[llvm] r217451 - When merging two common GlobalValues, keep the largest.

[Rafael Espindola]

Author: rafael
Date: Tue Sep  9 10:59:12 2014
New Revision: 217451

URL: http://llvm.org/viewvc/llvm-project?rev=217451&view=rev
Log:
When merging two common GlobalValues, keep the largest.

Modified:
    llvm/trunk/lib/Linker/LinkModules.cpp
    llvm/trunk/test/Linker/Inputs/linkage2.ll
    llvm/trunk/test/Linker/linkage2.ll

Modified: llvm/trunk/lib/Linker/LinkModules.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Linker/LinkModules.cpp?rev=217451&r1=217450&r2=217451&view=diff
==============================================================================
--- llvm/trunk/lib/Linker/LinkModules.cpp (original)
+++ llvm/trunk/lib/Linker/LinkModules.cpp Tue Sep  9 10:59:12 2014
@@ -688,6 +688,9 @@ bool ModuleLinker::shouldLinkFromSource(
   bool SrcIsDeclaration = isDeclaration(Src);
   bool DestIsDeclaration = isDeclaration(Dest);
 
+  // FIXME: Make datalayout mandatory and just use getDataLayout().
+  DataLayout DL(Dest.getParent());
+
   if (SrcIsDeclaration) {
     // If Src is external or if both Src & Dest are external..  Just link the
     // external globals, we aren't adding anything.
@@ -702,14 +705,26 @@ bool ModuleLinker::shouldLinkFromSource(
     // If Dest is external but Src is not:
     return true;
 
+  if (Src.hasCommonLinkage()) {
+    if (Dest.hasLinkOnceLinkage() || Dest.hasWeakLinkage())
+      return true;
+
+    if (!Dest.hasCommonLinkage())
+      return false;
+
+    uint64_t DestSize = DL.getTypeAllocSize(Dest.getType()->getElementType());
+    uint64_t SrcSize = DL.getTypeAllocSize(Src.getType()->getElementType());
+    return SrcSize > DestSize;
+  }
+
   if (Src.isWeakForLinker()) {
     assert(!Dest.hasExternalWeakLinkage());
     assert(!Dest.hasAvailableExternallyLinkage());
+
     if (Dest.hasLinkOnceLinkage() && Src.hasWeakLinkage())
       return true;
 
-    return (Dest.hasLinkOnceLinkage() || Dest.hasWeakLinkage()) &&
-           Src.hasCommonLinkage();
+    return false;
   }
 
   if (Dest.isWeakForLinker()) {

Modified: llvm/trunk/test/Linker/Inputs/linkage2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Linker/Inputs/linkage2.ll?rev=217451&r1=217450&r2=217451&view=diff
==============================================================================
--- llvm/trunk/test/Linker/Inputs/linkage2.ll (original)
+++ llvm/trunk/test/Linker/Inputs/linkage2.ll Tue Sep  9 10:59:12 2014
@@ -1,3 +1,5 @@
 @test1_a = weak global i8 1
 
 @test2_a = external dllimport global i8
+
+ at test3_a = common global i16 0

Modified: llvm/trunk/test/Linker/linkage2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Linker/linkage2.ll?rev=217451&r1=217450&r2=217451&view=diff
==============================================================================
--- llvm/trunk/test/Linker/linkage2.ll (original)
+++ llvm/trunk/test/Linker/linkage2.ll Tue Sep  9 10:59:12 2014
@@ -2,7 +2,10 @@
 ; RUN: llvm-link %p/Inputs/linkage2.ll %s -S | FileCheck %s
 
 @test1_a = common global i8 0
-; CHECK: @test1_a = common global i8 0
+; CHECK-DAG: @test1_a = common global i8 0
 
 @test2_a = global i8 0
-; CHECK: @test2_a = global i8 0
+; CHECK-DAG: @test2_a = global i8 0
+
+ at test3_a = common global i8 0
+; CHECK-DAG: @test3_a = common global i16 0