- 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 nonpositive constant. */
- if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
- && tree_int_cst_lt (TREE_OPERAND (expr, 1), integer_one_node))
- goto trunc1;
- break;
-
- case LSHIFT_EXPR:
- /* We can pass truncation down through left shifting
- when the shift count is a nonnegative constant. */
- if (TREE_CODE (TREE_OPERAND (expr, 1)) == INTEGER_CST
- && ! tree_int_cst_lt (TREE_OPERAND (expr, 1), integer_zero_node)
- && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
- {
- /* If shift count is less than the width of the truncated type,
- really shift. */
- if (tree_int_cst_lt (TREE_OPERAND (expr, 1), TYPE_SIZE (type)))
- /* In this case, shifting is like multiplication. */
- goto trunc1;
- else
- /* If it is >= that width, result is zero.
- Handling this with trunc1 would give the wrong result:
- (int) ((long long) a << 32) is well defined (as 0)
- but (int) a << 32 is undefined and would get a warning. */
- return convert_to_integer (type, integer_zero_node);
- }
- break;
-
- 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 either of 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))
- || TREE_UNSIGNED (TREE_TYPE (arg1)))
- ? unsigned_type (typex) : signed_type (typex));
- return convert (type,
- build_binary_op (ex_form,
- convert (typex, arg0),
- convert (typex, arg1),
- 0));
- }
- }
- }
- break;
-
- case NEGATE_EXPR:
- case BIT_NOT_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,
- fold (build (COND_EXPR, typex,
- TREE_OPERAND (expr, 0),
- convert (typex, arg1),
- convert (typex, arg2))));
- }
- else
- /* It is sometimes worthwhile
- to push the narrowing down through the conditional. */
- return fold (build (COND_EXPR, type,
- TREE_OPERAND (expr, 0),
- convert (type, TREE_OPERAND (expr, 1)),
- convert (type, TREE_OPERAND (expr, 2))));
- }
- }
- }
-
- return build1 (NOP_EXPR, type, expr);
- }
-
- if (form == REAL_TYPE)
- return build1 (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;
- }
-}