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/* -----------------------------------------------------------------------------
*
* (c) Lennart Augustsson
* (c) The GHC Team, 1998-2000
*
* Miscellaneous support for floating-point primitives
*
* ---------------------------------------------------------------------------*/
#include "rts/PosixSource.h"
#include "Rts.h"
#include "StgPrimFloat.h"
#include <math.h>
#include <float.h>
#include <limits.h>
#define IEEE_FLOATING_POINT 1
#if FLT_RADIX != 2
# error FLT_RADIX != 2 not supported
#endif
/*
* 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)))
/** #15271: Some large ratios are converted into double incorrectly.
* This occurs when StgInt has 64 bits and C int has 32 bits, where wrapping
* occurs and an incorrect signed value is passed into ldexp */
STATIC_INLINE int
truncExponent(I_ e)
{
#if INT_MAX < STG_INT_MAX
if (RTS_UNLIKELY(e > INT_MAX))
e = INT_MAX;
#endif
#if INT_MIN > STG_INT_MIN
if (RTS_UNLIKELY(e < INT_MIN))
e = INT_MIN;
#endif
return e;
}
/* 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, truncExponent(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, truncExponent(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, truncExponent(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, truncExponent(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;
}
}
/* This is expected to replace uses of __decodeDouble_2Int() in the long run */
StgInt
__decodeDouble_Int64 (StgInt64 *const mantissa, const StgDouble dbl)
{
#if 0
// We can't use this yet as-is, see ticket #9810
if (dbl) {
int exp = 0;
*mantissa = (StgInt64)scalbn(frexp(dbl, &exp), DBL_MANT_DIG);
return exp-DBL_MANT_DIG;
} else {
*mantissa = 0;
return 0;
}
#else
I_ man_sign = 0;
W_ man_high = 0, man_low = 0;
I_ exp = 0;
__decodeDouble_2Int (&man_sign, &man_high, &man_low, &exp, dbl);
ASSIGN_Int64((W_*)mantissa, ((((StgInt64)man_high << 32)
| (StgInt64)man_low)
* (StgInt64)man_sign));
return exp;
#endif
}
/* 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;
}
}
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