[llvm] [PowerPC] Fix ppc-reduce-cr-ops mishandling of subregister uses (PR #144405)

[Nemanja Ivanovic via llvm-commits]

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@@ -535,26 +542,17 @@ PPCReduceCRLogicals::createCRLogicalOpInfo(MachineInstr &MIParam) {
 MachineInstr *PPCReduceCRLogicals::lookThroughCRCopy(unsigned Reg,
                                                      unsigned &Subreg,
                                                      MachineInstr *&CpDef) {
-  Subreg = -1;
   if (!Register::isVirtualRegister(Reg))
     return nullptr;
   MachineInstr *Copy = MRI->getVRegDef(Reg);
   CpDef = Copy;
   if (!Copy->isCopy())
     return Copy;
   Register CopySrc = Copy->getOperand(1).getReg();
-  Subreg = Copy->getOperand(1).getSubReg();
+  // If the copy defines a register with a subreg, set that as the Subreg.
+  Subreg = Copy->getOperand(0).getSubReg();
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nemanjai wrote:

Ah, yes. OK, I think the `Subreg` handling should completely be removed from this function.

https://github.com/llvm/llvm-project/pull/144405