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.

2 files changed, 6 insertions, 5 deletions

diff --git a/stdlib/strfmon.c b/stdlib/strfmon.c
index 01980d3..3058b3e 100644
--- a/stdlib/strfmon.c
+++ b/stdlib/strfmon.c
@@ -30,7 +30,8 @@ __strfmon (char *s, size_t maxsize, const char *format, ...)
 
   va_start (ap, format);
 
-  ssize_t res = __vstrfmon_l (s, maxsize, _NL_CURRENT_LOCALE, format, ap);
+  ssize_t res = __vstrfmon_l_internal (s, maxsize, _NL_CURRENT_LOCALE,
+				       format, ap, 0);
 
   va_end (ap);
 
diff --git a/stdlib/strfmon_l.c b/stdlib/strfmon_l.c
index cd3796c..5293104 100644
--- a/stdlib/strfmon_l.c
+++ b/stdlib/strfmon_l.c
@@ -76,8 +76,8 @@
    too.  Some of the information contradicts the information which can
    be specified in format string.  */
 ssize_t
-__vstrfmon_l (char *s, size_t maxsize, locale_t loc, const char *format,
-	      va_list ap)
+__vstrfmon_l_internal (char *s, size_t maxsize, locale_t loc,
+		       const char *format, va_list ap, unsigned int flags)
 {
   struct __locale_data *current = loc->__locales[LC_MONETARY];
   _IO_strfile f;
@@ -268,7 +268,7 @@ __vstrfmon_l (char *s, size_t maxsize, locale_t loc, const char *format,
       if (*fmt == 'L')
 	{
 	  ++fmt;
-	  if (!__ldbl_is_dbl)
+	  if (__glibc_likely ((flags & STRFMON_LDBL_IS_DBL) == 0))
 	    is_long_double = 1;
 	}
 
@@ -608,7 +608,7 @@ ___strfmon_l (char *s, size_t maxsize, locale_t loc, const char *format, ...)
 
   va_start (ap, format);
 
-  ssize_t res = __vstrfmon_l (s, maxsize, loc, format, ap);
+  ssize_t res = __vstrfmon_l_internal (s, maxsize, loc, format, ap, 0);
 
   va_end (ap);