[llvm] r358728 - MergeFunc: preserve COMDAT information when creating a thunk

[Saleem Abdulrasool via llvm-commits]

Author: compnerd
Date: Thu Apr 18 18:48:36 2019
New Revision: 358728

URL: http://llvm.org/viewvc/llvm-project?rev=358728&view=rev
Log:
MergeFunc: preserve COMDAT information when creating a thunk

We would previously drop the COMDAT on the thunk we generated when replacing a
function body with the forwarding thunk. This would result in a function that
may have been multiply emitted and multiply merged to be emitted with the same
name without the COMDAT. This is a hard error with PE/COFF where the COMDAT is
used for the deduplication of Value Witness functions for Swift.

Added:
    llvm/trunk/test/Transforms/MergeFunc/comdat.ll
Modified:
    llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp

Modified: llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp?rev=358728&r1=358727&r2=358728&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp Thu Apr 18 18:48:36 2019
@@ -703,6 +703,7 @@ void MergeFunctions::writeThunk(Function
   } else {
     NewG = Function::Create(G->getFunctionType(), G->getLinkage(),
                             G->getAddressSpace(), "", G->getParent());
+    NewG->setComdat(G->getComdat());
     BB = BasicBlock::Create(F->getContext(), "", NewG);
   }
 

Added: llvm/trunk/test/Transforms/MergeFunc/comdat.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/MergeFunc/comdat.ll?rev=358728&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/MergeFunc/comdat.ll (added)
+++ llvm/trunk/test/Transforms/MergeFunc/comdat.ll Thu Apr 18 18:48:36 2019
@@ -0,0 +1,24 @@
+; RUN: opt -S -mergefunc %s | FileCheck %s
+
+ at symbols = linkonce_odr global <{ i8*, i8* }> <{ i8* bitcast (i32 (i32, i32)* @f to i8*), i8* bitcast (i32 (i32, i32)* @g to i8*) }>
+
+$f = comdat any
+$g = comdat any
+
+define linkonce_odr hidden i32 @f(i32 %x, i32 %y) comdat {
+  %sum = add i32 %x, %y
+  %sum2 = add i32 %x, %sum
+  %sum3 = add i32 %x, %sum
+  ret i32 %sum3
+}
+
+define linkonce_odr hidden i32 @g(i32 %x, i32 %y) comdat {
+  %sum = add i32 %x, %y
+  %sum2 = add i32 %x, %sum
+  %sum3 = add i32 %x, %sum
+  ret i32 %sum3
+}
+
+; CHECK-DAG: define linkonce_odr hidden i32 @f(i32 %x, i32 %y) comdat
+; CHECK-DAG: define linkonce_odr hidden i32 @g(i32, i32) comdat
+