From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25562 invoked by alias); 11 Mar 2004 22:29:47 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org Received: (qmail 25550 invoked by uid 48); 11 Mar 2004 22:29:46 -0000 Date: Thu, 11 Mar 2004 22:29:00 -0000 Message-ID: <20040311222946.25549.qmail@sources.redhat.com> From: "kazu at cs dot umass dot edu" To: gcc-bugs@gcc.gnu.org In-Reply-To: <20040309171658.14504.stl@caltech.edu> References: <20040309171658.14504.stl@caltech.edu> Reply-To: gcc-bugzilla@gcc.gnu.org Subject: [Bug optimization/14504] Missed Bit Twiddling Optimization X-Bugzilla-Reason: CC X-SW-Source: 2004-03/txt/msg01451.txt.bz2 List-Id: ------- Additional Comments From kazu at cs dot umass dot edu 2004-03-11 22:29 ------- Err, i386 is a two-address machine with only a few registers, so cmove doesn't work as well in this case. typedef _Bool bool; unsigned long cond_mask (bool flag, unsigned long mask, unsigned long target) { unsigned long l = target | mask; unsigned long r = target & ~mask; return flag ? l : r; #if 0 pushl %ebx movl %eax, %ebx ; %bl = flag movl %ecx, %eax orl %edx, %eax ; %eax = target | mask notl %edx ; ~mask andl %ecx, %edx ; %edx = target & ~mask testb %bl, %bl popl %ebx cmove %edx, %eax #endif } -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14504