On Wed, 14 Jan 2015, Richard Biener wrote:
>
> This fixes an issue in dependence analysis and how we make pointer
> dereferences visible to it. Basically dependence analysis works
> on indices (assuming we deal with arrays) and thus never needs
> sth like an access size (because indices are non-sparse and
> different index means a different memory area). Dereferences
> breaks this because we present dependence analysis with a
> sparse index space. Thus to rule out partially overlapping
> accesses we have to make sure to separate bases (only equal
> bases get treated this way).
>
> The following ensures this by making the indices multiples of
> the access size (and shifting the byte offset modulo the access
> size to the base object).
>
> Bootstrap and regtest running on x86_64-unknown-linux-gnu.
I have applied the following variant which also handles NULL
TYPE_SIZE_UNIT and treats those cases less conservative by
simply forcing the index to be always zero.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk
sofar.
Richard.
2015-01-15 Richard Biener <rguent...@suse.de>
PR middle-end/64365
* tree-data-ref.c (dr_analyze_indices): Make sure that accesses
for MEM_REF access functions with the same base can never partially
overlap.
* gcc.dg/torture/pr64365.c: New testcase.
Index: gcc/tree-data-ref.c
===================================================================
--- gcc/tree-data-ref.c (revision 219603)
+++ gcc/tree-data-ref.c (working copy)
@@ -992,6 +994,22 @@ dr_analyze_indices (struct data_referenc
fold_convert (ssizetype, memoff));
memoff = build_int_cst (TREE_TYPE (memoff), 0);
}
+ /* Adjust the offset so it is a multiple of the access type
+ size and thus we separate bases that can possibly be used
+ to produce partial overlaps (which the access_fn machinery
+ cannot handle). */
+ wide_int rem;
+ if (TYPE_SIZE_UNIT (TREE_TYPE (ref))
+ && TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (ref))) == INTEGER_CST
+ && !integer_zerop (TYPE_SIZE_UNIT (TREE_TYPE (ref))))
+ rem = wi::mod_trunc (off, TYPE_SIZE_UNIT (TREE_TYPE (ref)), SIGNED);
+ else
+ /* If we can't compute the remainder simply force the initial
+ condition to zero. */
+ rem = off;
+ off = wide_int_to_tree (ssizetype, wi::sub (off, rem));
+ memoff = wide_int_to_tree (TREE_TYPE (memoff), rem);
+ /* And finally replace the initial condition. */
access_fn = chrec_replace_initial_condition
(access_fn, fold_convert (orig_type, off));
/* ??? This is still not a suitable base object for
Index: gcc/testsuite/gcc.dg/torture/pr64365.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr64365.c (revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr64365.c (working copy)
@@ -0,0 +1,37 @@
+/* { dg-do run } */
+/* { dg-require-effective-target int32plus } */
+
+extern void abort (void);
+extern int memcmp (const void * , const void *, __SIZE_TYPE__);
+
+void __attribute__((noinline,noclone))
+foo(int *in)
+{
+ int i;
+ for (i = 62; i >= 10; i--)
+ {
+ in[i - 8] -= in[i];
+ in[i - 5] += in[i] * 2;
+ in[i - 4] += in[i];
+ }
+}
+
+int main()
+{
+ int x[64];
+ int y[64] = { 0, 1, -2380134, -1065336, -1026376, 3264240, 3113534, 2328130,
3632054, 3839634, 2380136, 1065339, 1026380, 1496037, 1397286, 789976, 386408,
450984, 597112, 497464, 262008, 149184, 194768, 231519, 173984, 87753, 60712,
82042, 87502, 60014, 30050, 25550, 33570, 32386, 20464, 10675, 10868, 13329,
11794, 6892, 3988, 4564, 5148, 4228, 2284, 1568, 1848, 1943, 1472, 741, 628,
702, 714, 474, 230, 234, 238, 242, 120, 59, 60, 61, 62, 63 };
+ int i;
+
+ for (i = 0; i < 64; ++i)
+ {
+ x[i] = i;
+ __asm__ volatile ("");
+ }
+
+ foo (x);
+
+ if (memcmp (x, y, sizeof (x)) != 0)
+ abort ();
+
+ return 0;
+}
