From 0e79f7d11d6a76c8509554bde344d0270fea814d Mon Sep 17 00:00:00 2001
From: Rong Xu <xur@google.com>
Date: Thu, 6 Oct 2016 20:38:13 +0000
Subject: [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

llvm-svn: 283490
---
 llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'llvm/lib')

diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
index 4d6a5048797..c2e42177661 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -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>::renameComdatFunction() {
     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.
-- 
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