[PGO] Make needsComdatForCounter() available (NFC)

[xur]

Summary

Move needsComdatForCounter() to lib/ProfileData/InstrProf.cpp from lib/Transforms/Instrumentation/InstrProfiling.cpp to make is available for other files.

[davidxl]

lgtm

include/llvm/ProfileData/InstrProf.h

 /// declared by users only.
 void createPGOFuncNameMetadata(Function &F, StringRef PGOFuncName);
 
+/// Check if we can use Comdat for profile variables. This will eliminate
+/// the duplicated profile variables for Comdat functions.
+bool needsComdatForCounter(const Function &F, const Module &M);
+
 const std::error_category &instrprof_category();
 
 enum class instrprof_error {

lib/ProfileData/InstrProf.cpp

 
 #include "llvm/ProfileData/InstrProf.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/Triple.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalVariable.h"

   F.setMetadata(getPGOFuncNameMetadataName(), N);
 }
 
+bool needsComdatForCounter(const Function &F, const Module &M) {
+  if (F.hasComdat())
+    return true;
+
+  Triple TT(M.getTargetTriple());
+  if (!TT.isOSBinFormatELF())
+    return false;
+
+  // See createPGOFuncNameVar for more details. To avoid link errors, profile
+  // counters for function with available_externally linkage needs to be changed
+  // to linkonce linkage. On ELF based systems, this leads to weak symbols to be
+  // created. Without using comdat, duplicate entries won't be removed by the
+  // linker leading to increased data segement size and raw profile size. Even
+  // worse, since the referenced counter from profile per-function data object
+  // will be resolved to the common strong definition, the profile counts for
+  // available_externally functions will end up being duplicated in raw profile
+  // data. This can result in distorted profile as the counts of those dups
+  // will be accumulated by the profile merger.
+  GlobalValue::LinkageTypes Linkage = F.getLinkage();
+  if (Linkage != GlobalValue::ExternalWeakLinkage &&
+      Linkage != GlobalValue::AvailableExternallyLinkage)
+    return false;
+
+  return true;
+}
 } // end namespace llvm

lib/Transforms/Instrumentation/InstrProfiling.cpp

   return F->hasAddressTaken() || F->hasLinkOnceLinkage();
 }
 
-static inline bool needsComdatForCounter(Function &F, Module &M) {
-
-  if (F.hasComdat())
-    return true;
-
-  Triple TT(M.getTargetTriple());
-  if (!TT.isOSBinFormatELF())
-    return false;
-
-  // See createPGOFuncNameVar for more details. To avoid link errors, profile
-  // counters for function with available_externally linkage needs to be changed
-  // to linkonce linkage. On ELF based systems, this leads to weak symbols to be
-  // created. Without using comdat, duplicate entries won't be removed by the
-  // linker leading to increased data segement size and raw profile size. Even
-  // worse, since the referenced counter from profile per-function data object
-  // will be resolved to the common strong definition, the profile counts for
-  // available_externally functions will end up being duplicated in raw profile
-  // data. This can result in distorted profile as the counts of those dups
-  // will be accumulated by the profile merger.
-  GlobalValue::LinkageTypes Linkage = F.getLinkage();
-  if (Linkage != GlobalValue::ExternalWeakLinkage &&
-      Linkage != GlobalValue::AvailableExternallyLinkage)
-    return false;
-
-  return true;
-}
-
 static inline Comdat *getOrCreateProfileComdat(Module &M, Function &F,
                                                InstrProfIncrementInst *Inc) {
   if (!needsComdatForCounter(F, M))