Thank you for your reminder, Jeff! I just noticed Richard's comment. I
have modified the patch according to that.
The new patch is attached.
thanks,
Cong
On Tue, Oct 15, 2013 at 12:33 PM, Jeff Law <l...@redhat.com> wrote:
> On 10/14/13 17:31, Cong Hou wrote:
>>
>> Any comment on this patch?
>
> Richi replied in the BZ you opened.
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58508
>
> Essentially he said emit the load on the edge rather than in the block
> itself.
> jeff
>
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8a38316..2637309 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2013-10-15 Cong Hou <co...@google.com>
+
+ * tree-vect-loop-manip.c (vect_loop_versioning): Hoist loop invariant
+ statement that contains data refs with zero-step.
+
2013-10-14 David Malcolm <dmalc...@redhat.com>
* dumpfile.h (gcc::dump_manager): New class, to hold state
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 075d071..9d0f4a5 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2013-10-15 Cong Hou <co...@google.com>
+
+ * gcc.dg/vect/pr58508.c: New test.
+
2013-10-14 Tobias Burnus <bur...@net-b.de>
PR fortran/58658
diff --git a/gcc/testsuite/gcc.dg/vect/pr58508.c
b/gcc/testsuite/gcc.dg/vect/pr58508.c
new file mode 100644
index 0000000..cb22b50
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr58508.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-vectorize -fdump-tree-vect-details" } */
+
+
+/* The GCC vectorizer generates loop versioning for the following loop
+ since there may exist aliasing between A and B. The predicate checks
+ if A may alias with B across all iterations. Then for the loop in
+ the true body, we can assert that *B is a loop invariant so that
+ we can hoist the load of *B before the loop body. */
+
+void foo (int* a, int* b)
+{
+ int i;
+ for (i = 0; i < 100000; ++i)
+ a[i] = *b + 1;
+}
+
+
+/* { dg-final { scan-tree-dump-times "hoist" 2 "vect" } } */
+/* { dg-final { cleanup-tree-dump "vect" } } */
diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
index 574446a..f4fdec2 100644
--- a/gcc/tree-vect-loop-manip.c
+++ b/gcc/tree-vect-loop-manip.c
@@ -2477,6 +2477,92 @@ vect_loop_versioning (loop_vec_info loop_vinfo,
adjust_phi_and_debug_stmts (orig_phi, e, PHI_RESULT (new_phi));
}
+
+ /* Extract load and store statements on pointers with zero-stride
+ accesses. */
+ if (LOOP_REQUIRES_VERSIONING_FOR_ALIAS (loop_vinfo))
+ {
+ /* In the loop body, we iterate each statement to check if it is a load
+ or store. Then we check the DR_STEP of the data reference. If
+ DR_STEP is zero, then we will hoist the load statement to the loop
+ preheader, and move the store statement to the loop exit. */
+
+ for (gimple_stmt_iterator si = gsi_start_bb (loop->header);
+ !gsi_end_p (si);)
+ {
+ gimple stmt = gsi_stmt (si);
+ stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
+ struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
+
+ if (dr && integer_zerop (DR_STEP (dr)))
+ {
+ if (DR_IS_READ (dr))
+ {
+ if (dump_enabled_p ())
+ {
+ dump_printf_loc
+ (MSG_NOTE, vect_location,
+ "hoist the statement to outside of the loop ");
+ dump_gimple_stmt (MSG_NOTE, TDF_SLIM, stmt, 0);
+ dump_printf (MSG_NOTE, "\n");
+ }
+
+ gsi_remove (&si, false);
+ gsi_insert_on_edge_immediate (loop_preheader_edge (loop),
stmt);
+ }
+ /* TODO: We also consider vectorizing loops containing zero-step
+ data refs as writes. For example:
+
+ int a[N], *s;
+ for (i = 0; i < N; i++)
+ *s += a[i];
+
+ In this case the write to *s can be also moved after the
+ loop. */
+
+ continue;
+ }
+ else if (!dr)
+ {
+ bool hoist = true;
+ for (size_t i = 0; i < gimple_num_ops (stmt); i++)
+ {
+ tree op = gimple_op (stmt, i);
+ if (TREE_CODE (op) == INTEGER_CST
+ || TREE_CODE (op) == REAL_CST)
+ continue;
+ if (TREE_CODE (op) == SSA_NAME)
+ {
+ gimple def = SSA_NAME_DEF_STMT (op);
+ if (def == stmt
+ || gimple_nop_p (def)
+ || !flow_bb_inside_loop_p (loop, gimple_bb (def)))
+ continue;
+ }
+ hoist = false;
+ break;
+ }
+
+ if (hoist)
+ {
+ gsi_remove (&si, false);
+ gsi_insert_on_edge_immediate (loop_preheader_edge (loop), stmt);
+
+ if (dump_enabled_p ())
+ {
+ dump_printf_loc
+ (MSG_NOTE, vect_location,
+ "hoist the statement to outside of the loop ");
+ dump_gimple_stmt (MSG_NOTE, TDF_SLIM, stmt, 0);
+ dump_printf (MSG_NOTE, "\n");
+ }
+ continue;
+ }
+ }
+ gsi_next (&si);
+ }
+ }
+
/* End loop-exit-fixes after versioning. */
if (cond_expr_stmt_list)
