| //===-- floatdidf.c - Implement __floatdidf -------------------------------===// |
| // |
| // 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 __floatdidf for the compiler_rt library. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "int_lib.h" |
| |
| // Returns: convert a to a double, rounding toward even. |
| |
| // Assumption: double is a IEEE 64 bit floating point type |
| // di_int is a 64 bit integral type |
| |
| // seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm |
| // mmmm |
| |
| #ifndef __SOFTFP__ |
| // Support for systems that have hardware floating-point; we'll set the inexact |
| // flag as a side-effect of this computation. |
| |
| COMPILER_RT_ABI double __floatdidf(di_int a) { |
| static const double twop52 = 4503599627370496.0; // 0x1.0p52 |
| static const double twop32 = 4294967296.0; // 0x1.0p32 |
| |
| union { |
| int64_t x; |
| double d; |
| } low = {.d = twop52}; |
| |
| const double high = (int32_t)(a >> 32) * twop32; |
| low.x |= a & INT64_C(0x00000000ffffffff); |
| |
| const double result = (high - twop52) + low.d; |
| return result; |
| } |
| |
| #else |
| // Support for systems that don't have hardware floating-point; there are no |
| // flags to set, and we don't want to code-gen to an unknown soft-float |
| // implementation. |
| |
| COMPILER_RT_ABI double __floatdidf(di_int a) { |
| if (a == 0) |
| return 0.0; |
| const unsigned N = sizeof(di_int) * CHAR_BIT; |
| const di_int s = a >> (N - 1); |
| a = (a ^ s) - s; |
| int sd = N - __builtin_clzll(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 = ((du_int)a >> (sd - (DBL_MANT_DIG + 2))) | |
| ((a & ((du_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 & ((du_int)1 << DBL_MANT_DIG)) { |
| a >>= 1; |
| ++e; |
| } |
| // 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 = ((su_int)s & 0x80000000) | // sign |
| ((su_int)(e + 1023) << 20) | // exponent |
| ((su_int)(a >> 32) & 0x000FFFFF); // mantissa-high |
| fb.u.s.low = (su_int)a; // mantissa-low |
| return fb.f; |
| } |
| #endif |
| |
| #if defined(__ARM_EABI__) |
| #if defined(COMPILER_RT_ARMHF_TARGET) |
| AEABI_RTABI double __aeabi_l2d(di_int a) { return __floatdidf(a); } |
| #else |
| COMPILER_RT_ALIAS(__floatdidf, __aeabi_l2d) |
| #endif |
| #endif |
| |
| #if defined(__MINGW32__) && defined(__arm__) |
| COMPILER_RT_ALIAS(__floatdidf, __i64tod) |
| #endif |