> From: owner-xz-de...@tukaani.org [mailto:owner-xz-de...@tukaani.org] On
> Behalf Of Lasse Collin
> Sent: Wednesday, January 10, 2018 4:46 PM
> To: xz-devel@tukaani.org
> Subject: Re: [xz-devel] patch for Intel compiler - use of Intel compiler 
> intrinsics
> e.g. bit-scan-reverse
> Thanks! Committed.
[Blower, Melanie] Thanks a lot. 
> > BTW I see there is something in "configure" to automatically include
> > immintrin.h and it's referred to in the file
> > ./src/liblzma/common/memcmplen.h; I'm not sure if that's working
> > correctly.
> I'm quite sure it's working correctly. Check config.h after you have run
> configure. It should have
>     #define HAVE_IMMINTRIN_H 1
> somewhere in it. If it doesn't, something needs to be fixed.
[Blower, Melanie] OK I'll check it.
> It's not any kind of automatic include. configure only adds the above line to
> config.h, which the C code can use to test if the header is available for 
> use. So
> far it's used only in memcmplen.h because so far that was the only place where
> the intrinsics were needed.
> memcmplen.h uses _BitScanForward64 on Windows. I believe I read some docs
> that it (among the preprocessor test "defined(_M_X64)") should work on Intel C
> compiler on Windows.
[Blower, Melanie] Yes that should work, I always need to test and verify to be 
absolutely certain
> It would be useful if you could test memcmplen.h and verify that the Intel
> compiler specific #ifs and functions are correct even for the unreleased 
> version.
> There are five implementations of the same functionality in memcmplen.h. Four
> of these are compatible with 64-bit
> x86 (the big endian variant (fourth) isn't). The first two test for 
> preprocessor-
> specific macros and use compiler-specific code and thus are worth testing with
> Intel C compiler.
> With Intel compiler, the first variant should get used on 64-bit x86 by 
> default. If
> you comment it out (or turn it to "#if 0"), the second version should get used
> instead. The second variant works on 32-bit x86 too, assuming that -march is 
> set
> so that SSE2 is available.
[Blower, Melanie] I'll see about this. It will take me some time
> > I don't know how to configure the "git clone" from configure.ac--I
> > couldn't build.
> If you have the required GNU tools installed, it's enough to run "autoreconf 
> -fi"
> to create "configure" and other build files.
> > So I downloaded the tar.bz file for xz.5.2.3, configure and build on
> > Linux with CC=icc; in a separate build/ directory.
> This is fine in this case. The files having compiler-specific code are 
> identical in
> the master branch.
> > As well it is possible to get a free developer license for the Intel
> > c++ compiler for certain open source usages.
> Thanks, but no thanks, at least for now. I know it could be useful for testing
> compiler-specific things, but since I already have trouble getting things 
> done, I
> probably am not going spend time on setting it up etc. in the foreseeable 
> future.
[Blower, Melanie] Understood!! 

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