Fix bug 24715

[vincentqiuuu]

Summary

Fix for https://llvm.org/bugs/show_bug.cgi?id=24715
Boolean flag Changed in GVN::performPRE(Function &F) is not correctly updated.

[llvm-commits]

LGTM.

Looking a related code, it looks like we're failing to consider the
return value of the same function at it's other call site. Any interest
in fixing that too?

Philip

• msg-20974-289.txt162 BDownload

[mehdi_amini]

Committed in r253518.

Please submit another patch for the other cases :)

lib/Transforms/Scalar/GVN.cpp

for (BasicBlock *CurrentBlock : depth_first(&F.getEntryBlock())) {
     // Don't perform PRE on an EH pad.
     if (CurrentBlock->isEHPad())
       continue;
 
     for (BasicBlock::iterator BI = CurrentBlock->begin(),
                               BE = CurrentBlock->end();
          BI != BE;) {
       Instruction *CurInst = &*BI++;
-      Changed = performScalarPRE(CurInst);
+      Changed |= performScalarPRE(CurInst);
     }
   }
 
   if (splitCriticalEdges())
     Changed = true;
 
   return Changed;
 }