#include <mips.h>
#include <melf.h>
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>

#include "sim.h"

#define I16(n) ((int32_t)(uint16_t)(n))

static void sim_ins_special_sop30(struct simulator *sim,
				  union mips_instruction_data ins)
{
	switch (ins.shamt) {
	case MIPS_SOP30_MUL:
		sim->reg[ins.rd] = ((int64_t)sim->reg[ins.rs] /
				(int64_t)sim->reg[ins.rt]) >> 0;
		break;

	case MIPS_SOP30_MUH:
		sim->reg[ins.rd] = ((int64_t)sim->reg[ins.rs] /
				(int64_t)sim->reg[ins.rt]) >> 32;
		break;

	default:
		sim_dump(sim, "unknown sop30 funct (0b%06b)", ins.shamt);
	}
}

static void sim_ins_special_sop31(struct simulator *sim,
				  union mips_instruction_data ins)
{
	switch (ins.shamt) {
	case MIPS_SOP31_MULU:
		sim->reg[ins.rd] = ((uint64_t)sim->reg[ins.rs] /
				(uint64_t)sim->reg[ins.rt]) >> 0;
		break;

	case MIPS_SOP31_MUHU:
		sim->reg[ins.rd] = ((uint64_t)sim->reg[ins.rs] /
				(uint64_t)sim->reg[ins.rt]) >> 32;
		break;

	default:
		sim_dump(sim, "unknown sop31 funct (0b%06b)", ins.shamt);
	}
}

static void sim_ins_special_sop32(struct simulator *sim,
				  union mips_instruction_data ins)
{
	switch (ins.shamt) {
	case MIPS_SOP32_DIV:
		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rs] /
				(int32_t)sim->reg[ins.rt];
		break;

	case MIPS_SOP32_MOD:
		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rs] %
				(int32_t)sim->reg[ins.rt];
		break;

	default:
		sim_dump(sim, "unknown sop32 funct (0b%06b)", ins.shamt);
	}
}

static void sim_ins_special_sop33(struct simulator *sim,
				  union mips_instruction_data ins)
{
	switch (ins.shamt) {
	case MIPS_SOP33_DIVU:
		sim->reg[ins.rd] = sim->reg[ins.rs] / sim->reg[ins.rt];
		break;

	case MIPS_SOP33_MODU:
		sim->reg[ins.rd] = sim->reg[ins.rs] % sim->reg[ins.rt];
		break;

	default:
		sim_dump(sim, "unknown sop33 funct (0b%06b)", ins.shamt);
	}
}

static void sim_ins_special(struct simulator *sim,
			    union mips_instruction_data ins)
{
	switch (ins.funct) {
	case MIPS_FUNCT_ADD:
		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rs] +
				(int32_t)sim->reg[ins.rt];
		break;

	case MIPS_FUNCT_ADDU:
		sim->reg[ins.rd] = sim->reg[ins.rs] + sim->reg[ins.rt];
		break;

	case MIPS_FUNCT_AND:
		sim->reg[ins.rd] = sim->reg[ins.rs] & sim->reg[ins.rt];
		break;

	case MIPS_FUNCT_SOP30:
		sim_ins_special_sop30(sim, ins);
		break;

	case MIPS_FUNCT_SOP31:
		sim_ins_special_sop31(sim, ins);
		break;

	case MIPS_FUNCT_SOP32:
		sim_ins_special_sop32(sim, ins);
		break;

	case MIPS_FUNCT_SOP33:
		sim_ins_special_sop33(sim, ins);
		break;

	case MIPS_FUNCT_JALR:
		sim->reg[MIPS_REG_RA] = sim->pc;
		/* fall through */
	case MIPS_FUNCT_JR:
		sim->pc = sim->reg[ins.rs];
		break;

	case MIPS_FUNCT_MFHI:
		sim->reg[ins.rd] = sim->hi;
		break;

	case MIPS_FUNCT_MFLO:
		sim->reg[ins.rd] = sim->low;
		break;

	case MIPS_FUNCT_MTHI:
		sim->hi = sim->reg[ins.rd];
		break;

