re PR tree-optimization/18687 (>200% compile time regression compared to gcc-3.4)

	PR tree-optimization/18687
	* tree-flow.h (find_loop_niter): Declare.
	* tree-ssa-loop-ivcanon.c (canonicalize_loop_induction_variables):
	Try using scev even for loops with more than one exit.
	* tree-ssa-loop-ivopts.c (struct loop_data): Removed niter field.
	(struct ivopts_data): Added niters field.
	(struct nfe_cache_elt): New.
	(nfe_hash, nfe_eq, niter_for_exit, niter_for_single_dom_exit): New
	functions.
	(tree_ssa_iv_optimize_init): Initialize niters cache.
	(determine_number_of_iterations): Removed.
	(find_induction_variables): Do not call determine_number_of_iterations.
	Access niters for single exit through niter_for_single_dom_exit.
	(add_iv_outer_candidates): Access niters for single exit through
	niter_for_single_dom_exit.
	(may_eliminate_iv): Take data argument.  Use niter_for_exit.  Do not use
	number_of_iterations_cond.
	(iv_period): New function.
	(determine_use_iv_cost_condition): Pass data to may_eliminate_iv.
	(may_replace_final_value): Take data argument.  Use
	niter_for_single_dom_exit.
	(determine_use_iv_cost_outer): Pass data to may_replace_final_value.
	(rewrite_use_compare): Pass data to may_eliminate_iv.
	(rewrite_use_outer): Pass data to may_replace_final_value.
	(free_loop_data): Clean up the niters cache.
	(tree_ssa_iv_optimize_finalize): Free the niters cache.
	(tree_ssa_iv_optimize_loop): Do not call loop_commit_inserts.
	* tree-ssa-loop-niter.c (find_loop_niter): New function.
	(find_loop_niter_by_eval): Use tree_int_cst_lt.
	(num_ending_zeros): Moved to tree.c.
	* tree.h (num_ending_zeros): Declare.
	* tree.c (num_ending_zeros): Moved from tree.c.

From-SVN: r94787

gcc/ChangeLog

+2005-02-09  Zdenek Dvorak  <dvorakz@suse.cz>
+
+	PR tree-optimization/18687
+	* tree-flow.h (find_loop_niter): Declare.
+	* tree-ssa-loop-ivcanon.c (canonicalize_loop_induction_variables):
+	Try using scev even for loops with more than one exit.
+	* tree-ssa-loop-ivopts.c (struct loop_data): Removed niter field.
+	(struct ivopts_data): Added niters field.
+	(struct nfe_cache_elt): New.
+	(nfe_hash, nfe_eq, niter_for_exit, niter_for_single_dom_exit): New
+	functions.
+	(tree_ssa_iv_optimize_init): Initialize niters cache.
+	(determine_number_of_iterations): Removed.
+	(find_induction_variables): Do not call determine_number_of_iterations.
+	Access niters for single exit through niter_for_single_dom_exit.
+	(add_iv_outer_candidates): Access niters for single exit through
+	niter_for_single_dom_exit.
+	(may_eliminate_iv): Take data argument.  Use niter_for_exit.  Do not use
+	number_of_iterations_cond.
+	(iv_period): New function.
+	(determine_use_iv_cost_condition): Pass data to may_eliminate_iv.
+	(may_replace_final_value): Take data argument.  Use
+	niter_for_single_dom_exit.
+	(determine_use_iv_cost_outer): Pass data to may_replace_final_value.
+	(rewrite_use_compare): Pass data to may_eliminate_iv.
+	(rewrite_use_outer): Pass data to may_replace_final_value.
+	(free_loop_data): Clean up the niters cache.
+	(tree_ssa_iv_optimize_finalize): Free the niters cache.
+	(tree_ssa_iv_optimize_loop): Do not call loop_commit_inserts.
+	* tree-ssa-loop-niter.c (find_loop_niter): New function.
+	(find_loop_niter_by_eval): Use tree_int_cst_lt.
+	(num_ending_zeros): Moved to tree.c.
+	* tree.h (num_ending_zeros): Declare.
+	* tree.c (num_ending_zeros): Moved from tree.c.
+
 2005-02-09  Richard Henderson  <rth@redhat.com>
 
