[InstrProf] Add options to profile function groups

Add two options, `-fprofile-function-groups=N` and `-fprofile-selected-function-group=i` used to partition functions into `N` groups and only instrument the functions in group `i`. Similar options were added to xray in https://reviews.llvm.org/D87953 and the goal is the same; to reduce instrumented size overhead by spreading the overhead across multiple builds. Raw profiles from different groups can be added like normal using the `llvm-profdata merge` command.

Reviewed By: ianlevesque

Differential Revision: https://reviews.llvm.org/D129594

1 files changed, 17 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index bdee31b504ae..1e90b0914538 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -58,6 +58,7 @@
 #include "llvm/IR/Module.h"
 #include "llvm/IR/ProfileSummary.h"
 #include "llvm/ProfileData/InstrProfReader.h"
+#include "llvm/Support/CRC.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ConvertUTF.h"
@@ -2843,8 +2844,8 @@ bool CodeGenModule::imbueXRayAttrs(llvm::Function *Fn, SourceLocation Loc,
   return true;
 }
 
-bool CodeGenModule::isProfileInstrExcluded(llvm::Function *Fn,
-                                           SourceLocation Loc) const {
+bool CodeGenModule::isFunctionBlockedByProfileList(llvm::Function *Fn,
+                                                   SourceLocation Loc) const {
   const auto &ProfileList = getContext().getProfileList();
   // If the profile list is empty, then instrument everything.
   if (ProfileList.isEmpty())
@@ -2871,6 +2872,20 @@ bool CodeGenModule::isProfileInstrExcluded(llvm::Function *Fn,
   return ProfileList.getDefault();
 }
 
+bool CodeGenModule::isFunctionBlockedFromProfileInstr(
+    llvm::Function *Fn, SourceLocation Loc) const {
+  if (isFunctionBlockedByProfileList(Fn, Loc))
+    return true;
+
+  auto NumGroups = getCodeGenOpts().ProfileTotalFunctionGroups;
+  if (NumGroups > 1) {
+    auto Group = llvm::crc32(arrayRefFromStringRef(Fn->getName())) % NumGroups;
+    if (Group != getCodeGenOpts().ProfileSelectedFunctionGroup)
+      return true;
+  }
+  return false;
+}
+
 bool CodeGenModule::MustBeEmitted(const ValueDecl *Global) {
   // Never defer when EmitAllDecls is specified.
   if (LangOpts.EmitAllDecls)