Makefile.in (tree-chrec.o): Depend on params.h.

	PR/20742
	* Makefile.in (tree-chrec.o): Depend on params.h.
	* params.def (PARAM_SCEV_MAX_EXPR_SIZE): New parameter with
	default value 20.
	* tree-chrec.c: Depend on params.h.  Replace build with buildN,
	and fold build with fold_buildN.
	(chrec_fold_plus_1): Fail with a chrec_don_know when the size of
	the expression exceeds PARAM_SCEV_MAX_EXPR_SIZE.
	(tree_contains_chrecs): Compute an estimation of the size of the
	given expression.
	* tree-chrec.h (tree_contains_chrecs): Modify its declaration.
	(tree_does_not_contain_chrecs): Update the use of tree_contains_chrecs.
	* tree-scalar-evolution.c (simple_iv): Ditto.
	* doc/invoke.texi (scev-max-expr-size): Documented.

From-SVN: r98497

gcc/ChangeLog

+2005-04-21  Sebastian Pop  <pop@cri.ensmp.fr>
+
+	PR/20742
+	* Makefile.in (tree-chrec.o): Depend on params.h.
+	* params.def (PARAM_SCEV_MAX_EXPR_SIZE): New parameter with
+	default value 20.
+	* tree-chrec.c: Depend on params.h.  Replace build with buildN,
+	and fold build with fold_buildN.
+	(chrec_fold_plus_1): Fail with a chrec_don_know when the size of
+	the expression exceeds PARAM_SCEV_MAX_EXPR_SIZE.
+	(tree_contains_chrecs): Compute an estimation of the size of the
+	given expression.
+	* tree-chrec.h (tree_contains_chrecs): Modify its declaration.
+	(tree_does_not_contain_chrecs): Update the use of tree_contains_chrecs.
+	* tree-scalar-evolution.c (simple_iv): Ditto.
+	* doc/invoke.texi (scev-max-expr-size): Documented.
+
 2005-04-21  Richard Sandiford  <rsandifo@redhat.com>
 
 	* config.gcc (*-*-darwin*): Add darwin.opt to $extra_options.

gcc/Makefile.in

@@ -1795,7 +1795,7 @@ tree-browser.o : tree-browser.c tree-browser.def $(CONFIG_H) $(SYSTEM_H) \
    $(TREE_H) errors.h tree-inline.h diagnostic.h $(HASHTAB_H) \
    $(TM_H) coretypes.h
 tree-chrec.o: tree-chrec.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) \
-   errors.h $(GGC_H) $(TREE_H) tree-chrec.h tree-pass.h
+   errors.h $(GGC_H) $(TREE_H) tree-chrec.h tree-pass.h $(PARAMS_H)
 tree-scalar-evolution.o: tree-scalar-evolution.c $(CONFIG_H) $(SYSTEM_H) \
    coretypes.h $(TM_H) errors.h $(GGC_H) $(TREE_H) $(RTL_H) \
    $(BASIC_BLOCK_H) diagnostic.h $(TREE_FLOW_H) $(TREE_DUMP_H) \

gcc/doc/invoke.texi

@@ -5680,6 +5680,10 @@ If number of candidates in the set is smaller than this value,
 we always try to remove unnecessary ivs from the set during its
 optimization when a new iv is added to the set.
 
+@item scev-max-expr-size
+Bound on size of expressions used in the scalar evolutions analyzer.
+Large expressions slow the analyzer.
+
 @item max-iterations-to-track
 
 The maximum number of iterations of a loop the brute force algorithm

gcc/params.def

@@ -372,6 +372,11 @@ DEFPARAM(PARAM_IV_ALWAYS_PRUNE_CAND_SET_BOUND,
 	 "If number of candidates in the set is smaller, we always try to remove unused ivs during its optimization",
 	 10, 0, 0)
 
+DEFPARAM(PARAM_SCEV_MAX_EXPR_SIZE,
+ 	 "scev-max-expr-size",
+	 "Bound on size of expressions used in the scalar evolutions analyzer",
+	 20, 0, 0)
+
 /* The product of the next two is used to decide whether or not to
    use .GLOBAL_VAR.  See tree-dfa.c.  */
 DEFPARAM(PARAM_GLOBAL_VAR_THRESHOLD,

gcc/tree-chrec.c

@@ -35,6 +35,7 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 #include "varray.h"
 #include "tree-chrec.h"
 #include "tree-pass.h"
+#include "params.h"
 
 
 
