>Submitter-Id: net
>Originator: [EMAIL PROTECTED]
>Organization: The Debian project
>Confidential: no
>Synopsis: weird behaviour when incrementing volatile ints
>Severity: non-critical
>Priority: low
>Category: target
>Class: pessimizes-code
>Release: 3.0 (Debian GNU/Linux) and HEAD 20010701
>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 #89949.
Please CC [EMAIL PROTECTED] on replies.
Log of report can be found at http://bugs.debian.org/89949 ]
gcc generates non-intuitive code when one tries to increment a volatile int.
extern int x;
extern volatile int y;
void f() {
x++;
y++;
}
The move into %eax seems pointless.
-----------------------------------
gcc-3.0 and gcc CVS HEAD 20010701:
.file "bug-89949.i"
.text
.align 2
.globl f
.type f,@function
f:
pushl %ebp
movl %esp, %ebp
incl x
movl y, %eax
incl %eax
movl %eax, y
popl %ebp
ret
.Lfe1:
.size f,.Lfe1-f
.ident "GCC: (GNU) 3.1 20010701 (experimental)"
-----------------------------------
gcc-3.0 and gcc CVS HEAD 20010701 -O2:
.file "bug-89949.i"
.text
.align 2
.p2align 2,,3
.globl f
.type f,@function
f:
pushl %ebp
movl y, %eax
movl %esp, %ebp
incl %eax
incl x
popl %ebp
movl %eax, y
ret
.Lfe1:
.size f,.Lfe1-f
.ident "GCC: (GNU) 3.1 20010701 (experimental)"
-----------------------------------
>How-To-Repeat:
>Fix:
