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

Ensure registers used in instructions modified by `combineRLWINM()` are
added to list of `RegsToUpdate`.

Author: lei137

llvm/lib/Target/PowerPC/PPCMIPeephole.cpp

@@ -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());
           ++NumRotatesCollapsed;
         }
         break;

llvm/test/CodeGen/PowerPC/peephole-combineRLWINM-liveness.mir

@@ -0,0 +1,27 @@
+# RUN: llc -mtriple=powerpc-ibm-aix -verify-machineinstrs -run-pass=ppc-mi-peepholes -o - %s | FileCheck %s
+# RUN: llc -mtriple=powerpc64-ibm-aix -verify-machineinstrs -run-pass=ppc-mi-peepholes -o - %s | FileCheck %s
+# RUN: llc -mtriple=powerpc64-linux-gnu -verify-machineinstrs -run-pass=ppc-mi-peepholes -o - %s | FileCheck %s
+---
+
+name: testFoldRLWINM
+tracksRegLiveness: true
+
+body: |
+  bb.0.entry:
+    liveins: $r3
+    %0:gprc = COPY $r3
+    B %bb.1
+  bb.1:
+    B %bb.2
+  bb.2:
+    %1:gprc = RLWINM killed %0:gprc, 1, 0, 30
+    %2:gprc = RLWINM killed %1:gprc, 31, 0, 0
+    BLR8 implicit $lr8, implicit $rm
+
+...
+
+# CHECK-LABEL: testFoldRLWINM
+# CHECK:       bb.0.entry:
+# CHECK:         dead %0:gprc = COPY killed $r3
+# CHECK:       bb.2:
+# CHECK:         dead %2:gprc = LI 0