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* [Bug fortran/108329] New: IEEE_SET_ROUNDING_MODE ineffective with common subexpression elimination
@ 2023-01-07 12:24 tkoenig at gcc dot gnu.org
2023-01-07 12:33 ` [Bug fortran/108329] " tkoenig at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: tkoenig at gcc dot gnu.org @ 2023-01-07 12:24 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108329
Bug ID: 108329
Summary: IEEE_SET_ROUNDING_MODE ineffective with common
subexpression elimination
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: tkoenig at gcc dot gnu.org
Target Milestone: ---
Split from https://gcc.gnu.org/bugzilla/show_bug.cgi?id=34678#c47 .
The test case
$ cat y.f90
module y
implicit none
integer, parameter :: wp = selected_real_kind(15)
contains
subroutine foo(a,b,c)
use ieee_arithmetic
real(kind=wp), dimension(4), intent(out) :: a
real(kind=wp), intent(in) :: b, c
type (ieee_round_type), dimension(4), parameter :: mode = &
[ieee_nearest, ieee_to_zero, ieee_up, ieee_down]
call ieee_set_rounding_mode (mode(1))
a(1) = b + c
call ieee_set_rounding_mode (mode(2))
a(2) = b + c
call ieee_set_rounding_mode (mode(3))
a(3) = b + c
call ieee_set_rounding_mode (mode(4))
a(4) = b + c
end subroutine foo
end module y
program main
use y
real(kind=wp), dimension(4) :: a
call foo(a, 0.1_wp, 0.2_wp)
print *,a
end program main
$ gfortran -O y.f90 && ./a.out
0.30000000000000004 0.30000000000000004 0.30000000000000004
0.30000000000000004
$ gfortran y.f90 && ./a.out
0.30000000000000004 0.29999999999999999 0.30000000000000004
0.29999999999999999
shows that common subexpression removal causes the addition to be performed
only once.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug fortran/108329] IEEE_SET_ROUNDING_MODE ineffective with common subexpression elimination
2023-01-07 12:24 [Bug fortran/108329] New: IEEE_SET_ROUNDING_MODE ineffective with common subexpression elimination tkoenig at gcc dot gnu.org
@ 2023-01-07 12:33 ` tkoenig at gcc dot gnu.org
2023-01-07 12:47 ` tkoenig at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: tkoenig at gcc dot gnu.org @ 2023-01-07 12:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108329
Thomas Koenig <tkoenig at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Version|unknown |13.0
Depends on| |34678
Keywords| |wrong-code
Blocks| |105105
--- Comment #1 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
As long as PR 36678 is not fixed, I see one possible solution in
putting a memory barrier after ieee_set_rounding_mode.
This is a rather big hammer, but as long as the middle-end issue
is not fixed, I do not see an alternative.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=34678
[Bug 34678] Optimization generates incorrect code with -frounding-math option
(#pragma STDC FENV_ACCESS not implemented)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105105
[Bug 105105] [Meta] Fortran IEEE support
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug fortran/108329] IEEE_SET_ROUNDING_MODE ineffective with common subexpression elimination
2023-01-07 12:24 [Bug fortran/108329] New: IEEE_SET_ROUNDING_MODE ineffective with common subexpression elimination tkoenig at gcc dot gnu.org
2023-01-07 12:33 ` [Bug fortran/108329] " tkoenig at gcc dot gnu.org
@ 2023-01-07 12:47 ` tkoenig at gcc dot gnu.org
2023-01-07 15:50 ` tkoenig at gcc dot gnu.org
2023-01-09 15:27 ` tkoenig at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: tkoenig at gcc dot gnu.org @ 2023-01-07 12:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108329
--- Comment #2 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
(In reply to Thomas Koenig from comment #1)
> As long as PR 36678
That should be PR 34678 .
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug fortran/108329] IEEE_SET_ROUNDING_MODE ineffective with common subexpression elimination
2023-01-07 12:24 [Bug fortran/108329] New: IEEE_SET_ROUNDING_MODE ineffective with common subexpression elimination tkoenig at gcc dot gnu.org
2023-01-07 12:33 ` [Bug fortran/108329] " tkoenig at gcc dot gnu.org
2023-01-07 12:47 ` tkoenig at gcc dot gnu.org
@ 2023-01-07 15:50 ` tkoenig at gcc dot gnu.org
2023-01-09 15:27 ` tkoenig at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: tkoenig at gcc dot gnu.org @ 2023-01-07 15:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108329
Thomas Koenig <tkoenig at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Last reconfirmed| |2023-01-07
Assignee|unassigned at gcc dot gnu.org |tkoenig at gcc dot gnu.org
Status|UNCONFIRMED |ASSIGNED
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug fortran/108329] IEEE_SET_ROUNDING_MODE ineffective with common subexpression elimination
2023-01-07 12:24 [Bug fortran/108329] New: IEEE_SET_ROUNDING_MODE ineffective with common subexpression elimination tkoenig at gcc dot gnu.org
` (2 preceding siblings ...)
2023-01-07 15:50 ` tkoenig at gcc dot gnu.org
@ 2023-01-09 15:27 ` tkoenig at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: tkoenig at gcc dot gnu.org @ 2023-01-09 15:27 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108329
Thomas Koenig <tkoenig at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |NEW
Assignee|tkoenig at gcc dot gnu.org |unassigned at gcc dot gnu.org
--- Comment #3 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Seems to be much more complicated than I thought, see the thrad starting at
https://gcc.gnu.org/pipermail/gcc-patches/2023-January/609532.html
^ permalink raw reply [flat|nested] 5+ messages in thread
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2023-01-07 12:24 [Bug fortran/108329] New: IEEE_SET_ROUNDING_MODE ineffective with common subexpression elimination tkoenig at gcc dot gnu.org
2023-01-07 12:33 ` [Bug fortran/108329] " tkoenig at gcc dot gnu.org
2023-01-07 12:47 ` tkoenig at gcc dot gnu.org
2023-01-07 15:50 ` tkoenig at gcc dot gnu.org
2023-01-09 15:27 ` tkoenig at gcc dot gnu.org
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