[llvm] r283490 - [PGO] Create weak alias for the renamed Comdat function

[Rong Xu via llvm-commits]

Author: xur
Date: Thu Oct  6 15:38:13 2016
New Revision: 283490

URL: http://llvm.org/viewvc/llvm-project?rev=283490&view=rev
Log:
[PGO] Create weak alias for the renamed Comdat function

Add a weak alias to the renamed Comdat function in IR level instrumentation,
using it's original name. This ensures the same behavior w/ and w/o IR
instrumentation, even for non standard conforming code.

Differential Revision: http://reviews.llvm.org/D25339

Modified:
    llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
    llvm/trunk/test/Transforms/PGOProfile/comdat_rename.ll

Modified: llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp?rev=283490&r1=283489&r2=283490&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/PGOInstrumentation.cpp Thu Oct  6 15:38:13 2016
@@ -439,9 +439,11 @@ template <class Edge, class BBInfo>
 void FuncPGOInstrumentation<Edge, BBInfo>::renameComdatFunction() {
   if (!canRenameComdat(F, ComdatMembers))
     return;
+  std::string OrigName = F.getName().str();
   std::string NewFuncName =
       Twine(F.getName() + "." + Twine(FunctionHash)).str();
   F.setName(Twine(NewFuncName));
+  GlobalAlias::create(GlobalValue::WeakAnyLinkage, OrigName, &F);
   FuncName = Twine(FuncName + "." + Twine(FunctionHash)).str();
   Comdat *NewComdat;
   Module *M = F.getParent();
@@ -467,7 +469,9 @@ void FuncPGOInstrumentation<Edge, BBInfo
     if (GlobalAlias *GA = dyn_cast<GlobalAlias>(CM.second)) {
       // For aliases, change the name directly.
       assert(dyn_cast<Function>(GA->getAliasee()->stripPointerCasts()) == &F);
+      std::string OrigGAName = GA->getName().str();
       GA->setName(Twine(GA->getName() + "." + Twine(FunctionHash)));
+      GlobalAlias::create(GlobalValue::WeakAnyLinkage, OrigGAName, GA);
       continue;
     }
     // Must be a function.

Modified: llvm/trunk/test/Transforms/PGOProfile/comdat_rename.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/PGOProfile/comdat_rename.ll?rev=283490&r1=283489&r2=283490&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/PGOProfile/comdat_rename.ll (original)
+++ llvm/trunk/test/Transforms/PGOProfile/comdat_rename.ll Thu Oct  6 15:38:13 2016
@@ -50,6 +50,12 @@ define linkonce_odr void @f_with_alias()
 
 ; Rename AvailableExternallyLinkage functions
 ; ELFONLY-DAG: $aef.[[SINGLEBB_HASH]] = comdat any
+
+; ELFONLY: @f = weak alias void (), void ()* @f.[[SINGLEBB_HASH]]
+; ELFONLY: @f_with_alias = weak alias void (), void ()* @f_with_alias.[[SINGLEBB_HASH]]
+; ELFONLY: @af = weak alias void (...), void (...)* @af.[[SINGLEBB_HASH]]
+; ELFONLY: @aef = weak alias void (), void ()* @aef.[[SINGLEBB_HASH]]
+
 define available_externally void @aef() {
 ; ELFONLY: define linkonce_odr void @aef.[[SINGLEBB_HASH]]() comdat {
 ; COFFONLY: define available_externally void @aef() {