[libgcrypt-1.7.0] SSE4.1 in crc-intel-pclmul.c

[Jeremie Courreges-Anglas]

Hi,

(looks like Werner has already forwarded this here, but the archive
shows the mail as mangled:
https://lists.gnupg.org/pipermail/gcrypt-devel/2016-May/003866.html).

compilation of crc-intel-pclmul.c from libgcrypt-1.7.0 fails on
OpenBSD/amd64:

$ ./configure && make
[...]
/bin/sh ../libtool --tag=CC --mode=compile
gcc -DHAVE_CONFIG_H -I. -I.. -I../src -I../src -I/usr/local/include -g -O2 -fvisibility=hidden -Wall -MT
crc-intel-pclmul.lo -MD -MP -MF .deps/crc-intel-pclmul.Tpo -c -o
crc-intel-pclmul.lo crc-intel-pclmul.c
libtool: compile:
gcc -DHAVE_CONFIG_H -I. -I.. -I../src -I../src -I/usr/local/include -g -O2 -fvisibility=hidden -Wall -MT
crc-intel-pclmul.lo -MD -MP -MF .deps/crc-intel-pclmul.Tpo -c
crc-intel-pclmul.c -fPIC -DPIC -o .libs/crc-intel-pclmul.o
/tmp//ccK05MkC.s: Assembler messages:
/tmp//ccK05MkC.s:113: Error: no such instruction: `pextrd $2,%xmm0,(%rdi)'
/tmp//ccK05MkC.s:130: Error: no such instruction: `pinsrd $1,-4(%rsi,%rcx),%xmm0'
/tmp//ccK05MkC.s:153: Error: no such instruction: `pextrd $2,%xmm0,(%rdi)'
/tmp//ccK05MkC.s:210: Error: no such instruction: `pextrd $1,%xmm0,(%rdi)'
/tmp//ccK05MkC.s:359: Error: no such instruction: `pextrd $1,%xmm0,(%rdi)'
/tmp//ccK05MkC.s:530: Error: no such instruction: `pinsrd $1,-4(%rsi,%rcx),%xmm0'
*** Error 1 in cipher (Makefile:643 'crc-intel-pclmul.lo')
*** Error 1 in . (Makefile:502 'all-recursive')
*** Error 1 in /tmp/libgcrypt-1.7.0 (Makefile:408 'all')

(This is after applying the diff from
http://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=commitdiff_plain;h=4545372c0f8dd35aef2a7abc12b588ed1a4a0363;hp=eecc081f8ae02c43454abaee4a4f72efaee42745)

The problem is that PCLMUL support is activated, since the OpenBSD
compiler supports it, but the asm also uses SSE4.1 instructions,
which the compiler doesn't support.

One possible way to fix this would be to implement autoconf tests for
the SSE4.1 instructions used above, and disable the PCLMUL CRC code if
appropriate.  Please find attached a patch for this, tested against gcc
from OpenBSD (pclmul/no sse4.1) and clang-3.7.1 (pclmul/sse4.1).

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