This is the mail archive of the
gcc-bugs@gcc.gnu.org
mailing list for the GCC project.
optimization/2960: Duplicate loop conditions even with -Os
- To: gcc-gnats at gcc dot gnu dot org
- Subject: optimization/2960: Duplicate loop conditions even with -Os
- From: Matthias Klose <doko at cs dot tu-berlin dot de>
- Date: Sat, 26 May 2001 20:28:59 +0200
- Cc: 94701-forwarded at bugs dot debian dot org, herbert at gondor dot apana dot org dot au
- Reply-To: 94701-quiet at bugs dot debian dot org
>Number: 2960
>Category: optimization
>Synopsis: Duplicate loop conditions even with -Os
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: unassigned
>State: open
>Class: pessimizes-code
>Submitter-Id: net
>Arrival-Date: Sat May 26 11:36:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: herbert@gondor.apana.org.au
>Release: 3.0 20010526 (Debian prerelease) (Debian testing/unstable)
>Organization:
Debian
>Environment:
System: Linux smile 2.2.17 #1 Sun Oct 8 19:26:41 MEST 2000 i686 unknown
Architecture: i686
host: i386-pc-linux-gnu
build: i386-pc-linux-gnu
target: i386-pc-linux-gnu
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-x --without-included-gettext --disable-checking --enable-threads=posix --enable-java-gc=boehm --with-cpp-install-dir=bin --enable-objc-gc i386-linux
>Description:
For the following program,
int k;
extern void b();
int a(int i) {
while (k < i) {
b();
}
}
GCC generates this on i386 (gcc -S -Os),
a:
pushl %ebp
movl %esp, %ebp
pushl %ebx
pushl %ecx
movl 8(%ebp), %ebx
cmpl %ebx, k
jge .L7
.p2align 2
.L5:
call b
cmpl %ebx, k
jl .L5
.L7:
popl %edx
popl %ebx
popl %ebp
ret
I don't see the reason why it isn't doing:
.p2align 2
.L5:
cmpl %ebx, k
jge .L7
call b
jmp .L5
.L7:
or
jmp .L7
.p2align 2
.L5:
call b
.L7:
cmpl %ebx, k
jl .L5
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted: