R600/SI: Fix using wrong operand indices when commuting

No test since the current SIISelLowering::legalizeOperands
effectively hides this, and the general uses seem to only fire
on SALU instructions which don't have modifiers between
the operands.

When trying to use legalizeOperands immediately after
instruction selection, it now sees a lot more patterns
it did not see before which break on this.

llvm-svn: 218527

1 files changed, 20 insertions, 11 deletions

diff --git a/llvm/lib/Target/R600/SIInstrInfo.cpp b/llvm/lib/Target/R600/SIInstrInfo.cpp
index fffd698d14f..3ad448ee421 100644
--- a/llvm/lib/Target/R600/SIInstrInfo.cpp
+++ b/llvm/lib/Target/R600/SIInstrInfo.cpp
@@ -684,19 +684,28 @@ bool SIInstrInfo::expandPostRAPseudo(MachineBasicBlock::iterator MI) const {
 
 MachineInstr *SIInstrInfo::commuteInstruction(MachineInstr *MI,
                                               bool NewMI) const {
+  if (MI->getNumOperands() < 3)
+    return nullptr;
+
+  int Src0Idx = AMDGPU::getNamedOperandIdx(MI->getOpcode(),
+                                           AMDGPU::OpName::src0);
+  assert(Src0Idx != -1 && "Should always have src0 operand");
 
-  if (MI->getNumOperands() < 3 || !MI->getOperand(1).isReg())
+  if (!MI->getOperand(Src0Idx).isReg())
     return nullptr;
 
+  int Src1Idx = AMDGPU::getNamedOperandIdx(MI->getOpcode(),
+                                           AMDGPU::OpName::src1);
+
   // Make sure it s legal to commute operands for VOP2.
-  if (isVOP2(MI->getOpcode()) &&
-      (!isOperandLegal(MI, 1, &MI->getOperand(2)) ||
-       !isOperandLegal(MI, 2, &MI->getOperand(1))))
+  if ((Src1Idx != -1) && isVOP2(MI->getOpcode()) &&
+      (!isOperandLegal(MI, Src0Idx, &MI->getOperand(Src1Idx)) ||
+       !isOperandLegal(MI, Src1Idx, &MI->getOperand(Src0Idx))))
     return nullptr;
 
-  if (!MI->getOperand(2).isReg()) {
+  if (Src1Idx != -1 && !MI->getOperand(Src1Idx).isReg()) {
     // XXX: Commute instructions with FPImm operands
-    if (NewMI || MI->getOperand(2).isFPImm() ||
+    if (NewMI || MI->getOperand(Src1Idx).isFPImm() ||
        (!isVOP2(MI->getOpcode()) && !isVOP3(MI->getOpcode()))) {
       return nullptr;
     }
@@ -716,11 +725,11 @@ MachineInstr *SIInstrInfo::commuteInstruction(MachineInstr *MI,
         (Src2Mods && Src2Mods->getImm()))
       return nullptr;
 
-    unsigned Reg = MI->getOperand(1).getReg();
-    unsigned SubReg = MI->getOperand(1).getSubReg();
-    MI->getOperand(1).ChangeToImmediate(MI->getOperand(2).getImm());
-    MI->getOperand(2).ChangeToRegister(Reg, false);
-    MI->getOperand(2).setSubReg(SubReg);
+    unsigned Reg = MI->getOperand(Src0Idx).getReg();
+    unsigned SubReg = MI->getOperand(Src0Idx).getSubReg();
+    MI->getOperand(Src0Idx).ChangeToImmediate(MI->getOperand(Src1Idx).getImm());
+    MI->getOperand(Src1Idx).ChangeToRegister(Reg, false);
+    MI->getOperand(Src1Idx).setSubReg(SubReg);
   } else {
     MI = TargetInstrInfo::commuteInstruction(MI, NewMI);
   }