[llvm] [PowerPC] eliminate RLWINM instruction following LBARX as possible (PR #144089)

[Lei Huang via llvm-commits]

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@@ -1281,7 +1281,40 @@ bool PPCMIPeephole::simplifyCode() {
         Simplified = true;
         break;
       }
-      case PPC::RLWINM:
+      case PPC::RLWINM: {
+        Register SrcReg = MI.getOperand(1).getReg();
+        MachineInstr *DefMI = MRI->getVRegDef(SrcReg);
+
+        if (DefMI) {
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lei137 wrote:

early exit for `if (!DefMI)`

https://github.com/llvm/llvm-project/pull/144089