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Re: About the prefetch
Yang_Jialin@emc.com writes:
> About the prefetch data of gcc, with optimization option "-O0", some gcc
> versions have defined "prefetch" and ''prefetchw" function, whether with
> operations or not.
> But for other gcc versions , they have not been defined, e.g. 3.4 . I am
> now confused about what version defines it and which not. Can you tell
> me about this?
BUILT_IN_PREFETCH was added here:
r47582 | janis | 2001-12-04 00:50:35 +0000 (Tue, 04 Dec 2001) | 6 lines
* builtin-types.def (BT_FN_VOID_PTR_INT_INT): New.
* builtins.def (BUILT_IN_PREFETCH): New.
* builtins.c (expand_builtin_expect): New.
(expand_builtin): Call it.
* doc/extend.texi: Document __builtin_expect.
So every version of gcc that branched since then has it. That would
be, I think, 3.1 onwards.
Whether __builtin_prefetc does anything or not depends on the
particular back end you're using.
Andrew.