gh-104263: Rely on Py_NAN and introduce Py_INFINITY (GH-104202)

This PR removes `_Py_dg_stdnan` and `_Py_dg_infinity` in favour of
using the standard `NAN` and `INFINITY` macros provided by C99.
This change has the side-effect of fixing a bug on MIPS where the
hard-coded value used by `_Py_dg_stdnan` gave a signalling NaN
rather than a quiet NaN.
---------

Co-authored-by: Mark Dickinson <dickinsm@gmail.com>

1 files changed, 0 insertions, 34 deletions

diff --git a/Python/dtoa.c b/Python/dtoa.c
index 6ea60ac..c5e343b 100644
--- a/Python/dtoa.c
+++ b/Python/dtoa.c
@@ -273,11 +273,6 @@ typedef union { double d; ULong L[2]; } U;
 #define Big0 (Frac_mask1 | Exp_msk1*(DBL_MAX_EXP+Bias-1))
 #define Big1 0xffffffff
 
-/* Standard NaN used by _Py_dg_stdnan. */
-
-#define NAN_WORD0 0x7ff80000
-#define NAN_WORD1 0
-
 /* Bits of the representation of positive infinity. */
 
 #define POSINF_WORD0 0x7ff00000
@@ -1399,35 +1394,6 @@ bigcomp(U *rv, const char *s0, BCinfo *bc)
     return 0;
 }
 
-/* Return a 'standard' NaN value.
-
-   There are exactly two quiet NaNs that don't arise by 'quieting' signaling
-   NaNs (see IEEE 754-2008, section 6.2.1).  If sign == 0, return the one whose
-   sign bit is cleared.  Otherwise, return the one whose sign bit is set.
-*/
-
-double
-_Py_dg_stdnan(int sign)
-{
-    U rv;
-    word0(&rv) = NAN_WORD0;
-    word1(&rv) = NAN_WORD1;
-    if (sign)
-        word0(&rv) |= Sign_bit;
-    return dval(&rv);
-}
-
-/* Return positive or negative infinity, according to the given sign (0 for
- * positive infinity, 1 for negative infinity). */
-
-double
-_Py_dg_infinity(int sign)
-{
-    U rv;
-    word0(&rv) = POSINF_WORD0;
-    word1(&rv) = POSINF_WORD1;
-    return sign ? -dval(&rv) : dval(&rv);
-}
 
 double
 _Py_dg_strtod(const char *s00, char **se)