+/* Language-level data type conversion for GNU C.
+ Copyright (C) 1987, 1988 Free Software Foundation, Inc.
+
+This file is part of GNU CC.
+
+GNU CC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 1, or (at your option)
+any later version.
+
+GNU CC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU CC; see the file COPYING. If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+
+/* This file contains the functions for converting C expressions
+ to different data types. The only entry point is `convert'.
+ Every language front end must have a `convert' function
+ but what kind of conversions it does will depend on the language. */
+
+#include "config.h"
+#include "tree.h"
+
+/* Change of width--truncation and extension of integers or reals--
+ is represented with NOP_EXPR. Proper functioning of many things
+ assumes that no other conversions can be NOP_EXPRs.
+
+ Conversion between integer and pointer is represented with CONVERT_EXPR.
+ Converting integer to real uses FLOAT_EXPR
+ and real to integer uses FIX_TRUNC_EXPR.
+
+ Here is a list of all the functions that assume that widening and
+ narrowing is always done with a NOP_EXPR:
+ In c-convert.c, convert_to_integer.
+ In c-typeck.c, build_binary_op_nodefault (boolean ops),
+ and truthvalue_conversion.
+ In expr.c: expand_expr, for operands of a MULT_EXPR.
+ In fold-const.c: fold.
+ In tree.c: get_narrower and get_unwidened. */
+\f
+/* Subroutines of `convert'. */
+
+static tree
+convert_to_pointer (type, expr)
+ tree type, expr;
+{
+ register tree intype = TREE_TYPE (expr);
+ register enum tree_code form = TREE_CODE (intype);
+
+ if (integer_zerop (expr))
+ {
+ if (type == TREE_TYPE (null_pointer_node))
+ return null_pointer_node;
+ expr = build_int_2 (0, 0);
+ TREE_TYPE (expr) = type;
+ return expr;
+ }
+
+ if (form == POINTER_TYPE)
+ return build (NOP_EXPR, type, expr);
+
+
+ if (form == INTEGER_TYPE || form == ENUMERAL_TYPE)
+ {
+ if (type_precision (intype) == POINTER_SIZE)
+ return build (CONVERT_EXPR, type, expr);
+ return convert_to_pointer (type,
+ convert (type_for_size (POINTER_SIZE, 0),
+ expr));
+ }
+
+ error ("cannot convert to a pointer type");
+
+ return null_pointer_node;
+}
+
+static tree
+convert_to_real (type, expr)
+ tree type, expr;
+{
+ register enum tree_code form = TREE_CODE (TREE_TYPE (expr));
+ extern int flag_float_store;
+
+ if (form == REAL_TYPE)
+ return build (flag_float_store ? CONVERT_EXPR : NOP_EXPR,
+ type, expr);
+
+ if (form == INTEGER_TYPE || form == ENUMERAL_TYPE)
+ return build (FLOAT_EXPR, type, expr);
+
+ if (form == POINTER_TYPE)
+ error ("pointer value used where a float was expected");
+ else
+ error ("aggregate value used where a float was expected");
+
+ {
+ register tree tem = make_node (REAL_CST);
+ TREE_TYPE (tem) = type;
+ TREE_REAL_CST (tem) = REAL_VALUE_ATOF ("0.0");
+ return tem;
+ }
+}
+\f
+/* The result of this is always supposed to be a newly created tree node
+ not in use in any existing structure. */
+
+static tree
+convert_to_integer (type, expr)
+ tree type, expr;
+{
+ register tree intype = TREE_TYPE (expr);
+ register enum tree_code form = TREE_CODE (intype);
+ extern tree build_binary_op_nodefault ();
+ extern tree build_unary_op ();
+
+ if (form == POINTER_TYPE)
+ {
+ if (integer_zerop (expr))
+ expr = integer_zero_node;
+ else
+ expr = fold (build (CONVERT_EXPR,
+ type_for_size (POINTER_SIZE, 0), expr));
+ intype = TREE_TYPE (expr);
+ form = TREE_CODE (intype);
+ if (intype == type)
+ return expr;
+ }
+
+ if (form == INTEGER_TYPE || form == ENUMERAL_TYPE)
+ {
+ register int outprec = TYPE_PRECISION (type);
+ register int inprec = TYPE_PRECISION (intype);
+ register enum tree_code ex_form = TREE_CODE (expr);
+
+ if (outprec >= inprec)
+ return build (NOP_EXPR, type, expr);
+
+/* Here detect when we can distribute the truncation down past some arithmetic.
+ For example, if adding two longs and converting to an int,
+ we can equally well convert both to ints and then add.
+ For the operations handled here, such truncation distribution
+ is always safe.
+ It is desirable in these cases:
+ 1) when truncating down to full-word from a larger size
+ 2) when truncating takes no work.
