http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3507
Daniel Santos <daniel.santos at pobox dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |daniel.santos at pobox dot
| |com
--- Comment #13 from Daniel Santos <daniel.santos at pobox dot com> 2012-07-10
10:23:08 UTC ---
Well here's another test case for the same problem:
extern print_gt(void);
extern print_lt(void);
extern print_eq(void);
void cmp_and_branch(long a, long b)
{
long diff = a - b;
if (diff > 0) {
print_gt();
} else if (diff < 0) {
print_lt();
} else {
print_eq();
}
}
In this case, the result of the subtraction is directly used in the branch
code. However, gcc -O2 -S still generates this output:
.file "gcc_cmp_and_branch_test2.c"
.text
.p2align 4,,15
.globl cmp_and_branch
.type cmp_and_branch, @function
cmp_and_branch:
.LFB0:
.cfi_startproc
subq %rsi, %rdi
cmpq $0, %rdi
jg .L5
jne .L6
jmp print_eq
.p2align 4,,10
.p2align 3
.L5:
jmp print_gt
.p2align 4,,10
.p2align 3
.L6:
jmp print_lt
.cfi_endproc
.LFE0:
.size cmp_and_branch, .-cmp_and_branch
.ident "GCC: (Gentoo 4.7.1) 4.7.1"
.section .note.GNU-stack,"",@progbits
I'm using Gentoo x86_64:
Using built-in specs.
COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/4.7.1/gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.7.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /tmp/portage/sys-devel/gcc-4.7.1/work/gcc-4.7.1/configure
--prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.7.1
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.1/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.1
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.1/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.1/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.1/include/g++-v4
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec
--disable-fixed-point --with-ppl --with-cloog --disable-ppl-version-check
--with-cloog-include=/usr/include/cloog-ppl --enable-lto --enable-nls
--without-included-gettext --with-system-zlib --enable-obsolete
--disable-werror --enable-secureplt --enable-multilib
--with-multilib-list=m32,m64 --enable-libmudflap --disable-libssp
--enable-libgomp
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.7.1/python
--enable-checking=release --enable-java-awt=gtk --enable-objc-gc
--enable-languages=c,c++,java,objc,obj-c++,fortran --enable-shared
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
--enable-targets=all --with-bugurl=http://bugs.gentoo.org/
--with-pkgversion='Gentoo 4.7.1'
Thread model: posix
gcc version 4.7.1 (Gentoo 4.7.1)
I do hope this can be addressed sometime soon. Thanks.
