[llvm-commits] [llvm] r114781 - /llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp

[Eric Christopher]

Author: echristo
Date: Fri Sep 24 19:57:26 2010
New Revision: 114781

URL: http://llvm.org/viewvc/llvm-project?rev=114781&view=rev
Log:
If we're changing the source of a memcpy we need to use the alignment
of the source, not the original alignment since it may no longer
be valid.

Fixes rdar://8400094

Modified:
    llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp?rev=114781&r1=114780&r2=114781&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp Fri Sep 24 19:57:26 2010
@@ -697,14 +697,16 @@
                                  M->getParent()->getParent()->getParent(),
                                  M->getIntrinsicID(), ArgTys, 3);
     
+  // Make sure to use the alignment of the source since we're changing the
+  // location we're reading from.
+  // TODO: Is this worth it if we're creating a less aligned memcpy? For
+  // example we could be moving from movaps -> movq on x86.
   Value *Args[5] = {
     M->getRawDest(), MDep->getRawSource(), M->getLength(),
-    M->getAlignmentCst(), M->getVolatileCst()
+    MDep->getAlignmentCst(), M->getVolatileCst()
   };
-  
   CallInst *C = CallInst::Create(MemCpyFun, Args, Args+5, "", M);
   
-  
   // If C and M don't interfere, then this is a valid transformation.  If they
   // did, this would mean that the two sources overlap, which would be bad.
   if (MD.getDependency(C) == dep) {