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List:       flac-dev
Subject:    Re: [flac-dev] FLAC__SSE_OS change
From:       lvqcl <lvqcl.mail () gmail ! com>
Date:       2016-06-28 16:41:58
Message-ID: op.yjr0n8jqcba0by () userhome-pc
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Erik de Castro Lopo wrote:

> No, what is needed is a way to disable SSE at run time even if it has
> been compiled in at build time.

It's not possible if ALL flac/libFLAC files are built with
-msse2 option. So the only solution is to remove -msse2 option
 from configure.ac.

Unfortunately it will disable all intrinsics for GCC 4.8
and older (and afaik for clang): only if a file was
compiled with -msse option then sse intrinsics are allowed.
-msse2 enables sse and sse2 intrinsics, and so on.


The common way is to compile different files with different
options. For libFLAC it means that all *_sse.c files should be
compiled with -msse switch, all *_sse2.c files should be compiled
with -msse2, and so on. But unfortunately it's not supported in
the current build system.

OTOH, GCC 4.9 (and newer) doesn't require those switches:
now it's possible to set supported instruction set on a per-function
basis. That's what libFLAC does with FLAC__SSE_TARGET(x) macro.
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