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//===-- floattisf.c - Implement __floattisf -------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements __floattisf for the compiler_rt library.
//
//===----------------------------------------------------------------------===//
#include "int_lib.h"
#ifdef CRT_HAS_128BIT
// Returns: convert a to a float, rounding toward even.
// Assumption: float is a IEEE 32 bit floating point type
// ti_int is a 128 bit integral type
// seee eeee emmm mmmm mmmm mmmm mmmm mmmm
COMPILER_RT_ABI float __floattisf(ti_int a) {
if (a == 0)
return 0.0F;
const unsigned N = sizeof(ti_int) * CHAR_BIT;
const ti_int s = a >> (N - 1);
a = (a ^ s) - s;
int sd = N - __clzti2(a); // number of significant digits
int e = sd - 1; // exponent
if (sd > FLT_MANT_DIG) {
// start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
// finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
// 12345678901234567890123456
// 1 = msb 1 bit
// P = bit FLT_MANT_DIG-1 bits to the right of 1
// Q = bit FLT_MANT_DIG bits to the right of 1
// R = "or" of all bits to the right of Q
switch (sd) {
case FLT_MANT_DIG + 1:
a <<= 1;
break;
case FLT_MANT_DIG + 2:
break;
default:
a = ((tu_int)a >> (sd - (FLT_MANT_DIG + 2))) |
((a & ((tu_int)(-1) >> ((N + FLT_MANT_DIG + 2) - sd))) != 0);
};
// finish:
a |= (a & 4) != 0; // Or P into R
++a; // round - this step may add a significant bit
a >>= 2; // dump Q and R
// a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits
if (a & ((tu_int)1 << FLT_MANT_DIG)) {
a >>= 1;
++e;
}
// a is now rounded to FLT_MANT_DIG bits
} else {
a <<= (FLT_MANT_DIG - sd);
// a is now rounded to FLT_MANT_DIG bits
}
float_bits fb;
fb.u = ((su_int)s & 0x80000000) | // sign
((e + 127) << 23) | // exponent
((su_int)a & 0x007FFFFF); // mantissa
return fb.f;
}
#endif // CRT_HAS_128BIT
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