[clang] [llvm] [InstrPGO] Instrument sampling profile based cold function (PR #109837)

Lei Wang via cfe-commits cfe-commits at lists.llvm.org
Tue Oct 1 15:53:17 PDT 2024


https://github.com/wlei-llvm updated https://github.com/llvm/llvm-project/pull/109837

>From 07a2cab3fa5df2965f9f7da9ee2d3603581a47f1 Mon Sep 17 00:00:00 2001
From: wlei <wlei at fb.com>
Date: Sun, 22 Sep 2024 20:23:20 -0700
Subject: [PATCH 1/2] [InstrPGO] Instrument sampling profile based cold
 function

---
 clang/include/clang/Driver/Options.td         |  6 +++++
 clang/lib/Driver/ToolChain.cpp                |  4 +++-
 clang/lib/Driver/ToolChains/Clang.cpp         | 18 ++++++++++++++
 clang/test/CodeGen/Inputs/pgo-cold-func.prof  |  2 ++
 .../test/CodeGen/pgo-cold-function-coverage.c | 12 ++++++++++
 llvm/lib/Passes/PassBuilderPipelines.cpp      | 18 ++++++++++++++
 .../Instrumentation/PGOInstrumentation.cpp    | 16 +++++++++++++
 .../PGOProfile/instr-gen-cold-function.ll     | 24 +++++++++++++++++++
 8 files changed, 99 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/CodeGen/Inputs/pgo-cold-func.prof
 create mode 100644 clang/test/CodeGen/pgo-cold-function-coverage.c
 create mode 100644 llvm/test/Transforms/PGOProfile/instr-gen-cold-function.ll

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 002f60350543d9..6bb92427f2d53f 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1784,6 +1784,12 @@ defm debug_info_for_profiling : BoolFOption<"debug-info-for-profiling",
   PosFlag<SetTrue, [], [ClangOption, CC1Option],
           "Emit extra debug info to make sample profile more accurate">,
   NegFlag<SetFalse>>;
+def fprofile_generate_cold_function_coverage : Flag<["-"], "fprofile-generate-cold-function-coverage">, 
+    Group<f_Group>, Visibility<[ClangOption, CLOption]>,
+    HelpText<"Generate instrumented code to cold functions into default.profraw file (overridden by '=' form of option or LLVM_PROFILE_FILE env var)">;
+def fprofile_generate_cold_function_coverage_EQ : Joined<["-"], "fprofile-generate-cold-function-coverage=">, 
+    Group<f_Group>, Visibility<[ClangOption, CLOption]>, MetaVarName<"<directory>">,
+    HelpText<"Generate instrumented code to cold functions into <directory>/default.profraw (overridden by LLVM_PROFILE_FILE env var)">; 
 def fprofile_instr_generate : Flag<["-"], "fprofile-instr-generate">,
     Group<f_Group>, Visibility<[ClangOption, CLOption]>,
     HelpText<"Generate instrumented code to collect execution counts into default.profraw file (overridden by '=' form of option or LLVM_PROFILE_FILE env var)">;
diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 16f9b629fc538c..e56db150c6b47e 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -889,7 +889,9 @@ bool ToolChain::needsProfileRT(const ArgList &Args) {
          Args.hasArg(options::OPT_fprofile_instr_generate) ||
          Args.hasArg(options::OPT_fprofile_instr_generate_EQ) ||
          Args.hasArg(options::OPT_fcreate_profile) ||
-         Args.hasArg(options::OPT_forder_file_instrumentation);
+         Args.hasArg(options::OPT_forder_file_instrumentation) ||
+         Args.hasArg(options::OPT_fprofile_generate_cold_function_coverage) ||
+         Args.hasArg(options::OPT_fprofile_generate_cold_function_coverage_EQ);
 }
 
 bool ToolChain::needsGCovInstrumentation(const llvm::opt::ArgList &Args) {
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 0bab48caf1a5e2..00602a08232ba2 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -649,6 +649,24 @@ static void addPGOAndCoverageFlags(const ToolChain &TC, Compilation &C,
     }
   }
 
