-mtune for Glibc

Bruce Dubbs bruce.dubbs at gmail.com
Fri Oct 5 16:43:55 PDT 2007

Jeremy Huntwork wrote:
> On Fri, Oct 05, 2007 at 10:19:42AM -0700, Dan Nicholson wrote:
>> Reading Greg's post again, if -mtune=generic is the default on
>> gcc-4.2, then I think that's what we should restore. Then the
>> explanation makes more sense: "-mtune=generic restores the default GCC
>> settings from those implied by the -march parameter." Eh, that stills
>> sounds like gibberish.
> Dan, I went to correct some syntax errors in the jh branch and realized
> that Bruce had actually added '-mtune=native' to the explanatory text. I
> had thought that he was going to add '-mtune=generic' based on the
> above.
> After thinking about it, in part based on your comments, I think that
> '-mtune=native' would be better if we were encouraging users to
> optimize. Then they could use that among other optimizations scattered
> throughout the build. Restoring default settings seems safer and more in
> line with the book's intent. Can you provide me with a more solid
> explanation of why we're using generic and I'll drop that into the
> branch? We'll also want to update trunk since, as Greg pointed out, it's
> currently tuned for i486.

I used 'native' in my proposal earlier.  'generic' may be a bit more
conservative, but I think 'native' would be better for most people.  If
you change it, how about adding another sentence that 'native' is an
option but issues may arise if you copy the libraries to another system
with a different processor.

  -- Bruce

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