1//===-- int_to_fp_impl.inc - integer to floating point conversion ---------===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// Thsi file implements a generic conversion from an integer type to an 10// IEEE-754 floating point type, allowing a common implementation to be hsared 11// without copy and paste. 12// 13//===----------------------------------------------------------------------===// 14 15#include "int_to_fp.h" 16 17static __inline dst_t __floatXiYf__(src_t a) { 18 if (a == 0) 19 return 0.0; 20 21 enum { 22 dstMantDig = dstSigBits + 1, 23 srcBits = sizeof(src_t) * CHAR_BIT, 24 srcIsSigned = ((src_t)-1) < 0, 25 }; 26 27 const src_t s = srcIsSigned ? a >> (srcBits - 1) : 0; 28 29 a = (usrc_t)(a ^ s) - s; 30 int sd = srcBits - clzSrcT(a); // number of significant digits 31 int e = sd - 1; // exponent 32 if (sd > dstMantDig) { 33 // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx 34 // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR 35 // 12345678901234567890123456 36 // 1 = msb 1 bit 37 // P = bit dstMantDig-1 bits to the right of 1 38 // Q = bit dstMantDig bits to the right of 1 39 // R = "or" of all bits to the right of Q 40 if (sd == dstMantDig + 1) { 41 a <<= 1; 42 } else if (sd == dstMantDig + 2) { 43 // Do nothing. 44 } else { 45 a = ((usrc_t)a >> (sd - (dstMantDig + 2))) | 46 ((a & ((usrc_t)(-1) >> ((srcBits + dstMantDig + 2) - sd))) != 0); 47 } 48 // finish: 49 a |= (a & 4) != 0; // Or P into R 50 ++a; // round - this step may add a significant bit 51 a >>= 2; // dump Q and R 52 // a is now rounded to dstMantDig or dstMantDig+1 bits 53 if (a & ((usrc_t)1 << dstMantDig)) { 54 a >>= 1; 55 ++e; 56 } 57 // a is now rounded to dstMantDig bits 58 } else { 59 a <<= (dstMantDig - sd); 60 // a is now rounded to dstMantDig bits 61 } 62 const int dstBits = sizeof(dst_t) * CHAR_BIT; 63 const dst_rep_t dstSignMask = DST_REP_C(1) << (dstBits - 1); 64 const int dstExpBits = dstBits - dstSigBits - 1; 65 const int dstExpBias = (1 << (dstExpBits - 1)) - 1; 66 const dst_rep_t dstSignificandMask = (DST_REP_C(1) << dstSigBits) - 1; 67 // Combine sign, exponent, and mantissa. 68 const dst_rep_t result = ((dst_rep_t)s & dstSignMask) | 69 ((dst_rep_t)(e + dstExpBias) << dstSigBits) | 70 ((dst_rep_t)(a) & dstSignificandMask); 71 return dstFromRep(result); 72} 73