#include "objects.h"

#include "codegen_pic.h"

#include "list.h"

#include "imdtcode.h"

#include <stdio.h>

#include <stdlib.h>

#include <assert.h>

#include <string.h>

/* The code generator lays out the memory like this:

*

* 0x0c: Stack pointer (points to topmost allocated byte on stack)

* 0x0d: Temporary register

* 0x0e: Last byte of stack

* ... : Stack

* 0x4e: Example global variable

* 0x4f: First byte of stack

*

* A stack frame looks like this (inspired by x86 stack frame layout):

*

* 0x3a: Stack variable at offset 0 (stack pointer = 0x3a)

* 0x3b: Stack variable at offset 1

* 0x3c: Stack variable at offset 2

* 0x3d: Saved stack pointer (this is moved into 0x0c at function return)

* 0x3e: Start of previous stack frame

*/

FILE *output;

ImdtCode *bytecode;

int label_base = 0;

int temporary = 0x0d;

void codegen_pic(FILE *file, ImdtCode *program)

{

printf("Starting code generation\n");

output = file;

bytecode = program;

printf("Generating preamble\n");

write_preamble();

printf("Generating global variables\n");

write_globals();

printf("Generating function variables and code\n");

write_functions();

printf("Code generation complete\n");

}

void write_preamble()

{

// TODO: All of that "initializing ports" crap will go here

fprintf(output, "\t#include <p16f884.inc>\n");

fprintf(output, "\torg 0\n\n");

fprintf(output, "\tbsf STATUS, RP0\n");

fprintf(output, "\tclrf TRISB\n");

fprintf(output, "\tbcf STATUS, RP0\n");

fprintf(output, "; Initializing stack frame pointer\n");

fprintf(output, "\tmovlw H'4f'\n");

fprintf(output, "\tmovwf H'0c'\n\n");

}

void write_globals()

{

int globals_width = list_length(bytecode->globals);

printf("Need to allocate %i bytes for global variables\n", globals_width);

if(globals_width == 0) return;

fprintf(output, ";Declaring global variables\n");

fprintf(output, "\tmovlw %i\n", globals_width);

fprintf(output, "\tsubwf H'0c'\n\n"); // Move frame pointer to make room for globals

allocate_variables(bytecode->globals);

}

void write_functions()

{

fprintf(output, "main_loop:\n");

fprintf(output, "\tcall func_main\n");

fprintf(output, "\tgoto main_loop\n");

List *functions = (List *) bytecode->functions;

while(functions->data != NULL)

{

Function *function = functions->data;

// Write function label

fprintf(output, "func_%s:\n", function->name);

// A stack frame needs 1 byte per static variable + 1 byte for saved frame pointer

int frame_width = list_length(function->symbol_table) + 1;

printf("Need to allocate %i byte stack frame for function %s\n", frame_width, function->name);

fprintf(output, "; Saving frame pointer\n");

fprintf(output, "\tmovf H'0c', 0\n"); // Load top of stack - 1 into FSR

fprintf(output, "\taddlw -1\n");

fprintf(output, "\tmovwf H'04'\n");

fprintf(output, "\tmovf H'0c', 0\n"); // Store the current frame pointer into the top of the stack

fprintf(output, "\tmovwf H'00'\n");

fprintf(output, "\tmovlw %i\n", frame_width); // Now set the new frame pointer

fprintf(output, "\tsubwf H'0c'\n\n");

allocate_variables(function->symbol_table);

List *quads = function->statements;

while(quads->data != NULL)

{

Quad *quad = quads->data;

write_quad(quad, function);

quads = quads->next;

}

// Restore previous frame pointer and return

fprintf(output, "; Restoring previous frame pointer\n");

fprintf(output, "\tmovf H'0c', 0\n"); // Load previous frame pointer

fprintf(output, "\taddlw %i\n", frame_width - 1);

fprintf(output, "\tmovwf H'04'\n");

fprintf(output, "\tmovf H'00', 0\n");

fprintf(output, "\tmovwf H'0c'\n");

fprintf(output, "\treturn\n\n");

functions = functions->next;

}

fprintf(output, "\tend\n");

}

void allocate_variables(List *symbol_table)

{

int offset = 0;

while(symbol_table->data != NULL)

{

Variable *variable = symbol_table->data;

fprintf(output, "; Allocating variable '%s'\n", variable->name);

fprintf(output, "\tmovf H'0c', 0\n"); // Load next stack position

fprintf(output, "\taddlw %i\n", offset);

fprintf(output, "\tmovwf H'04'\n");

fprintf(output, "\tmovlw %i\n", variable->value); // Store this variable there

fprintf(output, "\tmovwf H'00'\n\n");

offset++;

symbol_table = symbol_table->next;

