/* real.c - software floating point emulation.
- Copyright (C) 1993-2019 Free Software Foundation, Inc.
+ Copyright (C) 1993-2020 Free Software Foundation, Inc.
Contributed by Stephen L. Moshier (moshier@world.std.com).
Re-written by Richard Henderson <rth@redhat.com>
for (i = 0; i < w; ++i)
r->sig[i] = 0;
- r->sig[w] &= ~(((unsigned long)1 << (n % HOST_BITS_PER_LONG)) - 1);
+ /* We are actually passing N == SIGNIFICAND_BITS which would result
+ in an out-of-bound access below. */
+ if (n % HOST_BITS_PER_LONG != 0)
+ r->sig[w] &= ~(((unsigned long)1 << (n % HOST_BITS_PER_LONG)) - 1);
}
/* Divide the significands of A and B, placing the result in R. Return
do_multiply (&u, &v, ten);
- /* Stop if we're now >= 1. */
- if (REAL_EXP (&u) > 0)
+ /* Stop if we're now >= 1 or zero. */
+ if (REAL_EXP (&u) > 0 || u.cl == rvc_zero)
break;
v = u;
/* Nonzero value, possibly overflowing or underflowing. */
mpfr_init2 (m, SIGNIFICAND_BITS);
- inexact = mpfr_strtofr (m, str, NULL, 10, GMP_RNDZ);
+ inexact = mpfr_strtofr (m, str, NULL, 10, MPFR_RNDZ);
/* The result should never be a NaN, and because the rounding is
toward zero should never be an infinity. */
gcc_assert (!mpfr_nan_p (m) && !mpfr_inf_p (m));
}
else
{
- real_from_mpfr (r, m, NULL_TREE, GMP_RNDZ);
+ real_from_mpfr (r, m, NULL_TREE, MPFR_RNDZ);
/* 1 to 3 bits may have been shifted off (with a sticky bit)
because the hex digits used in real_from_mpfr did not
start with a digit 8 to f, but the exponent bounds above
{
mpfr_t m;
mpfr_init2 (m, SIGNIFICAND_BITS);
- mpfr_set_ui (m, 1, GMP_RNDN);
- mpfr_exp (m, m, GMP_RNDN);
- real_from_mpfr (&value, m, NULL_TREE, GMP_RNDN);
+ mpfr_set_ui (m, 1, MPFR_RNDN);
+ mpfr_exp (m, m, MPFR_RNDN);
+ real_from_mpfr (&value, m, NULL_TREE, MPFR_RNDN);
mpfr_clear (m);
}
{
mpfr_t m;
mpfr_init2 (m, SIGNIFICAND_BITS);
- mpfr_sqrt_ui (m, 2, GMP_RNDN);
- real_from_mpfr (&value, m, NULL_TREE, GMP_RNDN);
+ mpfr_sqrt_ui (m, 2, MPFR_RNDN);
+ real_from_mpfr (&value, m, NULL_TREE, MPFR_RNDN);
mpfr_clear (m);
}
return &value;
}
}
+/* Encode arm_bfloat types. */
+static void
+encode_arm_bfloat_half (const struct real_format *fmt, long *buf,
+ const REAL_VALUE_TYPE *r)
+{
+ unsigned long image, sig, exp;
+ unsigned long sign = r->sign;
+ bool denormal = (r->sig[SIGSZ-1] & SIG_MSB) == 0;
+
+ image = sign << 15;
+ sig = (r->sig[SIGSZ-1] >> (HOST_BITS_PER_LONG - 8)) & 0x7f;
+
+ switch (r->cl)
+ {
+ case rvc_zero:
+ break;
+
+ case rvc_inf:
+ if (fmt->has_inf)
+ image |= 255 << 7;
+ else
+ image |= 0x7fff;
+ break;
+
+ case rvc_nan:
+ if (fmt->has_nans)
+ {
+ if (r->canonical)
+ sig = (fmt->canonical_nan_lsbs_set ? (1 << 6) - 1 : 0);
+ if (r->signalling == fmt->qnan_msb_set)
+ sig &= ~(1 << 6);
+ else
+ sig |= 1 << 6;
+ if (sig == 0)
+ sig = 1 << 5;
+
+ image |= 255 << 7;
+ image |= sig;
+ }
+ else
+ image |= 0x7fff;
+ break;
+
+ case rvc_normal:
+ if (denormal)
+ exp = 0;
+ else
+ exp = REAL_EXP (r) + 127 - 1;
+ image |= exp << 7;
+ image |= sig;
+ break;
+
+ default:
+ gcc_unreachable ();
+ }
+
+ buf[0] = image;
+}
+
+/* Decode arm_bfloat types. */
+static void
+decode_arm_bfloat_half (const struct real_format *fmt, REAL_VALUE_TYPE *r,
+ const long *buf)
+{
+ unsigned long image = buf[0] & 0xffff;
+ bool sign = (image >> 15) & 1;
+ int exp = (image >> 7) & 0xff;
+
+ memset (r, 0, sizeof (*r));
+ image <<= HOST_BITS_PER_LONG - 8;
+ image &= ~SIG_MSB;
+
+ if (exp == 0)
+ {
+ if (image && fmt->has_denorm)
+ {
+ r->cl = rvc_normal;
+ r->sign = sign;
+ SET_REAL_EXP (r, -126);
+ r->sig[SIGSZ-1] = image << 1;
+ normalize (r);
+ }
+ else if (fmt->has_signed_zero)
+ r->sign = sign;
+ }
+ else if (exp == 255 && (fmt->has_nans || fmt->has_inf))
+ {
+ if (image)
+ {
+ r->cl = rvc_nan;
+ r->sign = sign;
+ r->signalling = (((image >> (HOST_BITS_PER_LONG - 2)) & 1)
+ ^ fmt->qnan_msb_set);
+ r->sig[SIGSZ-1] = image;
+ }
+ else
+ {
+ r->cl = rvc_inf;
+ r->sign = sign;
+ }
+ }
+ else
+ {
+ r->cl = rvc_normal;
+ r->sign = sign;
+ SET_REAL_EXP (r, exp - 127 + 1);
+ r->sig[SIGSZ-1] = image | SIG_MSB;
+ }
+}
+
/* Half-precision format, as specified in IEEE 754R. */
const struct real_format ieee_half_format =
{
false,
"arm_half"
};
+
+/* ARM Bfloat half-precision format. This format resembles a truncated
+ (16-bit) version of the 32-bit IEEE 754 single-precision floating-point
+ format. */
+const struct real_format arm_bfloat_half_format =
+ {
+ encode_arm_bfloat_half,
+ decode_arm_bfloat_half,
+ 2,
+ 8,
+ 8,
+ -125,
+ 128,
+ 15,
+ 15,
+ 0,
+ false,
+ true,
+ true,
+ true,
+ true,
+ true,
+ true,
+ false,
+ "arm_bfloat_half"
+ };
+
\f
/* A synthetic "format" for internal arithmetic. It's the size of the
internal significand minus the two bits needed for proper rounding.