 	* builtins.c (DEF_BUILTIN): Add COND argument.

gcc/tree-flow.h

@@ -667,6 +667,7 @@ void number_of_iterations_cond (tree, tree, tree, enum tree_code, tree, tree,
 				struct tree_niter_desc *);
 bool number_of_iterations_exit (struct loop *, edge,
 				struct tree_niter_desc *niter);
+tree find_loop_niter (struct loop *, edge *);
 tree loop_niter_by_eval (struct loop *, edge);
 tree find_loop_niter_by_eval (struct loop *, edge *);
 void estimate_numbers_of_iterations (struct loops *);

gcc/tree-ssa-loop-ivcanon.c

@@ -220,12 +220,23 @@ canonicalize_loop_induction_variables (struct loops *loops, struct loop *loop,
       niter = fold (build2 (MINUS_EXPR, TREE_TYPE (niter), niter,
 			    build_int_cst (TREE_TYPE (niter), 1)));
     }
-  else if (try_eval)
-    niter = find_loop_niter_by_eval (loop, &exit);
-
-  if (chrec_contains_undetermined (niter)
-      || TREE_CODE (niter) != INTEGER_CST)
-    return false;
+  else
+    {
+      /* If the loop has more than one exit, try checking all of them
+	 for # of iterations determinable through scev.  */
+      if (!loop->single_exit)
+	niter = find_loop_niter (loop, &exit);
+
+      /* Finally if everything else fails, try brute force evaluation.  */
+      if (try_eval
+	  && (chrec_contains_undetermined (niter)
+	      || TREE_CODE (niter) != INTEGER_CST))
+	niter = find_loop_niter_by_eval (loop, &exit);
+
+      if (chrec_contains_undetermined (niter)
+	  || TREE_CODE (niter) != INTEGER_CST)
+	return false;
+    }
 
   if (dump_file && (dump_flags & TDF_DETAILS))
     {

gcc/tree-ssa-loop-niter.c

@@ -80,44 +80,6 @@ nonzero_p (tree arg)
   return (TREE_INT_CST_LOW (arg) != 0 || TREE_INT_CST_HIGH (arg) != 0);
 }
 
-/* Returns number of zeros at the end of binary representation of X.
-   
-   ??? Use ffs if available?  */
-
-static tree
-num_ending_zeros (tree x)
-{
-  unsigned HOST_WIDE_INT fr, nfr;
-  unsigned num, abits;
-  tree type = TREE_TYPE (x);
-
-  if (TREE_INT_CST_LOW (x) == 0)
-    {
-      num = HOST_BITS_PER_WIDE_INT;
-      fr = TREE_INT_CST_HIGH (x);
-    }
-  else
-    {
-      num = 0;
-      fr = TREE_INT_CST_LOW (x);
-    }
-
-  for (abits = HOST_BITS_PER_WIDE_INT / 2; abits; abits /= 2)
-    {
-      nfr = fr >> abits;
-      if (nfr << abits == fr)
-	{
-	  num += abits;
-	  fr = nfr;
-	}
-    }
-
-  if (num > TYPE_PRECISION (type))
-    num = TYPE_PRECISION (type);
-
-  return build_int_cst_type (type, num);
-}
-
 /* Returns inverse of X modulo 2^s, where MASK = 2^s-1.  */
 
 static tree
@@ -823,6 +785,75 @@ number_of_iterations_exit (struct loop *loop, edge exit,
   return integer_onep (niter->assumptions);
 }
 
