[llvm] [PowerPC] Ensure MI peephole knows about instr modified by combineRLWINM() (PR #97134)

[Chen Zheng via llvm-commits]

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@@ -1291,6 +1291,10 @@ bool PPCMIPeephole::simplifyCode() {
           addRegToUpdate(OrigOp1Reg);
           if (MI.getOperand(1).isReg())
             addRegToUpdate(MI.getOperand(1).getReg());
+          if (ToErase && ToErase->getOperand(1).isReg())
+            for (auto UseReg: ToErase->explicit_uses())
+              if (UseReg.isReg())
+                addRegToUpdate(UseReg.getReg());
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chenzheng1030 wrote:

We have `recomputeLVForDyingInstr()` to recompute the liveness for  operands of`ToErase` instructions. But this function only does the computation for the defs and the regs added by `addRegToUpdate()`.

For now, it is OK we fix this case by adding the use operands of `ToErase` to the update container at this place. If we continue to meet new issues, we may need to revisit the way we recompute the liveness for `ToErase` instructions.

https://github.com/llvm/llvm-project/pull/97134