Prepare vfprintf to use __printf_fp/__printf_fphex with float128 arg

On powerpc64le, long double can currently take two formats: the same as
double (-mlong-double-64) or IBM Extended Precision (default with
-mlong-double-128 or explicitly with -mabi=ibmlongdouble).  The internal
implementation of printf-like functions is aware of these possibilities
and properly parses floating-point values from the variable arguments,
before making calls to __printf_fp and __printf_fphex.  These functions
are also aware of the format possibilities and know how to convert both
formats to string.

When library support for TS 18661-3 was added to glibc, __printf_fp and
__printf_fphex were extended with support for an additional type
(__float128/_Float128) with a different format (binary128).  Now that
powerpc64le is getting support for its third long double format, and
taking into account that this format is the same as the format of
__float128/_Float128, this patch extends __vfprintf_internal to properly
call __printf_fp and __printf_fphex with this new format.

Tested for powerpc64le (with additional patches to actually enable the
use of these preparations) and for x86_64.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

1 files changed, 16 insertions, 4 deletions

diff --git a/libio/libioP.h b/libio/libioP.h
index afa46cc..8db24e1 100644
--- a/libio/libioP.h
+++ b/libio/libioP.h
@@ -712,10 +712,22 @@ extern int __vswprintf_internal (wchar_t *string, size_t maxlen,
    defined to 1 or 2.  Otherwise, such checks are ignored.
 
    PRINTF_CHK indicates, to the internal function being called, that the
-   call is originated from one of the __*printf_chk functions.  */
-#define PRINTF_LDBL_IS_DBL 0x0001
-#define PRINTF_FORTIFY     0x0002
-#define PRINTF_CHK	   0x0004
+   call is originated from one of the __*printf_chk functions.
+
+   PRINTF_LDBL_USES_FLOAT128 is used on platforms where the long double
+   format used to be different from the IEC 60559 double format *and*
+   also different from the Quadruple 128-bits IEC 60559 format (such as
+   the IBM Extended Precision format on powerpc or the 80-bits IEC 60559
+   format on x86), but was later converted to the Quadruple 128-bits IEC
+   60559 format, which is the same format that the _Float128 always has
+   (hence the `USES_FLOAT128' suffix in the name of the flag).  When set
+   to one, this macro indicates that long double values are to be
+   handled as having this new format.  Otherwise, they should be handled
+   as the previous format on that platform.  */
+#define PRINTF_LDBL_IS_DBL		0x0001
+#define PRINTF_FORTIFY			0x0002
+#define PRINTF_CHK			0x0004
+#define PRINTF_LDBL_USES_FLOAT128	0x0008
 
 extern size_t _IO_getline (FILE *,char *, size_t, int, int);
 libc_hidden_proto (_IO_getline)