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From: "bruno at clisp dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/6585] Redundant store/load instruction pairs on ix86 Date: Mon, 11 Oct 2004 11:55:00 -0000 [thread overview] Message-ID: <20041011115528.30147.qmail@sourceware.org> (raw) In-Reply-To: <20020506130600.6585.bruno@clisp.org> ------- Additional Comments From bruno at clisp dot org 2004-10-11 11:55 ------- This result is even better: shorter than the previous ones, and there are no useless moves between registers any more. However, there are more useless moves from register to stack slot and back from stack slot to register. They could be eliminated. Commented listing: mul: subl $20, %esp movl 32(%esp), %ecx b0 movl 24(%esp), %eax a0 movl %ebx, 8(%esp) ; save %ebx movl 36(%esp), %ebx b1 movl %edi, 12(%esp) ; save %edi movl 24(%esp), %edi a0 movl %ebp, 16(%esp) ; save %ebp mull %ecx %edx:%eax := a0*b0 imull 28(%esp), %ecx a1*b0 imull %ebx, %edi a0*b1 movl 8(%esp), %ebx ; restore %ebx movl %edx, %ebp hi movl %eax, (%esp) USELESS! addl %edi, %ebp hi+a0*b1 movl (%esp), %eax USELESS! leal (%ebp,%ecx), %ecx hi+a0*b1+a1*b0 COULD GO INTO %edx DIRECTLY movl 12(%esp), %edi ; restore %edi movl %ecx, 4(%esp) USELESS! movl 16(%esp), %ebp ; restore %ebp movl 4(%esp), %edx USELESS! addl $20, %esp ret -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=6585
next prev parent reply other threads:[~2004-10-11 11:55 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <20020506130600.6585.bruno@clisp.org> 2003-07-04 11:09 ` [Bug optimization/6585] useless memory store instructions on x86 steven at gcc dot gnu dot org 2003-07-10 20:09 ` [Bug optimization/6585] Reduntant store/load instruction pairs on ix86 steven at gcc dot gnu dot org 2003-08-23 1:38 ` [Bug optimization/6585] Redundant " dhazeghi at yahoo dot com 2003-11-25 7:51 ` pinskia at gcc dot gnu dot org 2004-03-17 8:03 ` kazu at cs dot umass dot edu 2004-03-17 12:10 ` bruno at clisp dot org 2004-10-11 2:57 ` [Bug rtl-optimization/6585] " pinskia at gcc dot gnu dot org 2004-10-11 11:55 ` bruno at clisp dot org [this message] 2005-06-26 13:35 ` steven at gcc dot gnu dot org 2005-06-27 11:50 ` bruno at clisp dot org [not found] <bug-6585-128@http.gcc.gnu.org/bugzilla/> 2007-11-23 6:02 ` ismail at pardus dot org dot tr 2007-11-23 7:37 ` steven at gcc dot gnu dot org 2007-11-23 7:43 ` ubizjak at gmail dot com 2007-11-23 20:43 ` rask at gcc dot gnu dot org 2007-11-23 20:48 ` steven at gcc dot gnu dot org 2007-12-19 14:15 ` rask at gcc dot gnu dot org 2008-09-06 16:19 ` ubizjak at gmail dot com
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