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Re: [PATCH] ix86: Disable AVX512F when disabling AVX2
>>> On 19.03.19 at 03:51, <hjl.tools@gmail.com> wrote:
> On Mon, Mar 18, 2019 at 7:31 PM Jan Beulich <JBeulich@suse.com> wrote:
>>
>> >>> On 16.03.19 at 23:48, <hjl.tools@gmail.com> wrote:
>> > We can optimize 512-bit EVEX to 128-bit EVEX encoding for upper 16
>> > vector registers only when AVX512VL is enabled. We can't optimize
>> > EVEX to 128-bit VEX encoding when AVX isn't enabled.
>>
>> I don't understand the last sentence: AVX is a prereq to anything
>> that's EVEX-encoded, at least as of now. "-march=+noavx" should
>> really result in all of AVX512 to also get disabled.
>
> I opened:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=24359
>
> and enclosed a patch here.
Looks good for the specific purpose, but I think there's further
cleanup potential then since you had committed the earlier
patch already: The cpuavx conditionals become pointless when
we already know the encoding is vex_encoding_evex or
is_evex_encoding() has returned true.
Jan