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, 3 deletions

diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-compat.h b/sysdeps/ieee754/ldbl-opt/nldbl-compat.h
index b7e938f785..b7606c3c2d 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-compat.h
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-compat.h
@@ -64,7 +64,6 @@ NLDBL_DECL (vsyslog);
 NLDBL_DECL (qecvt);
 NLDBL_DECL (qfcvt);
 NLDBL_DECL (qgcvt);
-NLDBL_DECL (__vstrfmon_l);
 NLDBL_DECL (__isoc99_scanf);
 NLDBL_DECL (__isoc99_fscanf);
 NLDBL_DECL (__isoc99_sscanf);
@@ -78,10 +77,13 @@ NLDBL_DECL (__isoc99_vwscanf);
 NLDBL_DECL (__isoc99_vfwscanf);
 NLDBL_DECL (__isoc99_vswscanf);
 
-/* This one does not exist in the normal interface, only
-   __nldbl___vstrfmon really exists.  */
+/* These do not exist in the normal interface, but must exist in the
+   __nldbl interface so that they can be called from libnldbl.  */
 extern ssize_t __nldbl___vstrfmon (char *, size_t, const char *, va_list)
   __THROW;
+extern ssize_t __nldbl___vstrfmon_l (char *, size_t, locale_t, const char *,
+				     va_list)
+  __THROW;
 
 /* These don't use __typeof because they were not declared by the headers,
    since we don't compile with _FORTIFY_SOURCE.  */