>Submitter-Id: net
>Originator: [EMAIL PROTECTED]
>Organization: The Debian project
>Confidential: no
>Synopsis: i386 optimisation: joining tests
>Severity: non-critical
>Priority: low
>Category: optimization
>Class: sw-bug
>Release: 3.0 (Debian GNU/Linux)
>Environment:
System: Debian GNU/Linux (testing/unstable)
Architecture: i386
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 #105309.
Please CC [EMAIL PROTECTED] on replies.
Log of report can be found at http://bugs.debian.org/105309 ]
Here's another segment that needs to have an assembler optimiser run over it:
int foo(char c) {
if (c && !(c & 0x80)) {
a();
} else {
b();
}
}
produces with -O2:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: 83 ec 08 sub $0x8,%esp
6: 8a 45 08 mov 0x8(%ebp),%al
9: 84 c0 test %al,%al
b: 74 04 je 11 <foo+0x11>
d: 84 c0 test %al,%al
f: 79 07 jns 18 <foo+0x18>
9-f can be rewritten as:
test %al, %al
jg 18
11: e8 fc ff ff ff call 12 <foo+0x12>
12: R_386_PC32 b
16: c9 leave
17: c3 ret
18: e8 fc ff ff ff call 19 <foo+0x19>
19: R_386_PC32 a
1d: eb f7 jmp 16 <foo+0x16>
And what purpose does this jmp serve? Surely it can be replaced with
leave
ret
1f: 90 nop
>How-To-Repeat:
>Fix:
