From 1b79a34a56378f5b75fb0abd03bb7029ea1c60ec Mon Sep 17 00:00:00 2001 From: Arthur Eubanks Date: Fri, 19 Apr 2024 09:30:47 -0700 Subject: [clang] Add flag to experiment with cold function attributes (#89298) To be removed and promoted to a proper driver flag if experiments turn out fruitful. For now, this can be experimented with `-mllvm -pgo-cold-func-opt=[optsize|minsize|optnone|default] -mllvm -enable-pgo-force-function-attrs`. Original LLVM patch for this functionality: #69030 --- clang/lib/CodeGen/BackendUtil.cpp | 57 ++++++++++++++++---------- clang/test/CodeGen/pgo-force-function-attrs.ll | 12 ++++++ 2 files changed, 47 insertions(+), 22 deletions(-) create mode 100644 clang/test/CodeGen/pgo-force-function-attrs.ll diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp index 6cc00b8..22c3f86 100644 --- a/clang/lib/CodeGen/BackendUtil.cpp +++ b/clang/lib/CodeGen/BackendUtil.cpp @@ -104,6 +104,21 @@ static cl::opt ClSanitizeOnOptimizerEarlyEP( "sanitizer-early-opt-ep", cl::Optional, cl::desc("Insert sanitizers on OptimizerEarlyEP.")); +// Experiment to mark cold functions as optsize/minsize/optnone. +// TODO: remove once this is exposed as a proper driver flag. +static cl::opt ClPGOColdFuncAttr( + "pgo-cold-func-opt", cl::init(PGOOptions::ColdFuncOpt::Default), cl::Hidden, + cl::desc( + "Function attribute to apply to cold functions as determined by PGO"), + cl::values(clEnumValN(PGOOptions::ColdFuncOpt::Default, "default", + "Default (no attribute)"), + clEnumValN(PGOOptions::ColdFuncOpt::OptSize, "optsize", + "Mark cold functions with optsize."), + clEnumValN(PGOOptions::ColdFuncOpt::MinSize, "minsize", + "Mark cold functions with minsize."), + clEnumValN(PGOOptions::ColdFuncOpt::OptNone, "optnone", + "Mark cold functions with optnone."))); + extern cl::opt ProfileCorrelate; // Re-link builtin bitcodes after optimization @@ -768,42 +783,41 @@ void EmitAssemblyHelper::RunOptimizationPipeline( CodeGenOpts.InstrProfileOutput.empty() ? getDefaultProfileGenName() : CodeGenOpts.InstrProfileOutput, "", "", CodeGenOpts.MemoryProfileUsePath, nullptr, PGOOptions::IRInstr, - PGOOptions::NoCSAction, PGOOptions::ColdFuncOpt::Default, + PGOOptions::NoCSAction, ClPGOColdFuncAttr, CodeGenOpts.DebugInfoForProfiling, /*PseudoProbeForProfiling=*/false, CodeGenOpts.AtomicProfileUpdate); else if (CodeGenOpts.hasProfileIRUse()) { // -fprofile-use. auto CSAction = CodeGenOpts.hasProfileCSIRUse() ? PGOOptions::CSIRUse : PGOOptions::NoCSAction; - PGOOpt = PGOOptions( - CodeGenOpts.ProfileInstrumentUsePath, "", - CodeGenOpts.ProfileRemappingFile, CodeGenOpts.MemoryProfileUsePath, VFS, - PGOOptions::IRUse, CSAction, PGOOptions::ColdFuncOpt::Default, - CodeGenOpts.DebugInfoForProfiling); + PGOOpt = PGOOptions(CodeGenOpts.ProfileInstrumentUsePath, "", + CodeGenOpts.ProfileRemappingFile, + CodeGenOpts.MemoryProfileUsePath, VFS, + PGOOptions::IRUse, CSAction, ClPGOColdFuncAttr, + CodeGenOpts.DebugInfoForProfiling); } else if (!CodeGenOpts.SampleProfileFile.empty()) // -fprofile-sample-use PGOOpt = PGOOptions( CodeGenOpts.SampleProfileFile, "", CodeGenOpts.ProfileRemappingFile, CodeGenOpts.MemoryProfileUsePath, VFS, PGOOptions::SampleUse, - PGOOptions::NoCSAction, PGOOptions::ColdFuncOpt::Default, + PGOOptions::NoCSAction, ClPGOColdFuncAttr, CodeGenOpts.DebugInfoForProfiling, CodeGenOpts.PseudoProbeForProfiling); else if (!CodeGenOpts.MemoryProfileUsePath.empty()) // -fmemory-profile-use (without any of the above options) PGOOpt = PGOOptions("", "", "", CodeGenOpts.MemoryProfileUsePath, VFS, PGOOptions::NoAction, PGOOptions::NoCSAction, - PGOOptions::ColdFuncOpt::Default, - CodeGenOpts.DebugInfoForProfiling); + ClPGOColdFuncAttr, CodeGenOpts.DebugInfoForProfiling); else if (CodeGenOpts.PseudoProbeForProfiling) // -fpseudo-probe-for-profiling - PGOOpt = PGOOptions("", "", "", /*MemoryProfile=*/"", nullptr, - PGOOptions::NoAction, PGOOptions::NoCSAction, - PGOOptions::ColdFuncOpt::Default, - CodeGenOpts.DebugInfoForProfiling, true); + PGOOpt = + PGOOptions("", "", "", /*MemoryProfile=*/"", nullptr, + PGOOptions::NoAction, PGOOptions::NoCSAction, + ClPGOColdFuncAttr, CodeGenOpts.DebugInfoForProfiling, true); else if (CodeGenOpts.DebugInfoForProfiling) // -fdebug-info-for-profiling PGOOpt = PGOOptions("", "", "", /*MemoryProfile=*/"", nullptr, PGOOptions::NoAction, PGOOptions::NoCSAction, - PGOOptions::ColdFuncOpt::Default, true); + ClPGOColdFuncAttr, true); // Check to see if we want to generate a CS profile. if (CodeGenOpts.hasProfileCSIRInstr()) { @@ -820,14 +834,13 @@ void EmitAssemblyHelper::RunOptimizationPipeline( : CodeGenOpts.InstrProfileOutput; PGOOpt->CSAction = PGOOptions::CSIRInstr; } else - PGOOpt = - PGOOptions("", - CodeGenOpts.InstrProfileOutput.empty() - ? getDefaultProfileGenName() - : CodeGenOpts.InstrProfileOutput, - "", /*MemoryProfile=*/"", nullptr, PGOOptions::NoAction, - PGOOptions::CSIRInstr, PGOOptions::ColdFuncOpt::Default, - CodeGenOpts.DebugInfoForProfiling); + PGOOpt = PGOOptions("", + CodeGenOpts.InstrProfileOutput.empty() + ? getDefaultProfileGenName() + : CodeGenOpts.InstrProfileOutput, + "", /*MemoryProfile=*/"", nullptr, + PGOOptions::NoAction, PGOOptions::CSIRInstr, + ClPGOColdFuncAttr, CodeGenOpts.DebugInfoForProfiling); } if (TM) TM->setPGOOption(PGOOpt); diff --git a/clang/test/CodeGen/pgo-force-function-attrs.ll b/clang/test/CodeGen/pgo-force-function-attrs.ll new file mode 100644 index 0000000..3e9ea95 --- /dev/null +++ b/clang/test/CodeGen/pgo-force-function-attrs.ll @@ -0,0 +1,12 @@ +; RUN: %clang_cc1 -O2 -mllvm -pgo-cold-func-opt=optsize -mllvm -enable-pgo-force-function-attrs -fprofile-sample-use=%S/Inputs/pgo-sample.prof %s -emit-llvm -o - | FileCheck %s --check-prefix=OPTSIZE +; Check that no profile means no optsize +; RUN: %clang_cc1 -O2 -mllvm -pgo-cold-func-opt=optsize -mllvm -enable-pgo-force-function-attrs %s -emit-llvm -o - | FileCheck %s --check-prefix=NONE +; Check that no -pgo-cold-func-opt=optsize means no optsize +; RUN: %clang_cc1 -O2 -mllvm -enable-pgo-force-function-attrs -fprofile-sample-use=%S/Inputs/pgo-sample.prof %s -emit-llvm -o - | FileCheck %s --check-prefix=NONE + +; NONE-NOT: optsize +; OPTSIZE: optsize + +define void @f() cold { + ret void +} -- cgit v1.1