIntrinsicID() == Intrinsic::allow_ubsan_check) {
auto *Kind = cast<ConstantInt>(II->getArgOperand(0));
if (Kind->getZExtValue() < cutoffs.size())
return cutoffs[Kind->getZExtValue()];
}
return 0;
};
auto ShouldRemoveHot = [&](const BasicBlock &BB, unsigned int cutoff) {
return (cutoff == 1000000) ||
(PSI && PSI->isHotCountNthPercentile(
cutoff, BFI.getBlockProfileCount(&BB).value_or(0)));
};
auto ShouldRemoveRandom = [&]() {
@@ -92,8 +106,9 @@ static bool removeUbsanTraps(Function &F, const BlockFrequencyInfo &BFI,
!std::bernoulli_distribution(RandomRate)(GetRng());
};
auto ShouldRemove = [&](const BasicBlock &BB) {
return ShouldRemoveRandom() || ShouldRemoveHot(BB);
auto ShouldRemove = [&](const IntrinsicInst *II) {
unsigned int cutoff = GetCutoff(II);
return ShouldRemoveRandom() || ShouldRemoveHot(*(II->getParent()), cutoff);
};
for (BasicBlock &BB : F) {
@@ -107,7 +122,8 @@ static bool removeUbsanTraps(Function &F, const BlockFrequencyInfo &BFI,
case Intrinsic::allow_runtime_check: {
++NumChecksTotal;
bool ToRemove = ShouldRemove(BB);
bool ToRemove = ShouldRemove(II);
ReplaceWithValue.push_back({
II,
ToRemove,
@@ -142,11 +158,37 @@ PreservedAnalyses LowerAllowCheckPass::run(Function &F,
OptimizationRemarkEmitter &ORE =
AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
return removeUbsanTraps(F, BFI, PSI, ORE) ? PreservedAnalyses::none()
: PreservedAnalyses::all();
return removeUbsanTraps(F, BFI, PSI, ORE, Opts.cutoffs)
? PreservedAnalyses::none()
: PreservedAnalyses::all();
}
bool LowerAllowCheckPass::IsRequested() {
return RandomRate.getNumOccurrences() ||
HotPercentileCutoff.getNumOccurrences();
}
void LowerAllowCheckPass::printPipeline(
raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
static_cast<PassInfoMixin<LowerAllowCheckPass> *>(this)->printPipeline(
OS, MapClassName2PassName);
OS << "<";
// Format is <cutoffs[0,1,2]=70000;cutoffs[5,6,8]=90000>
// but it's equally valid to specify
// cutoffs[0]=70000;cutoffs[1]=70000;cutoffs[2]=70000;cutoffs[5]=90000;...
// and that's what we do here. It is verbose but valid and easy to verify
// correctness.
// TODO: print shorter output by combining adjacent runs, etc.
int i = 0;
for (unsigned int cutoff : Opts.cutoffs) {
if (cutoff > 0) {
if (i > 0)
OS << ";";
OS << "cutoffs[" << i << "]=" << cutoff;
}
i++;
}
OS << '>';
}

8
llvm/test/Transforms/lower-builtin-allow-check.ll
View File

@@ -2,6 +2,14 @@
; RUN: opt < %s -passes='function(lower-allow-check)' -S | FileCheck %s --check-prefixes=NOPROFILE
; RUN: opt < %s -passes='function(lower-allow-check)' -lower-allow-check-random-rate=0 -S | FileCheck %s --check-prefixes=NONE
; RUN: opt < %s -passes='function(lower-allow-check)' -lower-allow-check-random-rate=1 -S | FileCheck %s --check-prefixes=ALL
;
; RUN: opt < %s -passes='require<profile-summary>,function(lower-allow-check<cutoffs[22]=990000>)' -S | FileCheck %s --check-prefixes=HOT99
; RUN: opt < %s -passes='require<profile-summary>,function(lower-allow-check<cutoffs[22]=700000>)' -S | FileCheck %s --check-prefixes=HOT70
; RUN: opt < %s -passes='require<profile-summary>,function(lower-allow-check<cutoffs[22]=990000>)' -lower-allow-check-random-rate=0 -S | FileCheck %s --check-prefixes=NONE99
; RUN: opt < %s -passes='require<profile-summary>,function(lower-allow-check<cutoffs[22]=700000>)' -lower-allow-check-random-rate=1 -S | FileCheck %s --check-prefixes=ALL70
;
; -lower-allow-check-percentile-cutoff is deprecated and will be removed in the future;
; use the cutoffs parameter to the lower-allow-check pass, as shown above.
; RUN: opt < %s -passes='require<profile-summary>,function(lower-allow-check)' -lower-allow-check-percentile-cutoff-hot=990000 -S | FileCheck %s --check-prefixes=HOT99
; RUN: opt < %s -passes='require<profile-summary>,function(lower-allow-check)' -lower-allow-check-percentile-cutoff-hot=700000 -S | FileCheck %s --check-prefixes=HOT70
; RUN: opt < %s -passes='require<profile-summary>,function(lower-allow-check)' -lower-allow-check-random-rate=0 -lower-allow-check-percentile-cutoff-hot=990000 -S | FileCheck %s --check-prefixes=NONE99