57b08b0944
to reflect the new license. These used slightly different spellings that defeated my regular expressions. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351648
115 lines
3.6 KiB
C
115 lines
3.6 KiB
C
/*===-- floatdidf.c - Implement __floatdidf -------------------------------===
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*
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* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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* See https://llvm.org/LICENSE.txt for license information.
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* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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*
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*===----------------------------------------------------------------------===
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*
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* This file implements __floatdidf for the compiler_rt library.
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*
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*===----------------------------------------------------------------------===
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*/
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#include "int_lib.h"
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/* Returns: convert a to a double, rounding toward even. */
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/* Assumption: double is a IEEE 64 bit floating point type
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* di_int is a 64 bit integral type
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*/
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/* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */
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#ifndef __SOFT_FP__
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/* Support for systems that have hardware floating-point; we'll set the inexact flag
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* as a side-effect of this computation.
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*/
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COMPILER_RT_ABI double
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__floatdidf(di_int a)
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{
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static const double twop52 = 4503599627370496.0; // 0x1.0p52
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static const double twop32 = 4294967296.0; // 0x1.0p32
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union { int64_t x; double d; } low = { .d = twop52 };
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const double high = (int32_t)(a >> 32) * twop32;
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low.x |= a & INT64_C(0x00000000ffffffff);
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const double result = (high - twop52) + low.d;
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return result;
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}
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#else
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/* Support for systems that don't have hardware floating-point; there are no flags to
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* set, and we don't want to code-gen to an unknown soft-float implementation.
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*/
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COMPILER_RT_ABI double
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__floatdidf(di_int a)
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{
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if (a == 0)
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return 0.0;
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const unsigned N = sizeof(di_int) * CHAR_BIT;
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const di_int s = a >> (N-1);
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a = (a ^ s) - s;
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int sd = N - __builtin_clzll(a); /* number of significant digits */
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int e = sd - 1; /* exponent */
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if (sd > DBL_MANT_DIG)
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{
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/* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
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* finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
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* 12345678901234567890123456
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* 1 = msb 1 bit
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* P = bit DBL_MANT_DIG-1 bits to the right of 1
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* Q = bit DBL_MANT_DIG bits to the right of 1
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* R = "or" of all bits to the right of Q
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*/
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switch (sd)
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{
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case DBL_MANT_DIG + 1:
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a <<= 1;
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break;
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case DBL_MANT_DIG + 2:
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break;
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default:
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a = ((du_int)a >> (sd - (DBL_MANT_DIG+2))) |
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((a & ((du_int)(-1) >> ((N + DBL_MANT_DIG+2) - sd))) != 0);
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};
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/* finish: */
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a |= (a & 4) != 0; /* Or P into R */
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++a; /* round - this step may add a significant bit */
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a >>= 2; /* dump Q and R */
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/* a is now rounded to DBL_MANT_DIG or DBL_MANT_DIG+1 bits */
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if (a & ((du_int)1 << DBL_MANT_DIG))
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{
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a >>= 1;
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++e;
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}
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/* a is now rounded to DBL_MANT_DIG bits */
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}
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else
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{
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a <<= (DBL_MANT_DIG - sd);
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/* a is now rounded to DBL_MANT_DIG bits */
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}
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double_bits fb;
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fb.u.s.high = ((su_int)s & 0x80000000) | /* sign */
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((e + 1023) << 20) | /* exponent */
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((su_int)(a >> 32) & 0x000FFFFF); /* mantissa-high */
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fb.u.s.low = (su_int)a; /* mantissa-low */
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return fb.f;
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}
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#endif
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#if defined(__ARM_EABI__)
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#if defined(COMPILER_RT_ARMHF_TARGET)
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AEABI_RTABI double __aeabi_l2d(di_int a) {
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return __floatdidf(a);
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}
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#else
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AEABI_RTABI double __aeabi_l2d(di_int a) COMPILER_RT_ALIAS(__floatdidf);
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#endif
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#endif
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