+  if (auto *ColdFuncCoverageArg = Args.getLastArg(
+          options::OPT_fprofile_generate_cold_function_coverage,
+          options::OPT_fprofile_generate_cold_function_coverage_EQ)) {
+    SmallString<128> Path(
+        ColdFuncCoverageArg->getOption().matches(
+            options::OPT_fprofile_generate_cold_function_coverage_EQ)
+            ? ColdFuncCoverageArg->getValue()
+            : "");
+    llvm::sys::path::append(Path, "default_%m.profraw");
+    CmdArgs.push_back("-mllvm");
+    CmdArgs.push_back(Args.MakeArgString(
+        Twine("--instrument-sample-cold-function-path=") + Path));
+    CmdArgs.push_back("-mllvm");
+    CmdArgs.push_back("--instrument-cold-function-coverage");
+    CmdArgs.push_back("-mllvm");
+    CmdArgs.push_back("--pgo-function-entry-coverage");
+  }
+
   Arg *PGOGenArg = nullptr;
   if (PGOGenerateArg) {
     assert(!CSPGOGenerateArg);
diff --git a/clang/test/CodeGen/Inputs/pgo-cold-func.prof b/clang/test/CodeGen/Inputs/pgo-cold-func.prof
new file mode 100644
index 00000000000000..e50be02e0a8545
--- /dev/null
+++ b/clang/test/CodeGen/Inputs/pgo-cold-func.prof
@@ -0,0 +1,2 @@
+foo:1:1
+ 1: 1
diff --git a/clang/test/CodeGen/pgo-cold-function-coverage.c b/clang/test/CodeGen/pgo-cold-function-coverage.c
new file mode 100644
index 00000000000000..0d2767c022b9f1
--- /dev/null
+++ b/clang/test/CodeGen/pgo-cold-function-coverage.c
@@ -0,0 +1,12 @@
+// Test -fprofile-generate-cold-function-coverage 
+// RUN: %clang -O2 -fprofile-generate-cold-function-coverage=/xxx/yyy/ -fprofile-sample-accurate -fprofile-sample-use=%S/Inputs/pgo-cold-func.prof  -S -emit-llvm -o - %s | FileCheck %s
+
+// CHECK: @__llvm_profile_filename = {{.*}} c"/xxx/yyy/default_%m.profraw\00"
+
+// CHECK: @__profc_bar
+// CHECK-NOT: @__profc_foo
+
+int bar(int x) { return x;}
+int foo(int x) { 
+    return x;
+}
diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 8f151a99b11709..f75abe0c7c7649 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -296,7 +296,13 @@ static cl::opt<bool> UseLoopVersioningLICM(
     "enable-loop-versioning-licm", cl::init(false), cl::Hidden,
     cl::desc("Enable the experimental Loop Versioning LICM pass"));
 
+static cl::opt<std::string> InstrumentSampleColdFuncPath(
+    "instrument-sample-cold-function-path", cl::init(""),
+    cl::desc("File path for instrumenting sampling PGO guided cold functions"),
+    cl::Hidden);
+
 extern cl::opt<std::string> UseCtxProfile;
+extern cl::opt<bool> InstrumentColdFunctionCoverage;
 
 namespace llvm {
 extern cl::opt<bool> EnableMemProfContextDisambiguation;
@@ -1119,6 +1125,18 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
       // removed.
       MPM.addPass(
           PGOIndirectCallPromotion(true /* IsInLTO */, true /* SamplePGO */));
+
+    if (InstrumentSampleColdFuncPath.getNumOccurrences() &&
+        Phase != ThinOrFullLTOPhase::ThinLTOPostLink) {
+      assert(!InstrumentSampleColdFuncPath.empty() &&
+             "File path is requeired for instrumentation generation");
+      InstrumentColdFunctionCoverage = true;
+      addPreInlinerPasses(MPM, Level, Phase);
+      addPGOInstrPasses(MPM, Level, /* RunProfileGen */ true,
+                        /* IsCS */ false, /* AtomicCounterUpdate */ false,
+                        InstrumentSampleColdFuncPath, "",
+                        IntrusiveRefCntPtr<vfs::FileSystem>());
+    }
   }
 
   // Try to perform OpenMP specific optimizations on the module. This is a
diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
index 10442fa0bb9003..890ad853d86461 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -319,6 +319,18 @@ static cl::opt<unsigned> PGOFunctionCriticalEdgeThreshold(
     cl::desc("Do not instrument functions with the number of critical edges "
              " greater than this threshold."));
 
