[PATCH, rs6000] Improve TREE_TYPE comparisons in fold_mergehl_helper()

[Will Schmidt]

Hi,
This is a follow-up to an earlier patch that enabled gimple folding of
vec_mergeh and vec_mergel for the float and double data types.

Per feedback from Richard, use the types_compatible_p helper to ensure
we also catch any qualified types matching the V2DF_ or V4SF_ types.
    
Regtests ran clean.   OK for trunk?
    
Thanks,
-Will
    
[gcc]
    
2018-08-20  Will Schmidt  <will_schm...@vnet.ibm.com>

        * config/rs6000/rs6000.c (fold_mergehl_helper): Add types_compatible_p
        wrappers around TREE_TYPE comparisons.

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 97b922f..5f77afd 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -15135,13 +15135,15 @@ fold_mergehl_helper (gimple_stmt_iterator *gsi, 
gimple *stmt, int use_high)
   tree permute_type;
   if (INTEGRAL_TYPE_P (TREE_TYPE (lhs_type)))
     permute_type = lhs_type;
   else
     {
-      if (TREE_TYPE (lhs_type) == TREE_TYPE (V2DF_type_node))
+      if (types_compatible_p (TREE_TYPE (lhs_type),
+                             TREE_TYPE (V2DF_type_node)))
        permute_type = V2DI_type_node;
-      else if (TREE_TYPE (lhs_type) == TREE_TYPE (V4SF_type_node))
+      else if (types_compatible_p (TREE_TYPE (lhs_type),
+                                  TREE_TYPE (V4SF_type_node)))
        permute_type = V4SI_type_node;
       else
        gcc_unreachable ();
     }
   tree_vector_builder elts (permute_type, VECTOR_CST_NELTS (arg0), 1);