/* real.c - software floating point emulation.
Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999,
- 2000, 2002, 2003, 2004, 2005, 2007 Free Software Foundation, Inc.
+ 2000, 2002, 2003, 2004, 2005, 2007, 2008 Free Software Foundation, Inc.
Contributed by Stephen L. Moshier (moshier@world.std.com).
Re-written by Richard Henderson <rth@redhat.com>
false
};
\f
-/* The "twos-complement" c4x format is officially defined as
-
- x = s(~s).f * 2**e
-
- This is rather misleading. One must remember that F is signed.
- A better description would be
-
- x = -1**s * ((s + 1 + .f) * 2**e
-
- So if we have a (4 bit) fraction of .1000 with a sign bit of 1,
- that's -1 * (1+1+(-.5)) == -1.5. I think.
-
- The constructions here are taken from Tables 5-1 and 5-2 of the
- TMS320C4x User's Guide wherein step-by-step instructions for
- conversion from IEEE are presented. That's close enough to our
- internal representation so as to make things easy.
-
- See http://www-s.ti.com/sc/psheets/spru063c/spru063c.pdf */
-
-static void encode_c4x_single (const struct real_format *fmt,
- long *, const REAL_VALUE_TYPE *);
-static void decode_c4x_single (const struct real_format *,
- REAL_VALUE_TYPE *, const long *);
-static void encode_c4x_extended (const struct real_format *fmt,
- long *, const REAL_VALUE_TYPE *);
-static void decode_c4x_extended (const struct real_format *,
- REAL_VALUE_TYPE *, const long *);
-
-static void
-encode_c4x_single (const struct real_format *fmt ATTRIBUTE_UNUSED,
- long *buf, const REAL_VALUE_TYPE *r)
-{
- unsigned long image, exp, sig;
-
- switch (r->cl)
- {
- case rvc_zero:
- exp = -128;
- sig = 0;
- break;
-
- case rvc_inf:
- case rvc_nan:
- exp = 127;
- sig = 0x800000 - r->sign;
- break;
-
- case rvc_normal:
- exp = REAL_EXP (r) - 1;
- sig = (r->sig[SIGSZ-1] >> (HOST_BITS_PER_LONG - 24)) & 0x7fffff;
- if (r->sign)
- {
- if (sig)
- sig = -sig;
- else
- exp--;
- sig |= 0x800000;
- }
- break;
-
- default:
- gcc_unreachable ();
- }
-
- image = ((exp & 0xff) << 24) | (sig & 0xffffff);
- buf[0] = image;
-}
-
-static void
-decode_c4x_single (const struct real_format *fmt ATTRIBUTE_UNUSED,
- REAL_VALUE_TYPE *r, const long *buf)
-{
- unsigned long image = buf[0];
- unsigned long sig;
- int exp, sf;
-
- exp = (((image >> 24) & 0xff) ^ 0x80) - 0x80;
- sf = ((image & 0xffffff) ^ 0x800000) - 0x800000;
-
- memset (r, 0, sizeof (*r));
-
- if (exp != -128)
- {
- r->cl = rvc_normal;
-
- sig = sf & 0x7fffff;
- if (sf < 0)
- {
- r->sign = 1;
- if (sig)
- sig = -sig;
- else
- exp++;
- }
- sig = (sig << (HOST_BITS_PER_LONG - 24)) | SIG_MSB;
-
- SET_REAL_EXP (r, exp + 1);
- r->sig[SIGSZ-1] = sig;
- }
-}
-
-static void
-encode_c4x_extended (const struct real_format *fmt ATTRIBUTE_UNUSED,
- long *buf, const REAL_VALUE_TYPE *r)
-{
- unsigned long exp, sig;
-
- switch (r->cl)
- {
- case rvc_zero:
- exp = -128;
- sig = 0;
- break;
-
- case rvc_inf:
- case rvc_nan:
- exp = 127;
- sig = 0x80000000 - r->sign;
- break;
-
- case rvc_normal:
- exp = REAL_EXP (r) - 1;
-
- sig = r->sig[SIGSZ-1];
- if (HOST_BITS_PER_LONG == 64)
- sig = sig >> 1 >> 31;
- sig &= 0x7fffffff;
-
- if (r->sign)
- {
- if (sig)
- sig = -sig;
- else
- exp--;
- sig |= 0x80000000;
- }
- break;
-
- default:
- gcc_unreachable ();
- }
-
- exp = (exp & 0xff) << 24;
- sig &= 0xffffffff;
-
- if (FLOAT_WORDS_BIG_ENDIAN)
- buf[0] = exp, buf[1] = sig;
- else
- buf[0] = sig, buf[0] = exp;
-}
-
-static void
-decode_c4x_extended (const struct real_format *fmt ATTRIBUTE_UNUSED,
- REAL_VALUE_TYPE *r, const long *buf)
-{
- unsigned long sig;
- int exp, sf;
-
- if (FLOAT_WORDS_BIG_ENDIAN)
- exp = buf[0], sf = buf[1];
- else
- sf = buf[0], exp = buf[1];
-
- exp = (((exp >> 24) & 0xff) & 0x80) - 0x80;
- sf = ((sf & 0xffffffff) ^ 0x80000000) - 0x80000000;
-
- memset (r, 0, sizeof (*r));
-
- if (exp != -128)
- {
- r->cl = rvc_normal;
-
- sig = sf & 0x7fffffff;
- if (sf < 0)
- {
- r->sign = 1;
- if (sig)
- sig = -sig;
- else
- exp++;
- }
- if (HOST_BITS_PER_LONG == 64)
- sig = sig << 1 << 31;
- sig |= SIG_MSB;
-
- SET_REAL_EXP (r, exp + 1);
- r->sig[SIGSZ-1] = sig;
- }
-}
-
-const struct real_format c4x_single_format =
- {
- encode_c4x_single,
- decode_c4x_single,
- 2,
- 24,
- 24,
- -126,
- 128,
- 23,
- -1,
- false,
- false,
- false,
- false,
- false,
- false
- };
-
-const struct real_format c4x_extended_format =
- {
- encode_c4x_extended,
- decode_c4x_extended,
- 2,
- 32,
- 32,
- -126,
- 128,
- 31,
- -1,
- false,
- false,
- false,
- false,
- false,
- false
- };
-
-\f
/* A synthetic "format" for internal arithmetic. It's the size of the
internal significand minus the two bits needed for proper rounding.
The encode and decode routines exist only to satisfy our paranoia
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