+ 3) when at least one operand of the arithmetic has been extended
+ (as by C's default conversions). In this case we need two conversions
+ if we do the arithmetic as already requested, so we might as well
+ truncate both and then combine. Perhaps that way we need only one.
+
+ Note that in general we cannot do the arithmetic in a type
+ shorter than the desired result of conversion, even if the operands
+ are both extended from a shorter type, because they might overflow
+ if combined in that type. The exceptions to this--the times when
+ two narrow values can be combined in their narrow type even to
+ make a wider result--are handled by "shorten" in build_binary_op. */
+
+ switch (ex_form)
+ {
+ case RSHIFT_EXPR:
+ /* We can pass truncation down through right shifting
+ when the shift count is a negative constant. */
+ if (TREE_CODE (TREE_OPERAND (expr, 1)) != INTEGER_CST
+ || TREE_INT_CST_LOW (TREE_OPERAND (expr, 1)) > 0)
+ break;
+ goto trunc1;
+
+ case LSHIFT_EXPR:
+ /* We can pass truncation down through left shifting
+ when the shift count is a positive constant. */
+ if (TREE_CODE (TREE_OPERAND (expr, 1)) != INTEGER_CST
+ || TREE_INT_CST_LOW (TREE_OPERAND (expr, 1)) < 0)
+ break;
+ /* In this case, shifting is like multiplication. */
+ goto trunc1;
+
+ case MAX_EXPR:
+ case MIN_EXPR:
+ case MULT_EXPR:
+ {
+ tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
+ tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
+
+ /* Don't distribute unless the output precision is at least as big
+ as the actual inputs. Otherwise, the comparison of the
+ truncated values will be wrong. */
+ if (outprec >= TYPE_PRECISION (TREE_TYPE (arg0))
+ && outprec >= TYPE_PRECISION (TREE_TYPE (arg1))
+ /* If signedness of arg0 and arg1 don't match,
+ we can't necessarily find a type to compare them in. */
+ && (TREE_UNSIGNED (TREE_TYPE (arg0))
+ == TREE_UNSIGNED (TREE_TYPE (arg1))))
+ goto trunc1;
+ break;
+ }
+
+ case PLUS_EXPR:
+ case MINUS_EXPR:
+ case BIT_AND_EXPR:
+ case BIT_IOR_EXPR:
+ case BIT_XOR_EXPR:
+ case BIT_ANDTC_EXPR:
+ trunc1:
+ {
+ tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
+ tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
+
+ if (outprec >= BITS_PER_WORD
+ || TRULY_NOOP_TRUNCATION (outprec, inprec)
+ || inprec > TYPE_PRECISION (TREE_TYPE (arg0))
+ || inprec > TYPE_PRECISION (TREE_TYPE (arg1)))
+ {
+ /* Do the arithmetic in type TYPEX,
+ then convert result to TYPE. */
+ register tree typex = type;
+
+ /* Can't do arithmetic in enumeral types
+ so use an integer type that will hold the values. */
+ if (TREE_CODE (typex) == ENUMERAL_TYPE)
+ typex = type_for_size (TYPE_PRECISION (typex),
+ TREE_UNSIGNED (typex));
+
+ /* But now perhaps TYPEX is as wide as INPREC.
+ In that case, do nothing special here.
+ (Otherwise would recurse infinitely in convert. */
+ if (TYPE_PRECISION (typex) != inprec)
+ {
+ /* Don't do unsigned arithmetic where signed was wanted,
+ or vice versa.
+ Exception: if the original operands were unsigned
+ then can safely do the work as unsigned.
+ And we may need to do it as unsigned
+ if we truncate to the original size. */
+ typex = ((TREE_UNSIGNED (TREE_TYPE (expr))
+ || TREE_UNSIGNED (TREE_TYPE (arg0)))
+ ? unsigned_type (typex) : signed_type (typex));
+ return convert (type,
+ build_binary_op_nodefault (ex_form,
+ convert (typex, arg0),
+ convert (typex, arg1),
+ ex_form));
+ }
+ }
+ }
+ break;
+
+ case EQ_EXPR:
+ case NE_EXPR:
+ case GT_EXPR:
+ case GE_EXPR:
+ case LT_EXPR:
+ case LE_EXPR:
+ case TRUTH_AND_EXPR:
+ case TRUTH_ANDIF_EXPR:
+ case TRUTH_OR_EXPR:
+ case TRUTH_ORIF_EXPR:
+ case TRUTH_NOT_EXPR:
+ /* If we want result of comparison converted to a byte,
+ we can just regard it as a byte, since it is 0 or 1. */
+ TREE_TYPE (expr) = type;
+ return expr;
+
+ case NEGATE_EXPR:
+ case BIT_NOT_EXPR:
+ case ABS_EXPR:
+ {
+ register tree typex = type;
+
+ /* Can't do arithmetic in enumeral types
+ so use an integer type that will hold the values. */
+ if (TREE_CODE (typex) == ENUMERAL_TYPE)
+ typex = type_for_size (TYPE_PRECISION (typex),
+ TREE_UNSIGNED (typex));
+
+ /* But now perhaps TYPEX is as wide as INPREC.
