[PATCH v5] Prepare vfprintf to use __printf_fp/__printf_fphex with float128 arg

["Gabriel F. T. Gomes" <gabriel at inconstante dot eti dot br>]

Changes since v4:

  - Fixed typo in comment (s/macros/macro).
  - Replaced macros with inline functions.

Changes since v3

  - Update after the commit 2d9837c1fbf4 ('Set behavior of sprintf-like
    functions with overlapping source and destination').

Changes since v2:

  - Fixed style error in `do { ... } while (0)' blocks.
  - Zero-initialize args_value[cnt] with memset, rather than relying on
    the `.pa_long_double' member being the largest of the members.

Changes since v1:

  - Updated to the revised and integrated patches for __ldbl_is_dbl
    removal, i.e.: the patches in the following thread:
    <https://sourceware.org/ml/libc-alpha/2018-12/msg00186.html>.
    - Added description for the PRINTF_LDBL_USES_FLOAT128 macro.
    - Removed the LDBL_USES_FLOAT128 macro.
  - Added `do { } while (0)' to the PARSE_FLOAT_VA_ARG_EXTENDED,
    PARSE_FLOAT_VA_ARG, and SETUP_FLOAT128_INFO macros.  Appended
    expansions with `;', accordingly.

-- 8< --
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.

	* libio/libioP.h (PRINTF_LDBL_USES_FLOAT128): New macro to be
	used as a mask for the mode argument of __vfprintf_internal.
	* stdio-common/printf-parse.h (printf_arg): New union member:
	pa_float128.
	* stdio-common/vfprintf-internal.c (parse_float_va_arg)
	(setup_float128_info): New functions.
	(process_arg): Use parse_float_va_arg and setup_float128_info.
	[__HAVE_FLOAT128_UNLIKE_LDBL] (printf_positional): Write
	floating-point value to the new union member, pa_float128.
	(printf_positional): Zero-initialize args_value[cnt] with memset.
---
 libio/libioP.h                   | 20 +++++++++++---
 stdio-common/printf-parse.h      |  3 ++
 stdio-common/vfprintf-internal.c | 60 +++++++++++++++++++++++++++++++---------
 3 files changed, 66 insertions(+), 17 deletions(-)

diff --git a/libio/libioP.h b/libio/libioP.h
index 7bdec86a62..8e7e7ff9b3 100644
--- a/libio/libioP.h
+++ b/libio/libioP.h
@@ -708,10 +708,22 @@ 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)
diff --git a/stdio-common/printf-parse.h b/stdio-common/printf-parse.h
index 397508638d..00f3280b8a 100644
--- a/stdio-common/printf-parse.h
+++ b/stdio-common/printf-parse.h
@@ -57,6 +57,9 @@ union printf_arg
     unsigned long long int pa_u_long_long_int;
     double pa_double;
     long double pa_long_double;
+#if __HAVE_FLOAT128_UNLIKE_LDBL
+    _Float128 pa_float128;
+#endif
     const char *pa_string;
     const wchar_t *pa_wstring;
     void *pa_pointer;
diff --git a/stdio-common/vfprintf-internal.c b/stdio-common/vfprintf-internal.c
index ead2b04cb9..1e98208078 100644
--- a/stdio-common/vfprintf-internal.c
+++ b/stdio-common/vfprintf-internal.c
@@ -150,6 +150,42 @@ typedef wchar_t THOUSANDS_SEP_T;
 /* Include the shared code for parsing the format string.  */
 #include "printf-parse.h"
 
+static void
+parse_float_va_arg (struct printf_info *info, union printf_arg *the_arg,
+		    int is_long_double, unsigned int mode_flags,
+		    va_list *ap)
+{
+#if __HAVE_FLOAT128_UNLIKE_LDBL
+  if (is_long_double && (mode_flags & PRINTF_LDBL_USES_FLOAT128) != 0)
+    {
+      info->is_binary128 = 1;
+      the_arg->pa_float128 = va_arg (*ap, _Float128);
+    }
+  else
+#endif
+    {
+      info->is_binary128 = 0;
+      if (is_long_double)
+	the_arg->pa_long_double = va_arg (*ap, long double);
+      else
+	the_arg->pa_double = va_arg (*ap, double);
+    }
+}
+
+static void
+setup_float128_info (struct printf_info *info, int is_long_double,
+		     unsigned int mode_flags)
+{
+#if __HAVE_FLOAT128_UNLIKE_LDBL
+  if ((mode_flags & PRINTF_LDBL_USES_FLOAT128) != 0)
+    info->is_binary128 = is_long_double;
+  else
+    info->is_binary128 = 0;
+#else
+  info->is_binary128 = 0;
+#endif
+}
+
 
