http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54767
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Component|fortran |tree-optimization
AssignedTo|unassigned at gcc dot |rguenth at gcc dot gnu.org
|gnu.org |
--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> 2013-01-15
10:49:49 UTC ---
I don't see anything wrong by what VRP does:
Visiting statement:
prephitmp_2 = _79;
Found new range for prephitmp_2: [_79, _79]
Simulating statement (from ssa_edges): iaii_23 = PHI <iaii_1(11),
prephitmp_2(10)>
Visiting PHI node: iaii_23 = PHI <iaii_1(11), prephitmp_2(10)>
Argument #0 (11 -> 12 executable)
iaii_1
Value: [_79, _79]
Argument #1 (10 -> 12 executable)
prephitmp_2
Value: [_79, _79] EQUIVALENCES: { _79 } (1 elements)
Meeting
[_79, _79]
and
[_79, _79] EQUIVALENCES: { _79 } (1 elements)
to
[_79, _79]
Found new range for iaii_23: [_79, _79]
Simulating statement (from ssa_edges): _35 = prephitmp_2 - iaii_23;
Visiting statement:
_35 = prephitmp_2 - iaii_23;
Found new range for _35: [0, 0]
Visiting statement:
ivvv.5_36 = _35 + 1;
Found new range for ivvv.5_36: [1, 1]
Now changed behavior is from:
Visiting PHI node: iaii_1 = PHI <iaii_18(D)(4), iaii_48(17)>
Argument #0 (4 -> 5 executable)
iaii_18(D)
Value: UNDEFINED
Argument #1 (17 -> 5 executable)
iaii_48
Value: [_79, _79]
Meeting
UNDEFINED
and
[_79, _79]
to
[_79, _79]
Found new range for iaii_1: [_79, _79]
and this is all in a cycle.
I think this may be mixing _79 from different iterations. Reduced testcase,
maybe easier to look at:
SUBROUTINE XXX (IL, IU)
implicit none
integer, INTENT(IN) :: IL, IU
integer :: NXX (3) = (/ 0, 1, 2 /)
integer :: ivvv, ia, ja, iaii
logical :: qop
QOP=.FALSE.
DO IA=IL,IU
JA=NXX(IA)
IF (.NOT. QOP .and. JA.GT.0) THEN
IAII=IA
QOP=.TRUE.
ENDIF
IF (QOP) THEN
ivvv=IA-IAII+1 ! mis-compiled
ENDIF
ENDDO
IF (ivvv.NE.2) THEN
call abort
ENDIF
END subroutine
program p
implicit none
CALL XXX (1, 3)
end
