Messages in this thread | | | Date | Mon, 21 Apr 2003 15:05:51 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] Runtime memory barrier patching |
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On Mon, 21 Apr 2003, Ulrich Drepper wrote:
> Linus Torvalds wrote: > > > They may _work_ for intel, but quite frankly they suck for most Intel (and > > probably non-intel too) CPU's. Using prefixes tends to almost always mess > > up the instruction decoders on most CPU's out there. > > Indeed, using prefixes is terrible.
I would not be surprised if both AMD and Intel are playing some "benchmarking games" by trying to select nop's that work badly for the other side, and then showing how _their_ new CPU's are so much better by having the compilers emit the "preferred" no-ops.
But maybe I'm just too cynical. And I do suspect the Hammer optimization guide was meant for the 64-bit mode only, because I'm pretty certain even AMD does badly on prefixes at least in older CPU generations.
Linus
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