Use STRFMON_LDBL_IS_DBL instead of __ldbl_is_dbl.

On platforms where long double used to have the same format as double,
but later switched to a different format (alpha, s390, sparc, and
powerpc), accessing the older behavior is possible and it happens via
__nldbl_* functions (not on the API, but accessible from header
redirection and from compat symbols).  These functions write to the
global flag __ldbl_is_dbl, which tells other functions that long double
variables should be handled as double.  This patch takes the first step
towards removing this global flag and creates __vstrfmon_l_internal,
which takes an explicit flags parameter.

This change arguably makes the generated code slightly worse on
architectures where __ldbl_is_dbl is never true; right now, on those
architectures, it's a compile-time constant; after this change, the
compiler could theoretically prove that __vstrfmon_l_internal was
never called with a nonzero flags argument, but it would probably need
LTO to do it.  This is not performance critical code and I tend to
think that the maintainability benefits of removing action at a
distance are worth it.  However, we _could_ wrap the runtime flag
check with a macro that was defined to ignore its argument and always
return false on architectures where __ldbl_is_dbl is never true, if
people think the codegen benefits are important.

Tested for powerpc and powerpc64le.

1 files changed, 5 insertions, 4 deletions

diff --git a/manual/locale.texi b/manual/locale.texi
index dabb959f9e..720e0ca952 100644
--- a/manual/locale.texi
+++ b/manual/locale.texi
@@ -1209,10 +1209,11 @@ numbers according to these rules.
 
 @deftypefun ssize_t strfmon (char *@var{s}, size_t @var{maxsize}, const char *@var{format}, @dots{})
 @safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@ascuheap{}}@acunsafe{@acsmem{}}}
-@c It (and strfmon_l) both call vstrfmon_l, which, besides accessing the
-@c locale object passed to it, accesses the active locale through
-@c isdigit (but to_digit assumes ASCII digits only).  It may call
-@c __printf_fp (@mtslocale @ascuheap @acsmem) and guess_grouping (safe).
+@c It (and strfmon_l) both call __vstrfmon_l_internal, which, besides
+@c accessing the locale object passed to it, accesses the active
+@c locale through isdigit (but to_digit assumes ASCII digits only).
+@c It may call __printf_fp (@mtslocale @ascuheap @acsmem) and
+@c guess_grouping (safe).
 The @code{strfmon} function is similar to the @code{strftime} function
 in that it takes a buffer, its size, a format string,
 and values to write into the buffer as text in a form specified