[llvm] [LLVM][InstCombine] Enable constant folding for SVE asr,lsl and lsr intrinsics. (PR #137350)

[Paul Walker via llvm-commits]

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@@ -1571,7 +1583,11 @@ simplifySVEIntrinsicBinOp(InstCombiner &IC, IntrinsicInst &II,
   else
     SimpleII = simplifyBinOp(Opc, Op1, Op2, DL);
 
-  if (!SimpleII)
+  // An SVE intrinsic's result is always defined. However, this is not the case
+  // for its equivalent IR instruction (e.g. when shifting by an amount more
+  // than the data's bitwidth). Simplifications to an undefined result must be
+  // ignored to preserve the intrinsic's expected behaviour.
+  if (!SimpleII || isa<UndefValue>(SimpleII))
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paulwalker-arm wrote:

I've been cleaning up the SVE intrinsics combine tests so at the same time I also added a test for poison propagation. I've rebased this PR so that it shows the new expected behaviour (i.e. we shouldn't propagation poison).

https://github.com/llvm/llvm-project/pull/137350