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8286823: Default to UseAVX=2 on all Skylake/Cascade Lake CPUs #8731

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8286823: Default to UseAVX=2 on all Skylake/Cascade Lake CPUs #8731

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5 changes: 3 additions & 2 deletions src/hotspot/cpu/x86/vm_version_x86.cpp
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Expand Up @@ -895,8 +895,9 @@ void VM_Version::get_processor_features() {
}
}
if (FLAG_IS_DEFAULT(UseAVX)) {
// Don't use AVX-512 on older Skylakes unless explicitly requested.
if (use_avx_limit > 2 && is_intel_skylake() && _stepping < 5) {
// Don't use AVX-512 on Skylake (or the related Cascade Lake) CPUs unless explicitly
// requested - these instructions can cause performance issues on these processors.
if (use_avx_limit > 2 && is_intel_skylake()) {
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Maybe is_intel_skylake needs to be changed to is_cpu_model_intel_skylake? It will make clear that all CPUs based on Skylake model are excluded.

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I agree it's not necessarily a perfect name, but I haven't changed its behaviour so I figured I can avoid making my change any bigger than necessary. The intention of this particular usage is clarified in my comment. It's used in another place too, where it's evidently understood to include Cascade lake since the comment mentions Ice lake + (Cascade lake successor).

FLAG_SET_DEFAULT(UseAVX, 2);
} else {
FLAG_SET_DEFAULT(UseAVX, use_avx_limit);
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