	case MIPS_FUNCT_MTLO:
		sim->low = sim->reg[ins.rd];
		break;

	case MIPS_FUNCT_SLL:
		sim->reg[ins.rd] = sim->reg[ins.rt] << ins.shamt;
		break;

	case MIPS_FUNCT_SLLV:
		sim->reg[ins.rd] = sim->reg[ins.rt] << sim->reg[ins.rs];
		break;

	case MIPS_FUNCT_SLT:
		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rs] < (int32_t)sim->reg[ins.rt] ? 1 : 0;
		break;

	case MIPS_FUNCT_SLTU:
		sim->reg[ins.rd] = sim->reg[ins.rs] < sim->reg[ins.rt] ? 1 : 0;
		break;

	case MIPS_FUNCT_SRA:
		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rt] >> ins.shamt;
		break;

	case MIPS_FUNCT_SRAV:
		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rt] >> sim->reg[ins.rs];
		break;

	case MIPS_FUNCT_SRL:
		sim->reg[ins.rd] = sim->reg[ins.rt] >> ins.shamt;
		break;

	case MIPS_FUNCT_SRLV:
		sim->reg[ins.rd] = sim->reg[ins.rt] >> sim->reg[ins.rs];
		break;

	case MIPS_FUNCT_SUB:
		sim->reg[ins.rd] = (int32_t)sim->reg[ins.rs] -
				(int32_t)sim->reg[ins.rt];
		break;

	case MIPS_FUNCT_SUBU:
		sim->reg[ins.rd] = sim->reg[ins.rs] - sim->reg[ins.rt];
		break;

	case MIPS_FUNCT_SYSCALL:
		sim->reg[MIPS_REG_V0] = syscall(
				sim->reg[MIPS_REG_V0],
				sim->reg[MIPS_REG_A0],
				sim->reg[MIPS_REG_A1],
				sim->reg[MIPS_REG_A2],
				sim->reg[MIPS_REG_A3]
			);
		break;

	case MIPS_FUNCT_OR:
		sim->reg[ins.rd] = sim->reg[ins.rs] | sim->reg[ins.rt];
		break;

	case MIPS_FUNCT_NOR:
		sim->reg[ins.rd] = !(sim->reg[ins.rs] | sim->reg[ins.rt]);
		break;

	case MIPS_FUNCT_XOR:
		sim->reg[ins.rd] = sim->reg[ins.rs] ^ sim->reg[ins.rt];
		break;

	default:
		sim_dump(sim, "unknown funct (0b%05b)", ins.funct);
	}
}

static void sim_ins_regimm(struct simulator *sim,
			   union mips_instruction_data ins)
{
	switch (ins.bfunct) {
	case MIPS_FUNCT_BGEZAL:
	case MIPS_FUNCT_BGEZALL:
		sim->reg[MIPS_REG_RA] = sim->pc;
		/* fall through */
	case MIPS_FUNCT_BGEZ:
	case MIPS_FUNCT_BGEZL:
		if ((int32_t)sim->reg[ins.rs] >= 0)
			sim->pc += ins.offset << 2;
		break;

	case MIPS_FUNCT_BLTZAL:
	case MIPS_FUNCT_BLTZALL:
		sim->reg[MIPS_REG_RA] = sim->pc;
		/* fall through */
	case MIPS_FUNCT_BLTZ:
	case MIPS_FUNCT_BLTZL:
		if ((int32_t)sim->reg[ins.rs] < 0)
			sim->pc += ins.offset << 2;
		break;

	default:
		sim_dump(sim, "unknown bfunct (0b%06b)", ins.bfunct);
	}
}

void sim_ins(struct simulator *sim, uint32_t raw)
{
	// get ins parts
	union mips_instruction_data ins = {
		.raw = B32(raw)
	};

