[TwoAddressInstruction] When commuting an instruction don't assume that the destination register is operand 0. Pass it from the caller.

In practice it probably is 0 so this may not be a functional change.

llvm-svn: 281180

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
index 704f596e56f..0f1b2ed994b 100644
--- a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -109,7 +109,7 @@ class TwoAddressInstructionPass : public MachineFunctionPass {
   bool isProfitableToCommute(unsigned regA, unsigned regB, unsigned regC,
                              MachineInstr *MI, unsigned Dist);
 
-  bool commuteInstruction(MachineInstr *MI,
+  bool commuteInstruction(MachineInstr *MI, unsigned DstIdx,
                           unsigned RegBIdx, unsigned RegCIdx, unsigned Dist);
 
   bool isProfitableToConv3Addr(unsigned RegA, unsigned RegB);
@@ -651,6 +651,7 @@ isProfitableToCommute(unsigned regA, unsigned regB, unsigned regC,
 /// Commute a two-address instruction and update the basic block, distance map,
 /// and live variables if needed. Return true if it is successful.
 bool TwoAddressInstructionPass::commuteInstruction(MachineInstr *MI,
+                                                   unsigned DstIdx,
                                                    unsigned RegBIdx,
                                                    unsigned RegCIdx,
                                                    unsigned Dist) {
@@ -671,7 +672,7 @@ bool TwoAddressInstructionPass::commuteInstruction(MachineInstr *MI,
   // Update source register map.
   unsigned FromRegC = getMappedReg(RegC, SrcRegMap);
   if (FromRegC) {
-    unsigned RegA = MI->getOperand(0).getReg();
+    unsigned RegA = MI->getOperand(DstIdx).getReg();
     SrcRegMap[RegA] = FromRegC;
   }
 
@@ -1202,7 +1203,8 @@ bool TwoAddressInstructionPass::tryInstructionCommute(MachineInstr *MI,
     }
 
     // If it's profitable to commute, try to do so.
-    if (DoCommute && commuteInstruction(MI, BaseOpIdx, OtherOpIdx, Dist)) {
+    if (DoCommute && commuteInstruction(MI, DstOpIdx, BaseOpIdx, OtherOpIdx,
+                                        Dist)) {
       ++NumCommuted;
       if (AggressiveCommute)
         ++NumAggrCommuted;