// 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 "arch.h"

void i_add(ctx_t *ctx, acc_t *p1, acc_t *p2)
{
    if (p1->type != A_REG) {
        _except(ctx, E_ILL, "ADD into IMM");
    }
    
    if (p1->mem || p2->mem) {
        _except(ctx, E_IMP, "Memory access");
    }

    ctx->r[p1->val].val += p2->type >= A_IMM16 ? p2->val
                                           : ctx->r[p2->val].val;
}

void i_sub(ctx_t *ctx, acc_t *p1, acc_t *p2)
{
    if (p1->type != A_REG) {
        _except(ctx, E_ILL, "SUB into IMM");
    }
    
    if (p1->mem || p2->mem) {
        _except(ctx, E_IMP, "Memory access");
    }
    
    ctx->r[p1->val].val -= p2->type >= A_IMM16 ? p2->val
                                          : ctx->r[p2->val].val;
}

void i_mul(ctx_t *ctx, acc_t *p1, acc_t *p2)
{
    if (p1->mem) {
        _except(ctx, E_IMP, "Memory access");
    }
    
    // Adapted from www.codeproject.com/Tips/618570/UInt-Multiplication-Squaring

    ulong u = p1->type >= A_IMM16 ? p1->val : ctx->r[p1->val].val;
    ulong v = ctx->r[RAX].val;
    ulong u1 = u & 0xffffffff;
    ulong v1 = v & 0xffffffff;
    ulong t = (u1 * v1);
    ulong w3 = (t & 0xffffffff);
    ulong k = (t >> 32);
    
    u >>= 32;
    t = (u * v1) + k;
    k = (t & 0xffffffff);
    ulong w1 = (t >> 32);
    
    v >>= 32;
    t = (u1 * v) + k;
    k = (t >> 32);
    
    ctx->r[RDX].val = (u * v) + w1 + k;
    ctx->r[RAX].val = (t << 32) + w3;
}

void i_div(ctx_t *ctx, acc_t *p1, acc_t *p2)
{
    if (p1->mem) {
        _except(ctx, E_IMP, "Memory access");
    }

    ulong val = p1->type >= A_IMM16 ? p1->val : ctx->r[p1->val].val;

    ctx->r[RDX].val = ctx->r[RAX].val % val;
    ctx->r[RAX].val = ctx->r[RAX].val / val;
}

void i_inc(ctx_t *ctx, acc_t *p1, acc_t *p2)
{
    if (p1->type != A_REG) {
        _except(ctx, E_ILL, "INC on an IMM");
    }

    if (p1->mem) {
        _except(ctx, E_IMP, "Memory access");
    }
    
    ctx->r[p1->val].val++;
}

void i_dec(ctx_t *ctx, acc_t *p1, acc_t *p2)
{
    if (p1->type != A_REG) {
        _except(ctx, E_ILL, "DEC on an IMM");
    }

    if (p1->mem) {
        _except(ctx, E_IMP, "Memory access");
    }
    
    ctx->r[p1->val].val--;
}

void i_mov(ctx_t *ctx, acc_t *p1, acc_t *p2)
{
    if (p1->type != A_REG) {
        _except(ctx, E_ILL, "MOV into IMM");
    }
    
    if (p1->mem || p2->mem) {
        _except(ctx, E_IMP, "Memory access");
    }

    ctx->r[p1->val].val = p2->type >= A_IMM16 ? p2->val
                                        : ctx->r[p2->val].val;
}

void i_xchg(ctx_t *ctx, acc_t *p1, acc_t *p2)
{
    if (p1->type != A_REG || p2->type != A_REG) {
        _except(ctx, E_ILL, "XCHG of IMM(s)");
    }
    
    if (p1->mem || p2->mem) {
        _except(ctx, E_IMP, "Memory access");
    }

    ulong temp = ctx->r[p1->val].val;
    ctx->r[p1->val].val = ctx->r[p2->val].val;
    ctx->r[p2->val].val = temp;
}

instr_t arch_i[NINSTRS] =
{
    [I_ADD] = { "ADD", 2, i_add },
    [I_SUB] = { "SUB", 2, i_sub },
    [I_MUL] = { "MUL", 1, i_mul },
    [I_DIV] = { "DIV", 1, i_div },
    [I_INC] = { "INC", 1, i_inc },
    [I_DEC] = { "DEC", 1, i_dec },
    [I_MOV] = { "MOV", 2, i_mov },
    [I_XCHG] = { "XCHG", 2, i_xchg },
};