Simon Pilgrim 0c005be6eb [X86][SSE] getV4X86ShuffleImm8 - canonicalize broadcast masks ...

If the mask input to getV4X86ShuffleImm8 only refers to a single source element (+ undefs) then canonicalize to a full broadcast.

getV4X86ShuffleImm8 defaults to inline values for undefs, which can be useful for shuffle widening/narrowing but does leave SimplifyDemanded* calls thinking the shuffle depends on unnecessary elements.

I'm still investigating what we should do more generally to avoid these undemanded elements, but broadcast cases was a simpler win.

2020-07-29 11:32:44 +01:00

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