[X86] combineX86ShuffleChain - don't combine to VPERM2W/VPERM2B from just any single variable mask (#127914)

Despite them being more expensive than other variable mask shuffles, we
were combining shuffle chains to VPERM2W/VPERM2B if any shuffle in the
chain was a variable shuffle - including very cheap shuffles like PSHUFB
or AND mask patterns.

This patch adjusts the BWI VPERMV3 threshold - it still always permits
the merge if the chain (of 2 or more shuffles) contains any
X86ISD::VPERMV/VPERMV3 shuffles (including DQ variants), but otherwise
only reduces the depth threshold based off the number of other variable
shuffles we'd fold away.

0 files changed, 0 insertions, 0 deletions