Messages in this thread | | | Date | Wed, 03 Jan 2007 06:51:37 -0500 | From | Jeff Garzik <> | Subject | Re: kernel + gcc 4.1 = several problems |
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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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