floatunsidf.c revision 2d1fdb26e458c4ddc04155c1d421bced3ba90cd0 
1//===-- lib/floatunsidf.c - uint -> double-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 unsigned integer to double-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 DOUBLE_PRECISION
17#include "fp_lib.h"
18
19#include "int_lib.h"
20
21ARM_EABI_FNALIAS(ui2d, floatunsidf)
22
23COMPILER_RT_ABI fp_t
24__floatunsidf(unsigned 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) return fromRep(0);
30
31    // Exponent of (fp_t)a is the width of abs(a).
32    const int exponent = (aWidth - 1) - __builtin_clz(a);
33    rep_t result;
34
35    // Shift a into the significand field and clear the implicit bit.
36    const int shift = significandBits - exponent;
37    result = (rep_t)a << shift ^ implicitBit;
38
39    // Insert the exponent
40    result += (rep_t)(exponent + exponentBias) << significandBits;
41    return fromRep(result);
42}
43