Re: What CPU extensions can we assume are available by arch?

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Kevin Kofler <kevin.kofler@xxxxxxxxx> writes:

> Florian Weimer wrote:
>> In general, that is not true.  You can use the target function attribute
>> and function multiversioning instead in many cases.
>
> This may (or may not) have been recently fixed, but last I checked, 
> intrinsics for a vector instruction set XYZ2 were only available with the 
> corresponding -mxyz2 flag, which could only be set per compilation unit 
> (attempting to use the recently introduced flag pragmas for this purpose was 
> not supported either), and which would lead to GCC in some cases (out of the 
> library programmer's control) using XYZ2 instructions also in other 
> functions. As a result, the only safe way was to put all XYZ2 code in a 
> separate compilation unit compiled with -mxyz2 (and only that compilation 
> unit can use that flag). Has that situation improved recently (and how so)?

I haven't needed to try it so far, but I'd trust Florian on the topic,
given the GCC doc on function attributes and pragmas.  You might not
have intrinsics anyhow.
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