compilerUtils.ts

import { BinOp, ClassDef, Type, UniOp } from "./ast";
import { RuntimeErrors } from "./panic";
import { isObject } from "./tcUtils";

/**
 * Map of BinOps to their cooresponding WAT instructions. If it's not so simple,
 * you'll need to edit codeGenExpr.
 */
export const binOpToInstr: Map<BinOp, string> = new Map([
  [BinOp.ADD, "(i32.add)"],
  [BinOp.SUB, "(i32.sub)"],
  [BinOp.MUL, "(i32.mul)"],
  [BinOp.DIV, "(i32.div_s)"],
  [BinOp.MOD, "(i32.rem_s)"],
  [BinOp.EQ, "(i32.eq)"],
  [BinOp.NE, "(i32.ne)"],
  [BinOp.LT, "(i32.lt_s)"],
  [BinOp.LE, "(i32.le_s)"],
  [BinOp.GT, "(i32.gt_s)"],
  [BinOp.GE, "(i32.ge_s)"],
]);

export const uniOpToInstr: Map<UniOp, string> = new Map([
  [UniOp.NEG, "(i32.mul (i32.const -1))"],
  [UniOp.NOT, "(i32.xor (i32.const 1))"],
]);

type ClassEnv = Map<string, ClassDef<Type>>;

/**
 * Check the given object to see if it's None, if so panic at runtime.
 * Assumes an object address is on the stack. Will restore its argument.
 */
export const checkNone: string = [
  `(local.set $$scratch)`,
  `(local.get $$scratch)`,
  `(i32.eq (i32.const 0))`, // 0 is the representation of none
  `(if`,
  `(then`,
  `(call $panic (i32.const ${RuntimeErrors.OperationOnNone}))`,
  `)`,
  `)`,
  `(local.get $$scratch)`,
].join("\n");

/**
 * Find the index for a field based off an object type, a field, and a classenv.
 *
 * @param t An object type
 * @param fieldName the Field being retrieved
 * @param classes Environment of all classes in the program
 * @returns index of the field
 * @throws if `t` is not an object
 */
export function getFieldIndex(
  t: Type,
  fieldName: string,
  classes: ClassEnv
): number {
  if (!isObject(t))
    throw new Error(
      `This should be impossible - at compiler, getting field of nonobject ${t}`
    );
  const classdata = classes.get(t.class);
  const fieldIndex = classdata.fields.findIndex(
    (f) => f.typedVar.name === fieldName
  );

  return fieldIndex;
}