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Re: floor_log2_wide speedup

From: Richard Henderson <rth at redhat dot com>
To: DJ Delorie <dj at redhat dot com>
Cc: jsm at polyomino dot org dot uk, gcc-patches at gcc dot gnu dot org
Date: Fri, 28 May 2004 22:47:50 -0700
Subject: Re: floor_log2_wide speedup
References: <200405242134.i4OLYgia014267@greed.delorie.com> <Pine.LNX.4.58.0405242151470.1720@digraph.polyomino.org.uk> <200405290002.i4T02lCU013444@greed.delorie.com>

On Fri, May 28, 2004 at 08:02:47PM -0400, DJ Delorie wrote:
> floor_log2_wide (unsigned HOST_WIDE_INT x)
> {
>   int t=0;
>   if (x == 0)
>     return -1;
> #if (__GNUC__ * 1000 + __GNUC_MINOR__) >= 3004
>   return (sizeof(HOST_WIDE_INT)*8-1) - __builtin_clz(x);

You've got to choose the proper version of clz, clzl, clzll.


r~

References:
- floor_log2_wide speedup
  - From: DJ Delorie
- Re: floor_log2_wide speedup
  - From: Joseph S. Myers
- Re: floor_log2_wide speedup
  - From: DJ Delorie

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