Re: kernel + gcc 4.1 = several problems

[Jeff Garzik]

Grzegorz Kulewski wrote:
> On Wed, 3 Jan 2007, Alan wrote:
> > The proper fix for all of this mess is to fix the gcc compiler suite to
> > actually generate i686 code when told to use i686. CMOV is an optional
> > i686 extension which gcc uses without checking. In early PIV days it made
> > sense but on modern processors CMOV is so pointless the bug should be
> > fixed. At that point an i686 kernel would contain i686 instructions and
> > actually run on all i686 processors ending all the i586 pain for most
> > users and distributions.
>
> Could you explain why CMOV is pointless now? Are there any benchmarks 
> proving that?

In theory modern processors should have no trouble converting a 
test/move sequence into the same uops generated by a cmov instruction, 
for one.

	Jeff



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