Loop distribution fails to honor output dependences - the following
patch handles them the same as anti dependences. All the code gathering
up dependences is a little weird and probably needs some TLC.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2013-08-30 Richard Biener <rguent...@suse.de>
PR tree-optimization/58223
* tree-loop-distribution.c (has_anti_dependence): Rename to ...
(has_anti_or_output_dependence): ... this and adjust to also
look for output dependences.
(mark_nodes_having_upstream_mem_writes): Adjust.
(rdg_flag_uses): Likewise.
* gcc.dg/torture/pr58223.c: New testcase.
* gcc.dg/tree-ssa/ldist-16.c: Flip expected behavior.
Index: gcc/tree-loop-distribution.c
===================================================================
*** gcc/tree-loop-distribution.c (revision 202068)
--- gcc/tree-loop-distribution.c (working copy)
*************** already_processed_vertex_p (bitmap proce
*** 542,558 ****
|| !bitmap_bit_p (remaining_stmts, v));
}
! /* Returns NULL when there is no anti-dependence among the successors
! of vertex V, otherwise returns the edge with the anti-dep. */
static struct graph_edge *
! has_anti_dependence (struct vertex *v)
{
struct graph_edge *e;
if (v->succ)
for (e = v->succ; e; e = e->succ_next)
! if (RDGE_TYPE (e) == anti_dd)
return e;
return NULL;
--- 542,560 ----
|| !bitmap_bit_p (remaining_stmts, v));
}
! /* Returns NULL when there is no anti-dependence or output-dependence
! among the successors of vertex V, otherwise returns the edge with the
! dependency. */
static struct graph_edge *
! has_anti_or_output_dependence (struct vertex *v)
{
struct graph_edge *e;
if (v->succ)
for (e = v->succ; e; e = e->succ_next)
! if (RDGE_TYPE (e) == anti_dd
! || RDGE_TYPE (e) == output_dd)
return e;
return NULL;
*************** mark_nodes_having_upstream_mem_writes (s
*** 604,614 ****
|| predecessor_has_mem_write (rdg, &(rdg->vertices[x]))
/* In anti dependences the read should occur before
the write, this is why both the read and the write
! should be placed in the same partition. */
! || has_anti_dependence (&(rdg->vertices[x])))
! {
! bitmap_set_bit (upstream_mem_writes, x);
! }
}
nodes.release ();
--- 606,615 ----
|| predecessor_has_mem_write (rdg, &(rdg->vertices[x]))
/* In anti dependences the read should occur before
the write, this is why both the read and the write
! should be placed in the same partition. In output
! dependences the writes order need to be preserved. */
! || has_anti_or_output_dependence (&(rdg->vertices[x])))
! bitmap_set_bit (upstream_mem_writes, x);
}
nodes.release ();
*************** rdg_flag_uses (struct graph *rdg, int u,
*** 637,643 ****
use_operand_p use_p;
struct vertex *x = &(rdg->vertices[u]);
gimple stmt = RDGV_STMT (x);
! struct graph_edge *anti_dep = has_anti_dependence (x);
/* Keep in the same partition the destination of an antidependence,
because this is a store to the exact same location. Putting this
--- 638,644 ----
use_operand_p use_p;
struct vertex *x = &(rdg->vertices[u]);
gimple stmt = RDGV_STMT (x);
! struct graph_edge *anti_dep = has_anti_or_output_dependence (x);
/* Keep in the same partition the destination of an antidependence,
because this is a store to the exact same location. Putting this
Index: gcc/testsuite/gcc.dg/tree-ssa/ldist-16.c
===================================================================
*** gcc/testsuite/gcc.dg/tree-ssa/ldist-16.c (revision 202068)
--- gcc/testsuite/gcc.dg/tree-ssa/ldist-16.c (working copy)
*************** void foo (int n)
*** 14,21 ****
}
}
! /* We should apply loop distribution and generate a memset (0). */
! /* { dg-final { scan-tree-dump "distributed: split to 2" "ldist" } } */
! /* { dg-final { scan-tree-dump-times "generated memset zero" 1 "ldist" } } */
/* { dg-final { cleanup-tree-dump "ldist" } } */
--- 14,21 ----
}
}
! /* We should not apply loop distribution and not generate a memset (0). */
! /* { dg-final { scan-tree-dump "Loop 1 is the same" "ldist" } } */
! /* { dg-final { scan-tree-dump-times "generated memset zero" 0 "ldist" } } */
/* { dg-final { cleanup-tree-dump "ldist" } } */
Index: gcc/testsuite/gcc.dg/torture/pr58223.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr58223.c (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr58223.c (working copy)
***************
*** 0 ****
--- 1,16 ----
+ /* { dg-do run } */
+
+ extern void abort (void);
+ int a[2], b;
+
+ int main ()
+ {
+ for (b = 0; b < 2; b++)
+ {
+ a[0] = 1;
+ a[b] = 0;
+ }
+ if (a[0] != 1)
+ abort ();
+ return 0;
+ }
