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@keleshev
Last active Jun 20, 2022
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#include <stdio.h>
#include <stdlib.h>
typedef struct AST AST; // Forward reference
struct AST {
enum {
AST_MAIN,
AST_NUMBER,
AST_ADD,
AST_MUL,
} tag;
union {
struct AST_MAIN { AST *body; } AST_MAIN;
struct AST_NUMBER { int number; } AST_NUMBER;
struct AST_ADD { AST *left; AST *right; } AST_ADD;
struct AST_MUL { AST *left; AST *right; } AST_MUL;
} data;
};
AST *ast_new(AST ast) {
AST *ptr = malloc(sizeof(AST));
if (ptr) *ptr = ast;
return ptr;
}
void ast_free(AST *ptr) {
AST ast = *ptr;
switch (ast.tag) {
case AST_MAIN: {
struct AST_MAIN data = ast.data.AST_MAIN;
ast_free(data.body);
break;
}
case AST_NUMBER: {
struct AST_NUMBER data = ast.data.AST_NUMBER;
break;
}
case AST_ADD: {
struct AST_ADD data = ast.data.AST_ADD;
ast_free(data.left);
ast_free(data.right);
break;
}
case AST_MUL: {
struct AST_MUL data = ast.data.AST_MUL;
ast_free(data.left);
ast_free(data.right);
break;
}
}
free(ptr);
}
#define AST_NEW(tag, ...) ast_new((AST){tag, {.tag=(struct tag){__VA_ARGS__}}})
void ast_print(AST *ptr) {
AST ast = *ptr;
switch (ast.tag) {
case AST_MAIN: {
struct AST_MAIN data = ast.data.AST_MAIN;
printf("main() = ");
ast_print(data.body);
return;
}
case AST_NUMBER: {
struct AST_NUMBER data = ast.data.AST_NUMBER;
printf("%d", data.number);
return;
}
case AST_ADD: {
struct AST_ADD data = ast.data.AST_ADD;
printf("(");
ast_print(data.left);
printf(" + ");
ast_print(data.right);
printf(")");
return;
}
case AST_MUL: {
struct AST_MUL data = ast.data.AST_MUL;
printf("(");
ast_print(data.left);
printf(" * ");
ast_print(data.right);
printf(")");
return;
}
}
}
#define emitf printf
void ast_emit(AST *ptr) {
AST ast = *ptr;
switch (ast.tag) {
case AST_MAIN: {
struct AST_MAIN data = ast.data.AST_MAIN;
emitf(".global _main\n");
emitf("_main:\n");
ast_emit(data.body);
emitf(" ret\n");
emitf("\n");
return;
}
case AST_NUMBER: {
struct AST_NUMBER data = ast.data.AST_NUMBER;
emitf(" mov rax, %d\n", data.number);
return;
}
case AST_ADD: {
struct AST_ADD data = ast.data.AST_ADD;
ast_emit(data.left);
emitf(" push rax\n");
ast_emit(data.right);
emitf(" pop rbx\n");
emitf(" add rax, rbx\n");
return;
}
case AST_MUL: {
struct AST_MUL data = ast.data.AST_MUL;
ast_emit(data.left);
emitf(" push rax\n");
ast_emit(data.right);
emitf(" pop rbx\n");
emitf(" mul rbx\n");
return;
}
}
}
int main() {
// main() = 4 + 2 * 10 + 3 * (5 + 1)
AST *term = AST_NEW(AST_MAIN,
AST_NEW(AST_ADD,
AST_NEW(AST_NUMBER, 4),
AST_NEW(AST_ADD,
AST_NEW(AST_MUL,
AST_NEW(AST_NUMBER, 2),
AST_NEW(AST_NUMBER, 10),
),
AST_NEW(AST_MUL,
AST_NEW(AST_NUMBER, 3),
AST_NEW(AST_ADD,
AST_NEW(AST_NUMBER, 5),
AST_NEW(AST_NUMBER, 1),
),
),
),
),
);
printf("/* "); ast_print(term); printf(" */\n");
ast_emit(term);
ast_free(term);
}
type ast =
| Main of ast
| Number of int
| Add of ast * ast
| Mul of ast * ast
let emitf x = Printf.kprintf print_endline x
let rec emit = function
| Main body ->
emitf ".global _main";
emitf "_main:";
emit body;
emitf " ret"
| Number n ->
emitf " mov rax, %d" n
| Add (left, right) ->
emit left;
emitf " push rax";
emit right;
emitf " pop rbx";
emitf " add rax, rbx"
| Mul (left, right) ->
emit left;
emitf " push rax";
emit right;
emitf " pop rbx";
emitf " mul rbx"
let () =
(* main() = 4 + 2 * 10 + 3 * (5 + 1) *)
let term =
Main (
Add (
Number 4,
Add (
Mul (Number 2, Number 10),
Mul (Number 3, Add (Number 5, Number 1))
)
)
)
in
emit term
ast.exe: ast.c
gcc -Werror -Wswitch -Wimplicit-fallthrough ast.c -o ast.exe
clean:
rm -f *.o *.exe *.s a.out
test.s: ast.exe
./ast.exe > test.s
test.exe: test.s
gcc test.s -masm=intel -o test.exe
.PHONY: test
test: test.exe
./test.exe
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