[llvm-commits] [llvm] r71688 - /llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp

[Dale Johannesen]

Author: johannes
Date: Wed May 13 13:25:07 2009
New Revision: 71688

URL: http://llvm.org/viewvc/llvm-project?rev=71688&view=rev
Log:
Don't generate a select whose operand is load of a weak
external.  These may have address 0 and are not safe
to execute unconditionally.


Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=71688&r1=71687&r2=71688&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Wed May 13 13:25:07 2009
@@ -18,6 +18,7 @@
 #include "llvm/IntrinsicInst.h"
 #include "llvm/Type.h"
 #include "llvm/DerivedTypes.h"
+#include "llvm/GlobalVariable.h"
 #include "llvm/Support/CFG.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Analysis/ConstantFolding.h"
@@ -393,6 +394,11 @@
         if (!isa<AllocaInst>(I->getOperand(0)) &&
             !isa<Constant>(I->getOperand(0)))
           return false;
+        // External weak globals may have address 0, so we can't load them.
+        if (GlobalVariable* GV= dyn_cast<GlobalVariable>(I->getOperand(0))) {
+          if (GV->hasExternalWeakLinkage())
+            return false;
+        }
 
         // Finally, we have to check to make sure there are no instructions
         // before the load in its basic block, as we are going to hoist the loop