https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60406
--- Comment #3 from Uroš Bizjak <ubizjak at gmail dot com> ---
It looks that a hack, mentioned in Comment #0 should use asm goto instead of
goto. The following test:
--cut here--
extern void foo (void *);
int test_bad (int p1, int p2)
{
__label__ bla1;
foo (&&bla1);
goto bla1;
bla1:
return 0;
}
int test_good (int p1, int p2)
{
__label__ bla2;
foo (&&bla2);
asm goto ("" :::: bla2);
bla2:
return 0;
}
--cut here--
results in (-O2):
test_good:
subl $28, %esp
movl $.L5, (%esp)
call foo
.L6:
.L5:
xorl %eax, %eax
addl $28, %esp
ret
which is much better than:
test_bad:
.L2:
subl $28, %esp
movl $.L2, (%esp)
call foo
xorl %eax, %eax
addl $28, %esp
ret
Also checked on alpha:
test_good:
.frame $30,16,$26,0
.mask 0x4000000,-16
$LFB1:
.cfi_startproc
ldah $29,0($27) !gpdisp!4
lda $29,0($29) !gpdisp!4
$test_good..ng:
lda $30,-16($30)
.cfi_def_cfa_offset 16
cpys $f31,$f31,$f31
ldah $16,$L4($29) !gprelhigh
ldq $27,foo($29) !literal!5
stq $26,0($30)
.cfi_offset 26, -16
.prologue 1
lda $16,$L4($16) !gprellow
jsr $26,($27),foo !lituse_jsr!5
ldah $29,0($26) !gpdisp!6
lda $29,0($29) !gpdisp!6
.align 3 #realign
$L5:
$L4:
mov $31,$0
ldq $26,0($30)
lda $30,16($30)
.cfi_restore 26
.cfi_def_cfa_offset 0
ret $31,($26),1
Please note, that the check will still need some tolerance due to various label
alignment requirements, additional instructions, etc:
5c: 00 00 10 22 lda a0,0(a0)
5c: GPRELLOW .text+0x70 <- label loc
60: 00 40 5b 6b jsr ra,(t12),64 <test_good+0x24>
60: LITUSE .text+0x3
60: HINT foo
64: 00 00 ba 27 ldah gp,0(ra) <- retaddr
64: GPDISP .text+0x4
68: 00 00 bd 23 lda gp,0(gp)
6c: 00 00 fe 2f unop
70: 00 04 ff 47 clr v0
