diff options
Diffstat (limited to 'lib/builtins/floattitf.c')
| -rw-r--r-- | lib/builtins/floattitf.c | 112 |
1 files changed, 54 insertions, 58 deletions
diff --git a/lib/builtins/floattitf.c b/lib/builtins/floattitf.c index 994fded3947be..196cbdae14e02 100644 --- a/lib/builtins/floattitf.c +++ b/lib/builtins/floattitf.c @@ -1,9 +1,8 @@ //===-- lib/floattitf.c - int128 -> quad-precision conversion -----*- C -*-===// // -// 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. +// 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 // //===----------------------------------------------------------------------===// // @@ -17,66 +16,63 @@ #include "fp_lib.h" #include "int_lib.h" -/* Returns: convert a ti_int to a fp_t, rounding toward even. */ +// Returns: convert a ti_int to a fp_t, rounding toward even. -/* Assumption: fp_t is a IEEE 128 bit floating point type - * ti_int is a 128 bit integral type - */ +// Assumption: fp_t is a IEEE 128 bit floating point type +// ti_int is a 128 bit integral type -/* seee eeee eeee eeee mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | - * mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm - */ +// seee eeee eeee eeee mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm +// mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm +// mmmm mmmm mmmm #if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT) -COMPILER_RT_ABI fp_t -__floattitf(ti_int a) { - if (a == 0) - return 0.0; - const unsigned N = sizeof(ti_int) * CHAR_BIT; - const ti_int s = a >> (N-1); - a = (a ^ s) - s; - int sd = N - __clzti2(a); /* number of significant digits */ - int e = sd - 1; /* exponent */ - if (sd > LDBL_MANT_DIG) { - /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx - * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR - * 12345678901234567890123456 - * 1 = msb 1 bit - * P = bit LDBL_MANT_DIG-1 bits to the right of 1 - * Q = bit LDBL_MANT_DIG bits to the right of 1 - * R = "or" of all bits to the right of Q - */ - switch (sd) { - case LDBL_MANT_DIG + 1: - a <<= 1; - break; - case LDBL_MANT_DIG + 2: - break; - default: - a = ((tu_int)a >> (sd - (LDBL_MANT_DIG+2))) | - ((a & ((tu_int)(-1) >> ((N + LDBL_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 LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits */ - if (a & ((tu_int)1 << LDBL_MANT_DIG)) { - a >>= 1; - ++e; - } - /* a is now rounded to LDBL_MANT_DIG bits */ - } else { - a <<= (LDBL_MANT_DIG - sd); - /* a is now rounded to LDBL_MANT_DIG bits */ +COMPILER_RT_ABI fp_t __floattitf(ti_int a) { + if (a == 0) + return 0.0; + const unsigned N = sizeof(ti_int) * CHAR_BIT; + const ti_int s = a >> (N - 1); + a = (a ^ s) - s; + int sd = N - __clzti2(a); // number of significant digits + int e = sd - 1; // exponent + if (sd > LDBL_MANT_DIG) { + // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx + // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR + // 12345678901234567890123456 + // 1 = msb 1 bit + // P = bit LDBL_MANT_DIG-1 bits to the right of 1 + // Q = bit LDBL_MANT_DIG bits to the right of 1 + // R = "or" of all bits to the right of Q + switch (sd) { + case LDBL_MANT_DIG + 1: + a <<= 1; + break; + case LDBL_MANT_DIG + 2: + break; + default: + a = ((tu_int)a >> (sd - (LDBL_MANT_DIG + 2))) | + ((a & ((tu_int)(-1) >> ((N + LDBL_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 LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits + if (a & ((tu_int)1 << LDBL_MANT_DIG)) { + a >>= 1; + ++e; } + // a is now rounded to LDBL_MANT_DIG bits + } else { + a <<= (LDBL_MANT_DIG - sd); + // a is now rounded to LDBL_MANT_DIG bits + } - long_double_bits fb; - fb.u.high.all = (s & 0x8000000000000000LL) /* sign */ - | (du_int)(e + 16383) << 48 /* exponent */ - | ((a >> 64) & 0x0000ffffffffffffLL); /* significand */ - fb.u.low.all = (du_int)(a); - return fb.f; + long_double_bits fb; + fb.u.high.all = (s & 0x8000000000000000LL) // sign + | (du_int)(e + 16383) << 48 // exponent + | ((a >> 64) & 0x0000ffffffffffffLL); // significand + fb.u.low.all = (du_int)(a); + return fb.f; } #endif |