hoy created this revision.
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This change introduces a new clang switch `-fpseudo-probe-for-profiling` to
enable AutoFDO with pseudo instrumentation. Please refer to
https://reviews.llvm.org/D86193 for the whole story.
One implication from pseudo-probe instrumentation is that the profile is now
sensitive to CFG changes. We perform the pseudo instrumentation very early in
the pre-LTO pipeline, before any CFG transformation. This ensures that the CFG
instrumented and annotated is stable and optimization-resilient.
The early instrumentation also allows the inliner to duplicate probes for
inlined instances. When a probe along with the other instructions of a callee
function are inlined into its caller function, the GUID of the callee function
goes with the probe. This allows samples collected on inlined probes to be
reported for the original callee function.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D86502
Files:
clang/include/clang/Basic/CodeGenOptions.def
clang/include/clang/Driver/Options.td
clang/lib/CodeGen/BackendUtil.cpp
clang/lib/Driver/ToolChains/Clang.cpp
clang/lib/Frontend/CompilerInvocation.cpp
clang/test/CodeGen/emit-pseudo-probe.c
llvm/include/llvm/Passes/PassBuilder.h
llvm/lib/Passes/PassBuilder.cpp
Index: llvm/lib/Passes/PassBuilder.cpp
===================================================================
--- llvm/lib/Passes/PassBuilder.cpp
+++ llvm/lib/Passes/PassBuilder.cpp
@@ -901,6 +901,12 @@
OptimizationLevel Level, ThinLTOPhase Phase, bool DebugLogging) {
ModulePassManager MPM(DebugLogging);
+ // Place pseudo probe instrumentation as the first pass of the pipeline to
+ // minimize the impact of optimization changes.
+ if (PGOOpt && PGOOpt->PseudoProbeForProfiling &&
+ Phase != ThinLTOPhase::PostLink)
+ MPM.addPass(SampleProfileProbePass(TM));
+
bool HasSampleProfile = PGOOpt && (PGOOpt->Action == PGOOptions::SampleUse);
// In ThinLTO mode, when flattened profile is used, all the available
@@ -1254,7 +1260,7 @@
for (auto &C : PipelineStartEPCallbacks)
C(MPM);
- if (PGOOpt && PGOOpt->SamplePGOSupport)
+ if (PGOOpt && PGOOpt->DebugInfoForProfiling)
MPM.addPass(createModuleToFunctionPassAdaptor(AddDiscriminatorsPass()));
// Add the core simplification pipeline.
@@ -1278,7 +1284,7 @@
// Force any function attributes we want the rest of the pipeline to observe.
MPM.addPass(ForceFunctionAttrsPass());
- if (PGOOpt && PGOOpt->SamplePGOSupport)
+ if (PGOOpt && PGOOpt->DebugInfoForProfiling)
MPM.addPass(createModuleToFunctionPassAdaptor(AddDiscriminatorsPass()));
// Apply module pipeline start EP callback.
Index: llvm/include/llvm/Passes/PassBuilder.h
===================================================================
--- llvm/include/llvm/Passes/PassBuilder.h
+++ llvm/include/llvm/Passes/PassBuilder.h
@@ -36,11 +36,15 @@
enum CSPGOAction { NoCSAction, CSIRInstr, CSIRUse };
PGOOptions(std::string ProfileFile = "", std::string CSProfileGenFile = "",
std::string ProfileRemappingFile = "", PGOAction Action = NoAction,
- CSPGOAction CSAction = NoCSAction, bool SamplePGOSupport = false)
+ CSPGOAction CSAction = NoCSAction,
+ bool DebugInfoForProfiling = false,
+ bool PseudoProbeForProfiling = false)
: ProfileFile(ProfileFile), CSProfileGenFile(CSProfileGenFile),
ProfileRemappingFile(ProfileRemappingFile), Action(Action),
- CSAction(CSAction),
- SamplePGOSupport(SamplePGOSupport || Action == SampleUse) {
+ CSAction(CSAction), DebugInfoForProfiling(DebugInfoForProfiling ||
+ (Action == SampleUse &&
+ !PseudoProbeForProfiling)),
+ PseudoProbeForProfiling(PseudoProbeForProfiling) {
// Note, we do allow ProfileFile.empty() for Action=IRUse LTO can
// callback with IRUse action without ProfileFile.
@@ -55,16 +59,22 @@
// a profile.
assert(this->CSAction != CSIRUse || this->Action == IRUse);
- // If neither Action nor CSAction, SamplePGOSupport needs to be true.
+ // If neither Action nor CSAction, DebugInfoForProfiling or
+ // PseudoProbeForProfiling needs to be true.
assert(this->Action != NoAction || this->CSAction != NoCSAction ||
- this->SamplePGOSupport);
+ this->DebugInfoForProfiling || this->PseudoProbeForProfiling);
+
+ // Pseudo probe instrumentation should only work with autoFDO or no FDO.
+ assert(!this->PseudoProbeForProfiling || this->Action == NoAction ||
+ this->Action == SampleUse);
}
std::string ProfileFile;
std::string CSProfileGenFile;
std::string ProfileRemappingFile;
PGOAction Action;
CSPGOAction CSAction;
- bool SamplePGOSupport;
+ bool DebugInfoForProfiling;
+ bool PseudoProbeForProfiling;
};
/// Tunable parameters for passes in the default pipelines.