+cl::opt<bool> InstrumentColdFunctionCoverage(
+    "instrument-cold-function-coverage", cl::init(false), cl::Hidden,
+    cl::desc("Enable cold function coverage instrumentation (currently only "
+             "used under sampling "
+             " PGO pipeline))"));
+
+static cl::opt<uint64_t> ColdFuncCoverageMaxEntryCount(
+    "cold-function-coverage-max-entry-count", cl::init(0), cl::Hidden,
+    cl::desc("When enabling cold function coverage instrumentation, skip "
+             "instrumenting the "
+             "function whose entry count is above the given value"));
+
 extern cl::opt<unsigned> MaxNumVTableAnnotations;
 
 namespace llvm {
@@ -1891,6 +1903,10 @@ static bool skipPGOGen(const Function &F) {
     return true;
   if (F.getInstructionCount() < PGOFunctionSizeThreshold)
     return true;
+  if (InstrumentColdFunctionCoverage &&
+      (!F.getEntryCount() ||
+       F.getEntryCount()->getCount() > ColdFuncCoverageMaxEntryCount))
+    return true;
   return false;
 }
 
diff --git a/llvm/test/Transforms/PGOProfile/instr-gen-cold-function.ll b/llvm/test/Transforms/PGOProfile/instr-gen-cold-function.ll
new file mode 100644
index 00000000000000..ba1a11f7184356
--- /dev/null
+++ b/llvm/test/Transforms/PGOProfile/instr-gen-cold-function.ll
@@ -0,0 +1,24 @@
+; RUN: opt < %s  --passes=pgo-instr-gen -instrument-cold-function-coverage -S  | FileCheck --check-prefixes=COLD %s
+; RUN: opt < %s  --passes=pgo-instr-gen -instrument-cold-function-coverage -cold-function-coverage-max-entry-count=1 -S  | FileCheck --check-prefixes=ENTRY-COUNT %s
+
+; COLD: call void @llvm.instrprof.increment(ptr @__profn_foo, i64  [[#]], i32 1, i32 0)
+; COLD-NOT: __profn_main
+
+; ENTRY-COUNT: call void @llvm.instrprof.increment(ptr @__profn_foo, i64  [[#]], i32 1, i32 0)
+; ENTRY-COUNT: call void @llvm.instrprof.increment(ptr @__profn_main, i64 [[#]], i32 1, i32 0)
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @foo() !prof !0 {
+entry:
+  ret void
+}
+
+define i32 @main() !prof !1 {
+entry:
+  ret i32 0
+}
+
+!0 = !{!"function_entry_count", i64 0}
+!1 = !{!"function_entry_count", i64 1}

>From b3054f05007d60900cb02301cf59711c68e70120 Mon Sep 17 00:00:00 2001
From: wlei <wlei at fb.com>
Date: Tue, 1 Oct 2024 15:51:37 -0700
Subject: [PATCH 2/2] fix lint in cl desc msg

---
 .../Instrumentation/PGOInstrumentation.cpp        | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
index 890ad853d86461..aba1d8cc88c224 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -319,17 +319,16 @@ static cl::opt<unsigned> PGOFunctionCriticalEdgeThreshold(
     cl::desc("Do not instrument functions with the number of critical edges "
              " greater than this threshold."));
 
-cl::opt<bool> InstrumentColdFunctionCoverage(
-    "instrument-cold-function-coverage", cl::init(false), cl::Hidden,
-    cl::desc("Enable cold function coverage instrumentation (currently only "
-             "used under sampling "
-             " PGO pipeline))"));
-
 static cl::opt<uint64_t> ColdFuncCoverageMaxEntryCount(
     "cold-function-coverage-max-entry-count", cl::init(0), cl::Hidden,
     cl::desc("When enabling cold function coverage instrumentation, skip "
-             "instrumenting the "
-             "function whose entry count is above the given value"));
+             "instrumenting the function whose entry count is above the given "
+             "value"));
+
+cl::opt<bool> InstrumentColdFunctionCoverage(
+    "instrument-cold-function-coverage", cl::init(false), cl::Hidden,
+    cl::desc("Enable cold function coverage instrumentation (currently only "
+             "used under sampling PGO pipeline)"));
 
 extern cl::opt<unsigned> MaxNumVTableAnnotations;
 



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