Simon Pilgrim 2492075add [X86][SSE] lowerShuffleAsBitRotate - lower to vXi8 shuffles to ROTL on pre-SSSE3 targets ...

Without PSHUFB we are better using ROTL (expanding to OR(SHL,SRL)) than using the generic v16i8 shuffle lowering - but if we can widen to v8i16 or more then the existing shuffles are still the better option.

REAPPLIED: Original commit rG11c16e71598d was reverted at rGde1d90299b16 as it wasn't accounting for later lowering. This version emits ROTLI or the OR(VSHLI/VSRLI) directly to avoid the issue.

2020-02-14 11:55:18 +00:00

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