Hi!
Honza has removed types_compatible_p call from operand_equal_p of *MEM_REF.
This breaks tree-data-ref.c stuff, as the access fns are built with the
assumption that they refer to the same stuff (array indices or field bit
offsets) between all DRs whose bases are operand_equal_p, but now that
it ensures just that they have the same size, one could have a type of
single element array of records, the other the record itself, or one could
be a record with a single field, another that field's type, and we suddenly
can have DR_ACCESS_FN (, 0) in one DR being array index and bitfield offset
in another one etc.
To me the safest fix looks to be just to revert to what 5.x used to do here
for initialize_data_dependence_relation, i.e. require compatible types,
perhaps later we could carefully lift up that restriction to either
not creating access fns for single element arrays (but watch for flexible
array-like arrays) or fields over whole structure side, or compare types
more losely, or compare also sizes of refs themselves, ...
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2016-03-08 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/70127
* tree-data-ref.c (initialize_data_dependence_relation): Return
chrec_dont_know if types of DR_BASE_OBJECT aren't compatible.
* gcc.c-torture/execute/pr70127.c: New test.
--- gcc/tree-data-ref.c.jj 2016-01-27 12:38:52.000000000 +0100
+++ gcc/tree-data-ref.c 2016-03-08 12:01:11.865034378 +0100
@@ -1539,7 +1539,13 @@ initialize_data_dependence_relation (str
/* If the references do not access the same object, we do not know
whether they alias or not. */
- if (!operand_equal_p (DR_BASE_OBJECT (a), DR_BASE_OBJECT (b), 0))
+ if (!operand_equal_p (DR_BASE_OBJECT (a), DR_BASE_OBJECT (b), 0)
+ /* operand_equal_p checked just type sizes; with single element
+ array types and/or fields that have the same size as containing
+ struct/union those could match, even when DR_ACCESS_FN count
+ different things between the two DRs. See PR70127. */
+ || !types_compatible_p (TREE_TYPE (DR_BASE_OBJECT (a)),
+ TREE_TYPE (DR_BASE_OBJECT (b))))
{
DDR_ARE_DEPENDENT (res) = chrec_dont_know;
return res;
--- gcc/testsuite/gcc.c-torture/execute/pr70127.c.jj 2016-03-08
12:11:11.890835632 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr70127.c 2016-03-08
12:10:58.000000000 +0100
@@ -0,0 +1,23 @@
+/* PR tree-optimization/70127 */
+
+struct S { int f; signed int g : 2; } a[1], c = {5, 1}, d;
+short b;
+
+__attribute__((noinline, noclone)) void
+foo (int x)
+{
+ if (x != 1)
+ __builtin_abort ();
+}
+
+int
+main ()
+{
+ while (b++ <= 0)
+ {
+ struct S e = {1, 1};
+ d = e = a[0] = c;
+ }
+ foo (a[0].g);
+ return 0;
+}
Jakub
