https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64277
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2015-01-26
Ever confirmed|0 |1
--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed btw. I believe we have plenty of dups of this report - it is usually
the last peeled iteration we warn for.
The interesting thing is that we have
# RANGE [1, 11] NONZERO 15
i_385 = i_369 + 1;
...
<bb 52>:
# RANGE [1, 11] NONZERO 15
i_461 = ASSERT_EXPR <i_385, i_385 < prephitmp_422>;
...
<bb 20>:
# RANGE [0, 10] NONZERO 15
# i_82 = PHI <i_461(52)>
still we compute
i_461: [14, 32766] EQUIVALENCES: { i_385 } (1 elements)
so sth is bogus here (the above ranges are simply copied in unrolling
but that's ok - they are conservatively correct).
We should be able to rely on the previous ranges and use them to our advantage,
like with
Index: gcc/tree-vrp.c
===================================================================
--- gcc/tree-vrp.c (revision 220107)
+++ gcc/tree-vrp.c (working copy)
@@ -847,6 +847,23 @@ update_value_range (const_tree var, valu
value_range_t *old_vr;
bool is_new;
+ /* If there is a value-range on the SSA name from earlier analysis
+ factor that in. */
+ if (INTEGRAL_TYPE_P (TREE_TYPE (var)))
+ {
+ wide_int min, max;
+ value_range_type rtype = get_range_info (var, &min, &max);
+ if (rtype == VR_RANGE || rtype == VR_ANTI_RANGE)
+ {
+ value_range_d nr;
+ nr.type = rtype;
+ nr.min = wide_int_to_tree (TREE_TYPE (var), min);
+ nr.max = wide_int_to_tree (TREE_TYPE (var), max);
+ nr.equiv = NULL;
+ vrp_intersect_ranges (new_vr, &nr);
+ }
+ }
+
/* Update the value range, if necessary. */
old_vr = get_value_range (var);
is_new = old_vr->type != new_vr->type
which cuts down the number of warnings to
t.c: In function 'foo':
t.c:18:16: warning: array subscript is above array bounds [-Warray-bounds]
a[i] = f1[i];
^
t.c:18:16: warning: array subscript is above array bounds [-Warray-bounds]
t.c:12:14: warning: 'f1' may be used uninitialized in this function
[-Wmaybe-uninitialized]
f1[i] = f1[i] + 1;
^
from
t.c: In function 'foo':
t.c:18:16: warning: array subscript is above array bounds [-Warray-bounds]
a[i] = f1[i];
^
t.c:18:16: warning: array subscript is above array bounds [-Warray-bounds]
t.c:18:16: warning: array subscript is above array bounds [-Warray-bounds]
t.c:18:16: warning: array subscript is above array bounds [-Warray-bounds]
t.c:18:16: warning: array subscript is above array bounds [-Warray-bounds]
t.c:12:14: warning: 'f1' may be used uninitialized in this function
[-Wmaybe-uninitialized]
f1[i] = f1[i] + 1;
^
