The following patch makes us handle invariant loads during vectorization.
Dependence analysis currently isn't clever enough to disambiguate them
thus we insert versioning-for-alias checks. For the testcase hoisting
the load is still always possible though, and for a read-after-write
dependence it would be possible for the vectorized loop copy as the
may-aliasing write is varying by the scalar variable size.
The existing code for vectorizing invariant accesses looks very
suspicious - it generates a vector load at the scalar address
to then just extract the first vector element. Huh. IMHO this
can be simplified as done, by just re-using the scalar load result.
But maybe this code was supposed to deal with something entirely
different?
This patch gives a 33% speedup to the phoronix himeno testcase
if you bump the maximum alias versioning checks we want to insert.
I'm currently re-bootstrapping & testing this but an earlier version
was ok on x86_64-unknown-linux-gnu.
2011-06-29 Richard Guenther <rguent...@suse.de>
PR tree-optimization/46787
* tree-data-ref.c (dr_address_invariant_p): Remove.
(find_data_references_in_stmt): Invariant accesses are ok now.
* tree-vect-stmts.c (vectorizable_load): Handle invariant
loads.
* tree-vect-data-refs.c (vect_analyze_data_ref_access): Allow
invariant loads.
* gcc.dg/vect/vect-121.c: New testcase.
Index: gcc/tree-data-ref.c
===================================================================
--- gcc/tree-data-ref.c (revision 175531)
+++ gcc/tree-data-ref.c (working copy)
@@ -919,21 +919,6 @@ dr_analyze_alias (struct data_reference
}
}
-/* Returns true if the address of DR is invariant. */
-
-static bool
-dr_address_invariant_p (struct data_reference *dr)
-{
- unsigned i;
- tree idx;
-
- FOR_EACH_VEC_ELT (tree, DR_ACCESS_FNS (dr), i, idx)
- if (tree_contains_chrecs (idx, NULL))
- return false;
-
- return true;
-}
-
/* Frees data reference DR. */
void
@@ -4228,19 +4213,6 @@ find_data_references_in_stmt (struct loo
dr = create_data_ref (nest, loop_containing_stmt (stmt),
*ref->pos, stmt, ref->is_read);
gcc_assert (dr != NULL);
-
- /* FIXME -- data dependence analysis does not work correctly for objects
- with invariant addresses in loop nests. Let us fail here until the
- problem is fixed. */
- if (dr_address_invariant_p (dr) && nest)
- {
- free_data_ref (dr);
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file, "\tFAILED as dr address is invariant\n");
- ret = false;
- break;
- }
-
VEC_safe_push (data_reference_p, heap, *datarefs, dr);
}
VEC_free (data_ref_loc, heap, references);
Index: gcc/tree-vect-stmts.c
===================================================================
--- gcc/tree-vect-stmts.c (revision 175531)
+++ gcc/tree-vect-stmts.c (working copy)
@@ -4076,7 +4076,8 @@ vectorizable_load (gimple stmt, gimple_s
&& code != COMPONENT_REF
&& code != IMAGPART_EXPR
&& code != REALPART_EXPR
- && code != MEM_REF)
+ && code != MEM_REF
+ && TREE_CODE_CLASS (code) != tcc_declaration)
return false;
if (!STMT_VINFO_DATA_REF (stmt_info))
@@ -4527,30 +4528,14 @@ vectorizable_load (gimple stmt, gimple_s
if (inv_p && !bb_vinfo)
{
gcc_assert (!strided_load);
- gcc_assert (nested_in_vect_loop_p (loop, stmt));
if (j == 0)
{
- int k;
- tree t = NULL_TREE;
- tree vec_inv, bitpos, bitsize = TYPE_SIZE (scalar_type);
-
- /* CHECKME: bitpos depends on endianess? */
- bitpos = bitsize_zero_node;
- vec_inv = build3 (BIT_FIELD_REF, scalar_type, new_temp,
- bitsize, bitpos);
- vec_dest = vect_create_destination_var (scalar_dest,
- NULL_TREE);
- new_stmt = gimple_build_assign (vec_dest, vec_inv);
- new_temp = make_ssa_name (vec_dest, new_stmt);
- gimple_assign_set_lhs (new_stmt, new_temp);
- vect_finish_stmt_generation (stmt, new_stmt, gsi);
-
- for (k = nunits - 1; k >= 0; --k)
- t = tree_cons (NULL_TREE, new_temp, t);
- /* FIXME: use build_constructor directly. */
- vec_inv = build_constructor_from_list (vectype, t);
+ tree vec_inv;
+ gimple_stmt_iterator gsi2 = *gsi;
+ gsi_next (&gsi2);
+ vec_inv = build_vector_from_val (vectype, scalar_dest);
new_temp = vect_init_vector (stmt, vec_inv,
- vectype, gsi);
+ vectype, &gsi2);
new_stmt = SSA_NAME_DEF_STMT (new_temp);
}
else
Index: gcc/tree-vect-data-refs.c
===================================================================
--- gcc/tree-vect-data-refs.c (revision 175531)
+++ gcc/tree-vect-data-refs.c (working copy)
@@ -2302,9 +2302,9 @@ vect_analyze_data_ref_access (struct dat
return false;
}
- /* Don't allow invariant accesses in loops. */
+ /* Allow invariant loads in loops. */
if (loop_vinfo && dr_step == 0)
- return false;
+ return DR_IS_READ (dr);
if (loop && nested_in_vect_loop_p (loop, stmt))
{
Index: gcc/testsuite/gcc.dg/vect/vect-121.c
===================================================================
--- gcc/testsuite/gcc.dg/vect/vect-121.c (revision 0)
+++ gcc/testsuite/gcc.dg/vect/vect-121.c (revision 0)
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target vect_float } */
+
+float *x;
+float parm;
+float
+test (int start, int end)
+{
+ int i;
+ for (i = start; i < end; ++i)
+ {
+ float tem = x[i];
+ x[i] = parm * tem;
+ }
+}
+
+/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" } } */
+/* { dg-final { cleanup-tree-dump "vect" } } */