real_convert (r, fmt, r);
}
+/* Return true (including 0) if integer part of R is even, else return
+ false. The function is not valid for rvc_inf and rvc_nan classes. */
+
+static bool
+is_even (REAL_VALUE_TYPE *r)
+{
+ gcc_assert (r->cl != rvc_inf);
+ gcc_assert (r->cl != rvc_nan);
+
+ if (r->cl == rvc_zero)
+ return true;
+
+ /* For (-1,1), number is even. */
+ if (REAL_EXP (r) <= 0)
+ return true;
+
+ /* Check lowest bit, if not set, return true. */
+ else if (REAL_EXP (r) <= SIGNIFICAND_BITS)
+ {
+ unsigned int n = SIGNIFICAND_BITS - REAL_EXP (r);
+ int w = n / HOST_BITS_PER_LONG;
+
+ unsigned long num = ((unsigned long)1 << (n % HOST_BITS_PER_LONG));
+
+ if ((r->sig[w] & num) == 0)
+ return true;
+ }
+ else
+ return true;
+
+ return false;
+}
+
+/* Return true if R is halfway between two integers, else return
+ false. */
+
+static bool
+is_halfway_below (const REAL_VALUE_TYPE *r)
+{
+ if (r->cl != rvc_normal)
+ return false;
+
+ /* For numbers (-0.5,0) and (0,0.5). */
+ if (REAL_EXP (r) < 0)
+ return false;
+
+ else if (REAL_EXP (r) < SIGNIFICAND_BITS)
+ {
+ unsigned int n = SIGNIFICAND_BITS - REAL_EXP (r) - 1;
+ int w = n / HOST_BITS_PER_LONG;
+
+ for (int i = 0; i < w; ++i)
+ if (r->sig[i] != 0)
+ return false;
+
+ unsigned long num = 1UL << (n % HOST_BITS_PER_LONG);
+
+ if ((r->sig[w] & num) != 0 && (r->sig[w] & (num - 1)) == 0)
+ return true;
+ }
+ return false;
+}
+
+/* Round X to nearest integer, rounding halfway cases towards even. */
+
+void
+real_roundeven (REAL_VALUE_TYPE *r, format_helper fmt,
+ const REAL_VALUE_TYPE *x)
+{
+ if (is_halfway_below (x))
+ {
+ /* Special case as -0.5 rounds to -0.0 and
+ similarly +0.5 rounds to +0.0. */
+ if (REAL_EXP (x) == 0)
+ {
+ *r = *x;
+ clear_significand_below (r, SIGNIFICAND_BITS);
+ }
+ else
+ {
+ do_add (r, x, &dconsthalf, x->sign);
+ if (!is_even (r))
+ do_add (r, r, &dconstm1, x->sign);
+ }
+ if (fmt)
+ real_convert (r, fmt, r);
+ }
+ else
+ real_round (r, fmt, x);
+}
+
/* Set the sign of R to the sign of X. */
void
/* 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;
*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
mpfr_inits (mpfr_const1, mpfr_c, mpfr_maxval, NULL);
- mpfr_from_real (mpfr_const1, &dconst1, GMP_RNDN);
- mpfr_from_real (mpfr_maxval, &maxval, GMP_RNDN);
+ mpfr_from_real (mpfr_const1, &dconst1, MPFR_RNDN);
+ mpfr_from_real (mpfr_maxval, &maxval, MPFR_RNDN);
- mpfr_sub (mpfr_c, mpfr_maxval, mpfr_const1, GMP_RNDN);
- mpfr_sqrt (mpfr_c, mpfr_c, GMP_RNDZ);
+ mpfr_sub (mpfr_c, mpfr_maxval, mpfr_const1, MPFR_RNDN);
+ mpfr_sqrt (mpfr_c, mpfr_c, MPFR_RNDZ);
- real_from_mpfr (r, mpfr_c, fmt, GMP_RNDZ);
+ real_from_mpfr (r, mpfr_c, fmt, MPFR_RNDZ);
mpfr_clears (mpfr_const1, mpfr_c, mpfr_maxval, NULL);
}
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