compiler-rt/lib/builtins/floatsidf.c

   1 //===-- lib/floatsidf.c - integer -> double-precision conversion --*- C -*-===//
   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 integer to double-precision conversion for the
  10 // compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
  11 // mode.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #define DOUBLE_PRECISION
  16 #include "fp_lib.h"
  17
  18 #include "int_lib.h"
  19
  20 COMPILER_RT_ABI fp_t __floatsidf(si_int a) {
  21
  22   const int aWidth = sizeof a * CHAR_BIT;
  23
  24   // Handle zero as a special case to protect clz
  25   if (a == 0)
  26     return fromRep(0);
  27
  28   // All other cases begin by extracting the sign and absolute value of a
  29   rep_t sign = 0;
  30   su_int aAbs = (su_int)a;
  31   if (a < 0) {
  32     sign = signBit;
  33     aAbs = -aAbs;
  34   }
  35
  36   // Exponent of (fp_t)a is the width of abs(a).
  37   const int exponent = (aWidth - 1) - clzsi(aAbs);
  38   rep_t result;
  39
  40   // Shift a into the significand field and clear the implicit bit.  Extra
  41   // cast to unsigned int is necessary to get the correct behavior for
  42   // the input INT_MIN.
  43   const int shift = significandBits - exponent;
  44   result = (rep_t)aAbs << shift ^ implicitBit;
  45
  46   // Insert the exponent
  47   result += (rep_t)(exponent + exponentBias) << significandBits;
  48   // Insert the sign bit and return
  49   return fromRep(result | sign);
  50 }
  51
  52 #if defined(__ARM_EABI__)
  53 #if defined(COMPILER_RT_ARMHF_TARGET)
  54 AEABI_RTABI fp_t __aeabi_i2d(si_int a) { return __floatsidf(a); }
  55 #else
  56 COMPILER_RT_ALIAS(__floatsidf, __aeabi_i2d)
  57 #endif
  58 #endif