add a flag to control unprofiled function

Author: wlei-llvm

clang/lib/Driver/ToolChains/Clang.cpp

@@ -660,7 +660,7 @@ static void addPGOAndCoverageFlags(const ToolChain &TC, Compilation &C,
     llvm::sys::path::append(Path, "default_%m.profraw");
     CmdArgs.push_back("-mllvm");
     CmdArgs.push_back(Args.MakeArgString(
-        Twine("--instrument-sample-cold-function-path=") + Path));
+        Twine("--instrument-cold-function-coverage-path=") + Path));
     CmdArgs.push_back("-mllvm");
     CmdArgs.push_back("--instrument-cold-function-coverage");
     CmdArgs.push_back("-mllvm");

clang/test/Driver/fprofile-generate-cold-function-coverage.c

@@ -1,9 +1,9 @@
 // RUN: %clang -### -c -fprofile-generate-cold-function-coverage %s 2>&1 | FileCheck %s
-// CHECK: "--instrument-sample-cold-function-path=default_%m.profraw" 
+// CHECK: "--instrument-cold-function-coverage-path=default_%m.profraw" 
 // CHECK: "--instrument-cold-function-coverage" 
 // CHECK: "--pgo-function-entry-coverage"
 // CHECK-NOT:  "-fprofile-instrument"
 // CHECK-NOT:  "-fprofile-instrument-path=
 
-// RUN: %clang -### -c -fprofile-generate-cold-function-coverage=dir %s 2>&1 | FileCheck %s --check-prefix=CHECK-PATH
-// CHECK-PATH: "--instrument-sample-cold-function-path=dir{{/|\\\\}}default_%m.profraw" 
+// RUN: %clang -### -c -fprofile-generate-cold-function-coverage=dir %s 2>&1 | FileCheck %s --check-prefix=CHECK-EQ
+// CHECK-EQ: "--instrument-cold-function-coverage-path=dir{{/|\\\\}}default_%m.profraw" 

llvm/include/llvm/Transforms/Instrumentation/PGOInstrumentation.h

@@ -53,6 +53,8 @@ class PGOInstrumentationGenCreateVar
   bool ProfileSampling;
 };
 
+enum class InstrColdFuncCovMode { Conservative = 0, Optimistic };
+
 enum class PGOInstrumentationType { Invalid = 0, FDO, CSFDO, CTXPROF };
 /// The instrumentation (profile-instr-gen) pass for IR based PGO.
 class PGOInstrumentationGen : public PassInfoMixin<PGOInstrumentationGen> {

llvm/lib/Passes/PassBuilderPipelines.cpp

@@ -298,7 +298,7 @@ static cl::opt<bool> UseLoopVersioningLICM(
 
 static cl::opt<std::string> InstrumentColdFuncCoveragePath(
     "instrument-cold-function-coverage-path", cl::init(""),
-    cl::desc("File path for cold function coverage instrumentation"));,
+    cl::desc("File path for cold function coverage instrumentation"),
     cl::Hidden);
 
 extern cl::opt<std::string> UseCtxProfile;

llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp

@@ -325,6 +325,18 @@ static cl::opt<uint64_t> ColdFuncCoverageMaxEntryCount(
              "instrumenting the function whose entry count is above the given "
              "value"));
 
+static cl::opt<InstrColdFuncCovMode> InstrumentColdFunctionCoverageMode(
+    "instrument-cold-function-coverage-mode",
+    cl::init(InstrColdFuncCovMode::Conservative), cl::Hidden,
+    cl::desc("Control whether instrumenting unprofiled functions for cold "
+             "function coverage."),
+    cl::values(
+        clEnumValN(InstrColdFuncCovMode::Conservative, "conservative",
+                   "Assume unprofiled functions are not cold, skip "
+                   "instrumenting them."),
+        clEnumValN(InstrColdFuncCovMode::Optimistic, "optimistic",
+                   "Treat unprofiled functions as cold and instrument them.")));
+
 cl::opt<bool> InstrumentColdFunctionCoverage(
     "instrument-cold-function-coverage", cl::init(false), cl::Hidden,
     cl::desc("Enable cold function coverage instrumentation (currently only "
@@ -1902,10 +1914,12 @@ static bool skipPGOGen(const Function &F) {
     return true;
   if (F.getInstructionCount() < PGOFunctionSizeThreshold)
     return true;
-  if (InstrumentColdFunctionCoverage &&
-      (!F.getEntryCount() ||
-       F.getEntryCount()->getCount() > ColdFuncCoverageMaxEntryCount))
-    return true;
+  if (InstrumentColdFunctionCoverage) {
+    if (!F.getEntryCount())
+      return InstrumentColdFunctionCoverageMode ==
+             InstrColdFuncCovMode::Conservative;
+    return F.getEntryCount()->getCount() > ColdFuncCoverageMaxEntryCount;
+  }
   return false;
 }
 

llvm/test/Transforms/PGOProfile/instr-gen-cold-function.ll

@@ -1,15 +1,26 @@
 ; RUN: opt < %s  --passes=pgo-instr-gen -instrument-cold-function-coverage -pgo-function-entry-coverage -S  | FileCheck --check-prefixes=COLD %s
 ; RUN: opt < %s  --passes=pgo-instr-gen -instrument-cold-function-coverage -pgo-function-entry-coverage -cold-function-coverage-max-entry-count=1 -S  | FileCheck --check-prefixes=ENTRY-COUNT %s
+; RUN: opt < %s  --passes=pgo-instr-gen -instrument-cold-function-coverage -pgo-function-entry-coverage -instrument-cold-function-coverage-mode=optimistic -S  | FileCheck --check-prefixes=UNPROFILED-FUNC %s
 
 ; COLD: call void @llvm.instrprof.cover(ptr @__profn_foo, i64  [[#]], i32 1, i32 0)
 ; COLD-NOT: __profn_main
+; COLD-NOT: __profn_bar
 
 ; ENTRY-COUNT: call void @llvm.instrprof.cover(ptr @__profn_foo, i64  [[#]], i32 1, i32 0)
 ; ENTRY-COUNT: call void @llvm.instrprof.cover(ptr @__profn_main, i64 [[#]], i32 1, i32 0)
 
+; UNPROFILED-FUNC: call void @llvm.instrprof.cover(ptr @__profn_bar, i64  [[#]], i32 1, i32 0)
+; UNPROFILED-FUNC: call void @llvm.instrprof.cover(ptr @__profn_foo, 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 @bar() {
+entry:
+  ret void
+}
+
 define void @foo() !prof !0 {
 entry:
   ret void