------- Comment #5 from fxcoudert at gcc dot gnu dot org 2008-04-23 08:11
-------
It's not about constantness, but about creating a temporary or not. The
following testcase uses a constant mask and it still gives the right answer:
REAL DDA(100)
logical, parameter :: mask(1:100) = (/(J1,J1=1,100)/) > 50
dda = (/(J1,J1=1,100)/)
IDS = MAXLOC(DDA,1, mask)
print *, ids ! expect 100
END
while the following also uses a compile-time constant mask and gives the wrong
answer (51 when it should be 50):
REAL DDA(100)
logical, parameter :: mask(1:100) = (/(J1,J1=1,100)/) > 50
dda = (/(J1,J1=1,100)/)
IDS = MAXLOC(DDA,1, .not. mask)
print *, ids ! expect 50
END
The code in question is in gfc_conv_intrinsic_minmaxloc (trans-intrinsic.c):
/* Remember where we are. An offset must be added to the loop
counter to obtain the required position. */
if (loop.temp_dim)
tmp = build_int_cst (gfc_array_index_type, 1);
else
tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
gfc_index_one_node, loop.from[0]);
All the failing cases I've seen so far happen in the (loop.temp_dim == true)
branch, and would be fixed by putting a zero there instead of the 1. But...
that's not all! It can also be something else than an off-by-one, it can be
off-by-more-than-that:
REAL DDA(5:104)
dda = (/(J1,J1=1,100)/)
IDS = MAXLOC(DDA,1)
print *, ids ! expect 100
IDS = MAXLOC(DDA,1, (/(J1,J1=1,100)/) > 50)
print *, ids ! expect 100
END
gives 105 instead of 100 for the second call to MAXLOC. I'm not too sure what
is the correct approach, maybe something like (can't test right now):
Index: trans-intrinsic.c
===================================================================
--- trans-intrinsic.c (revision 134439)
+++ trans-intrinsic.c (working copy)
@@ -2171,11 +2171,11 @@
/* Remember where we are. An offset must be added to the loop
counter to obtain the required position. */
- if (loop.temp_dim)
+ if (loop.from[0])
tmp = build_int_cst (gfc_array_index_type, 1);
else
- tmp =fold_build2 (MINUS_EXPR, gfc_array_index_type,
- gfc_index_one_node, loop.from[0]);
+ tmp = fold_build2 (MINUS_EXPR, gfc_array_index_type,
+ gfc_index_one_node, loop.from[0]);
gfc_add_modify_expr (&block, offset, tmp);
tmp = fold_build2 (PLUS_EXPR, TREE_TYPE (pos),
(the loop.temp_dim vs. loop.from[0] is important, the rest is whitespace
change).
--
fxcoudert at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |fxcoudert at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35994
