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, 14 insertions, 3 deletions

diff --git a/include/monetary.h b/include/monetary.h
index c130ed5..f59bdf9 100644
--- a/include/monetary.h
+++ b/include/monetary.h
@@ -2,7 +2,18 @@
 #ifndef _ISOMAC
 #include <stdarg.h>
 
-extern ssize_t __vstrfmon_l (char *s, size_t maxsize, locale_t loc,
-			     const char *format, va_list ap)
-     attribute_hidden;
+extern ssize_t
+__vstrfmon_l_internal (char *s, size_t maxsize, locale_t loc,
+		       const char *format, va_list ap,
+		       unsigned int flags)
+  attribute_hidden;
+
+/* Flags for __vstrfmon_l_internal.
+
+   STRFMON_LDBL_IS_DBL is a one-bit mask for the flags parameter that
+   indicates whether long double values are to be handled as having the
+   same format as double, in which case the flag should be set to one,
+   or as another format, otherwise.  */
+#define STRFMON_LDBL_IS_DBL 0x0001
+
 #endif