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, 17 insertions, 25 deletions

diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-compat.c b/sysdeps/ieee754/ldbl-opt/nldbl-compat.c
index ffb5fabebe..7a1e89c1a3 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-compat.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-compat.c
@@ -51,8 +51,6 @@ libc_hidden_proto (__nldbl___vswprintf_chk)
 libc_hidden_proto (__nldbl___vasprintf_chk)
 libc_hidden_proto (__nldbl___vdprintf_chk)
 libc_hidden_proto (__nldbl___obstack_vprintf_chk)
-libc_hidden_proto (__nldbl___vstrfmon)
-libc_hidden_proto (__nldbl___vstrfmon_l)
 libc_hidden_proto (__nldbl___isoc99_vsscanf)
 libc_hidden_proto (__nldbl___isoc99_vfscanf)
 libc_hidden_proto (__nldbl___isoc99_vswscanf)
@@ -780,12 +778,13 @@ attribute_compat_text_section
 __nldbl_strfmon (char *s, size_t maxsize, const char *format, ...)
 {
   va_list ap;
-  ssize_t res;
+  ssize_t ret;
 
   va_start (ap, format);
-  res = __nldbl___vstrfmon (s, maxsize, format, ap);
+  ret = __vstrfmon_l_internal (s, maxsize, _NL_CURRENT_LOCALE, format, ap,
+			       STRFMON_LDBL_IS_DBL);
   va_end (ap);
-  return res;
+  return ret;
 }
 
 ssize_t
@@ -794,12 +793,13 @@ __nldbl___strfmon_l (char *s, size_t maxsize, locale_t loc,
 		     const char *format, ...)
 {
   va_list ap;
-  ssize_t res;
+  ssize_t ret;
 
   va_start (ap, format);
-  res = __nldbl___vstrfmon_l (s, maxsize, loc, format, ap);
+  ret = __vstrfmon_l_internal (s, maxsize, loc, format, ap,
+			       STRFMON_LDBL_IS_DBL);
   va_end (ap);
-  return res;
+  return ret;
 }
 weak_alias (__nldbl___strfmon_l, __nldbl_strfmon_l)
 
@@ -807,28 +807,18 @@ ssize_t
 attribute_compat_text_section
 __nldbl___vstrfmon (char *s, size_t maxsize, const char *format, va_list ap)
 {
-  ssize_t res;
-  __no_long_double = 1;
-  res = __vstrfmon_l (s, maxsize, _NL_CURRENT_LOCALE, format, ap);
-  __no_long_double = 0;
-  va_end (ap);
-  return res;
+  return __vstrfmon_l_internal (s, maxsize, _NL_CURRENT_LOCALE, format, ap,
+				STRFMON_LDBL_IS_DBL);
 }
-libc_hidden_def (__nldbl___vstrfmon)
 
 ssize_t
 attribute_compat_text_section
 __nldbl___vstrfmon_l (char *s, size_t maxsize, locale_t loc,
 		      const char *format, va_list ap)
 {
-  ssize_t res;
-  __no_long_double = 1;
-  res = __vstrfmon_l (s, maxsize, loc, format, ap);
-  __no_long_double = 0;
-  va_end (ap);
-  return res;
+  return __vstrfmon_l_internal (s, maxsize, loc, format, ap,
+				STRFMON_LDBL_IS_DBL);
 }
-libc_hidden_def (__nldbl___vstrfmon_l)
 
 void
 attribute_compat_text_section
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.  */