Author: Vitaly Buka Date: 2024-03-11T12:07:28-07:00 New Revision: eaa71a97f9155ea9df33141ef2fb369dc8fc464f
URL: https://github.com/llvm/llvm-project/commit/eaa71a97f9155ea9df33141ef2fb369dc8fc464f DIFF: https://github.com/llvm/llvm-project/commit/eaa71a97f9155ea9df33141ef2fb369dc8fc464f.diff LOG: [clang] Add optional pass to remove UBSAN traps using PGO (#84214) With #83471 it reduces UBSAN overhead from 44% to 6%. Measured as "Geomean difference" on "test-suite/MultiSource/Benchmarks" with PGO build. On real large server binary we see 95% of code is still instrumented, with 10% -> 1.5% UBSAN overhead improvements. We can pass this test only with subset of UBSAN, so base overhead is smaller. We have followup patches to improve it even further. Added: clang/test/CodeGen/remote-traps.c Modified: clang/lib/CodeGen/BackendUtil.cpp Removed: ################################################################################ diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp index 7310e3817c79a1..82b30b8d815629 100644 --- a/clang/lib/CodeGen/BackendUtil.cpp +++ b/clang/lib/CodeGen/BackendUtil.cpp @@ -76,6 +76,7 @@ #include "llvm/Transforms/Instrumentation/MemProfiler.h" #include "llvm/Transforms/Instrumentation/MemorySanitizer.h" #include "llvm/Transforms/Instrumentation/PGOInstrumentation.h" +#include "llvm/Transforms/Instrumentation/RemoveTrapsPass.h" #include "llvm/Transforms/Instrumentation/SanitizerBinaryMetadata.h" #include "llvm/Transforms/Instrumentation/SanitizerCoverage.h" #include "llvm/Transforms/Instrumentation/ThreadSanitizer.h" @@ -83,6 +84,7 @@ #include "llvm/Transforms/Scalar/EarlyCSE.h" #include "llvm/Transforms/Scalar/GVN.h" #include "llvm/Transforms/Scalar/JumpThreading.h" +#include "llvm/Transforms/Scalar/SimplifyCFG.h" #include "llvm/Transforms/Utils/Debugify.h" #include "llvm/Transforms/Utils/EntryExitInstrumenter.h" #include "llvm/Transforms/Utils/ModuleUtils.h" @@ -98,6 +100,10 @@ using namespace llvm; namespace llvm { extern cl::opt<bool> PrintPipelinePasses; +cl::opt<bool> ClRemoveTraps("clang-remove-traps", cl::Optional, + cl::desc("Insert remove-traps pass."), + cl::init(false)); + // Experiment to move sanitizers earlier. static cl::opt<bool> ClSanitizeOnOptimizerEarlyEP( "sanitizer-early-opt-ep", cl::Optional, @@ -744,6 +750,21 @@ static void addSanitizers(const Triple &TargetTriple, // LastEP does not need GlobalsAA. PB.registerOptimizerLastEPCallback(SanitizersCallback); } + + if (ClRemoveTraps) { + // We can optimize after inliner, and PGO profile matching. The hook below + // is called at the end `buildFunctionSimplificationPipeline`, which called + // from `buildInlinerPipeline`, which called after profile matching. + PB.registerScalarOptimizerLateEPCallback( + [](FunctionPassManager &FPM, OptimizationLevel Level) { + // RemoveTrapsPass expects trap blocks preceded by conditional + // branches, which usually is not the case without SimplifyCFG. + // TODO: Remove `SimplifyCFGPass` after switching to dedicated + // intrinsic. + FPM.addPass(SimplifyCFGPass()); + FPM.addPass(RemoveTrapsPass()); + }); + } } void EmitAssemblyHelper::RunOptimizationPipeline( diff --git a/clang/test/CodeGen/remote-traps.c b/clang/test/CodeGen/remote-traps.c new file mode 100644 index 00000000000000..f053d1bd157f80 --- /dev/null +++ b/clang/test/CodeGen/remote-traps.c @@ -0,0 +1,15 @@ +// RUN: %clang_cc1 -O1 -emit-llvm -fsanitize=signed-integer-overflow -fsanitize-trap=signed-integer-overflow %s -o - | FileCheck %s +// RUN: %clang_cc1 -O1 -emit-llvm -fsanitize=signed-integer-overflow -fsanitize-trap=signed-integer-overflow -mllvm -clang-remove-traps -mllvm -remove-traps-random-rate=1 %s -o - | FileCheck %s --implicit-check-not="call void @llvm.ubsantrap" --check-prefixes=REMOVE + +int f(int x) { + return x + 123; +} + +// CHECK-LABEL: define dso_local noundef i32 @f( +// CHECK: call { i32, i1 } @llvm.sadd.with.overflow.i32( +// CHECK: trap: +// CHECK-NEXT: call void @llvm.ubsantrap(i8 0) +// CHECK-NEXT: unreachable + +// REMOVE-LABEL: define dso_local noundef i32 @f( +// REMOVE: call { i32, i1 } @llvm.sadd.with.overflow.i32( _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
