[llvm-commits] [llvm] r65289 - /llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp

[Dan Gohman]

Author: djg
Date: Sun Feb 22 12:06:32 2009
New Revision: 65289

URL: http://llvm.org/viewvc/llvm-project?rev=65289&view=rev
Log:
Revert the part of 64623 that attempted to align the source in a
memcpy to match the alignment of the destination. It isn't necessary
for making loads and stores handled like the SSE loadu/storeu
intrinsics, and it was causing a performance regression in
MultiSource/Applications/JM/lencod.

The problem appears to have been a memcpy that copies from some
highly aligned array into an alloca; the alloca was then being
assigned a large alignment, which required codegen to perform
dynamic stack-pointer re-alignment, which forced the enclosing
function to have a frame pointer, which led to increased spilling.

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

Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=65289&r1=65288&r2=65289&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Sun Feb 22 12:06:32 2009
@@ -9286,7 +9286,7 @@
 
 Instruction *InstCombiner::SimplifyMemTransfer(MemIntrinsic *MI) {
   unsigned DstAlign = GetOrEnforceKnownAlignment(MI->getOperand(1));
-  unsigned SrcAlign = GetOrEnforceKnownAlignment(MI->getOperand(2), DstAlign);
+  unsigned SrcAlign = GetOrEnforceKnownAlignment(MI->getOperand(2));
   unsigned MinAlign = std::min(DstAlign, SrcAlign);
   unsigned CopyAlign = MI->getAlignment()->getZExtValue();