Commit 569204be authored by Andy Polyakov's avatar Andy Polyakov
Browse files

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



Reviewed-by: default avatarRichard Levitte <levitte@openssl.org>
parent 2b406990

doc/man3/OPENSSL_ia32cap.pod

+20 −1
Original line number Diff line number Diff line
@@ -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