Add C2x *_NORM_MAX constants to <float.h>

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Add C2x *_NORM_MAX constants to <float.h>

Joseph Myers
C2x adds <float.h> constants FLT_NORM_MAX, DBL_NORM_MAX and
LDBL_NORM_MAX.  These are for the maximum "normalized" finite
floating-point number, where the given definition of normalized is
that all possible values with MANT_DIG significand digits (leading one
not zero) can be represented with that exponent.  The effect of that
definition is that these macros are the same as the corresponding MAX
macros for all formats except IBM long double, where the NORM_MAX
value has exponent 1 smaller than the MAX one so that all 106 digits
can be 1.

This patch adds those macros to GCC.  They are only defined for float,
double and long double; C2x does not include such macros for DFP
types, and while the integration of TS 18661-3 into C2x has not yet
occurred, the draft proposed text does not add them for the _FloatN /
_FloatNx types (where they would always be the same as the MAX
macros).

Bootstrapped with no regressions on x86_64-pc-linux-gnu.  Also tested
compilation of the new test for powerpc-linux-gnu to confirm the check
of LDBL_NORM_MAX in the IBM long double case does get properly
optimized out.  OK to commit?

gcc:
2019-11-09  Joseph Myers  <[hidden email]>

        * ginclude/float.c [__STDC_VERSION__ > 201710L] (FLT_NORM_MAX,
        DBL_NORM_MAX, LDBL_NORM_MAX): Define.
        * real.c (get_max_float): Add norm_max argument.
        * real.h (get_max_float): Update prototype.
        * builtins.c (fold_builtin_interclass_mathfn): Update calls to
        get_max_float.

gcc/c-family:
2019-11-09  Joseph Myers  <[hidden email]>

        * c-cppbuiltin.c (builtin_define_float_constants): Also define
        NORM_MAX constants.  Update call to get_max_float.
        (LAZY_HEX_FP_VALUES_CNT): Update value to include NORM_MAX
        constants.

gcc/d:
2019-11-09  Joseph Myers  <[hidden email]>

        * d-target.cc (define_float_constants): Update call to
        get_max_float.

gcc/testsuite:
2019-11-09  Joseph Myers  <[hidden email]>

        * gcc.dg/c11-float-3.c, gcc.dg/c2x-float-1.c: New tests.

Index: gcc/builtins.c
===================================================================
--- gcc/builtins.c (revision 277989)
+++ gcc/builtins.c (working copy)
@@ -9039,7 +9039,7 @@ fold_builtin_interclass_mathfn (location_t loc, tr
     mode = DFmode;
     arg = fold_build1_loc (loc, NOP_EXPR, type, arg);
   }
- get_max_float (REAL_MODE_FORMAT (mode), buf, sizeof (buf));
+ get_max_float (REAL_MODE_FORMAT (mode), buf, sizeof (buf), false);
  real_from_string (&r, buf);
  result = build_call_expr (isgr_fn, 2,
   fold_build1_loc (loc, ABS_EXPR, type, arg),
@@ -9063,7 +9063,7 @@ fold_builtin_interclass_mathfn (location_t loc, tr
     mode = DFmode;
     arg = fold_build1_loc (loc, NOP_EXPR, type, arg);
   }
- get_max_float (REAL_MODE_FORMAT (mode), buf, sizeof (buf));
+ get_max_float (REAL_MODE_FORMAT (mode), buf, sizeof (buf), false);
  real_from_string (&r, buf);
  result = build_call_expr (isle_fn, 2,
   fold_build1_loc (loc, ABS_EXPR, type, arg),
@@ -9102,7 +9102,7 @@ fold_builtin_interclass_mathfn (location_t loc, tr
   }
  arg = fold_build1_loc (loc, ABS_EXPR, type, arg);
 
