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From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 21 Oct 2021 17:40:33 -0700
Message-ID: <CAMe9rOrF4Ve2pUmYs5MiG57vMPA42E_w9239uN73QtT5wkH9+A@mail.gmail.com>
Subject: Re: [PATCH v8 2/3] String: Add hidden defs for __memcmpeq() to enable
 internal usage
To: Joseph Myers <joseph@codesourcery.com>
Cc: Noah Goldstein <goldstein.w.n@gmail.com>,
 GNU C Library <libc-alpha@sourceware.org>
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On Thu, Oct 21, 2021 at 5:19 PM Joseph Myers <joseph@codesourcery.com> wrote:
>
> On Thu, 21 Oct 2021, Noah Goldstein via Libc-alpha wrote:
>
> > > > The compiler knows other semantics of memcmp (it might sometimes expand a
> > > > memcmp with a small fixed size inline, for example).  So changing to a
> > > > direct call to __memcmpeq by hand isn't even always an optimization;
> > Will compilers not implement the same optimization for __memcmpeq?
>
> Why should they?  It's intended as an ABI, not an API - that is, an
> alternative assembler name the compiler name generate calls to, not a
> function for which it should find calls in its input.
>

Compiler builtin optimization doesn't work well for glibc:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67220


-- 
H.J.