[llvm] r194684 - Add a comment

[Matt Arsenault]

Author: arsenm
Date: Thu Nov 14 02:06:38 2013
New Revision: 194684

URL: http://llvm.org/viewvc/llvm-project?rev=194684&view=rev
Log:
Add a comment

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

Modified: llvm/trunk/lib/Target/R600/SIInstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/R600/SIInstrInfo.cpp?rev=194684&r1=194683&r2=194684&view=diff
==============================================================================
--- llvm/trunk/lib/Target/R600/SIInstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/R600/SIInstrInfo.cpp Thu Nov 14 02:06:38 2013
@@ -440,7 +440,9 @@ void SIInstrInfo::legalizeOperands(Machi
   // Legalize VOP2
   if (isVOP2(MI->getOpcode()) && Src1Idx != -1) {
     MachineOperand &Src1 = MI->getOperand(Src1Idx);
-    // Legalize VOP2 instructions where src1 is not a VGPR.
+
+    // Legalize VOP2 instructions where src1 is not a VGPR. An SGPR input must
+    // be the first operand, and there can only be one.
     if (Src1.isImm() || Src1.isFPImm() ||
         (Src1.isReg() && RI.isSGPRClass(MRI.getRegClass(Src1.getReg())))) {
       if (MI->isCommutable()) {