https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79956
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |NEW
Component|bootstrap |libfortran
Assignee|rguenth at gcc dot gnu.org |unassigned at gcc dot
gnu.org
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
We do
rank = GFC_DESCRIPTOR_RANK (array) - 1;
(expands to ((array)->dtype & 0x07) - 1 and thus is [-1, 6])
as result rank is one less than source rank(?) and
for (n = 0; n < rank; n++)
{
count[n] = 0;
dstride[n] = GFC_DESCRIPTOR_STRIDE(retarray,n);
if (extent[n] <= 0)
return;
}
thus we initialize up to dstride[5] (and we figure that out, peeling the
init loop completely and never initializing dstride[5]).
The innermost loop
n = 0;
while (count[n] == extent[n])
{
/* When we get to the end of a dimension, reset it and increment
the next dimension. */
count[n] = 0;
/* We could precalculate these products, but this is a less
frequently used path so probably not worth it. */
base -= sstride[n] * extent[n];
dest -= dstride[n] * extent[n];
n++;
if (n == rank)
{
/* Break out of the look. */
continue_loop = 0;
break;
}
else
{
count[n]++;
base += sstride[n];
dest += dstride[n];
}
}
is peeled completely as well but we somehow are not able to optimize the
remaining
if (rank == 6)
test to true as the dominating tests are in loops forming
if (rank == 1)
;
else
if (rank == 2)
;
else
if (rank == 3)
...
if (rank == 6)
and that's too complicated for us to analyze.
Note that with LIM enabled we run into the issue that LIM happily hoists
uninitialized reads (kind of PR39612). So we'd have to optimize this
before LIM runs (VRP1) where we end up with
rank_396: [-1, 6] EQUIVALENCES: { rank_111 rank_387 rank_391 rank_392 rank_393
rank_394 rank_395 } (7 elements)
which is ok (all equivalences have the same range). Ideally it would be
[-1, 0] U [6, 6] but then the cases -1 and 0 still would not allow this to
be optimized.
Note that the retarray->base_addr == NULL case explicitely accesses
extent[rank - 1] which means that rank != 0 as well. But nothing tells
GCC about this (retarray->base_addr may not actually be NULL).
Index: libgfortran/generated/parity_l8.c
===================================================================
--- libgfortran/generated/parity_l8.c (revision 245968)
+++ libgfortran/generated/parity_l8.c (working copy)
@@ -54,6 +54,8 @@ parity_l8 (gfc_array_l8 * const restrict
/* Make dim zero based to avoid confusion. */
dim = (*pdim) - 1;
rank = GFC_DESCRIPTOR_RANK (array) - 1;
+ if (rank < 1)
+ runtime_error ("oops");
len = GFC_DESCRIPTOR_EXTENT(array,dim);
if (len < 0)
fixes this (and the warning).
Can fortran people please fix this?
