[llvm-commits] [llvm] r137313 - /llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

[Nadav Rotem]

Author: nadav
Date: Thu Aug 11 12:05:47 2011
New Revision: 137313

URL: http://llvm.org/viewvc/llvm-project?rev=137313&view=rev
Log:
Add a comment, per Bruno's CR.

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=137313&r1=137312&r2=137313&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Thu Aug 11 12:05:47 2011
@@ -12593,6 +12593,9 @@
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
 
   // If we are saving a concatination of two XMM registers, perform two stores.
+  // This is better in Sandy Bridge cause one 256-bit mem op is done via two
+  // 128-bit ones. If in the future the cost becomes only one memory access the
+  // first version would be better.
   if (VT.getSizeInBits() == 256 &&
     StoredVal.getNode()->getOpcode() == ISD::CONCAT_VECTORS &&
     StoredVal.getNumOperands() == 2) {