From: "H. Peter Anvin" <hpa@zytor.com>
To: Gabriel Paubert <paubert@iram.es>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [2.6.6-BK] x86_64 has buggy ffs() implementation
Date: Wed, 12 May 2004 15:29:08 -0700 [thread overview]
Message-ID: <40A2A534.9080004@zytor.com> (raw)
In-Reply-To: <20040512211124.GA6005@iram.es>
Gabriel Paubert wrote:
>
> Either I'm asleep or you are emulating bsrl, not bsfl. It
> should rather be:
>
> if ( y & 0x00000001) return 1;
> if ( y & 0x00000002) return 2;
> if ( y & 0x00000004) return 3;
> ...
> if ( y & 0x80000000) return 32;
> return 0;
>
> No need for the else clauses either because of the return.
> But maybe even __builtin_ffs(y) would work in this case.
>
If __builtin_ffs() works *AND HAS THE RIGHT SEMANTICS* it's probably the
best thing to use.
Otherwise, yes, generic_ffs() can clearly be used inside the
__builtin_constant_p() clause.
-hpa
prev parent reply other threads:[~2004-05-12 22:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-05-12 13:43 [2.6.6-BK] x86_64 has buggy ffs() implementation Anton Altaparmakov
2004-05-12 14:02 ` Andi Kleen
2004-05-12 20:31 ` H. Peter Anvin
2004-05-12 21:08 ` Anton Altaparmakov
2004-05-12 21:11 ` Gabriel Paubert
2004-05-12 22:29 ` H. Peter Anvin [this message]
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