CAR/include/defs.h

#ifndef _CAR_INCLUDE_DEFS_H
#define _CAR_INCLUDE_DEFS_H

#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>

#include <stdlib.h>

//#define _DEBUG


typedef struct
{
	uint32_t gprs[32]; // register 31 is the control register (change maybe?)
	
	uint32_t flags;
	
	uint32_t pc;
	uint32_t sp;
	
	uint32_t* memory;
	size_t memory_size; // Never let addresses go past this, or we wil get a segsev
} pstate_t;

int processor_start(pstate_t* state);

void dump_regs(pstate_t* s);

#define FLAG_CARRY           (1 << 0)
#define FLAG_SIGN            (1 << 1)
#define FLAG_OVERFLOW        (1 << 2)
#define FLAG_ZERO            (1 << 3)
#define FLAG_INTERRUPTS      (1 << 4)
#define FLAG_ERROR           (1 << 5)
#define FLAG_DIRECTION_ERROR (1 << 6)
#define FLAG_DIVISION_ERROR  (1 << 7)

typedef uint32_t raw_instruction_t;

/*
Instruction encoding for misc operations:
	instruction group: bits 0 to 1 (2 bits) {NOTE: for misc operations, should be set to 0b00}
	opcode:            bits 2 to 7 (6 bits)
	imm:               bits 8 to 31 {NOTE: depending on the opcode, could be an address, or a register indirection}


Instruction encoding for register operations:
	instruction group: bits 0 to 1 (2 bits) {NOTE: for register operations, should be set to 0b01}
	opcode:            bits 2 to 8 (7 bits)
	dest:              bits 9 to 14 (5 bits)
	src1               bits 15 to 20 (5 bits)
	src2               bits 21 to 26 (5 bits)
	all other bits unused, however should be set to zero


Instruction encoding for load/store operations:
	instruction group: bits 0 to 1 (2 bits) {NOTE: for load/store operations, should be set to 0b10}
	opcode:            bits 2 to 5 (4 bits)
	register:          bits 6 to 10 (5 bits)
	imm:               bits 11 to 31 {NOTE: depending on the opcode, could be an address, or register indirect, or an immediate}
		is be one of:
			A) signed 21-bit offset from PC
			B) signed 21-bit offset from SP
			C) base register (5 bits) and a 16-bit signed offset from PC
			D) signed 21 bit immediate
*/

typedef struct
{
	uint8_t opcode;
	
	uint32_t imm;
} misc_instruction_t;

typedef struct
{
	uint8_t opcode;
	
	uint8_t dest;
	uint8_t src1;
	uint8_t src2;
} register_instruction_t;

typedef struct
{
	uint8_t opcode;
	
	uint8_t reg;
	
	uint32_t imm;
} ls_instruction_t;


misc_instruction_t convert_raw2misc(raw_instruction_t* r);
register_instruction_t convert_raw2register(raw_instruction_t* r);
ls_instruction_t convert_raw2ls(raw_instruction_t* r);

static inline uint8_t get_instruction_group(raw_instruction_t* r)
{
	return ((uint32_t) (*r)) >> 30;
}


#define get_reg_from_imm(x) ((x & 0x1F0000) >> 16)
#define get_imm_from_imm(x) (x & ~0x1F0000)

typedef struct
{
	bool do_inc_pc;
	bool exiting_error;
} op_return_t;

#define DEFINE_OP(name) \
	op_return_t op_##name(raw_instruction_t* ri, \
                          pstate_t* state)
                          
static const op_return_t _OP_RETV_NORMAL = { .do_inc_pc = true, .exiting_error = false };                   
static const op_return_t _OP_RETV_EXITING_ERROR = { .do_inc_pc = true, .exiting_error = true };                   

#define OP_RETURN_NORMAL return _OP_RETV_NORMAL;
#define OP_RETURN_EXITING_ERROR return _OP_RETV_EXITING_ERROR;
                          
typedef op_return_t (*op)(raw_instruction_t*, pstate_t*);

static DEFINE_OP(nop)
{
	OP_RETURN_NORMAL
}

static const op misc_ops[] =
{
	op_nop,
};
static const size_t NUM_MISC_OPCODES = sizeof(misc_ops) / sizeof(misc_ops[0]);

DEFINE_OP(add);
DEFINE_OP(sub);
DEFINE_OP(mul);
DEFINE_OP(divide);
DEFINE_OP(modulus);

DEFINE_OP(shl);
DEFINE_OP(shr);
DEFINE_OP(ahr);
DEFINE_OP(ror);

DEFINE_OP(band);
DEFINE_OP(bor);
DEFINE_OP(bxor);
DEFINE_OP(bnot);

DEFINE_OP(xchg);

static const op reg_ops[] =
{
	op_add,
	op_sub,
	op_mul,
	op_divide,
	op_modulus,
	
	op_shl,
	op_shr,
	op_ahr, // Arithmetic sHift Right
	op_ror,
	
	op_band,
	op_bor,
	op_bxor,
	op_bnot,
	
	op_xchg,
};
static const size_t NUM_REG_OPCODES = sizeof(reg_ops) / sizeof(reg_ops[0]);

DEFINE_OP(ldr);
DEFINE_OP(lds);
DEFINE_OP(ldb);
DEFINE_OP(ldi);

DEFINE_OP(str);
DEFINE_OP(sts);
DEFINE_OP(stb);

DEFINE_OP(ldh);

DEFINE_OP(sti);
DEFINE_OP(stj);

static const op ls_ops[] =
{
	op_ldr,
	op_lds,
	op_ldb,
	op_ldi,
	
	op_str,
	op_sts,
	op_stb,
	
	op_ldh,
	
	op_sti,
	op_stj,
};
static const size_t NUM_LS_OPCODES = sizeof(ls_ops) / sizeof(ls_ops[0]);

#endif // _CAR_INCLUDE_DEFS_H