Messages in this thread | | | Subject | RE: [BK+PATCH] remove __constant_memcpy | Date | Wed, 16 Apr 2003 19:22:33 -0700 | From | "Nakajima, Jun" <> |
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I think the fear is valid. Intel compiler, for example, uses FP if it's required to optimize the code with a particular option. And the option is not necessary obvious when telling if it uses FP or not (and it does not matter for most users). This could happen with gcc.
I think we can do it better than the compiler does, because we know the usage better, e.g. alignment, typical size, etc.
Thanks, Jun
> -----Original Message----- > From: Linus Torvalds [mailto:torvalds@transmeta.com] > Sent: Wednesday, April 16, 2003 7:06 PM > To: Jeff Garzik > Cc: LKML > Subject: Re: [BK+PATCH] remove __constant_memcpy > > > On Wed, 16 Apr 2003, Jeff Garzik wrote: > > > > gcc's __builtin_memcpy performs the same function (and more) as the > > kernel's __constant_memcpy. So, let's remove __constant_memcpy, and let > > the compiler do it. > > Please don't. > > There's no way gcc will EVER get the SSE2 cases right. It just cannot do > it. In fact, I live in fear that we will have to turn off the compiler > intrisics entirely some day just because there is always the worry that > gcc will start using FP. > > So the advantage of doing our own memcpy() is not that it's necessarily > faster than the gcc built-in, but simply because I do not believe that the > gcc people care enough about the kernel to let them make the choice. > > Linus > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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