@@ -286,11 +287,17 @@ chrec_fold_plus_1 (enum tree_code code,
 				    build_int_cst_type (type, -1)));
 
 	default:
-	  if (tree_contains_chrecs (op0)
-	      || tree_contains_chrecs (op1))
-	    return build (code, type, op0, op1);
-	  else
-	    return fold (build (code, type, op0, op1));
+	  {
+	    int size = 0;
+	    if ((tree_contains_chrecs (op0, &size)
+		 || tree_contains_chrecs (op1, &size))
+		&& size < PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
+	      return build2 (code, type, op0, op1);
+	    else if (size < PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
+	      return fold_build2 (code, type, op0, op1);
+	    else
+	      return chrec_dont_know;
+	  }
 	}
     }
 }
@@ -374,7 +381,7 @@ chrec_fold_multiply (tree type,
 	    return op0;
 	  if (integer_zerop (op1))
 	    return build_int_cst_type (type, 0);
-	  return fold (build (MULT_EXPR, type, op0, op1));
+	  return fold_build2 (MULT_EXPR, type, op0, op1);
 	}
     }
 }
@@ -478,8 +485,8 @@ chrec_evaluate (unsigned var, tree chrec, tree n, unsigned int k)
       binomial_n_k = tree_fold_binomial (type, n, k);
       if (!binomial_n_k)
 	return chrec_dont_know;
-      arg1 = fold (build2 (MULT_EXPR, type,
-			   CHREC_LEFT (chrec), binomial_n_k));
+      arg1 = fold_build2 (MULT_EXPR, type,
+			  CHREC_LEFT (chrec), binomial_n_k);
       return chrec_fold_plus (type, arg0, arg1);
     }
 
@@ -487,7 +494,7 @@ chrec_evaluate (unsigned var, tree chrec, tree n, unsigned int k)
   if (!binomial_n_k)
     return chrec_dont_know;
   
-  return fold (build2 (MULT_EXPR, type, chrec, binomial_n_k));
+  return fold_build2 (MULT_EXPR, type, chrec, binomial_n_k);
 }
 
 /* Evaluates "CHREC (X)" when the varying variable is VAR.  
@@ -717,7 +724,7 @@ reset_evolution_in_loop (unsigned loop_num,
 {
   if (TREE_CODE (chrec) == POLYNOMIAL_CHREC
       && CHREC_VARIABLE (chrec) > loop_num)
-    return build 
+    return build2 
       (TREE_CODE (chrec), 
        build_int_cst (NULL_TREE, CHREC_VARIABLE (chrec)), 
        reset_evolution_in_loop (loop_num, CHREC_LEFT (chrec), new_evol), 
@@ -862,29 +869,34 @@ chrec_contains_undetermined (tree chrec)
     }
 }
 
-/* Determines whether the tree EXPR contains chrecs.  */
+/* Determines whether the tree EXPR contains chrecs, and increment
+   SIZE if it is not a NULL pointer by an estimation of the depth of
+   the tree.  */
 
 bool
-tree_contains_chrecs (tree expr)
+tree_contains_chrecs (tree expr, int *size)
 {
   if (expr == NULL_TREE)
     return false;
+
+  if (size)
+    (*size)++;
   
   if (tree_is_chrec (expr))
     return true;
-  
+
   switch (TREE_CODE_LENGTH (TREE_CODE (expr)))
     {
     case 3:
-      if (tree_contains_chrecs (TREE_OPERAND (expr, 2)))
+      if (tree_contains_chrecs (TREE_OPERAND (expr, 2), size))
 	return true;
       
     case 2:
-      if (tree_contains_chrecs (TREE_OPERAND (expr, 1)))
+      if (tree_contains_chrecs (TREE_OPERAND (expr, 1), size))
 	return true;
       
     case 1:
-      if (tree_contains_chrecs (TREE_OPERAND (expr, 0)))
+      if (tree_contains_chrecs (TREE_OPERAND (expr, 0), size))
 	return true;
       
     default:

gcc/tree-chrec.h

@@ -87,7 +87,7 @@ extern bool chrec_is_positive (tree, bool *);
 extern bool chrec_contains_symbols (tree);
 extern bool chrec_contains_symbols_defined_in_loop (tree, unsigned);
 extern bool chrec_contains_undetermined (tree);
-extern bool tree_contains_chrecs (tree);
+extern bool tree_contains_chrecs (tree, int *);
 extern bool evolution_function_is_affine_multivariate_p (tree);
 extern bool evolution_function_is_univariate_p (tree);
 extern unsigned nb_vars_in_chrec (tree);
@@ -183,7 +183,7 @@ evolution_function_is_affine_or_constant_p (tree chrec)
 static inline bool
 tree_does_not_contain_chrecs (tree expr)
 {
-  return !tree_contains_chrecs (expr);
+  return !tree_contains_chrecs (expr, NULL);
 }
 
 /* Determines whether CHREC is a loop invariant with respect to LOOP_NUM.  

gcc/tree-scalar-evolution.c

@@ -2582,7 +2582,7 @@ simple_iv (struct loop *loop, tree stmt, tree op, tree *base, tree *step)
   if (TREE_CODE (*step) != INTEGER_CST)
     return false;
   *base = CHREC_LEFT (ev);
-  if (tree_contains_chrecs (*base)
+  if (tree_contains_chrecs (*base, NULL)
       || chrec_contains_symbols_defined_in_loop (*base, loop->num))
     return false;