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1//===-- floattixf.c - Implement __floattixf -------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file implements __floattixf for the compiler_rt library.10//11//===----------------------------------------------------------------------===//12 13#include "int_lib.h"14 15#ifdef CRT_HAS_128BIT16 17// Returns: convert a to a long double, rounding toward even.18 19// Assumption: long double is a IEEE 80 bit floating point type padded to 12820// bits ti_int is a 128 bit integral type21 22// gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee23// eeee | 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm24// mmmm mmmm mmmm25 26COMPILER_RT_ABI xf_float __floattixf(ti_int a) {27 if (a == 0)28 return 0.0;29 const unsigned N = sizeof(ti_int) * CHAR_BIT;30 const ti_int s = a >> (N - 1);31 a = (a ^ s) - s;32 int sd = N - __clzti2(a); // number of significant digits33 int e = sd - 1; // exponent34 if (sd > LDBL_MANT_DIG) {35 // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx36 // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR37 // 1234567890123456789012345638 // 1 = msb 1 bit39 // P = bit LDBL_MANT_DIG-1 bits to the right of 140 // Q = bit LDBL_MANT_DIG bits to the right of 141 // R = "or" of all bits to the right of Q42 switch (sd) {43 case LDBL_MANT_DIG + 1:44 a <<= 1;45 break;46 case LDBL_MANT_DIG + 2:47 break;48 default:49 a = ((tu_int)a >> (sd - (LDBL_MANT_DIG + 2))) |50 ((a & ((tu_int)(-1) >> ((N + LDBL_MANT_DIG + 2) - sd))) != 0);51 };52 // finish:53 a |= (a & 4) != 0; // Or P into R54 ++a; // round - this step may add a significant bit55 a >>= 2; // dump Q and R56 // a is now rounded to LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits57 if (a & ((tu_int)1 << LDBL_MANT_DIG)) {58 a >>= 1;59 ++e;60 }61 // a is now rounded to LDBL_MANT_DIG bits62 } else {63 a <<= (LDBL_MANT_DIG - sd);64 // a is now rounded to LDBL_MANT_DIG bits65 }66 xf_bits fb;67 fb.u.high.s.low = ((su_int)s & 0x8000) | // sign68 (e + 16383); // exponent69 fb.u.low.all = (du_int)a; // mantissa70 return fb.f;71}72 73#endif // CRT_HAS_128BIT74