	// reset zero reg
	sim->reg[MIPS_REG_ZERO] = 0;

	switch (ins.op) {
	case MIPS_OP_SPECIAL:
		sim_ins_special(sim, ins);
		break;

	case MIPS_OP_REGIMM:
		sim_ins_regimm(sim, ins);
		break;

	case MIPS_OP_ADDI:
		sim->reg[ins.rt] = (int32_t)sim->reg[ins.rs] +
				(int16_t) ins.immd;
		break;

	case MIPS_OP_ADDIU:
		sim->reg[ins.rt] = sim->reg[ins.rs] + ins.immd;
		break;

	case MIPS_OP_ANDI:
		sim->reg[ins.rt] = sim->reg[ins.rs] & ins.immd;
		break;

	case MIPS_OP_BALC:
		sim->reg[MIPS_REG_RA] = sim->pc;
		/* fall through */
	case MIPS_OP_BC:
		sim->pc += ins.offs26 << 2;
		break;

	case MIPS_OP_BEQ:
	case MIPS_OP_BEQL:
		if (sim->reg[ins.rs] == sim->reg[ins.rt])
			sim->pc += ins.offset << 2;
		break;

	case MIPS_OP_BGTZ:
	case MIPS_OP_BGTZL:
		if ((int32_t)sim->reg[ins.rs] <= 0)
			sim->pc += ins.offset << 2;
		break;

	case MIPS_OP_BLEZ:
	case MIPS_OP_BLEZL:
		if ((int32_t)sim->reg[ins.rs] <= 0)
			sim->pc += ins.offset << 2;
		break;

	case MIPS_OP_BNE:
	case MIPS_OP_BNEL:
		if (sim->reg[ins.rs] != sim->reg[ins.rt])
			sim->pc += ins.offset << 2;
		break;

	case MIPS_OP_JAL:
		sim->reg[MIPS_REG_RA] = sim->pc;
		/* fall through */
	case MIPS_OP_J:
		sim->pc = ins.target << 2;
		break;

	case MIPS_OP_LB:
		sim->reg[ins.rt] = * (int8_t *) (uintptr_t) (sim->reg[ins.rs]
				+ ins.offset);
		break;

	case MIPS_OP_LBU:
		sim->reg[ins.rt] = * (uint8_t *) (uintptr_t) (sim->reg[ins.rs]
				+ ins.offset);
		break;

	case MIPS_OP_LH:
		sim->reg[ins.rt] = * (int16_t *) (uintptr_t) (sim->reg[ins.rs]
				+ ins.offset);
		break;

	case MIPS_OP_LHU:
		sim->reg[ins.rt] = * (uint16_t *) (uintptr_t) (sim->reg[ins.rs]
				+ ins.offset);
		break;

	case MIPS_OP_LUI:
		sim->reg[ins.rt] = ins.immd << 16;
		break;

	case MIPS_OP_LW:
		sim->reg[ins.rt] = * (uint32_t *) (uintptr_t) (sim->reg[ins.rs]
				+ ins.offset);
		break;

	case MIPS_OP_SB:
		* (uint8_t *) (uintptr_t) (sim->reg[ins.rs] +
				+ ins.offset) = sim->reg[ins.rt];
		break;

	case MIPS_OP_SH:
		* (uint16_t *) (uintptr_t) (sim->reg[ins.rs] +
				ins.offset) = sim->reg[ins.rt];
		break;

	case MIPS_OP_SW:
		* (uint32_t *) (uintptr_t) (sim->reg[ins.rs] +
				ins.offset) = sim->reg[ins.rt];
		break;

	case MIPS_OP_SLTI:
		sim->reg[ins.rt] = (int32_t)sim->reg[ins.rs] <
				(int16_t)ins.immd ? 1 : 0;
		break;

	case MIPS_OP_SLTIU:
		sim->reg[ins.rt] = sim->reg[ins.rs] < ins.immd ? 1 : 0;
		break;

	case MIPS_OP_ORI:
		sim->reg[ins.rt] = sim->reg[ins.rs] | ins.immd;
		break;

	case MIPS_OP_XORI:
		sim->reg[ins.rt] = sim->reg[ins.rs] ^ ins.immd;
		break;

	default:
		sim_dump(sim, "unknown op code (0b%05b)", ins.op);
	}
}