- get_max_float (REAL_MODE_FORMAT (mode), buf, sizeof (buf));
+ get_max_float (REAL_MODE_FORMAT (mode), buf, sizeof (buf), false);
  real_from_string (&rmax, buf);
  sprintf (buf, "0x1p%d", REAL_MODE_FORMAT (orig_mode)->emin - 1);
  real_from_string (&rmin, buf);
Index: gcc/c-family/c-cppbuiltin.c
===================================================================
--- gcc/c-family/c-cppbuiltin.c (revision 277989)
+++ gcc/c-family/c-cppbuiltin.c (working copy)
@@ -259,11 +259,16 @@ builtin_define_float_constants (const char *name_p
   /* Since, for the supported formats, B is always a power of 2, we
      construct the following numbers directly as a hexadecimal
      constants.  */
-  get_max_float (fmt, buf, sizeof (buf));
+  get_max_float (fmt, buf, sizeof (buf), false);
 
   sprintf (name, "__%s_MAX__", name_prefix);
   builtin_define_with_hex_fp_value (name, type, decimal_dig, buf, fp_suffix, fp_cast);
 
+  get_max_float (fmt, buf, sizeof (buf), true);
+
+  sprintf (name, "__%s_NORM_MAX__", name_prefix);
+  builtin_define_with_hex_fp_value (name, type, decimal_dig, buf, fp_suffix, fp_cast);
+
   /* The minimum normalized positive floating-point number,
      b**(emin-1).  */
   sprintf (name, "__%s_MIN__", name_prefix);
@@ -1607,10 +1612,10 @@ struct GTY(()) lazy_hex_fp_value_struct
 };
 /* Number of the expensive to compute macros we should evaluate lazily.
    Each builtin_define_float_constants invocation calls
-   builtin_define_with_hex_fp_value 4 times and builtin_define_float_constants
+   builtin_define_with_hex_fp_value 5 times and builtin_define_float_constants
    is called for FLT, DBL, LDBL and up to NUM_FLOATN_NX_TYPES times for
    FLTNN*.  */
-#define LAZY_HEX_FP_VALUES_CNT (4 * (3 + NUM_FLOATN_NX_TYPES))
+#define LAZY_HEX_FP_VALUES_CNT (5 * (3 + NUM_FLOATN_NX_TYPES))
 static GTY(()) struct lazy_hex_fp_value_struct
   lazy_hex_fp_values[LAZY_HEX_FP_VALUES_CNT];
 static GTY(()) unsigned lazy_hex_fp_value_count;
Index: gcc/d/d-target.cc
===================================================================
--- gcc/d/d-target.cc (revision 277989)
+++ gcc/d/d-target.cc (working copy)
@@ -82,7 +82,7 @@ define_float_constants (tree type)
   const real_format *fmt = REAL_MODE_FORMAT (mode);
 
   /* The largest representable value that's not infinity.  */
-  get_max_float (fmt, buf, sizeof (buf));
+  get_max_float (fmt, buf, sizeof (buf), false);
   real_from_string (&T::max.rv (), buf);
 
   /* The smallest representable normalized value that's not 0.  */
Index: gcc/ginclude/float.h
===================================================================
--- gcc/ginclude/float.h (revision 277989)
+++ gcc/ginclude/float.h (working copy)
@@ -238,6 +238,18 @@ see the files COPYING3 and COPYING.RUNTIME respect
 
 #endif /* C11 */
 
+#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
+/* Maximum finite positive value with MANT_DIG digits in the
+   significand taking their maximum value.  */
+#undef FLT_NORM_MAX
+#undef DBL_NORM_MAX
+#undef LDBL_NORM_MAX
+#define FLT_NORM_MAX __FLT_NORM_MAX__
+#define DBL_NORM_MAX __DBL_NORM_MAX__
+#define LDBL_NORM_MAX __LDBL_NORM_MAX__
+
+#endif /* C2X */
+
 #ifdef __STDC_WANT_IEC_60559_BFP_EXT__
 /* Number of decimal digits for which conversions between decimal
    character strings and binary formats, in both directions, are
Index: gcc/real.c
===================================================================
--- gcc/real.c (revision 277989)
+++ gcc/real.c (working copy)
@@ -5242,13 +5242,19 @@ real_nextafter (REAL_VALUE_TYPE *r, format_helper
 /* Write into BUF the maximum representable finite floating-point
    number, (1 - b**-p) * b**emax for a given FP format FMT as a hex
    float string.  LEN is the size of BUF, and the buffer must be large
-   enough to contain the resulting string.  */
+   enough to contain the resulting string.  If NORM_MAX, instead write
+   the maximum representable finite normalized floating-point number,
+   defined to be such that all choices of digits for that exponent are
+   representable in the format (this only makes a difference for IBM
+   long double).  */
 
