| //===-- floattixf.c - Implement __floattixf -------------------------------===// |
| // |
| // 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 __floattixf for the compiler_rt library. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "int_lib.h" |
| |
| #ifdef CRT_HAS_128BIT |
| |
| // Returns: convert a to a long double, rounding toward even. |
| |
| // Assumption: long double is a IEEE 80 bit floating point type padded to 128 |
| // bits ti_int is a 128 bit integral type |
| |
| // gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee |
| // eeee | 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm |
| // mmmm mmmm mmmm |
| |
| COMPILER_RT_ABI long double __floattixf(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.s.low = ((su_int)s & 0x8000) | // sign |
| (e + 16383); // exponent |
| fb.u.low.all = (du_int)a; // mantissa |
| return fb.f; |
| } |
| |
| #endif // CRT_HAS_128BIT |