compiler-rt/lib/builtins/floatundixf.c

   1 //===-- floatundixf.c - Implement __floatundixf ---------------------------===//
   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 __floatundixf for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #if !_ARCH_PPC
  14
  15 #include "int_lib.h"
  16
  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 128
  20 // bits du_int is a 64 bit integral type
  21
  22 // gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee
  23 // eeee | 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm
  24 // mmmm mmmm mmmm
  25 COMPILER_RT_ABI xf_float __floatundixf(du_int a) {
  26   if (a == 0)
  27     return 0.0;
  28   const unsigned N = sizeof(du_int) * CHAR_BIT;
  29   int clz = __builtin_clzll(a);
  30   int e = (N - 1) - clz; // exponent
  31   xf_bits fb;
  32   fb.u.high.s.low = (e + 16383); // exponent
  33   fb.u.low.all = a << clz;       // mantissa
  34   return fb.f;
  35 }
  36
  37 #endif // _ARCH_PPC