[PATCH] D81634: Remove assert from ShuffleVectorInst

[Sam Parker via Phabricator via llvm-commits]

samparker marked an inline comment as done.
samparker added a comment.

> Was the failure only a fuzzer problem?

Not sure, but either it seems harsh to assert of technically legal IR.

Ideally, callers shouldn't be wasting their time on analysis of degenerate code, so that assert might have actually been useful for real code.

> I'll have a look into the callsites to see if it's easier enough to skip on undef masks.



================
Comment at: llvm/lib/IR/Instructions.cpp:2056
   }
-  assert((UsesLHS ^ UsesRHS) && "Should have selected from exactly 1 source");
   return true;
----------------
spatel wrote:
> I think it would be better to change to:
>   // Allow for degenerate case: completely undef mask means neither source is used.
>   return UsesLHS || UsesRHS;
Looks good.


Repository:
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  https://reviews.llvm.org/D81634/new/

https://reviews.llvm.org/D81634