RE: [RFC, vectorizer] Allow single element vector types for vector reduction operations

["Jon Beniston" <jon@beniston.com>]

Hi Richard,

> I think the issue is that with TARGET_VECTOR_MODE_SUPPORTED_P false 
> for V1SI you'll get a SImode vector type and the
>
>  if (VECTOR_BOOLEAN_TYPE_P (type_in)
>      || VECTOR_MODE_P (TYPE_MODE (type_in)))
>
>check fails.  Try changing that to || VECTOR_TYPE_P (type_in).
>The else path should be hopefully dead ...
>
>> It looks to me like the other call sites of optab_for_tree_code which 
>> are passing optab_default are mostly places where GCC is sure it is 
>> not a shift operation.
>> Given TYPE_IN is returned from get_vectype_for_scalar_type, is it 
>> safe to simply pass optab_vector in vect_pattern_recog_1?
>
>I guess so.  Can you also try the above?

Changing VECTOR_MODE_P check into VECTOR_TYPE_P check also works for me, I
verified the following patch could vectorize my dot product case and there
is no regression on gcc tests on my port.

Meanwhile x86-64 bootstraps OK and no regression on gcc/g++ test.

 Does this look OK?


gcc/
2017-08-30  Jon Beniston  <jon@beniston.com>
            Richard Biener  <rguenther@suse.de>

diff --git a/gcc/tree-vect-patterns.c b/gcc/tree-vect-patterns.c
index cfdb72c..5ebeac2 100644
--- a/gcc/tree-vect-patterns.c
+++ b/gcc/tree-vect-patterns.c
@@ -4150,7 +4150,7 @@ vect_pattern_recog_1 (vect_recog_func *recog_func,
   loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  
   if (VECTOR_BOOLEAN_TYPE_P (type_in)
-      || VECTOR_MODE_P (TYPE_MODE (type_in)))
+      || VECTOR_TYPE_P (type_in))
     {
       /* No need to check target support (already checked by the pattern
          recognition function).  */
diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
index 013fb1f..fc62efb 100644
--- a/gcc/tree-vect-stmts.c
+++ b/gcc/tree-vect-stmts.c
@@ -9098,7 +9098,8 @@ get_vectype_for_scalar_type_and_size (tree
scalar_type, unsigned size)
   else
     simd_mode = mode_for_vector (inner_mode, size / nbytes);
   nunits = GET_MODE_SIZE (simd_mode) / nbytes;
-  if (nunits <= 1)
+  /* NOTE: nunits == 1 is allowed to support single element vector types.
*/
+  if (nunits < 1)
     return NULL_TREE;
 
   vectype = build_vector_type (scalar_type, nunits);