[llvm] [X86][CodeGen] Transform NDD SUB to CMP if dest reg is dead (PR #79135)

[Phoebe Wang via llvm-commits]

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@@ -5130,39 +5162,51 @@ bool X86InstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, Register SrcReg,
     default:
       llvm_unreachable("Unreachable!");
     case X86::SUB64rm:
+    case X86::SUB64rm_ND:
       NewOpcode = X86::CMP64rm;
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phoebewang wrote:

Will it be a problem if `SUB64rm_ND` is assigned with EGPR reigsters?

https://github.com/llvm/llvm-project/pull/79135