[fixed-point] Patch for c_common_type and type_for_mode

["Fu, Chao-Ying" <fu at mips dot com>]

Hi,

  This patch fixed c_common_type to follow the sign of the fixed-point type,
if the other one has an integer type, in order to match the spec:
"Clause 6.3.1.8 - Usual arithmetic conversions, after the conversion rule
for conversion to float
  Otherwise, if one operand has fixed-point type and the other operand 
has integer type, then no conversions are needed; the result type shall
be the fixed-point type."

  Having this change may cause wrong comparison when mixing unsigned
fixed-point type and signed integer type.  This issue can be caught
by using "-Wsign-compare".
Ex: (bug59.c)
int test(unsigned _Fract a, int b)
{
  return a > b;
}
gcc -S bug59.c -Wsign-compare
bug59.c:3: warning: comparison between signed and unsigned

  And, this patch fixed two cases of "lang_hooks.types.type_for_mode()"
to pass the saturating flag as the 2nd parameter for fixed-point types.

  Thanks!

Regards,
Chao-ying

2007-04-10  Chao-ying Fu  <fu@mips.com>

	* fold-const.c (make_range): For fixed-point modes, we need to pass the
	saturating flag as the 2nd parameter.
	* c-typeck.c (c_common_type): Follow the sign of the fixed-point type,
	if the other one has an integer type.
	* tree-vect-generic.c (type_for_widest_vector_mode): Add one parameter
	for the saturating flag.  Pass it to type_for_mode for fixed-point
	types.
	(expand_vector_operations_1): Pass the saturating flag to
	type_for_widest_vector_mode.

Attachment: gcc.diff
Description: gcc.diff