From: <cutaway@bellsouth.net>
To: <linux-kernel@vger.kernel.org>
Subject: .../asm-i386/bitops.h performance improvements
Date: Wed, 15 Jun 2005 04:53:12 -0400 [thread overview]
Message-ID: <000b01c57187$ade6b9b0$2800000a@pc365dualp2> (raw)
In find_first_bit() there exists this the sequence:
shll $3,%%edi
addl %%edi,%%eax
LEA knows how to multiply by small powers of 2 and add all in one shot very
efficiently:
leal (%%eax,%%edi,8),%%eax
In find_first_zero_bit() the sequence:
shll $3,%%edi
addl %%edi,%%edx
could similarly become:
leal (%%edx,%%edi,8),%%edx
next reply other threads:[~2005-06-15 8:00 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-15 8:53 cutaway [this message]
2005-06-15 12:18 ` Gene Heskett
2005-06-15 13:06 ` Richard B. Johnson
2005-06-15 19:18 ` cutaway
2005-06-15 15:34 ` Maciej W. Rozycki
2005-06-15 23:48 ` cutaway
[not found] <4fB8l-73q-9@gated-at.bofh.it>
[not found] ` <4fF2j-1Lo-19@gated-at.bofh.it>
2005-06-15 14:57 ` Bodo Eggert
2005-06-15 15:30 ` Maciej W. Rozycki
2005-06-15 16:06 ` Richard B. Johnson
2005-06-15 16:29 ` Maciej W. Rozycki
2005-06-15 19:10 ` Bodo Eggert
2005-06-16 3:26 ` Stephen Rothwell
2005-06-16 7:10 ` Mikael Pettersson
2005-06-15 23:53 ` cutaway
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