+/* Try to determine the number of iterations of LOOP.  If we succeed,
+   expression giving number of iterations is returned and *EXIT is
+   set to the edge from that the information is obtained.  Otherwise
+   chrec_dont_know is returned.  */
+
+tree
+find_loop_niter (struct loop *loop, edge *exit)
+{
+  unsigned n_exits, i;
+  edge *exits = get_loop_exit_edges (loop, &n_exits);
+  edge ex;
+  tree niter = NULL_TREE, aniter;
+  struct tree_niter_desc desc;
+
+  *exit = NULL;
+  for (i = 0; i < n_exits; i++)
+    {
+      ex = exits[i];
+      if (!just_once_each_iteration_p (loop, ex->src))
+	continue;
+
+      if (!number_of_iterations_exit (loop, ex, &desc))
+	continue;
+
+      if (nonzero_p (desc.may_be_zero))
+	{
+	  /* We exit in the first iteration through this exit.
+	     We won't find anything better.  */
+	  niter = build_int_cst_type (unsigned_type_node, 0);
+	  *exit = ex;
+	  break;
+	}
+
+      if (!zero_p (desc.may_be_zero))
+	continue;
+
+      aniter = desc.niter;
+
+      if (!niter)
+	{
+	  /* Nothing recorded yet.  */
+	  niter = aniter;
+	  *exit = ex;
+	  continue;
+	}
+
+      /* Prefer constants, the lower the better.  */
+      if (TREE_CODE (aniter) != INTEGER_CST)
+	continue;
+
+      if (TREE_CODE (niter) != INTEGER_CST)
+	{
+	  niter = aniter;
+	  *exit = ex;
+	  continue;
+	}
+
+      if (tree_int_cst_lt (aniter, niter))
+	{
+	  niter = aniter;
+	  *exit = ex;
+	  continue;
+	}
+    }
+  free (exits);
+
+  return niter ? niter : chrec_dont_know;
+}
+
 /*
 
    Analysis of a number of iterations of a loop by a brute-force evaluation.
@@ -1055,13 +1086,11 @@ find_loop_niter_by_eval (struct loop *loop, edge *exit)
 	continue;
 
       aniter = loop_niter_by_eval (loop, ex);
-      if (chrec_contains_undetermined (aniter)
-	  || TREE_CODE (aniter) != INTEGER_CST)
+      if (chrec_contains_undetermined (aniter))
 	continue;
 
       if (niter
-	  && !nonzero_p (fold (build2 (LT_EXPR, boolean_type_node,
-					     aniter, niter))))
+	  && !tree_int_cst_lt (aniter, niter))
 	continue;
 
       niter = aniter;

gcc/tree.c

@@ -6311,4 +6311,42 @@ operand_equal_for_phi_arg_p (tree arg0, tree arg1)
   return operand_equal_p (arg0, arg1, 0);
 }
 
+/* Returns number of zeros at the end of binary representation of X.
+   
+   ??? Use ffs if available?  */
+
+tree
+num_ending_zeros (tree x)
+{
+  unsigned HOST_WIDE_INT fr, nfr;
+  unsigned num, abits;
+  tree type = TREE_TYPE (x);
+
+  if (TREE_INT_CST_LOW (x) == 0)
+    {
+      num = HOST_BITS_PER_WIDE_INT;
+      fr = TREE_INT_CST_HIGH (x);
+    }
+  else
+    {
+      num = 0;
+      fr = TREE_INT_CST_LOW (x);
+    }
+
+  for (abits = HOST_BITS_PER_WIDE_INT / 2; abits; abits /= 2)
+    {
+      nfr = fr >> abits;
+      if (nfr << abits == fr)
+	{
+	  num += abits;
+	  fr = nfr;
+	}
+    }
+
+  if (num > TYPE_PRECISION (type))
+    num = TYPE_PRECISION (type);
+
+  return build_int_cst_type (type, num);
+}
+
 #include "gt-tree.h"

gcc/tree.h

@@ -3275,6 +3275,7 @@ extern int integer_nonzerop (tree);
 
 extern bool zero_p (tree);
 extern bool cst_and_fits_in_hwi (tree);
+extern tree num_ending_zeros (tree);
 
 /* staticp (tree x) is nonzero if X is a reference to data allocated
    at a fixed address in memory.  Returns the outermost data.  */