compiler-rt/lib/builtins/floatundidf.c

   1 //===-- floatundidf.c - Implement __floatundidf ---------------------------===//
   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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements __floatundidf for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 // Returns: convert a to a double, rounding toward even.
  14
  15 // Assumption: double is a IEEE 64 bit floating point type
  16 //             du_int is a 64 bit integral type
  17
  18 // seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm
  19 // mmmm
  20
  21 #include "int_lib.h"
  22
  23 #ifndef __SOFTFP__
  24 // Support for systems that have hardware floating-point; we'll set the inexact
  25 // flag as a side-effect of this computation.
  26
  27 COMPILER_RT_ABI double __floatundidf(du_int a) {
  28   static const double twop52 = 4503599627370496.0;           // 0x1.0p52
  29   static const double twop84 = 19342813113834066795298816.0; // 0x1.0p84
  30   static const double twop84_plus_twop52 =
  31       19342813118337666422669312.0; // 0x1.00000001p84
  32
  33   union {
  34     uint64_t x;
  35     double d;
  36   } high = {.d = twop84};
  37   union {
  38     uint64_t x;
  39     double d;
  40   } low = {.d = twop52};
  41
  42   high.x |= a >> 32;
  43   low.x |= a & UINT64_C(0x00000000ffffffff);
  44
  45   const double result = (high.d - twop84_plus_twop52) + low.d;
  46   return result;
  47 }
  48
  49 #else
  50 // Support for systems that don't have hardware floating-point; there are no
  51 // flags to set, and we don't want to code-gen to an unknown soft-float
  52 // implementation.
  53
  54 #define SRC_U64
  55 #define DST_DOUBLE
  56 #include "int_to_fp_impl.inc"
  57
  58 COMPILER_RT_ABI double __floatundidf(du_int a) { return __floatXiYf__(a); }
  59 #endif
  60
  61 #if defined(__ARM_EABI__)
  62 #if defined(COMPILER_RT_ARMHF_TARGET)
  63 AEABI_RTABI double __aeabi_ul2d(du_int a) { return __floatundidf(a); }
  64 #else
  65 COMPILER_RT_ALIAS(__floatundidf, __aeabi_ul2d)
  66 #endif
  67 #endif
  68
  69 #if defined(__MINGW32__) && defined(__arm__)
  70 COMPILER_RT_ALIAS(__floatundidf, __u64tod)
  71 #endif