[PATCH 1/2] Add vect_finish_stmt_generation for sequences

The following attempts to make using gimple_build easier during
vectorizer code generation by providing an overload of
vect_finish_stmt_generation that handles a built sequence.
In addition to inserting and finishing stmts on the sequence the
ultimate result is made to be based on the passed vectorizer
temporary (that gets us the fancy names).

I have converted one instance in vectorizable_conversion which
I'll need to handle both NOP_EXPR and VIEW_CONVERT_EXPR which
gimple_build happily does correctly, but vect_gimple_build does
not.

Bootstrapped and tested on x86_64-unknown-linux-gnu.

Does this look sensible?  I can of course sepecial-case
VIEW_CONVERT_EXPR manually as well.

	* tree-vect-stmts.cc (vect_finish_stmt_generation): New
	overload for gimple_build sequences.
	(vectorizable_conversion): Convert one instance of
	vect_gimple_build to gimple_build plus
	vect_finish_stmt_generation.
---
 gcc/tree-vect-stmts.cc | 43 ++++++++++++++++++++++++++++++++----------
 1 file changed, 33 insertions(+), 10 deletions(-)

diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index a023977bc51..44090015e7a 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -1260,7 +1260,7 @@ vect_get_vec_defs (vec_info *, slp_tree slp_node,
 
 /* Helper function called by vect_finish_replace_stmt and
    vect_finish_stmt_generation.  Set the location of the new
-   statement and create and return a stmt_vec_info for it.  */
+   statement.  */
 
 static void
 vect_finish_stmt_generation_1 (vec_info *,
@@ -1285,8 +1285,7 @@ vect_finish_stmt_generation_1 (vec_info *,
 }
 
 /* Replace the scalar statement STMT_INFO with a new vector statement VEC_STMT,
-   which sets the same scalar result as STMT_INFO did.  Create and return a
-   stmt_vec_info for VEC_STMT.  */
+   which sets the same scalar result as STMT_INFO did.  */
 
 void
 vect_finish_replace_stmt (vec_info *vinfo,
@@ -1302,7 +1301,7 @@ vect_finish_replace_stmt (vec_info *vinfo,
 }
 
 /* Add VEC_STMT to the vectorized implementation of STMT_INFO and insert it
-   before *GSI.  Create and return a stmt_vec_info for VEC_STMT.  */
+   before *GSI.  */
 
 void
 vect_finish_stmt_generation (vec_info *vinfo,
@@ -1344,6 +1343,31 @@ vect_finish_stmt_generation (vec_info *vinfo,
   vect_finish_stmt_generation_1 (vinfo, stmt_info, vec_stmt);
 }
 
+/* Add the stmts in STMTS to the vectorized implementation of STMT_INFO and
+   insert them before *GSI.  Make sure the final stmt has a result
+   based on VAR.  */
+
+void
+vect_finish_stmt_generation (vec_info *vinfo,
+			     stmt_vec_info stmt_info, gimple_seq &stmts,
+			     tree var, gimple_stmt_iterator *gsi)
+{
+  auto si = gsi_start (stmts);
+  while (!gsi_end_p (si))
+    {
+      gimple *new_stmt = gsi_stmt (si);
+      gsi_remove (&si, false);
+      if (gsi_end_p (si))
+	{
+	  tree lhs = gimple_get_lhs (new_stmt);
+	  gcc_assert (!SSA_NAME_VAR (lhs));
+	  SET_SSA_NAME_VAR_OR_IDENTIFIER (lhs, var);
+	}
+      vect_finish_stmt_generation (vinfo, stmt_info, new_stmt, gsi);
+    }
+}
+
+
 /* We want to vectorize a call to combined function CFN with function
    decl FNDECL, using VECTYPE_OUT as the type of the output and VECTYPE_IN
    as the types of all inputs.  Check whether this is possible using
@@ -5797,12 +5821,11 @@ vectorizable_conversion (vec_info *vinfo,
 	    }
 	  else
 	    {
-	      new_stmt = vect_gimple_build (vec_dest, code1, vop0);
-	      new_temp = make_ssa_name (vec_dest, new_stmt);
-	      gimple_set_lhs (new_stmt, new_temp);
-	      vect_finish_stmt_generation (vinfo, stmt_info, new_stmt, gsi);
-
-	      slp_node->push_vec_def (new_stmt);
+	      gimple_seq stmts = NULL;
+	      new_temp = gimple_build (&stmts, code1, vectype_out, vop0);
+	      vect_finish_stmt_generation (vinfo, stmt_info,
+					   stmts, vec_dest, gsi);
+	      slp_node->push_vec_def (new_temp);
 	    }
 	}
       break;
-- 
2.51.0