RFA: Remove some code from c-lex.c:interpret_integer

[Richard Sandiford]

interpret_integer has:

  integer = cpp_interpret_integer (parse_in, token, flags);
  integer = cpp_num_sign_extend (integer, options->precision);
  if (integer.overflow)
    *overflow = OT_OVERFLOW;

where options->precision is the precision of (u)intmax_t.  Looking at
the implementation of cpp_num_sign_extend, it seems it would sign-extend
(u)intmax_t-sized !integer.unsigned literals that have their top bit set.
Smaller literals would stay zero-extended.

Is that extension needed though?  The rest of the function passes
"integer" to narrowest_unsigned_type and narrowest_signed_type,
both of which do unsigned comparisons between "integer" and various
TYPE_MAX_VALUEs.  It looks at face value like sign-extending here
would make the result depend on the host.  E.g. if uintmax_t occupies
2 HWIs with no excess bits, the extension would be a no-op and the
result would still be <= TYPE_MAX_VALUE (uintmax_type_node).  But if
uintmax_t occupies only one HWI, the sign-extended integer would be
greater than TYPE_MAX_VALUE (uintmax_type_node).

Looking at cpp_interpret_integer, I can't see off-hand how we would end
up with a !integer.unsigned literal that is still "negative" according
to options->precision.

Tested on powerpc64-linux-gnu and x86_64-linux-gnu.  OK to install?
Or, if the code is still needed, is there a testcase we could add?

Thanks,
Richard


gcc/c-family/
	* c-lex.c (interpret_integer): Remove call to cpp_num_sign_extend.

Index: gcc/c-family/c-lex.c
===================================================================
--- gcc/c-family/c-lex.c	2013-10-27 08:37:55.569236132 +0000
+++ gcc/c-family/c-lex.c	2013-10-27 11:03:57.721834320 +0000
@@ -595,12 +595,10 @@ interpret_integer (const cpp_token *toke
   tree value, type;
   enum integer_type_kind itk;
   cpp_num integer;
-  cpp_options *options = cpp_get_options (parse_in);
 
   *overflow = OT_NONE;
 
   integer = cpp_interpret_integer (parse_in, token, flags);
-  integer = cpp_num_sign_extend (integer, options->precision);
   if (integer.overflow)
     *overflow = OT_OVERFLOW;