On Tue, Jan 14, 2014 at 10:01:06AM +0100, Richard Biener wrote:
> Jakub, adding the new flag is ok with me.
So like this?
2014-01-14 Jakub Jelinek <ja...@redhat.com>
* tree-vectorizer.h (struct _loop_vec_info): Add no_data_dependencies
field.
(LOOP_VINFO_NO_DATA_DEPENDENCIES): Define.
* tree-vect-data-refs.c (vect_analyze_data_ref_dependence): Clear it
when not giving up or versioning for alias only because of
loop->safelen.
(vect_analyze_data_ref_dependences): Set to true.
* tree-vect-stmts.c (vectorizable_load): Use
LOOP_VINFO_NO_DATA_DEPENDENCIES instead of
LOOP_REQUIRES_VERSIONING_FOR_ALIAS.
--- gcc/tree-vectorizer.h.jj 2014-01-03 11:40:57.000000000 +0100
+++ gcc/tree-vectorizer.h 2014-01-14 13:10:00.477989924 +0100
@@ -347,6 +347,25 @@ typedef struct _loop_vec_info {
fix it up. */
bool operands_swapped;
+ /* True if there are no loop carried data dependencies in the loop.
+ If loop->safelen <= 1, then this is always true, either the loop
+ didn't have any loop carried data dependencies, or the loop is being
+ vectorized guarded with some runtime alias checks, or couldn't
+ be vectorized at all, but then this field shouldn't be used.
+ For loop->safelen >= 2, the user has asserted that there are no
+ backward dependencies, but there still could be loop carried forward
+ dependencies in such loops. This flag will be false if normal
+ vectorizer data dependency analysis would fail or require versioning
+ for alias, but because of loop->safelen >= 2 it has been vectorized
+ even without versioning for alias. E.g. in:
+ #pragma omp simd
+ for (int i = 0; i < m; i++)
+ a[i] = a[i + k] * c;
+ (or #pragma simd or #pragma ivdep) we can vectorize this and it will
+ DTRT even for k > 0 && k < m, but without safelen we would not
+ vectorize this, so this field would be false. */
+ bool no_data_dependencies;
+
/* If if-conversion versioned this loop before conversion, this is the
loop version without if-conversion. */
struct loop *scalar_loop;
@@ -385,6 +404,7 @@ typedef struct _loop_vec_info {
#define LOOP_VINFO_PEELING_FOR_GAPS(L) (L)->peeling_for_gaps
#define LOOP_VINFO_OPERANDS_SWAPPED(L) (L)->operands_swapped
#define LOOP_VINFO_PEELING_FOR_NITER(L) (L)->peeling_for_niter
+#define LOOP_VINFO_NO_DATA_DEPENDENCIES(L) (L)->no_data_dependencies
#define LOOP_VINFO_SCALAR_LOOP(L) (L)->scalar_loop
#define LOOP_REQUIRES_VERSIONING_FOR_ALIGNMENT(L) \
--- gcc/tree-vect-data-refs.c.jj 2014-01-10 00:38:26.000000000 +0100
+++ gcc/tree-vect-data-refs.c 2014-01-14 13:12:06.056342116 +0100
@@ -244,6 +244,7 @@ vect_analyze_data_ref_dependence (struct
{
if (loop->safelen < *max_vf)
*max_vf = loop->safelen;
+ LOOP_VINFO_NO_DATA_DEPENDENCIES (loop_vinfo) = false;
return false;
}
@@ -291,6 +292,7 @@ vect_analyze_data_ref_dependence (struct
{
if (loop->safelen < *max_vf)
*max_vf = loop->safelen;
+ LOOP_VINFO_NO_DATA_DEPENDENCIES (loop_vinfo) = false;
return false;
}
@@ -447,6 +449,7 @@ vect_analyze_data_ref_dependences (loop_
dump_printf_loc (MSG_NOTE, vect_location,
"=== vect_analyze_data_ref_dependences ===\n");
+ LOOP_VINFO_NO_DATA_DEPENDENCIES (loop_vinfo) = true;
if (!compute_all_dependences (LOOP_VINFO_DATAREFS (loop_vinfo),
&LOOP_VINFO_DDRS (loop_vinfo),
LOOP_VINFO_LOOP_NEST (loop_vinfo), true))
--- gcc/tree-vect-stmts.c.jj 2014-01-14 10:33:21.000000000 +0100
+++ gcc/tree-vect-stmts.c 2014-01-14 13:14:15.157677243 +0100
@@ -6381,10 +6381,11 @@ vectorizable_load (gimple stmt, gimple_s
if (inv_p && !bb_vinfo)
{
gcc_assert (!grouped_load);
- /* If we have versioned for aliasing then we are sure
- this is a loop invariant load and thus we can insert
- it on the preheader edge. */
- if (LOOP_REQUIRES_VERSIONING_FOR_ALIAS (loop_vinfo))
+ /* If we have versioned for aliasing or the loop doesn't
+ have any data dependencies that would preclude this,
+ then we are sure this is a loop invariant load and
+ thus we can insert it on the preheader edge. */
+ if (LOOP_VINFO_NO_DATA_DEPENDENCIES (loop_vinfo))
{
if (dump_enabled_p ())
{
Jakub
