floatsisf.c revision 2d1fdb26e458c4ddc04155c1d421bced3ba90cd0
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
21ARM_EABI_FNALIAS(i2f, floatsisf)
22
23COMPILER_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    if (a < 0) {
35        sign = signBit;
36        a = -a;
37    }
38
39    // Exponent of (fp_t)a is the width of abs(a).
40    const int exponent = (aWidth - 1) - __builtin_clz(a);
41    rep_t result;
42
43    // Shift a into the significand field, rounding if it is a right-shift
44    if (exponent <= significandBits) {
45        const int shift = significandBits - exponent;
46        result = (rep_t)a << shift ^ implicitBit;
47    } else {
48        const int shift = exponent - significandBits;
49        result = (rep_t)a >> shift ^ implicitBit;
50        rep_t round = (rep_t)a << (typeWidth - shift);
51        if (round > signBit) result++;
52        if (round == signBit) result += result & 1;
53    }
54
55    // Insert the exponent
56    result += (rep_t)(exponent + exponentBias) << significandBits;
57    // Insert the sign bit and return
58    return fromRep(result | sign);
59}
60