 void
-get_max_float (const struct real_format *fmt, char *buf, size_t len)
+get_max_float (const struct real_format *fmt, char *buf, size_t len,
+       bool norm_max)
 {
   int i, n;
   char *p;
+  bool is_ibm_extended = fmt->pnan < fmt->p;
 
   strcpy (buf, "0x0.");
   n = fmt->p;
@@ -5256,8 +5262,9 @@ void
     *p++ = 'f';
   if (i < n)
     *p++ = "08ce"[n - i];
-  sprintf (p, "p%d", fmt->emax);
-  if (fmt->pnan < fmt->p)
+  sprintf (p, "p%d",
+   (is_ibm_extended && norm_max) ? fmt->emax - 1 : fmt->emax);
+  if (is_ibm_extended && !norm_max)
     {
       /* This is an IBM extended double format made up of two IEEE
  doubles.  The value of the long double is the sum of the
Index: gcc/real.h
===================================================================
--- gcc/real.h (revision 277989)
+++ gcc/real.h (working copy)
@@ -524,7 +524,7 @@ extern bool real_nextafter (REAL_VALUE_TYPE *, for
 /* Write into BUF the maximum representable finite floating-point
    number, (1 - b**-p) * b**emax for a given FP format FMT as a hex
    float string.  BUF must be large enough to contain the result.  */
-extern void get_max_float (const struct real_format *, char *, size_t);
+extern void get_max_float (const struct real_format *, char *, size_t, bool);
 
 #ifndef GENERATOR_FILE
 /* real related routines.  */
Index: gcc/testsuite/gcc.dg/c11-float-3.c
===================================================================
--- gcc/testsuite/gcc.dg/c11-float-3.c (nonexistent)
+++ gcc/testsuite/gcc.dg/c11-float-3.c (working copy)
@@ -0,0 +1,17 @@
+/* Test *_NORM_MAX not defined for C11.  */
+/* { dg-do preprocess } */
+/* { dg-options "-std=c11 -pedantic-errors" } */
+
+#include <float.h>
+
+#ifdef FLT_NORM_MAX
+#error "FLT_NORM_MAX defined"
+#endif
+
+#ifdef DBL_NORM_MAX
+#error "DBL_NORM_MAX defined"
+#endif
+
+#ifdef LDBL_NORM_MAX
+#error "LDBL_NORM_MAX defined"
+#endif
Index: gcc/testsuite/gcc.dg/c2x-float-1.c
===================================================================
--- gcc/testsuite/gcc.dg/c2x-float-1.c (nonexistent)
+++ gcc/testsuite/gcc.dg/c2x-float-1.c (working copy)
@@ -0,0 +1,37 @@
+/* Test *_NORM_MAX macros.  */
+/* { dg-do run } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+#include <float.h>
+
+#ifndef FLT_NORM_MAX
+#error "FLT_NORM_MAX undefined"
+#endif
+
+#ifndef DBL_NORM_MAX
+#error "DBL_NORM_MAX undefined"
+#endif
+
+#ifndef LDBL_NORM_MAX
+#error "LDBL_NORM_MAX undefined"
+#endif
+
+extern void abort (void);
+extern void exit (int);
+
+int
+main (void)
+{
+  if (FLT_NORM_MAX != FLT_MAX)
+    abort ();
+  if (DBL_NORM_MAX != DBL_MAX)
+    abort ();
+#if LDBL_MANT_DIG == 106
+  if (LDBL_NORM_MAX != 0x0.ffffffffffffffffffffffffffcp1023L)
+    abort ();
+#else
+  if (LDBL_NORM_MAX != LDBL_MAX)
+    abort ();
+#endif
+  exit (0);
+}

--
Joseph S. Myers
[hidden email]
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Ping Re: Add C2x *_NORM_MAX constants to <float.h>

Joseph Myers
Ping.  This patch
<https://gcc.gnu.org/ml/gcc-patches/2019-11/msg00659.html> is pending
review.

--
Joseph S. Myers
[hidden email]
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Re: Ping Re: Add C2x *_NORM_MAX constants to <float.h>

Jakub Jelinek
On Wed, Nov 13, 2019 at 02:10:34PM +0000, Joseph Myers wrote:
> Ping.  This patch
> <https://gcc.gnu.org/ml/gcc-patches/2019-11/msg00659.html> is pending
> review.

Ok.

        Jakub