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/*
* Copyright (C) 2023 Johnny Richard
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include "gas_assembly_generator.h"
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static void
gas_assembly_generator_binary_operation(gas_assembly_generator_t *gen, ast_binary_operation_t *binary_operation);
static void
gas_assembly_generator_compile_function(gas_assembly_generator_t *gen, ast_function_declaration_t *func);
static void
gas_assembly_generator_compile_literal(gas_assembly_generator_t *gen, ast_literal_t *literal);
static void
gas_assembly_generator_compile_return_stmt(gas_assembly_generator_t *gen, ast_return_stmt_t *return_stmt);
static void
gas_assembly_generator_compile_variable_declaration(gas_assembly_generator_t *gen,
ast_variable_declaration_t *variable_declaration);
static void
gas_assembly_generator_compile_variable(gas_assembly_generator_t *gen, ast_variable_t *variable);
typedef struct ref_entry_t
{
ast_identifier_t *id;
int stack_offset;
} ref_entry_t;
// TODO: We need a destroy function for ref_entry.
static ref_entry_t *
ref_entry_new(void)
{
ref_entry_t *entry = (ref_entry_t *)malloc(sizeof(ref_entry_t));
if (entry == NULL) {
fprintf(stderr, "ref_entry_new: Out of memory: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
return entry;
}
void
gas_assembly_generator_init(gas_assembly_generator_t *gen, FILE *stream)
{
assert(gen && stream);
gen->stream = stream;
gen->refs = vector_new();
gen->stack_offset = 0;
}
void
gas_assembly_generator_compile(gas_assembly_generator_t *gen, ast_node_t *ast)
{
switch (ast->kind) {
case AST_BINARY_OPERATION:
gas_assembly_generator_binary_operation(gen, &ast->data.binary_operation);
break;
case AST_FUNCTION_DECLARATION:
gas_assembly_generator_compile_function(gen, &ast->data.function);
break;
case AST_LITERAL:
gas_assembly_generator_compile_literal(gen, &ast->data.literal);
break;
case AST_RETURN_STMT:
gas_assembly_generator_compile_return_stmt(gen, &ast->data.return_stmt);
break;
case AST_IDENTIFIER:
assert(false && "TODO: ast identifier not implemented yet");
break;
case AST_VARIABLE_DECLARATION:
gas_assembly_generator_compile_variable_declaration(gen, &ast->data.variable_declaration);
break;
case AST_VARIABLE:
gas_assembly_generator_compile_variable(gen, &ast->data.variable);
break;
case AST_UNKOWN_NODE:
assert(false && "unreachable");
}
}
static void
gas_assembly_generator_compile_function(gas_assembly_generator_t *gen, ast_function_declaration_t *func)
{
assert(func);
if (!string_view_eq(func->identifier.name, string_view_from_str("main"))) {
fprintf(stderr, "[ERROR]: no main function has been defined!\n");
exit(EXIT_FAILURE);
}
fprintf(gen->stream, ".global _start\n");
fprintf(gen->stream, ".text\n");
fprintf(gen->stream, "_start:\n");
fprintf(gen->stream, " push %%rbp\n");
fprintf(gen->stream, " mov %%rsp, %%rbp\n");
for (size_t i = 0; i < func->body->size; i++) {
gas_assembly_generator_compile(gen, vector_at(func->body, i));
}
fprintf(gen->stream, " pop %%rbp\n");
}
static void
gas_assembly_generator_compile_return_stmt(gas_assembly_generator_t *gen, ast_return_stmt_t *return_stmt)
{
assert(gen && return_stmt);
gas_assembly_generator_compile(gen, return_stmt->argument);
fprintf(gen->stream, " mov %%rax, %%rdi\n");
fprintf(gen->stream, " mov $60, %%rax\n");
fprintf(gen->stream, " syscall\n");
}
static void
gas_assembly_generator_compile_variable_declaration(gas_assembly_generator_t *gen,
ast_variable_declaration_t *variable_declaration)
{
gen->stack_offset -= 8;
gas_assembly_generator_compile(gen, variable_declaration->value);
ref_entry_t *entry = ref_entry_new();
*entry = (ref_entry_t){ .id = &variable_declaration->identifier, .stack_offset = gen->stack_offset };
vector_push_back(gen->refs, entry);
fprintf(gen->stream, " mov %%rax, %d(%%rbp)\n", entry->stack_offset);
}
static void
gas_assembly_generator_compile_variable(gas_assembly_generator_t *gen, ast_variable_t *variable)
{
ref_entry_t *entry = NULL;
for (int i = gen->refs->size - 1; i >= 0; --i) {
ref_entry_t *entry_tmp = (ref_entry_t *)vector_at(gen->refs, i);
if (entry_tmp->id == variable->identifier) {
entry = entry_tmp;
break;
}
}
assert(entry && "reference not found");
fprintf(gen->stream, " mov %d(%%rbp), %%rax\n", entry->stack_offset);
}
static void
gas_assembly_generator_compile_literal(gas_assembly_generator_t *gen, ast_literal_t *literal)
{
switch (literal->kind) {
case AST_LITERAL_INTEGER:
fprintf(gen->stream, " mov $%d, %%rax\n", literal->value.integer);
return;
default:
assert(false && "no code generation strategy.");
}
}
static void
gas_assembly_generator_binary_operation(gas_assembly_generator_t *gen, ast_binary_operation_t *binary_operation)
{
gas_assembly_generator_compile(gen, binary_operation->right);
gen->stack_offset -= 8;
fprintf(gen->stream, " mov %%rax, %d(%%rbp)\n", gen->stack_offset);
gas_assembly_generator_compile(gen, binary_operation->left);
fprintf(gen->stream, " mov %d(%%rbp), %%rcx\n", gen->stack_offset);
gen->stack_offset += 8;
if (binary_operation->kind == AST_BINOP_ADITION) {
fprintf(gen->stream, " add %%rcx, %%rax\n");
return;
}
if (binary_operation->kind == AST_BINOP_SUBTRACTION) {
fprintf(gen->stream, " sub %%rcx, %%rax\n");
return;
}
if (binary_operation->kind == AST_BINOP_MULTIPLICATION) {
fprintf(gen->stream, " mul %%rcx\n");
return;
}
if (binary_operation->kind == AST_BINOP_DIVISION) {
fprintf(gen->stream, " xor %%rdx, %%rdx\n");
fprintf(gen->stream, " div %%rcx\n");
return;
}
assert(false && "No strategy defined for binary operation");
}
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