https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64992
Bug ID: 64992
Summary: More optimize opportunity
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: ishiura-compiler at ml dot kwansei.ac.jp
The two programs (A.c) and (B.c) only differ by one line (marked by "//
<---HERE"),
where (B.c) simply replace local variable b by its initial value 2U.
The code (A.s) for (A.c) is less optimized than (B.s) for (B.c).
(org.c)
int main (void)
{
volatile int a = -1;
unsigned int b = 2U;
int c = a + 0;
unsigned d = b * (1 == c); //<---HERE
if (c == -1) ;
else __builtin_abort();
if (d == 0U) ;
else __builtin_abort();
return 0;
}
(opt.c)
int main (void)
{
volatile int a = -1;
unsigned int b = 2U;
int c = a + 0;
unsigned d = 2U * (1 == c); //<---HERE
if (c == -1) ;
else __builtin_abort();
if (d == 0U) ;
else __builtin_abort();
return 0;
}
(org.s)
main:
.LFB0:
.cfi_startproc
subq $24, %rsp
.cfi_def_cfa_offset 32
xorl %eax, %eax
movl $-1, 12(%rsp)
movl 12(%rsp), %edx
cmpl $1, %edx
sete %al
addl %eax, %eax
cmpl $-1, %edx
jne .L3
testl %eax, %eax
jne .L3
addq $24, %rsp
.cfi_remember_state
.cfi_def_cfa_offset 8
ret
.L3:
.cfi_restore_state
call abort
.cfi_endproc
.LFE0:
.size main, .-main
.section .text.unlikely
.LCOLDE0:
.section .text.startup
.LHOTE0:
.ident "GCC: (GNU) 5.0.0 20150205 (experimental)"
.section .note.GNU-stack,"",@progbits
(opt.s)
main:
.LFB0:
.cfi_startproc
subq $24, %rsp
.cfi_def_cfa_offset 32
movl $-1, 12(%rsp)
movl 12(%rsp), %eax
cmpl $-1, %eax
jne .L5
xorl %eax, %eax
addq $24, %rsp
.cfi_remember_state
.cfi_def_cfa_offset 8
ret
.L5:
.cfi_restore_state
call abort
.cfi_endproc
.LFE0:
.size main, .-main
.section .text.unlikely
.LCOLDE0:
.section .text.startup
.LHOTE0:
.ident "GCC: (GNU) 5.0.0 20150205 (experimental)"
.section .note.GNU-stack,"",@progbits
$ x86_64-unknown-linux-gnu-gcc-5.0.0 -v
Using built-in specs.
COLLECT_GCC=x86_64-unknown-linux-gnu-gcc-5.0.0
COLLECT_LTO_WRAPPER=/usr/local/x86_64-tools/gcc-5.0.0/libexec/gcc/x86_64-unknown-linux-gnu/5.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /home/iwatsuji/gcc/configure
--prefix=/usr/local/x86_64-tools/gcc-5.0.0/
--with-gmp=/usr/local/gmp-5.1.1/ --with-mpfr=/usr/local/mpfr-3.1.2/
--with-mpc=/usr/local/mpc-1.0.1/ --disable-multilib --disable-nls
--enable-languages=c
Thread model: posix
gcc version 5.0.0 20150205 (experimental) (GCC)
