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Re: __builtin_expect

To: Ulrich Drepper <drepper at cygnus dot com>
Subject: Re: __builtin_expect
From: Richard Henderson <rth at twiddle dot net>
Date: Sat, 22 Apr 2000 16:02:48 -0700
Cc: GNU libc hacker <libc-hacker at sourceware dot cygnus dot com>
References: <m3hfcvqsmx.fsf@localhost.localnet>

On Fri, Apr 21, 2000 at 10:19:02AM -0700, Ulrich Drepper wrote:
> In glibc this means __builtin_expect should be used everywhere the
> results of comparisons etc is statically predictable.  At the very
> least it should be used for error handling.  E.g.;
> 
> 	ptr = malloc (size);
> 	if (ptr == NULL)

Note that gcc's built in estimate_probabilities function is supposed
to get this right -- eq with NULL predicted false.

It doesn't hurt to mark it anyway though...

r~

References:
- __builtin_expect
  - From: Ulrich Drepper

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