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[X86][AVX] combineBitcastvxi1 - improve handling of vectors truncated to vXi1

Authored by RKSimon on Mar 24 2021, 7:05 AM.

Description

[X86][AVX] combineBitcastvxi1 - improve handling of vectors truncated to vXi1

If we're truncating to vXi1 from a wider type, then prefer the original wider vector as is simplifies folding the separate truncations + extensions.

AVX1 this is only worth it for v8i1 cases, not v4i1 where we're always better off truncating down to v4i32 for movmsk.

Helps with some regressions encountered in D96609

Details

Committed
RKSimonMar 24 2021, 7:05 AM
Parents
rG338d16275571: [clang-tidy] Ignore all spaces in the list of checks
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