[llvm] [X86][CodeGen] Fix crash when commute operands of Instruction for code size (PR #79245)

[Phoebe Wang via llvm-commits]

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@@ -2326,33 +2326,26 @@ MachineInstr *X86InstrInfo::commuteInstructionImpl(MachineInstr &MI, bool NewMI,
   case X86::VBLENDPSrri:
     // If we're optimizing for size, try to use MOVSD/MOVSS.
     if (MI.getParent()->getParent()->getFunction().hasOptSize()) {
-      unsigned Mask;
-      switch (Opc) {
-      default:
-        llvm_unreachable("Unreachable!");
-      case X86::BLENDPDrri:
-        Opc = X86::MOVSDrr;
-        Mask = 0x03;
-        break;
-      case X86::BLENDPSrri:
-        Opc = X86::MOVSSrr;
-        Mask = 0x0F;
-        break;
-      case X86::VBLENDPDrri:
-        Opc = X86::VMOVSDrr;
-        Mask = 0x03;
-        break;
-      case X86::VBLENDPSrri:
-        Opc = X86::VMOVSSrr;
-        Mask = 0x0F;
-        break;
-      }
+      unsigned Mask = (Opc == X86::BLENDPDrri || Opc == X86::VBLENDPDrri) ? 0x03: 0x0F;
       if ((MI.getOperand(3).getImm() ^ Mask) == 1) {
+#define FROM_TO(A, B)                                                          \
+  case X86::A:                                                                 \
+    Opc = X86::B;                                                              \
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phoebewang wrote:

Nit, using `FROM, TO` to replace `A, B`

https://github.com/llvm/llvm-project/pull/79245