[llvm] [AArch64] Drop poison-generating flags in `genSubAdd2SubSub` combiner (PR #90028)

[David Green via llvm-commits]

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@@ -6924,14 +6924,22 @@ genSubAdd2SubSub(MachineFunction &MF, MachineRegisterInfo &MRI,
     assert((Opcode == AArch64::SUBWrr || Opcode == AArch64::SUBXrr) &&
            "Unexpected instruction opcode.");
 
+  uint32_t RootFlags = Root.getFlags();
+  if (RootFlags & MachineInstr::NoSWrap)
+    Root.clearFlag(MachineInstr::NoSWrap);
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davemgreen wrote:

I think this can just call clearFlag, and it will clear it if it is present.

https://github.com/llvm/llvm-project/pull/90028