Index: clang/test/CodeGen/emit-pseudo-probe.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/emit-pseudo-probe.c
@@ -0,0 +1,17 @@
+// RUN: %clang -O2 -fexperimental-new-pass-manager -fpseudo-probe-for-profiling -g -emit-llvm -S -o - %s | FileCheck %s
+
+// Check the generation of pseudoprobe intrinsic call
+
+void bar();
+void go();
+
+void foo(int x) {
+ // CHECK: call void @llvm.pseudoprobe(i64 [[#GUID:]], i64 1)
+ if (x == 0)
+ // CHECK: call void @llvm.pseudoprobe(i64 [[#GUID]], i64 2)
+ bar();
+ else
+ // CHECK: call void @llvm.pseudoprobe(i64 [[#GUID]], i64 3)
+ go();
+ // CHECK: call void @llvm.pseudoprobe(i64 [[#GUID]], i64 4)
+}
Index: clang/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- clang/lib/Frontend/CompilerInvocation.cpp
+++ clang/lib/Frontend/CompilerInvocation.cpp
@@ -872,6 +872,9 @@
std::string(Args.getLastArgValue(OPT_fprofile_sample_use_EQ));
Opts.DebugInfoForProfiling = Args.hasFlag(
OPT_fdebug_info_for_profiling, OPT_fno_debug_info_for_profiling, false);
+ Opts.PseudoProbeForProfiling =
+ Args.hasFlag(OPT_fpseudo_probe_for_profiling,
+ OPT_fno_pseudo_probe_for_profiling, false);
Opts.DebugNameTable = static_cast<unsigned>(
Args.hasArg(OPT_ggnu_pubnames)
? llvm::DICompileUnit::DebugNameTableKind::GNU
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -5443,6 +5443,10 @@
}
Args.AddLastArg(CmdArgs, options::OPT_fprofile_remapping_file_EQ);
+ if (Args.hasFlag(options::OPT_fpseudo_probe_for_profiling,
+ options::OPT_fno_pseudo_probe_for_profiling, false))
+ CmdArgs.push_back("-fpseudo-probe-for-profiling");
+
RenderBuiltinOptions(TC, RawTriple, Args, CmdArgs);
if (!Args.hasFlag(options::OPT_fassume_sane_operator_new,
Index: clang/lib/CodeGen/BackendUtil.cpp
===================================================================
--- clang/lib/CodeGen/BackendUtil.cpp
+++ clang/lib/CodeGen/BackendUtil.cpp
@@ -1112,10 +1112,15 @@
CSAction, CodeGenOpts.DebugInfoForProfiling);
} else if (!CodeGenOpts.SampleProfileFile.empty())
// -fprofile-sample-use
+ PGOOpt = PGOOptions(
+ CodeGenOpts.SampleProfileFile, "", CodeGenOpts.ProfileRemappingFile,
+ PGOOptions::SampleUse, PGOOptions::NoCSAction,
+ CodeGenOpts.DebugInfoForProfiling, CodeGenOpts.PseudoProbeForProfiling);
+ else if (CodeGenOpts.PseudoProbeForProfiling)
+ // -fpseudo-probe-for-profiling
PGOOpt =
- PGOOptions(CodeGenOpts.SampleProfileFile, "",
- CodeGenOpts.ProfileRemappingFile, PGOOptions::SampleUse,
- PGOOptions::NoCSAction, CodeGenOpts.DebugInfoForProfiling);
+ PGOOptions("", "", "", PGOOptions::NoAction, PGOOptions::NoCSAction,
+ CodeGenOpts.DebugInfoForProfiling, true);
else if (CodeGenOpts.DebugInfoForProfiling)
// -fdebug-info-for-profiling
PGOOpt = PGOOptions("", "", "", PGOOptions::NoAction,
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -843,6 +843,12 @@
def fprofile_exclude_files_EQ : Joined<["-"], "fprofile-exclude-files=">,
Group<f_Group>, Flags<[CC1Option, CoreOption]>,
HelpText<"Instrument only functions from files where names don't match all the regexes separated by a semi-colon">;
+def fpseudo_probe_for_profiling : Flag<["-"], "fpseudo-probe-for-profiling">,
+ Group<f_Group>, Flags<[DriverOption, CC1Option]>,
+ HelpText<"Emit pseudo probes for sample profiler">;
+def fno_pseudo_probe_for_profiling : Flag<["-"], "fno-pseudo-probe-for-profiling">,
+ Group<f_Group>, Flags<[DriverOption, CC1Option]>,
+ HelpText<"Do not emit pseudo probes for sample profiler.">;
def forder_file_instrumentation : Flag<["-"], "forder-file-instrumentation">,
Group<f_Group>, Flags<[CC1Option, CoreOption]>,
HelpText<"Generate instrumented code to collect order file into default.profraw file (overridden by '=' form of option or LLVM_PROFILE_FILE env var)">;
Index: clang/include/clang/Basic/CodeGenOptions.def
===================================================================
--- clang/include/clang/Basic/CodeGenOptions.def
+++ clang/include/clang/Basic/CodeGenOptions.def
@@ -365,6 +365,9 @@
/// Whether emit extra debug info for sample pgo profile collection.
CODEGENOPT(DebugInfoForProfiling, 1, 0)
+/// Whether emit pseudo probes for sample pgo profile collection.
+CODEGENOPT(PseudoProbeForProfiling, 1, 0)
+
/// Whether 3-component vector type is preserved.
CODEGENOPT(PreserveVec3Type, 1, 0)
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