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      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 fp_t __floatsisf(int a) {
     24 
     25     const int aWidth = sizeof a * CHAR_BIT;
     26 
     27     // Handle zero as a special case to protect clz
     28     if (a == 0)
     29         return fromRep(0);
     30 
     31     // All other cases begin by extracting the sign and absolute value of a
     32     rep_t sign = 0;
     33     if (a < 0) {
     34         sign = signBit;
     35         a = -a;
     36     }
     37 
     38     // Exponent of (fp_t)a is the width of abs(a).
     39     const int exponent = (aWidth - 1) - __builtin_clz(a);
     40     rep_t result;
     41 
     42     // Shift a into the significand field, rounding if it is a right-shift
     43     if (exponent <= significandBits) {
     44         const int shift = significandBits - exponent;
     45         result = (rep_t)a << shift ^ implicitBit;
     46     } else {
     47         const int shift = exponent - significandBits;
     48         result = (rep_t)a >> shift ^ implicitBit;
     49         rep_t round = (rep_t)a << (typeWidth - shift);
     50         if (round > signBit) result++;
     51         if (round == signBit) result += result & 1;
     52     }
     53 
     54     // Insert the exponent
     55     result += (rep_t)(exponent + exponentBias) << significandBits;
     56     // Insert the sign bit and return
     57     return fromRep(result | sign);
     58 }
     59