Re: Question Regarding ERMS memcpy

[hpa]

On March 4, 2017 4:33:49 PM PST, Borislav Petkov <bp@xxxxxxx> wrote:
>On Sat, Mar 04, 2017 at 04:23:17PM -0800, hpa@xxxxxxxxx wrote:
>> What are the compilation flags? It may be that gcc still does TRT
>> depending on this call site. I'd check what gcc6 or 7 generates,
>> though.
>
>Well, I don't think that matters: if you're building a kernel on one
>machine to boot on another machine, the compiler can't know at build
>time what the best MOVS* variant would be for the target machine.
>That's
>why we're doing the alternatives patching at *boot* time.
>
>However, if the size is small enough, the CALL/patch overhead would be
>definitely too much.
>
>Hmm, I wish we were able to say, "let gcc decide for small sizes and
>let
>us do the patching for larger ones."

That's what the -march= and -mtune= option do!
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