[X86] X86InstrInfo.cpp - Remove dead code for memory folding, NFCI

`commuteInstruction(MI, false, OpNum, CommuteOpIdx2)` should never create
any new instruction, so we don't need to check and erase it.

Author: KanRobert

llvm/lib/Target/X86/X86InstrInfo.cpp

@@ -7205,27 +7205,7 @@ unsigned X86InstrInfo::commuteOperandsForFold(MachineInstr &MI,
   if ((HasDef && Reg0 == Reg1 && Tied1) || (HasDef && Reg0 == Reg2 && Tied2))
     return Idx1;
 
-  MachineInstr *CommutedMI = commuteInstruction(MI, false, Idx1, Idx2);
-  if (!CommutedMI) {
-    // Unable to commute.
-    return Idx1;
-  }
-  if (CommutedMI != &MI) {
-    // New instruction. We can't fold from this.
-    CommutedMI->eraseFromParent();
-    return Idx1;
-  }
-
-  return Idx2;
-}
-
-void X86InstrInfo::UndoCommuteForFold(MachineInstr &MI, unsigned Idx1,
-                                      unsigned Idx2) const {
-  // Folding failed again - undo the commute before returning.
-  MachineInstr *UncommutedMI = commuteInstruction(MI, false, Idx1, Idx2);
-  // New instruction. It doesn't need to be kept.
-  if (UncommutedMI && UncommutedMI != &MI)
-    UncommutedMI->eraseFromParent();
+  return commuteInstruction(MI, false, Idx1, Idx2) ? Idx2 : Idx1;
 }
 
 static void printFailMsgforFold(const MachineInstr &MI, unsigned Idx) {
@@ -7369,7 +7349,8 @@ MachineInstr *X86InstrInfo::foldMemoryOperandImpl(
                                   Alignment, /*AllowCommute=*/false);
     if (NewMI)
       return NewMI;
-    UndoCommuteForFold(MI, OpNum, CommuteOpIdx2);
+    // Folding failed again - undo the commute before returning.
+    commuteInstruction(MI, false, OpNum, CommuteOpIdx2);
   }
 
   printFailMsgforFold(MI, OpNum);
@@ -8156,7 +8137,8 @@ X86InstrInfo::foldMemoryBroadcast(MachineFunction &MF, MachineInstr &MI,
                             /*AllowCommute=*/false);
     if (NewMI)
       return NewMI;
-    UndoCommuteForFold(MI, OpNum, CommuteOpIdx2);
+    // Folding failed again - undo the commute before returning.
+    commuteInstruction(MI, false, OpNum, CommuteOpIdx2);
   }
 
   printFailMsgforFold(MI, OpNum);

llvm/lib/Target/X86/X86InstrInfo.h

@@ -699,9 +699,6 @@ class X86InstrInfo final : public X86GenInstrInfo {
   /// \returns the index of operand that is commuted with \p Idx1. If the method
   /// fails to commute the operands, it will return \p Idx1.
   unsigned commuteOperandsForFold(MachineInstr &MI, unsigned Idx1) const;
-
-  /// Undo the commute of operands of \p MI at index \p Idx1 and index \p Idx2.
-  void UndoCommuteForFold(MachineInstr &MI, unsigned Idx1, unsigned Idx2) const;
 };
 } // namespace llvm