diff options
Diffstat (limited to 'lib/builtins/floatuntidf.c')
| -rw-r--r-- | lib/builtins/floatuntidf.c | 128 |
1 files changed, 59 insertions, 69 deletions
diff --git a/lib/builtins/floatuntidf.c b/lib/builtins/floatuntidf.c index 960265d80..e69e65c1a 100644 --- a/lib/builtins/floatuntidf.c +++ b/lib/builtins/floatuntidf.c @@ -1,80 +1,70 @@ -/* ===-- floatuntidf.c - Implement __floatuntidf ---------------------------=== - * - * 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 __floatuntidf for the compiler_rt library. - * - * ===----------------------------------------------------------------------=== - */ +//===-- floatuntidf.c - Implement __floatuntidf ---------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file implements __floatuntidf for the compiler_rt library. +// +//===----------------------------------------------------------------------===// #include "int_lib.h" #ifdef CRT_HAS_128BIT -/* Returns: convert a to a double, rounding toward even. */ +// Returns: convert a to a double, rounding toward even. -/* Assumption: double is a IEEE 64 bit floating point type - * tu_int is a 128 bit integral type - */ +// Assumption: double is a IEEE 64 bit floating point type +// tu_int is a 128 bit integral type -/* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */ +// seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm +// mmmm -COMPILER_RT_ABI double -__floatuntidf(tu_int a) -{ - if (a == 0) - return 0.0; - const unsigned N = sizeof(tu_int) * CHAR_BIT; - int sd = N - __clzti2(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 = (a >> (sd - (DBL_MANT_DIG+2))) | - ((a & ((tu_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 & ((tu_int)1 << DBL_MANT_DIG)) - { - a >>= 1; - ++e; - } - /* a is now rounded to DBL_MANT_DIG bits */ +COMPILER_RT_ABI double __floatuntidf(tu_int a) { + if (a == 0) + return 0.0; + const unsigned N = sizeof(tu_int) * CHAR_BIT; + int sd = N - __clzti2(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 = (a >> (sd - (DBL_MANT_DIG + 2))) | + ((a & ((tu_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 & ((tu_int)1 << DBL_MANT_DIG)) { + a >>= 1; + ++e; } - else - { - a <<= (DBL_MANT_DIG - sd); - /* a is now rounded to DBL_MANT_DIG bits */ - } - double_bits fb; - fb.u.s.high = ((e + 1023) << 20) | /* exponent */ - ((su_int)(a >> 32) & 0x000FFFFF); /* mantissa-high */ - fb.u.s.low = (su_int)a; /* mantissa-low */ - return fb.f; + // 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 = ((e + 1023) << 20) | // exponent + ((su_int)(a >> 32) & 0x000FFFFF); // mantissa-high + fb.u.s.low = (su_int)a; // mantissa-low + return fb.f; } -#endif /* CRT_HAS_128BIT */ +#endif // CRT_HAS_128BIT |