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man3/OPENSSL_ia32cap.pod: clarify AVX512 support in clang context.

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Reviewed-by: Richard Levitte <levitte@openssl.org>
This commit is contained in:
Andy Polyakov 2016-12-14 13:33:40 +01:00
parent 2b40699082
commit 569204be90
1 changed files with 20 additions and 1 deletions
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doc/man3/OPENSSL_ia32cap.pod
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@ -101,6 +101,9 @@ and RORX;
=item bit #64+19 denoting availability of ADCX and ADOX instructions;
=item bit #64+21 denoting availability of VPMADD52[LH]UQ instructions,
a.k.a. AVX512IFMA extension;
=item bit #64+29 denoting availability of SHA extension;
=item bit #64+30 denoting availability of AVX512BW extension;
@ -125,7 +128,23 @@ requirements are summarized in below table:
AVX | 2.19 | 2.09 | 3.0
AVX2 | 2.22 | 2.10 | 3.1
ADCX/ADOX | 2.23 | 2.10 | 3.3
AVX512 | 2.25 | 2.11.8 | 3.6
AVX512 | 2.25 | 2.11.8 | see NOTES
AVX512IFMA | 2.26 | 2.11.8 | see NOTES
=head1 NOTES
Even though AVX512 support was implemented in llvm 3.6, compilation of
assembly modules apparently requires explicit -march flag. But then
compiler generates processor-specific code, which in turn contradicts
the mere idea of run-time switch execution facilitated by the variable
in question. Till the limitation is lifted, it's possible to work around
the problem by making build procedure use following script:
#!/bin/sh
exec clang -no-integrated-as "$@"
instead of real clang. In which case it doesn't matter which clang
version is used, as it is GNU assembler version that will be checked.
=head1 COPYRIGHT