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
79 lines
2.8 KiB
C
79 lines
2.8 KiB
C
//===-- lib/floatuntitf.c - uint128 -> quad-precision conversion --*- C -*-===//
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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 tu_int to quad-precision conversion for the
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// compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
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// mode.
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//
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//===----------------------------------------------------------------------===//
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#define QUAD_PRECISION
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#include "fp_lib.h"
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#include "int_lib.h"
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/* Returns: convert a tu_int to a fp_t, rounding toward even. */
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/* Assumption: fp_t is a IEEE 128 bit floating point type
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* tu_int is a 128 bit integral type
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*/
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/* seee eeee eeee eeee mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm |
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* mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm
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*/
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#if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
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COMPILER_RT_ABI fp_t
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__floatuntitf(tu_int a) {
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if (a == 0)
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return 0.0;
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const unsigned N = sizeof(tu_int) * CHAR_BIT;
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int sd = N - __clzti2(a); /* number of significant digits */
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int e = sd - 1; /* exponent */
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if (sd > LDBL_MANT_DIG) {
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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 LDBL_MANT_DIG-1 bits to the right of 1
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* Q = bit LDBL_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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case LDBL_MANT_DIG + 1:
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a <<= 1;
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break;
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case LDBL_MANT_DIG + 2:
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break;
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default:
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a = (a >> (sd - (LDBL_MANT_DIG+2))) |
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((a & ((tu_int)(-1) >> ((N + LDBL_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 LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits */
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if (a & ((tu_int)1 << LDBL_MANT_DIG)) {
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a >>= 1;
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++e;
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}
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/* a is now rounded to LDBL_MANT_DIG bits */
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} else {
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a <<= (LDBL_MANT_DIG - sd);
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/* a is now rounded to LDBL_MANT_DIG bits */
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}
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long_double_bits fb;
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fb.u.high.all = (du_int)(e + 16383) << 48 /* exponent */
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| ((a >> 64) & 0x0000ffffffffffffLL); /* significand */
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fb.u.low.all = (du_int)(a);
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return fb.f;
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}
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#endif
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