 #define	outchar(Ch)							      \
   do									      \
@@ -771,10 +807,8 @@ static const uint8_t jump_table[] =
 					.wide = sizeof (CHAR_T) != 1,	      \
 					.is_binary128 = 0};		      \
 									      \
-	    if (is_long_double)						      \
-	      the_arg.pa_long_double = va_arg (ap, long double);	      \
-	    else							      \
-	      the_arg.pa_double = va_arg (ap, double);			      \
+	    parse_float_va_arg (&info, &the_arg, is_long_double,	      \
+				mode_flags, &ap);			      \
 	    ptr = (const void *) &the_arg;				      \
 									      \
 	    function_done = __printf_fp (s, &info, &ptr);		      \
@@ -787,8 +821,7 @@ static const uint8_t jump_table[] =
 		fspec->data_arg_type = PA_DOUBLE;			      \
 		fspec->info.is_long_double = 0;				      \
 	      }								      \
-	    /* Not supported by *printf functions.  */			      \
-	    fspec->info.is_binary128 = 0;				      \
+	    setup_float128_info (&fspec->info, is_long_double, mode_flags);   \
 									      \
 	    function_done = __printf_fp (s, &fspec->info, &ptr);	      \
 	  }								      \
@@ -831,10 +864,8 @@ static const uint8_t jump_table[] =
 					.wide = sizeof (CHAR_T) != 1,	      \
 					.is_binary128 = 0};		      \
 									      \
-	    if (is_long_double)						      \
-	      the_arg.pa_long_double = va_arg (ap, long double);	      \
-	    else							      \
-	      the_arg.pa_double = va_arg (ap, double);			      \
+	    parse_float_va_arg (&info, &the_arg, is_long_double,	      \
+				mode_flags, &ap);			      \
 	    ptr = (const void *) &the_arg;				      \
 									      \
 	    function_done = __printf_fphex (s, &info, &ptr);		      \
@@ -844,8 +875,7 @@ static const uint8_t jump_table[] =
 	    ptr = (const void *) &args_value[fspec->data_arg];		      \
 	    if (__glibc_unlikely ((mode_flags & PRINTF_LDBL_IS_DBL) != 0))    \
 	      fspec->info.is_long_double = 0;				      \
-	    /* Not supported by *printf functions.  */			      \
-	    fspec->info.is_binary128 = 0;				      \
+	    setup_float128_info (&fspec->info, is_long_double, mode_flags);   \
 									      \
 	    function_done = __printf_fphex (s, &fspec->info, &ptr);	      \
 	  }								      \
@@ -1869,6 +1899,10 @@ printf_positional (FILE *s, const CHAR_T *format, int readonly_format,
 	    args_value[cnt].pa_double = va_arg (*ap_savep, double);
 	    args_type[cnt] &= ~PA_FLAG_LONG_DOUBLE;
 	  }
+#if __HAVE_FLOAT128_UNLIKE_LDBL
+	else if ((mode_flags & PRINTF_LDBL_USES_FLOAT128) != 0)
+	  args_value[cnt].pa_float128 = va_arg (*ap_savep, _Float128);
+#endif
 	else
 	  args_value[cnt].pa_long_double = va_arg (*ap_savep, long double);
 	break;
@@ -1887,7 +1921,7 @@ printf_positional (FILE *s, const CHAR_T *format, int readonly_format,
 	      (args_value[cnt].pa_user, ap_savep);
 	  }
 	else
-	  args_value[cnt].pa_long_double = 0.0;
+	  memset (&args_value[cnt], 0, sizeof (args_value[cnt]));
 	break;
       case -1:
 	/* Error case.  Not all parameters appear in N$ format
-- 
2.14.5