+ In that case, do nothing special here.
+ (Otherwise would recurse infinitely in convert. */
+ if (TYPE_PRECISION (typex) != inprec)
+ {
+ /* Don't do unsigned arithmetic where signed was wanted,
+ or vice versa. */
+ typex = (TREE_UNSIGNED (TREE_TYPE (expr))
+ ? unsigned_type (typex) : signed_type (typex));
+ return convert (type,
+ build_unary_op (ex_form,
+ convert (typex, TREE_OPERAND (expr, 0)),
+ 1));
+ }
+ }
+
+ case NOP_EXPR:
+ /* If truncating after truncating, might as well do all at once.
+ If truncating after extending, we may get rid of wasted work. */
+ return convert (type, get_unwidened (TREE_OPERAND (expr, 0), type));
+
+ case COND_EXPR:
+ /* Can treat the two alternative values like the operands
+ of an arithmetic expression. */
+ {
+ tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
+ tree arg2 = get_unwidened (TREE_OPERAND (expr, 2), type);
+
+ if (outprec >= BITS_PER_WORD
+ || TRULY_NOOP_TRUNCATION (outprec, inprec)
+ || inprec > TYPE_PRECISION (TREE_TYPE (arg1))
+ || inprec > TYPE_PRECISION (TREE_TYPE (arg2)))
+ {
+ /* Do the arithmetic in type TYPEX,
+ then convert result to TYPE. */
+ register tree typex = type;
+
+ /* Can't do arithmetic in enumeral types
+ so use an integer type that will hold the values. */
+ if (TREE_CODE (typex) == ENUMERAL_TYPE)
+ typex = type_for_size (TYPE_PRECISION (typex),
+ TREE_UNSIGNED (typex));
+
+ /* But now perhaps TYPEX is as wide as INPREC.
+ In that case, do nothing special here.
+ (Otherwise would recurse infinitely in convert. */
+ if (TYPE_PRECISION (typex) != inprec)
+ {
+ /* Don't do unsigned arithmetic where signed was wanted,
+ or vice versa. */
+ typex = (TREE_UNSIGNED (TREE_TYPE (expr))
+ ? unsigned_type (typex) : signed_type (typex));
+ return convert (type,
+ build (COND_EXPR, typex,
+ TREE_OPERAND (expr, 0),
+ convert (typex, arg1),
+ convert (typex, arg2)));
+ }
+ }
+ }
+
+ }
+
+ return build (NOP_EXPR, type, expr);
+ }
+
+ if (form == REAL_TYPE)
+ return build (FIX_TRUNC_EXPR, type, expr);
+
+ error ("aggregate value used where an integer was expected");
+
+ {
+ register tree tem = build_int_2 (0, 0);
+ TREE_TYPE (tem) = type;
+ return tem;
+ }
+}
+\f
+/* Create an expression whose value is that of EXPR,
+ converted to type TYPE. The TREE_TYPE of the value
+ is always TYPE. This function implements all reasonable
+ conversions; callers should filter out those that are
+ not permitted by the language being compiled. */
+
+tree
+convert (type, expr)
+ tree type, expr;
+{
+ register tree e = expr;
+ register enum tree_code code = TREE_CODE (type);
+
+ if (type == TREE_TYPE (expr) || TREE_CODE (expr) == ERROR_MARK)
+ return expr;
+ if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK)
+ return error_mark_node;
+ if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE)
+ {
+ error ("void value not ignored as it ought to be");
+ return error_mark_node;
+ }
+ if (code == VOID_TYPE)
+ return build (CONVERT_EXPR, type, e);
+#if 0
+ /* This is incorrect. A truncation can't be stripped this way.
+ Extensions will be stripped by the use of get_unwidened. */
+ if (TREE_CODE (expr) == NOP_EXPR)
+ return convert (type, TREE_OPERAND (expr, 0));
+#endif
+ if (code == INTEGER_TYPE || code == ENUMERAL_TYPE)
+ return fold (convert_to_integer (type, e));
+ if (code == POINTER_TYPE)
+ return fold (convert_to_pointer (type, e));
+ if (code == REAL_TYPE)
+ return fold (convert_to_real (type, e));
+
+ error ("conversion to non-scalar type requested");
+ return error_mark_node;
+}
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