[Bug target/89929] __attribute__((target("avx512bw"))) doesn't work on non avx512bw systems

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89929

--- Comment #14 from H.J. Lu <hjl.tools at gmail dot com> ---
Since all AVX512BW processors also have AVX512DQ and AVX512VL, we shouldn't
optimize a function with just  AVX512BW, but without AVX512DQ and AVX512VL.
We should add -misa=AVX512-subset to enable a subset of AVX512XX:

1. PTA_AVX512 = PTA_AVX512F | PTA_AVX512CD
2. PTA_AVX512SKYLAKE = PTA_AVX512 | PTA_AVX512VL | PTA_AVX512BW | PTA_AVX512DQ
....