src/libcompiler_builtins/compiler-rt/lib/builtins/floatsisf.c

   1 //===-- lib/floatsisf.c - integer -> single-precision conversion --*- C -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is dual licensed under the MIT and the University of Illinois Open
   6 // Source Licenses. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements integer to single-precision conversion for the
  11 // compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
  12 // mode.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #define SINGLE_PRECISION
  17 #include "fp_lib.h"
  18
  19 #include "int_lib.h"
  20
  21 ARM_EABI_FNALIAS(i2f, floatsisf)
  22
  23 COMPILER_RT_ABI fp_t
  24 __floatsisf(int a) {
  25
  26     const int aWidth = sizeof a * CHAR_BIT;
  27
  28     // Handle zero as a special case to protect clz
  29     if (a == 0)
  30         return fromRep(0);
  31
  32     // All other cases begin by extracting the sign and absolute value of a
  33     rep_t sign = 0;
  34     unsigned aAbs = (unsigned)a;
  35     if (a < 0) {
  36         sign = signBit;
  37         aAbs = ~(unsigned)a + 1U;
  38     }
  39
  40     // Exponent of (fp_t)a is the width of abs(a).
  41     const int exponent = (aWidth - 1) - __builtin_clz(aAbs);
  42     rep_t result;
  43
  44     // Shift a into the significand field, rounding if it is a right-shift
  45     if (exponent <= significandBits) {
  46         const int shift = significandBits - exponent;
  47         result = (rep_t)aAbs << shift ^ implicitBit;
  48     } else {
  49         const int shift = exponent - significandBits;
  50         result = (rep_t)aAbs >> shift ^ implicitBit;
  51         rep_t round = (rep_t)aAbs << (typeWidth - shift);
  52         if (round > signBit) result++;
  53         if (round == signBit) result += result & 1;
  54     }
  55
  56     // Insert the exponent
  57     result += (rep_t)(exponent + exponentBias) << significandBits;
  58     // Insert the sign bit and return
  59     return fromRep(result | sign);
  60 }