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SubjectRe: PPC should not use -fno-builtin (was Re: 2.3.47 imac build?)
Date
On Mon, 28 Feb 2000, Jeff Garzik wrote:

> So... you are choosing to lose extremely valuable optimizations because
> of a few prototype warnings? This logic seems bogus to me... it also

OK, the problem is that gcc expects size_t to be an unsigned int. We use
unsigned long for size_t in the kernel because we want it to be 64 bits on
64-bit PPCs (like it is on the other 64-bit platforms). Gcc doesn't like a
prototype for memcpy which has an unsigned long for the 3rd argument
(unless you use -fno-builtin).

The only optimization we lose with -fno-builtin (that I can see) is that
the compiler won't turn explicit calls to memcpy with a small constant 3rd
argument (<= 32) into a sequence of inline loads and stores. (It still
does small struct copies with inline loads and stores even with
-fno-builtin.)

--
Paul Mackerras, Senior Open Source Researcher, Linuxcare, Inc.
+61 2 6262 8990 tel, +61 2 6262 8991 fax
paulus@linuxcare.com.au, http://www.linuxcare.com.au/
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