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/* -----------------------------------------------------------------------------
*
* (c) Lennart Augustsson
* (c) The GHC Team, 1998-2000
*
* Miscellaneous support for floating-point primitives
*
* ---------------------------------------------------------------------------*/
#include "PosixSource.h"
#include "Rts.h"
#include "StgPrimFloat.h"
#include <math.h>
#include <float.h>
#define IEEE_FLOATING_POINT 1
/*
* Encoding and decoding Doubles. Code based on the HBC code
* (lib/fltcode.c).
*/
#if IEEE_FLOATING_POINT
#define MY_DMINEXP ((DBL_MIN_EXP) - (DBL_MANT_DIG) - 1)
/* DMINEXP is defined in values.h on Linux (for example) */
#define DHIGHBIT 0x00100000
#define DMSBIT 0x80000000
#define MY_FMINEXP ((FLT_MIN_EXP) - (FLT_MANT_DIG) - 1)
#define FHIGHBIT 0x00800000
#define FMSBIT 0x80000000
#endif
#if defined(WORDS_BIGENDIAN) || defined(FLOAT_WORDS_BIGENDIAN)
#define L 1
#define H 0
#else
#define L 0
#define H 1
#endif
#define __abs(a) (( (a) >= 0 ) ? (a) : (-(a)))
/* Special version for words */
StgDouble
__word_encodeDouble (W_ j, I_ e)
{
StgDouble r;
r = (StgDouble)j;
/* Now raise to the exponent */
if ( r != 0.0 ) /* Lennart suggests this avoids a bug in MIPS's ldexp */
r = ldexp(r, e);
return r;
}
/* Special version for small Integers */
StgDouble
__int_encodeDouble (I_ j, I_ e)
{
StgDouble r;
r = (StgDouble)__abs(j);
/* Now raise to the exponent */
if ( r != 0.0 ) /* Lennart suggests this avoids a bug in MIPS's ldexp */
r = ldexp(r, e);
/* sign is encoded in the size */
if (j < 0)
r = -r;
return r;
}
/* Special version for small Integers */
StgFloat
__int_encodeFloat (I_ j, I_ e)
{
StgFloat r;
r = (StgFloat)__abs(j);
/* Now raise to the exponent */
if ( r != 0.0 ) /* Lennart suggests this avoids a bug in MIPS's ldexp */
r = ldexp(r, e);
/* sign is encoded in the size */
if (j < 0)
r = -r;
return r;
}
/* Special version for small positive Integers */
StgFloat
__word_encodeFloat (W_ j, I_ e)
{
StgFloat r;
r = (StgFloat)j;
/* Now raise to the exponent */
if ( r != 0.0 ) /* Lennart suggests this avoids a bug in MIPS's ldexp */
r = ldexp(r, e);
return r;
}
/* This only supports IEEE floating point */
void
__decodeDouble_2Int (I_ *man_sign, W_ *man_high, W_ *man_low, I_ *exp, StgDouble dbl)
{
/* Do some bit fiddling on IEEE */
unsigned int low, high; /* assuming 32 bit ints */
int sign, iexp;
union { double d; unsigned int i[2]; } u; /* assuming 32 bit ints, 64 bit double */
ASSERT(sizeof(unsigned int ) == 4 );
ASSERT(sizeof(dbl ) == 8 );
ASSERT(sizeof(dbl ) == SIZEOF_DOUBLE);
u.d = dbl; /* grab chunks of the double */
low = u.i[L];
high = u.i[H];
if (low == 0 && (high & ~DMSBIT) == 0) {
*man_low = 0;
*man_high = 0;
*exp = 0L;
} else {
iexp = ((high >> 20) & 0x7ff) + MY_DMINEXP;
sign = high;
high &= DHIGHBIT-1;
if (iexp != MY_DMINEXP) /* don't add hidden bit to denorms */
high |= DHIGHBIT;
else {
iexp++;
/* A denorm, normalize the mantissa */
while (! (high & DHIGHBIT)) {
high <<= 1;
if (low & DMSBIT)
high++;
low <<= 1;
iexp--;
}
}
*exp = (I_) iexp;
*man_low = low;
*man_high = high;
*man_sign = (sign < 0) ? -1 : 1;
}
}
/* Convenient union types for checking the layout of IEEE 754 types -
based on defs in GNU libc <ieee754.h>
*/
void
__decodeFloat_Int (I_ *man, I_ *exp, StgFloat flt)
{
/* Do some bit fiddling on IEEE */
int high, sign; /* assuming 32 bit ints */
union { float f; int i; } u; /* assuming 32 bit float and int */
ASSERT(sizeof(int ) == 4 );
ASSERT(sizeof(flt ) == 4 );
ASSERT(sizeof(flt ) == SIZEOF_FLOAT );
u.f = flt; /* grab the float */
high = u.i;
if ((high & ~FMSBIT) == 0) {
*man = 0;
*exp = 0;
} else {
*exp = ((high >> 23) & 0xff) + MY_FMINEXP;
sign = high;
high &= FHIGHBIT-1;
if (*exp != MY_FMINEXP) /* don't add hidden bit to denorms */
high |= FHIGHBIT;
else {
(*exp)++;
/* A denorm, normalize the mantissa */
while (! (high & FHIGHBIT)) {
high <<= 1;
(*exp)--;
}
}
*man = high;
if (sign < 0)
*man = - *man;
}
}
// Local Variables:
// mode: C
// fill-column: 80
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// End:
|
