fold-const.c (split_tree): Don't assume a constant isn't splittable.

        * fold-const.c (split_tree): Don't assume a constant isn't splittable.
        (fold): Don't assume a constant isn't foldable.
        * tree.c (build): Set TREE_CONSTANT for an expression with no
        side-effects and constant operands.
        (build1): Likewise.

From-SVN: r39585

gcc/ChangeLog

+2001-02-11  Richard Henderson  <rth@redhat.com>
+
+	* fold-const.c (split_tree): Don't assume a constant isn't splittable.
+	(fold): Don't assume a constant isn't foldable.
+	* tree.c (build): Set TREE_CONSTANT for an expression with no
+	side-effects and constant operands.
+	(build1): Likewise.
+
 2001-02-10  Richard Henderson  <rth@redhat.com>
 
 	* jump.c (squeeze_notes): Revert 2000-05-12 change.

gcc/fold-const.c

@@ -1357,9 +1357,6 @@ split_tree (in, code, conp, litp, negate_p)
 
   if (TREE_CODE (in) == INTEGER_CST || TREE_CODE (in) == REAL_CST)
     *litp = in;
-  else if (TREE_CONSTANT (in))
-    *conp = in;
-
   else if (TREE_CODE (in) == code
 	   || (! FLOAT_TYPE_P (TREE_TYPE (in))
 	       /* We can associate addition and subtraction together (even
@@ -1399,6 +1396,8 @@ split_tree (in, code, conp, litp, negate_p)
       if (neg_conp_p) *conp = negate_expr (*conp);
       if (neg_var_p) var = negate_expr (var);
     }
+  else if (TREE_CONSTANT (in))
+    *conp = in;
   else
     var = in;
 
@@ -4711,7 +4710,7 @@ fold (expr)
   tree type = TREE_TYPE (expr);
   register tree arg0 = NULL_TREE, arg1 = NULL_TREE;
   register enum tree_code code = TREE_CODE (t);
-  register int kind;
+  register int kind = TREE_CODE_CLASS (code);
   int invert;
   /* WINS will be nonzero when the switch is done
      if all operands are constant.  */
@@ -4722,19 +4721,14 @@ fold (expr)
   if (code == RTL_EXPR || (code == SAVE_EXPR && SAVE_EXPR_RTL (t)) != 0)
     return t;
 
-  /* Return right away if already constant.  */
-  if (TREE_CONSTANT (t))
-    {
-      if (code == CONST_DECL)
-	return DECL_INITIAL (t);
+  /* Return right away if a constant.  */
+  if (kind == 'c')
     return t;
-    }
 
 #ifdef MAX_INTEGER_COMPUTATION_MODE
   check_max_integer_computation_mode (expr);
 #endif
 
-  kind = TREE_CODE_CLASS (code);
   if (code == NOP_EXPR || code == FLOAT_EXPR || code == CONVERT_EXPR)
     {
       tree subop;

gcc/tree.c

@@ -2323,6 +2323,7 @@ build VPARAMS ((enum tree_code code, tree tt, ...))
   register int length;
   register int i;
   int fro;
+  int constant;
 
   VA_START (p, tt);
 
@@ -2341,6 +2342,13 @@ build VPARAMS ((enum tree_code code, tree tt, ...))
      to do this.  */
   fro = first_rtl_op (code);
 
+  /* Expressions without side effects may be constant if their
+     arguments are as well.  */
+  constant = (TREE_CODE_CLASS (code) == '<'
+	      || TREE_CODE_CLASS (code) == '1'
+	      || TREE_CODE_CLASS (code) == '2'
+	      || TREE_CODE_CLASS (code) == 'c');
+
   if (length == 2)
     {
       /* This is equivalent to the loop below, but faster.  */
@@ -2356,6 +2364,8 @@ build VPARAMS ((enum tree_code code, tree tt, ...))
 	    TREE_SIDE_EFFECTS (t) = 1;
 	  if (!TREE_READONLY (arg0))
 	    TREE_READONLY (t) = 0;
+	  if (!TREE_CONSTANT (arg0))
+	    constant = 0;
 	}
 
       if (arg1 && fro > 1)
@@ -2364,6 +2374,8 @@ build VPARAMS ((enum tree_code code, tree tt, ...))
 	    TREE_SIDE_EFFECTS (t) = 1;
 	  if (!TREE_READONLY (arg1))
 	    TREE_READONLY (t) = 0;
+	  if (!TREE_CONSTANT (arg1))
+	    constant = 0;
 	}
     }
   else if (length == 1)
@@ -2390,10 +2402,14 @@ build VPARAMS ((enum tree_code code, tree tt, ...))
 	    {
 	      if (TREE_SIDE_EFFECTS (operand))
 		TREE_SIDE_EFFECTS (t) = 1;
+	      if (!TREE_CONSTANT (operand))
+		constant = 0;
 	    }
 	}
     }
   va_end (p);
+
+  TREE_CONSTANT (t) = constant;
   return t;
 }
 
@@ -2466,6 +2482,8 @@ build1 (code, type, node)
       break;
 
     default:
+      if (TREE_CODE_CLASS (code) == '1' && TREE_CONSTANT (node))
+	TREE_CONSTANT (t) = 1;
       break;
     }