[PATCH] Alternative fix for PR46172

[Richard Guenther]

This fixes the ICE occuring with dead vectorizer pattern stmts
during expand.  A proper fix is of course to rework the vectorizer
to not require the pattern stmts in the first place.

Bootstrap and regtest pending.

Richard.

2010-11-18  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/46172
	* tree-vect-loop-manip.c (remove_dead_stmts_from_loop): New
	function.
	(slpeel_tree_peel_loop_to_edge): Call it.

	* gcc.dg/torture/pr46172.c: New testcase.

Index: gcc/tree-vect-loop-manip.c
===================================================================
*** gcc/tree-vect-loop-manip.c	(revision 166902)
--- gcc/tree-vect-loop-manip.c	(working copy)
*************** set_prologue_iterations (basic_block bb_
*** 1107,1112 ****
--- 1107,1140 ----
  }
  
  
+ /* Remove dead assignments from loop NEW_LOOP.  */
+ 
+ static void
+ remove_dead_stmts_from_loop (struct loop *new_loop)
+ {
+   basic_block *bbs = get_loop_body (new_loop);
+   unsigned i;
+   for (i = 0; i < new_loop->num_nodes; ++i)
+     {
+       gimple_stmt_iterator gsi;
+       for (gsi = gsi_start_bb (bbs[i]); !gsi_end_p (gsi);)
+ 	{
+ 	  gimple stmt = gsi_stmt (gsi);
+ 	  if (is_gimple_assign (stmt)
+ 	      && TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME
+ 	      && has_zero_uses (gimple_assign_lhs (stmt)))
+ 	    {
+ 	      gsi_remove (&gsi, true);
+ 	      release_defs (stmt);
+ 	    }
+ 	  else
+ 	    gsi_next (&gsi);
+ 	}
+     }
+   free (bbs);
+ }
+ 
+ 
  /* Function slpeel_tree_peel_loop_to_edge.
  
     Peel the first (last) iterations of LOOP into a new prolog (epilog) loop
*************** slpeel_tree_peel_loop_to_edge (struct lo
*** 1237,1242 ****
--- 1265,1276 ----
    slpeel_update_phis_for_duplicate_loop (loop, new_loop, e == exit_e);
    rename_variables_in_loop (new_loop);
  
+   /* Remove all pattern statements from the loop copy.  They will confuse
+      the expander if DCE is disabled.
+      ???  The pattern recognizer should be split into an analysis and
+      a transformation phase that is then run only on the loop that is
+      going to be transformed.  */
+   remove_dead_stmts_from_loop (new_loop);
  
    /* 2.  Add the guard code in one of the following ways:
  
Index: gcc/testsuite/gcc.dg/torture/pr46172.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr46172.c	(revision 0)
--- gcc/testsuite/gcc.dg/torture/pr46172.c	(revision 0)
***************
*** 0 ****
--- 1,13 ----
+ /* { dg-do compile } */
+ /* { dg-options "-fno-tree-dce -ftree-vectorize" } */
+ 
+ extern short X[];
+ 
+ int foo (int len)
+ {
+   int i;
+   int s = 0;
+   for (i = 0; i < len; i++)
+     s += X[i] * X[i];
+   return s;
+ }