}

}

void write_quad(Quad *quad, Function *func)

{

QuadOperand *operand1 = quad->operand1;

QuadOperand *operand2 = quad->operand2;

QuadOperand *result = quad->result;

fprintf(output, "; '%c' operation\n", quad->operator);

switch(quad->operator)

{

case '+':

{

Variable *resvar = (Variable *) result->addr;

switch(operand1->type)

{

case Constant:

fprintf(output, "\tmovlw %i\n", operand1->value);

break;

case Pointer:

{

Variable *var = (Variable *) operand1->addr;

switch(var->scope)

{

int offset;

case Local:

offset = list_index(func->symbol_table, var);

fprintf(output, "\tmovf H'0c', 0\n");

fprintf(output, "\taddlw %i\n", offset);

fprintf(output, "\tmovwf H'04'\n");

fprintf(output, "\tmovf H'00', 0\n");

break;

case Global:

offset = list_length(bytecode->globals) - list_index(bytecode->globals, var);

fprintf(output, "\tmovf H'%x', 0\n", 0x4f - offset);

break;

}

}

}

switch(operand2->type)

{

case Constant:

fprintf(output, "\taddlw %i\n", operand2->value);

fprintf(output, "\tmovwf H'0d'\n");

break;

case Pointer:

{

fprintf(output, "\tmovwf H'0d'\n");

Variable *var = (Variable *) operand2->addr;

switch(var->scope)

{

int offset;

case Local:

offset = list_index(func->symbol_table, var);

fprintf(output, "\tmovf H'0c', 0\n");

fprintf(output, "\taddlw %i\n", offset);

fprintf(output, "\tmovwf H'04'\n");

fprintf(output, "\tmovf H'00', 0\n");

break;

case Global:

offset = list_length(bytecode->globals) - list_index(bytecode->globals, var);

fprintf(output, "\tmovf H'%x', 0\n", 0x4f - offset);

break;

}

fprintf(output, "\taddwf H'0d'\n");

break;

}

}

switch(resvar->scope)

{

int offset;

case Local:

offset = list_index(func->symbol_table, resvar);

fprintf(output, "\tmovf H'0c', 0\n");

fprintf(output, "\taddlw %i\n", offset);

fprintf(output, "\tmovwf H'04'\n");

fprintf(output, "\tmovf H'0d', 0\n");

fprintf(output, "\tmovwf H'00'\n");

break;

case Global:

offset = list_length(bytecode->globals) - list_index(bytecode->globals, resvar);

fprintf(output, "\tmovlw H'%x'\n", 0x4f - offset);

fprintf(output, "\tmovwf H'04'\n");

fprintf(output, "\tmovf H'0d', 0\n");

fprintf(output, "\tmovwf H'00'\n");

break;

case Temporary:

break;

}

break;

}

case 'c':

if(!strncmp(quad->operand1->name, "printf", 5))

{

List *characters = (List *) quad->operand2->addr;

while(characters->data != NULL)

{

Variable *character = (Variable *) characters->data;

switch(character->type)

{

case 'c':

fprintf(output, "\tmovlw D'%i'\n", (uint8_t)character->value);

fprintf(output, "\tmovwf H'06'\n");

break;

case 'i':

if(character->scope = Temporary)

{

fprintf(output, "\tmovf H'0d', 0\n");

fprintf(output, "\tmovwf H'06'\n");

break;

}

int offset;

switch(character->scope)

{

case Local:

offset = list_index(func->symbol_table, character);

fprintf(output, "\tmovf H'0c', 0\n");

fprintf(output, "\taddlw %i\n", offset);

break;

case Global:

offset = list_length(bytecode->globals) - list_index(bytecode->globals, character);

fprintf(output, "\tmovf H'%x', 0\n", 0x4f - offset);

}

fprintf(output, "\tmovwf H'04'\n");

fprintf(output, "\tmovf H'00, 0\n");

fprintf(output, "\tmovwf H'06'\n");

break;

}

characters = characters->next;

}

} else {

fprintf(output, "\tcall func_%s\n", quad->operand1->name);

}

break;

default:

fprintf(output, "\tINVALID OPERATOR %c\n", quad->operator);

}

}

char * gen_label()

{

char *label = (char *) malloc(6);

assert(label != NULL);

sprintf(label, "lbl_%i", label_base);

label_base++;

return label;

}