forked from OSchip/llvm-project
116 lines
3.6 KiB
C
116 lines
3.6 KiB
C
/*===-- floatdidf.c - Implement __floatdidf -------------------------------===
|
|
*
|
|
* The LLVM Compiler Infrastructure
|
|
*
|
|
* This file is dual licensed under the MIT and the University of Illinois Open
|
|
* Source Licenses. See LICENSE.TXT for details.
|
|
*
|
|
*===----------------------------------------------------------------------===
|
|
*
|
|
* This file implements __floatdidf for the compiler_rt library.
|
|
*
|
|
*===----------------------------------------------------------------------===
|
|
*/
|
|
|
|
#include "int_lib.h"
|
|
|
|
/* Returns: convert a to a double, rounding toward even. */
|
|
|
|
/* Assumption: double is a IEEE 64 bit floating point type
|
|
* di_int is a 64 bit integral type
|
|
*/
|
|
|
|
/* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */
|
|
|
|
#ifndef __SOFT_FP__
|
|
/* Support for systems that have hardware floating-point; we'll set the inexact flag
|
|
* as a side-effect of this computation.
|
|
*/
|
|
|
|
COMPILER_RT_ABI double
|
|
__floatdidf(di_int a)
|
|
{
|
|
static const double twop52 = 4503599627370496.0; // 0x1.0p52
|
|
static const double twop32 = 4294967296.0; // 0x1.0p32
|
|
|
|
union { int64_t x; double d; } low = { .d = twop52 };
|
|
|
|
const double high = (int32_t)(a >> 32) * twop32;
|
|
low.x |= a & INT64_C(0x00000000ffffffff);
|
|
|
|
const double result = (high - twop52) + low.d;
|
|
return result;
|
|
}
|
|
|
|
#else
|
|
/* Support for systems that don't have hardware floating-point; there are no flags to
|
|
* set, and we don't want to code-gen to an unknown soft-float implementation.
|
|
*/
|
|
|
|
COMPILER_RT_ABI double
|
|
__floatdidf(di_int a)
|
|
{
|
|
if (a == 0)
|
|
return 0.0;
|
|
const unsigned N = sizeof(di_int) * CHAR_BIT;
|
|
const di_int s = a >> (N-1);
|
|
a = (a ^ s) - s;
|
|
int sd = N - __builtin_clzll(a); /* number of significant digits */
|
|
int e = sd - 1; /* exponent */
|
|
if (sd > DBL_MANT_DIG)
|
|
{
|
|
/* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
|
|
* finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
|
|
* 12345678901234567890123456
|
|
* 1 = msb 1 bit
|
|
* P = bit DBL_MANT_DIG-1 bits to the right of 1
|
|
* Q = bit DBL_MANT_DIG bits to the right of 1
|
|
* R = "or" of all bits to the right of Q
|
|
*/
|
|
switch (sd)
|
|
{
|
|
case DBL_MANT_DIG + 1:
|
|
a <<= 1;
|
|
break;
|
|
case DBL_MANT_DIG + 2:
|
|
break;
|
|
default:
|
|
a = ((du_int)a >> (sd - (DBL_MANT_DIG+2))) |
|
|
((a & ((du_int)(-1) >> ((N + DBL_MANT_DIG+2) - sd))) != 0);
|
|
};
|
|
/* finish: */
|
|
a |= (a & 4) != 0; /* Or P into R */
|
|
++a; /* round - this step may add a significant bit */
|
|
a >>= 2; /* dump Q and R */
|
|
/* a is now rounded to DBL_MANT_DIG or DBL_MANT_DIG+1 bits */
|
|
if (a & ((du_int)1 << DBL_MANT_DIG))
|
|
{
|
|
a >>= 1;
|
|
++e;
|
|
}
|
|
/* a is now rounded to DBL_MANT_DIG bits */
|
|
}
|
|
else
|
|
{
|
|
a <<= (DBL_MANT_DIG - sd);
|
|
/* a is now rounded to DBL_MANT_DIG bits */
|
|
}
|
|
double_bits fb;
|
|
fb.u.s.high = ((su_int)s & 0x80000000) | /* sign */
|
|
((e + 1023) << 20) | /* exponent */
|
|
((su_int)(a >> 32) & 0x000FFFFF); /* mantissa-high */
|
|
fb.u.s.low = (su_int)a; /* mantissa-low */
|
|
return fb.f;
|
|
}
|
|
#endif
|
|
|
|
#if defined(__ARM_EABI__)
|
|
#if defined(COMPILER_RT_ARMHF_TARGET)
|
|
AEABI_RTABI double __aeabi_l2d(di_int a) {
|
|
return __floatdidf(a);
|
|
}
|
|
#else
|
|
AEABI_RTABI double __aeabi_l2d(di_int a) COMPILER_RT_ALIAS(__floatdidf);
|
|
#endif
|
|
#endif
|