kvisc/pc/instrs/arith.c

// The OS/K Team licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

#include "instrs.h"
#include "arch_i.h"

IMPL_COND(inc);
IMPL_COND(dec);
IMPL_COND(add);
IMPL_COND(sub);
IMPL_COND(mul);
IMPL_COND(div);
IMPL_COND(sgn);

//
// Unsigned arithmetic instructions
//

IMPL_START_2(add)
{
    v1 += v2;
}
IMPL_OUT;

IMPL_START_2(sub)
{
    v1 -= v2;
}
IMPL_OUT;

IMPL_START_1(mul)
{
    // Adapted from www.codeproject.com/Tips/618570/UInt-Multiplication-Squaring
    ulong v2 = v1;
    v1 = rax;

    ulong u1 = (v1 & 0xffffffff);
    ulong u2 = (v2 & 0xffffffff);
    ulong t = (u1 * u2);
    ulong w3 = (t & 0xffffffff);
    ulong k = (t >> 32);

    v1 >>= 32;
    t = (v1 * u2) + k;
    k = (t & 0xffffffff);
    ulong w1 = (t >> 32);

    v2 >>= 32;
    t = (u1 * v2) + k;
    k = (t >> 32);

    rdx = (v1 * v2) + w1 + k;
    rax = (t << 32) + w3;
}
IMPL_END;

IMPL_START_1(div)
{
    rdx = rax % v1;
    rax = rax / v1;
}
IMPL_END;

IMPL_START_1(inc)
{
    v1++;
}
IMPL_OUT;

IMPL_START_1(dec)
{
    v1--;
}
IMPL_OUT;

IMPL_START_2(sgn)
{
    v1 = (v2 ? ((long)v2 > 0 ? 1 : (ulong)-1L) : 0);
}
IMPL_OUT;