GCC -msse2 portability question

[Loic Dachary <loic@dachary.org>]

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Hi Laurent,

In the context of optimizing erasure code functions implemented by Kevin Greenan (cc'ed) and James Plank at https://bitbucket.org/jimplank/gf-complete/ we ran accross a question you may have the answer to: can gcc -msse2 (or -msse* for that matter ) have a negative impact on the portability of the compiled binary code ? 

In other words, if a code is compiled without -msse* and runs fine on all intel processors it targets, could it be that adding -msse* to the compilation of the same source code generate a binary that would fail on some processors ? This is assuming no sse specific functions were used in the source code.

In gf-complete, all sse specific instructions are carefully protected to not be run on a CPU that does not support them. The runtime detection is done by checking CPU id bits ( see https://bitbucket.org/jimplank/gf-complete/pull-request/7/probe-intel-sse-features-at-runtime/diff#Lsrc/gf_intel.cT28 )

The corresponding thread is at:

https://bitbucket.org/jimplank/gf-complete/pull-request/4/defer-the-decision-to-use-a-given-sse/diff#comment-1479296

Cheers

-- 
Loïc Dachary, Artisan Logiciel Libre


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