[llvm] r206501 - R600: Add comment clariying use of sext for result of MUL_U24

[Tom Stellard]

Author: tstellar
Date: Thu Apr 17 16:00:13 2014
New Revision: 206501

URL: http://llvm.org/viewvc/llvm-project?rev=206501&view=rev
Log:
R600: Add comment clariying use of sext for result of MUL_U24

Modified:
    llvm/trunk/lib/Target/R600/AMDGPUISelLowering.cpp

Modified: llvm/trunk/lib/Target/R600/AMDGPUISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/R600/AMDGPUISelLowering.cpp?rev=206501&r1=206500&r2=206501&view=diff
==============================================================================
--- llvm/trunk/lib/Target/R600/AMDGPUISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/R600/AMDGPUISelLowering.cpp Thu Apr 17 16:00:13 2014
@@ -1158,6 +1158,8 @@ SDValue AMDGPUTargetLowering::PerformDAG
         break;
       }
 
+      // We need to use sext even for MUL_U24, because MUL_U24 is used
+      // for signed multiply of 8 and 16-bit types.
       SDValue Reg = DAG.getSExtOrTrunc(Mul, DL, VT);
 
       return Reg;