(fold): Don't modify tree with newly-allocated nodes; instead make new

tree in those cases.

From-SVN: r8901

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index c17c1d70a5e4c7df59bcfa18c8f2c6c998553576..75bba1ff64a25b3fc55d866e01156c54c2a0e81c 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -3663,10 +3663,8 @@ fold (expr)
                    return t;
 
                  /* Otherwise return (CON +- ARG1) - VAR.  */
-                 TREE_SET_CODE (t, MINUS_EXPR);
-                 TREE_OPERAND (t, 1) = var;
-                 TREE_OPERAND (t, 0)
-                   = fold (build (code, TREE_TYPE (t), con, arg1));
+                 t = build (MINUS_EXPR, type,
+                            fold (build (code, type, con, arg1)), var);
                }
              else
                {
@@ -3682,9 +3680,9 @@ fold (expr)
                    return t;
 
                  /* Otherwise return VAR +- (ARG1 +- CON).  */
-                 TREE_OPERAND (t, 1) = tem
-                   = fold (build (code, TREE_TYPE (t), arg1, con));
-                 TREE_OPERAND (t, 0) = var;
+                 tem = fold (build (code, type, arg1, con));
+                 t = build (code, type, var, tem);
+
                  if (integer_zerop (tem)
                      && (code == PLUS_EXPR || code == MINUS_EXPR))
                    return convert (type, var);
@@ -3725,9 +3723,9 @@ fold (expr)
                                       convert (TREE_TYPE (t), con)));
                }
 
-             TREE_OPERAND (t, 0)
-               = fold (build (code, TREE_TYPE (t), arg0, con));
-             TREE_OPERAND (t, 1) = var;
+             t = build (TREE_CODE (t), type,
+                        fold (build (code, TREE_TYPE (t), arg0, con)), var);
+
              if (integer_zerop (TREE_OPERAND (t, 0))
                  && TREE_CODE (t) == PLUS_EXPR)
                return convert (TREE_TYPE (t), var);
@@ -4270,12 +4268,12 @@ fold (expr)
         and the other one.  */
       {
        tree constop = 0, varop;
-       tree *constoploc;
+       int constopnum = -1;
 
        if (TREE_CONSTANT (arg1))
-         constoploc = &TREE_OPERAND (t, 1), constop = arg1, varop = arg0;
+         constopnum = 1, constop = arg1, varop = arg0;
        if (TREE_CONSTANT (arg0))
-         constoploc = &TREE_OPERAND (t, 0), constop = arg0, varop = arg1;
+         constopnum = 0, constop = arg0, varop = arg1;
 
        if (constop && TREE_CODE (varop) == POSTINCREMENT_EXPR)
          {
@@ -4291,7 +4289,10 @@ fold (expr)
                  = fold (build (PLUS_EXPR, TREE_TYPE (varop),
                                 constop, TREE_OPERAND (varop, 1)));
                TREE_SET_CODE (varop, PREINCREMENT_EXPR);
-               *constoploc = newconst;
+
+               t = build (code, type, TREE_OPERAND (t, 0),
+                          TREE_OPERAND (t, 1));
+               TREE_OPERAND (t, constopnum) = newconst;
                return t;
              }
          }
@@ -4305,7 +4306,9 @@ fold (expr)
                  = fold (build (MINUS_EXPR, TREE_TYPE (varop),
                                 constop, TREE_OPERAND (varop, 1)));
                TREE_SET_CODE (varop, PREDECREMENT_EXPR);
-               *constoploc = newconst;
+               t = build (code, type, TREE_OPERAND (t, 0),
+                          TREE_OPERAND (t, 1));
+               TREE_OPERAND (t, constopnum) = newconst;
                return t;
              }
          }
@@ -4320,16 +4323,15 @@ fold (expr)
            {
            case GE_EXPR:
              code = GT_EXPR;
-             TREE_SET_CODE (t, code);
              arg1 = const_binop (MINUS_EXPR, arg1, integer_one_node, 0);
-             TREE_OPERAND (t, 1) = arg1;
+             t = build (code, type, TREE_OPERAND (t, 0), arg1);
              break;
 
            case LT_EXPR:
              code = LE_EXPR;
-             TREE_SET_CODE (t, code);
              arg1 = const_binop (MINUS_EXPR, arg1, integer_one_node, 0);
-             TREE_OPERAND (t, 1) = arg1;
+             t = build (code, type, TREE_OPERAND (t, 0), arg1);
+             break;
            }
        }
 
@@ -4734,10 +4736,10 @@ fold (expr)
 
          if (TREE_CODE (tem) != TRUTH_NOT_EXPR)
            {
-             arg0 = TREE_OPERAND (t, 0) = tem;
+             t = build (code, type, tem,
+                        TREE_OPERAND (t, 2), TREE_OPERAND (t, 1));
+             arg0 = tem;
              arg1 = TREE_OPERAND (t, 2);
-             TREE_OPERAND (t, 2) = TREE_OPERAND (t, 1);
-             TREE_OPERAND (t, 1) = arg1;
              STRIP_NOPS (arg1);
            }
        }
@@ -4837,8 +4839,9 @@ fold (expr)
              {
              case EQ_EXPR:
                /* We can replace A with C1 in this case.  */
-               arg1 = TREE_OPERAND (t, 1)
-                 = convert (type, TREE_OPERAND (arg0, 1));
+               arg1 = convert (type, TREE_OPERAND (arg0, 1));
+               t = build (code, type, TREE_OPERAND (t, 0), arg1,
+                          TREE_OPERAND (t, 2));
                break;
 
              case LT_EXPR:
@@ -4898,10 +4901,10 @@ fold (expr)
 
          if (TREE_CODE (tem) != TRUTH_NOT_EXPR)
            {
-             arg0 = TREE_OPERAND (t, 0) = tem;
+             t = build (code, type, tem,
+                        TREE_OPERAND (t, 2), TREE_OPERAND (t, 1));
+             arg0 = tem;
              arg1 = TREE_OPERAND (t, 2);
-             TREE_OPERAND (t, 2) = TREE_OPERAND (t, 1);
-             TREE_OPERAND (t, 1) = arg1;
              STRIP_NOPS (arg1);
            }
        }