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      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 
     21 COMPILER_RT_ABI fp_t
     22 __floatunsidf(unsigned int a) {
     23 
     24     const int aWidth = sizeof a * CHAR_BIT;
     25 
     26     // Handle zero as a special case to protect clz
     27     if (a == 0) return fromRep(0);
     28 
     29     // Exponent of (fp_t)a is the width of abs(a).
     30     const int exponent = (aWidth - 1) - __builtin_clz(a);
     31     rep_t result;
     32 
     33     // Shift a into the significand field and clear the implicit bit.
     34     const int shift = significandBits - exponent;
     35     result = (rep_t)a << shift ^ implicitBit;
     36 
     37     // Insert the exponent
     38     result += (rep_t)(exponent + exponentBias) << significandBits;
     39     return fromRep(result);
     40 }
     41 
     42 #if defined(__ARM_EABI__)
     43 #if defined(COMPILER_RT_ARMHF_TARGET)
     44 AEABI_RTABI fp_t __aeabi_ui2d(unsigned int a) {
     45   return __floatunsidf(a);
     46 }
     47 #else
     48 AEABI_RTABI fp_t __aeabi_ui2d(unsigned int a) COMPILER_RT_ALIAS(__floatunsidf);
     49 #endif
     50 #endif
     51