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      1 //===-- lib/floatditf.c - integer -> quad-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 di_int to quad-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 QUAD_PRECISION
     17 #include "fp_lib.h"
     18 
     19 #if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
     20 COMPILER_RT_ABI fp_t __floatditf(di_int a) {
     21 
     22     const int aWidth = sizeof a * CHAR_BIT;
     23 
     24     // Handle zero as a special case to protect clz
     25     if (a == 0)
     26         return fromRep(0);
     27 
     28     // All other cases begin by extracting the sign and absolute value of a
     29     rep_t sign = 0;
     30     du_int aAbs = (du_int)a;
     31     if (a < 0) {
     32         sign = signBit;
     33         aAbs = ~(du_int)a + 1U;
     34     }
     35 
     36     // Exponent of (fp_t)a is the width of abs(a).
     37     const int exponent = (aWidth - 1) - __builtin_clzll(aAbs);
     38     rep_t result;
     39 
     40     // Shift a into the significand field, rounding if it is a right-shift
     41     const int shift = significandBits - exponent;
     42     result = (rep_t)aAbs << shift ^ implicitBit;
     43 
     44     // Insert the exponent
     45     result += (rep_t)(exponent + exponentBias) << significandBits;
     46     // Insert the sign bit and return
     47     return fromRep(result | sign);
     48 }
     49 
     50 #endif
     51