optimization/2962: unnecessary instruction cwtl
Matthias Klose
doko@cs.tu-berlin.de
Sat May 26 11:46:00 GMT 2001
>Number: 2962
>Category: optimization
>Synopsis: unnecessary instruction cwtl
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: unassigned
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Sat May 26 11:45:59 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:
gcc-3.0 -Os wastes a byte in the following code on i386:
a:
pushl %ebp
movl %esp, %ebp
movl 8(%ebp), %eax
andl $1, %eax
cwtl
popl %ebp
ret
The cwtl is unnecessary since %eax has just been anded with 1.
The source is:
int a(short i) {
return i & 1;
}
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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