floatsidf.c revision 214152
1//===-- lib/floatsidf.c - integer -> double-precision conversion --*- C -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements 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 19fp_t __floatsidf(int a) { 20 21 const int aWidth = sizeof a * CHAR_BIT; 22 23 // Handle zero as a special case to protect clz 24 if (a == 0) 25 return fromRep(0); 26 27 // All other cases begin by extracting the sign and absolute value of a 28 rep_t sign = 0; 29 if (a < 0) { 30 sign = signBit; 31 a = -a; 32 } 33 34 // Exponent of (fp_t)a is the width of abs(a). 35 const int exponent = (aWidth - 1) - __builtin_clz(a); 36 rep_t result; 37 38 // Shift a into the significand field and clear the implicit bit. Extra 39 // cast to unsigned int is necessary to get the correct behavior for 40 // the input INT_MIN. 41 const int shift = significandBits - exponent; 42 result = (rep_t)(unsigned int)a << 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