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/*
* Copyright (c) 2020, the SerenityOS developers.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
// TODO: Is there a compiler flag we can use to still get these math functions? (and compile with -nostdlib)
// FIXME: What do we do with this regarding copyright stuff?
// code for math functions taken from here:
// https://gitlab.incom.co/CM-Shield/u-boot/commit/aa7839b39c2ee77f9ab8c393c56b8d812507dbb7
// https://github.com/zayac/qemu-arm/blob/master/qemu/roms/ipxe/src/libgcc/__udivmoddi4.c
// https://code.woboq.org/llvm/compiler-rt/lib/builtins/divdi3.c.html
#include "math.h"
extern "C" {
union overlay64 {
u64 longw;
struct {
u32 lower;
u32 higher;
} words;
};
u64 __ashldi3(u64 num, unsigned int shift)
{
union overlay64 output;
output.longw = num;
if (shift >= 32) {
output.words.higher = output.words.lower << (shift - 32);
output.words.lower = 0;
} else {
if (!shift)
return num;
output.words.higher = (output.words.higher << shift) | (output.words.lower >> (32 - shift));
output.words.lower = output.words.lower << shift;
}
return output.longw;
}
u64 __lshrdi3(u64 num, unsigned int shift)
{
union overlay64 output;
output.longw = num;
if (shift >= 32) {
output.words.lower = output.words.higher >> (shift - 32);
output.words.higher = 0;
} else {
if (!shift)
return num;
output.words.lower = output.words.lower >> shift | (output.words.higher << (32 - shift));
output.words.higher = output.words.higher >> shift;
}
return output.longw;
}
#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
static u64 _64bit_divide(u64 dividend, u64 divider, u64* rem_p)
{
u64 result = 0;
/*
* If divider is zero - let the rest of the system care about the
* exception.
*/
if (!divider)
return 1 / (u32)divider;
/* As an optimization, let's not use 64 bit division unless we must. */
if (dividend <= MAX_32BIT_UINT) {
if (divider > MAX_32BIT_UINT) {
result = 0;
if (rem_p)
*rem_p = divider;
} else {
result = (u32)dividend / (u32)divider;
if (rem_p)
*rem_p = (u32)dividend % (u32)divider;
}
return result;
}
while (divider <= dividend) {
u64 locald = divider;
u64 limit = __lshrdi3(dividend, 1);
int shifts = 0;
while (locald <= limit) {
shifts++;
locald = locald + locald;
}
result |= __ashldi3(1, shifts);
dividend -= locald;
}
if (rem_p)
*rem_p = dividend;
return result;
}
u64 __udivdi3(u64 num, u64 den)
{
return _64bit_divide(num, den, nullptr);
}
u64 __umoddi3(u64 num, u64 den)
{
u64 v = 0;
_64bit_divide(num, den, &v);
return v;
}
uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t* rem_p)
{
uint64_t quot = 0, qbit = 1;
if (den == 0) {
return 1 / ((unsigned)den); /* Intentional divide by zero, without
triggering a compiler warning which
would abort the build */
}
/* Left-justify denominator and count shift */
while ((int64_t)den >= 0) {
den <<= 1;
qbit <<= 1;
}
while (qbit) {
if (den <= num) {
num -= den;
quot += qbit;
}
den >>= 1;
qbit >>= 1;
}
if (rem_p)
*rem_p = num;
return quot;
}
int64_t __divdi3(int64_t a, int64_t b)
{
const int bits_in_dword_m1 = (int)(sizeof(int64_t) * 8) - 1;
int64_t s_a = a >> bits_in_dword_m1; // s_a = a < 0 ? -1 : 0
int64_t s_b = b >> bits_in_dword_m1; // s_b = b < 0 ? -1 : 0
a = (a ^ s_a) - s_a; // negate if s_a == -1
b = (b ^ s_b) - s_b; // negate if s_b == -1
s_a ^= s_b; // sign of quotient
return (__udivmoddi4(a, b, (uint64_t*)0) ^ s_a) - s_a; // negate if s_a == -1
}
int64_t __moddi3(int64_t a, int64_t b)
{
const int bits_in_dword_m1 = (int)(sizeof(int64_t) * 8) - 1;
int64_t s = b >> bits_in_dword_m1; // s = b < 0 ? -1 : 0
b = (b ^ s) - s; // negate if s == -1
s = a >> bits_in_dword_m1; // s = a < 0 ? -1 : 0
a = (a ^ s) - s; // negate if s == -1
uint64_t r;
__udivmoddi4(a, b, &r);
return ((int64_t)r ^ s) - s; // negate if s == -1
}
}
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