[llvm] [PowerPC] Add custom lowering for ssubo (PR #111748)

[Amy Kwan via llvm-commits]

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@@ -198,6 +198,10 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
     }
   }
 
+  if (!Subtarget.hasP10Vector() && isPPC64) {
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amy-kwan wrote:

Can we add a comment as to why we exclude P10 here?

https://github.com/llvm/llvm-project/pull/111748