[PATCH] Improve vectorizer code generation

[Richard Biener <rguenther at suse dot de>]

Currently for initial values for inductions the vectorizer generates

  stmp_var_.3_2 = 0 + 1;
  stmp_var_.3_19 = stmp_var_.3_2 + 1;
  stmp_var_.3_20 = stmp_var_.3_19 + 1;
  vect_cst_.4_21 = {0, stmp_var_.3_2, stmp_var_.3_19, stmp_var_.3_20};

instead of properly folding elements and eventually generate a
vector constant directly.  At the moment this is only cleaned up
by VRP later (DOM doesn't fold stmp_var_.3_2 = 0 + 1 because it
doesn't change ...).

Fixed by instead creating

  vect_cst_.4_2 = { 0, 1, 2, 3 };

in the vectorizer.

Bootstrap and regtest running on x86_64-unknown-linux-gnu.

Richard.

2013-04-11  Richard Biener  <rguenther@suse.de>

	* tree-vect-loop.c (get_initial_def_for_induction): Properly
	generate vector constants.

Index: gcc/tree-vect-loop.c
===================================================================
*** gcc/tree-vect-loop.c	(revision 197761)
--- gcc/tree-vect-loop.c	(working copy)
*************** get_initial_def_for_induction (gimple iv
*** 3226,3255 ****
  	}
  
        vec_alloc (v, nunits);
        CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, new_name);
        for (i = 1; i < nunits; i++)
  	{
  	  /* Create: new_name_i = new_name + step_expr  */
  	  enum tree_code code = POINTER_TYPE_P (scalar_type)
  				? POINTER_PLUS_EXPR : PLUS_EXPR;
! 	  init_stmt = gimple_build_assign_with_ops (code, new_var,
! 						    new_name, step_expr);
! 	  new_name = make_ssa_name (new_var, init_stmt);
! 	  gimple_assign_set_lhs (init_stmt, new_name);
! 
! 	  new_bb = gsi_insert_on_edge_immediate (pe, init_stmt);
! 	  gcc_assert (!new_bb);
! 
! 	  if (dump_enabled_p ())
  	    {
! 	      dump_printf_loc (MSG_NOTE, vect_location,
! 			       "created new init_stmt: ");
! 	      dump_gimple_stmt (MSG_NOTE, TDF_SLIM, init_stmt, 0);
  	    }
  	  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, new_name);
  	}
        /* Create a vector from [new_name_0, new_name_1, ..., new_name_nunits-1]  */
!       new_vec = build_constructor (vectype, v);
        vec_init = vect_init_vector (iv_phi, new_vec, vectype, NULL);
      }
  
--- 3226,3261 ----
  	}
  
        vec_alloc (v, nunits);
+       bool constant_p = is_gimple_min_invariant (new_name);
        CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, new_name);
        for (i = 1; i < nunits; i++)
  	{
  	  /* Create: new_name_i = new_name + step_expr  */
  	  enum tree_code code = POINTER_TYPE_P (scalar_type)
  				? POINTER_PLUS_EXPR : PLUS_EXPR;
! 	  new_name = fold_build2 (code, scalar_type, new_name, step_expr);
! 	  if (!is_gimple_min_invariant (new_name))
  	    {
! 	      init_stmt = gimple_build_assign (new_var, new_name);
! 	      new_name = make_ssa_name (new_var, init_stmt);
! 	      gimple_assign_set_lhs (init_stmt, new_name);
! 	      new_bb = gsi_insert_on_edge_immediate (pe, init_stmt);
! 	      gcc_assert (!new_bb);
! 	      if (dump_enabled_p ())
! 		{
! 		  dump_printf_loc (MSG_NOTE, vect_location,
! 				   "created new init_stmt: ");
! 		  dump_gimple_stmt (MSG_NOTE, TDF_SLIM, init_stmt, 0);
! 		}
! 	      constant_p = false;
  	    }
  	  CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, new_name);
  	}
        /* Create a vector from [new_name_0, new_name_1, ..., new_name_nunits-1]  */
!       if (constant_p)
! 	new_vec = build_vector_from_ctor (vectype, v);
!       else
! 	new_vec = build_constructor (vectype, v);
        vec_init = vect_init_vector (iv_phi, new_vec, vectype, NULL);
      }