10b57cec5SDimitry Andric //===-- floattixf.c - Implement __floattixf -------------------------------===// 20b57cec5SDimitry Andric // 30b57cec5SDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 40b57cec5SDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 50b57cec5SDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 60b57cec5SDimitry Andric // 70b57cec5SDimitry Andric //===----------------------------------------------------------------------===// 80b57cec5SDimitry Andric // 90b57cec5SDimitry Andric // This file implements __floattixf for the compiler_rt library. 100b57cec5SDimitry Andric // 110b57cec5SDimitry Andric //===----------------------------------------------------------------------===// 120b57cec5SDimitry Andric 130b57cec5SDimitry Andric #include "int_lib.h" 140b57cec5SDimitry Andric 150b57cec5SDimitry Andric #ifdef CRT_HAS_128BIT 160b57cec5SDimitry Andric 170b57cec5SDimitry Andric // Returns: convert a to a long double, rounding toward even. 180b57cec5SDimitry Andric 190b57cec5SDimitry Andric // Assumption: long double is a IEEE 80 bit floating point type padded to 128 200b57cec5SDimitry Andric // bits ti_int is a 128 bit integral type 210b57cec5SDimitry Andric 220b57cec5SDimitry Andric // gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee 230b57cec5SDimitry Andric // eeee | 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm 240b57cec5SDimitry Andric // mmmm mmmm mmmm 250b57cec5SDimitry Andric 26*5f757f3fSDimitry Andric COMPILER_RT_ABI xf_float __floattixf(ti_int a) { 270b57cec5SDimitry Andric if (a == 0) 280b57cec5SDimitry Andric return 0.0; 290b57cec5SDimitry Andric const unsigned N = sizeof(ti_int) * CHAR_BIT; 300b57cec5SDimitry Andric const ti_int s = a >> (N - 1); 310b57cec5SDimitry Andric a = (a ^ s) - s; 320b57cec5SDimitry Andric int sd = N - __clzti2(a); // number of significant digits 330b57cec5SDimitry Andric int e = sd - 1; // exponent 340b57cec5SDimitry Andric if (sd > LDBL_MANT_DIG) { 350b57cec5SDimitry Andric // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 360b57cec5SDimitry Andric // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 370b57cec5SDimitry Andric // 12345678901234567890123456 380b57cec5SDimitry Andric // 1 = msb 1 bit 390b57cec5SDimitry Andric // P = bit LDBL_MANT_DIG-1 bits to the right of 1 400b57cec5SDimitry Andric // Q = bit LDBL_MANT_DIG bits to the right of 1 410b57cec5SDimitry Andric // R = "or" of all bits to the right of Q 420b57cec5SDimitry Andric switch (sd) { 430b57cec5SDimitry Andric case LDBL_MANT_DIG + 1: 440b57cec5SDimitry Andric a <<= 1; 450b57cec5SDimitry Andric break; 460b57cec5SDimitry Andric case LDBL_MANT_DIG + 2: 470b57cec5SDimitry Andric break; 480b57cec5SDimitry Andric default: 490b57cec5SDimitry Andric a = ((tu_int)a >> (sd - (LDBL_MANT_DIG + 2))) | 500b57cec5SDimitry Andric ((a & ((tu_int)(-1) >> ((N + LDBL_MANT_DIG + 2) - sd))) != 0); 510b57cec5SDimitry Andric }; 520b57cec5SDimitry Andric // finish: 530b57cec5SDimitry Andric a |= (a & 4) != 0; // Or P into R 540b57cec5SDimitry Andric ++a; // round - this step may add a significant bit 550b57cec5SDimitry Andric a >>= 2; // dump Q and R 560b57cec5SDimitry Andric // a is now rounded to LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits 570b57cec5SDimitry Andric if (a & ((tu_int)1 << LDBL_MANT_DIG)) { 580b57cec5SDimitry Andric a >>= 1; 590b57cec5SDimitry Andric ++e; 600b57cec5SDimitry Andric } 610b57cec5SDimitry Andric // a is now rounded to LDBL_MANT_DIG bits 620b57cec5SDimitry Andric } else { 630b57cec5SDimitry Andric a <<= (LDBL_MANT_DIG - sd); 640b57cec5SDimitry Andric // a is now rounded to LDBL_MANT_DIG bits 650b57cec5SDimitry Andric } 66*5f757f3fSDimitry Andric xf_bits fb; 670b57cec5SDimitry Andric fb.u.high.s.low = ((su_int)s & 0x8000) | // sign 680b57cec5SDimitry Andric (e + 16383); // exponent 690b57cec5SDimitry Andric fb.u.low.all = (du_int)a; // mantissa 700b57cec5SDimitry Andric return fb.f; 710b57cec5SDimitry Andric } 720b57cec5SDimitry Andric 730b57cec5SDimitry Andric #endif // CRT_HAS_128BIT 74