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   if (a < 0) {
  31     sign = signBit;
  32     a = -a;
  33   }
  34
  35   // Exponent of (fp_t)a is the width of abs(a).
  36   const int exponent = (aWidth - 1) - clzsi(a);
  37   rep_t result;
  38
  39   // Shift a into the significand field and clear the implicit bit.  Extra
  40   // cast to unsigned int is necessary to get the correct behavior for
  41   // the input INT_MIN.
  42   const int shift = significandBits - exponent;
  43   result = (rep_t)(su_int)a << shift ^ implicitBit;
  44
  45   // Insert the exponent
  46   result += (rep_t)(exponent + exponentBias) << significandBits;
  47   // Insert the sign bit and return
  48   return fromRep(result | sign);
  49 }
  50
  51 #if defined(__ARM_EABI__)
  52 #if defined(COMPILER_RT_ARMHF_TARGET)
  53 AEABI_RTABI fp_t __aeabi_i2d(si_int a) { return __floatsidf(a); }
  54 #else
  55 COMPILER_RT_ALIAS(__floatsidf, __aeabi_i2d)
  56 #endif
  57 #endif