https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70696
Uroš Bizjak <ubizjak at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|FIXED |---
--- Comment #17 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to vehre from comment #9)
> Author: vehre
> Date: Fri Jan 13 10:22:21 2017
> New Revision: 244407
>
> URL: https://gcc.gnu.org/viewcvs?rev=244407&root=gcc&view=rev
> Log:
> gcc/testsuite/ChangeLog:
>
> 2017-01-13 Andre Vehreschild <ve...@gcc.gnu.org>
>
> PR fortran/70696
> * gfortran.dg/coarray/event_3.f08: New test.
What is this test supposed to test? The _.optimized dump shows only:
--cut here--
;; Function main (main, funcdef_no=2, decl_uid=952, cgraph_uid=3,
symbol_order=2) (executed once)
__attribute__((externally_visible))
main (integer(kind=4) argc, character(kind=1) * * argv)
{
struct FRAME.global_event FRAME.1;
static integer(kind=4) options.0[7] = {2116, 4095, 0, 1, 1, 0, 31};
integer(kind=4) _8;
<bb 2> [local count: 1073741824]:
_gfortran_set_args (argc_2(D), argv_3(D));
_gfortran_set_options (7, &options.0[0]);
_8 = FRAME.1.x;
if (_8 != 0)
goto <bb 3>; [0.04%]
else
goto <bb 4>; [99.96%]
<bb 3> [local count: 429497]:
_gfortran_error_stop_numeric (1, 0);
<bb 4> [local count: 1073312328]:
return 0;
}
--cut here--
which results in uninitialized load from FRAME.1. The resulting x86_64 assembly
is:
main:
.LFB2:
.cfi_startproc
subq $8, %rsp
.cfi_def_cfa_offset 16
call _gfortran_set_args
movl $options.0.3867, %esi
movl $7, %edi
call _gfortran_set_options
xorl %eax, %eax
addq $8, %rsp
.cfi_def_cfa_offset 8
ret
.cfi_endproc
which does not test anything. While x86_64 optimizers are able to eliminate
uninitialized load, it remains in alpha assembly:
main:
.frame $30,32,$26,0
.mask 0x4000000,-32
$LFB2:
.cfi_startproc
ldah $29,0($27) !gpdisp!1 #,,
lda $29,0($29) !gpdisp!1 #,,
$main..ng:
lda $30,-32($30) #,,
.cfi_def_cfa_offset 32
ldq $27,_gfortran_set_args($29) !literal!3 #,,,
stq $26,0($30) #,
.cfi_offset 26, -32
.prologue 1
# event_3.f08:10: call exchange
jsr $26,($27),_gfortran_set_args !lituse_jsr!3 #,,
ldah $29,0($26) !gpdisp!4 #
lda $16,7($31) #,
lda $29,0($29) !gpdisp!4 #,,
ldah $17,options.0.956($29) !gprelhigh # tmp75,,
lda $17,options.0.956($17) !gprellow #,, tmp75
ldq $27,_gfortran_set_options($29) !literal!5 #,,,
jsr $26,($27),_gfortran_set_options !lituse_jsr!5 #,,
ldah $29,0($26) !gpdisp!6 #
# event_3.f08:17: if (cnt /= 2) error stop 1
ldl $1,16($30) # FRAME.1.x, FRAME.1.x
# event_3.f08:10: call exchange
lda $29,0($29) !gpdisp!6 #,,
# event_3.f08:17: if (cnt /= 2) error stop 1
bis $31,$31,$31
bne $1,$L4 #, FRAME.1.x,
# event_3.f08:10: call exchange
mov $31,$0 #,
ldq $26,0($30) #,
lda $30,32($30) #,,
.cfi_remember_state
.cfi_restore 26
.cfi_def_cfa_offset 0
ret $31,($26),1
$L4:
.cfi_restore_state
# event_3.f08:17: if (cnt /= 2) error stop 1
mov $31,$17 #,
ldq $27,_gfortran_error_stop_numeric($29) !literal!2
#,,,
lda $16,1($31) #,
jsr $26,($27),_gfortran_error_stop_numeric !lituse_jsr!2
#,,
.cfi_endproc
$LFE2:
bis $31,$31,$31
.end main
Please note:
ldl $1,16($30) # FRAME.1.x, FRAME.1.x
...
bne $1,$L4 #, FRAME.1.x,
Which loads uninitialized value from the stack and later branches on non-zero
value. When the testcase is sun inside the debugger, it is evident that a
garbage value is loaded from the 16($30) stack location.
