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From: Matthias Klose <doko@klose.in-berlin.de>
To: gcc-gnats@gcc.gnu.org, debian-gcc@lists.debian.org
Subject: optimization/3511: Inlined strlen() could be smarter
Date: Sun, 01 Jul 2001 09:36:00 -0000 [thread overview]
Message-ID: <E15Gk29-000328-00@gate.local> (raw)
>Number: 3511
>Category: optimization
>Synopsis: Inlined strlen() could be smarter
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: unassigned
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Sun Jul 01 09:36:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: herbert@gondor.apana.org.au
>Release: 3.0 (Debian GNU/Linux) and HEAD 20010701
>Organization:
The Debian project
>Environment:
System: Debian GNU/Linux (testing/unstable)
Architecture: i686
host: i386-linux
build: i386-linux
target: i386-linux
configured with: ../src/configure -v --enable-languages=c,c++,java,f77,proto,objc --prefix=/usr --infodir=/share/info --mandir=/share/man --enable-shared --with-gnu-as --with-gnu-ld --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --disable-checking --enable-threads=posix --enable-java-gc=boehm --with-cpp-install-dir=bin --enable-objc-gc i386-linux
>Description:
[ Reported to the Debian BTS as report #86251.
Please CC 86251-quiet@bugs.debian.org on replies.
Log of report can be found at http://bugs.debian.org/86251 ]
gcc -S -O2 on the file
#include <string.h>
size_t mystrlen(const char *s) {
if (!s) {
s = "";
}
return strlen(s);
}
generates (on i386)
.file "bug-86251.c"
.section .rodata
.LC0:
.string ""
.text
.align 2
.p2align 2,,3
.globl mystrlen
.type mystrlen,@function
mystrlen:
pushl %ebp
movl %esp, %ebp
pushl %edi
movl 8(%ebp), %edi
testl %edi, %edi
je .L114
.L113:
xorl %eax, %eax
cld
movl $-1, %ecx
repnz
scasb
notl %ecx
leal -1(%ecx), %eax
movl (%esp), %edi
leave
ret
.p2align 2,,3
.L114:
movl $.LC0, %edi
jmp .L113
.Lfe1:
.size mystrlen,.Lfe1-mystrlen
.ident "GCC: (GNU) 3.1 20010701 (experimental)"
As you can see, strlen() is not optimised out in the !pat case.
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
next reply other threads:[~2001-07-01 9:36 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-07-01 9:36 Matthias Klose [this message]
2002-10-06 20:05 rth
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