[llvm] Fix [PowerPC] llc crashed at -O1/O2/O3: Assertion `isImm() && "Wrong MachineOperand mutator"' failed. (PR #170548)

[Lei Huang via llvm-commits]

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@@ -835,30 +837,58 @@ bool PPCMIPeephole::simplifyCode() {
           ToErase = &MI;
           Simplified = true;
         }
+
         // Splat fed by a shift. Usually when we align value to splat into
         // vector element zero.
         if (DefOpcode == PPC::XXSLDWI) {
-          Register ShiftRes = DefMI->getOperand(0).getReg();
           Register ShiftOp1 = DefMI->getOperand(1).getReg();
           Register ShiftOp2 = DefMI->getOperand(2).getReg();
-          unsigned ShiftImm = DefMI->getOperand(3).getImm();
-          unsigned SplatImm =
-              MI.getOperand(MyOpcode == PPC::XXSPLTW ? 2 : 1).getImm();
+
           if (ShiftOp1 == ShiftOp2) {
-            unsigned NewElem = (SplatImm + ShiftImm) & 0x3;
+            // For example, We can erase XXSLDWI from in following:
+            //    %2:vrrc = XXSLDWI killed %1:vrrc, %1:vrrc, 1
+            //    %6:vrrc = VSPLTB 15, killed %2:vrrc
+            //    %7:vsrc = XXLAND killed %6:vrrc, killed %1:vrrc
+            //
+            // --->
+            //
+            //     %6:vrrc = VSPLTB 3, killed %1:vrrc
+            //     %7:vsrc = XXLAND killed %6:vrrc, killed %1:vrrc
+
+            Register ShiftRes = DefMI->getOperand(0).getReg();
----------------
lei137 wrote:

can just inline to the call since only have 1 use.

https://github.com/llvm/llvm-project/pull/170548