Compiler Construction (CPSC 411) Project

Jackson Cougar Wiebe • University of Calgary • Winter 2020

Overview

Compiler written in c++ for compiling the fictional language J-- into WebAssembly. Only the text encoding of web assembly is supported (*.wat).

J--

J-- is a c style language that implements a subset of the Java syntax.

Valuetypes

• Integers
• Booleans

Strings

• Strings support a small set of escape sequences \',\",\n,\b,\t,\f,\\.
• Strings can only be used as arguments to system calls and cannot be used as valuetypes.

Functions

• arguments can be integer or boolean valuetypes.
• function can return valuetypes (void returning is also supported).

Operators

• built-in binary operators +,-,*,/,%,<,>,<=,>=,=,==,!=,!,&&,|| and unary operators -.

Control Statements

• break, return, if, if-else, and while

Scope

• Local and globals scopes; nested scopes can be create by opening and closing curly braces ({,}).

Strong Type Checking

• Everything is type checked at compiler time.

Example J-- program

    main() {
        prints("Hello, world!");
    }

Example WebAssembly output

;;begins auto generated .wasm code
(module
  ;;externs/imports
  (import "host" "exit" (func $halt))
  (import "host" "getchar" (func $getchar (result i32)))
  (import "host" "putchar" (func $putchar (param i32)))
  ;;data
...
  (data 0 (i32.const 9) "Hello, world!")
  ;;program
  ;;begins auto generated .wasm code
  (start $main)
  (func $main
    i32.const 9
    i32.const 13
    call $prints
  )
  ;;finished auto generated .wasm code
  ;;runtime system
 ...
  (memory 1)
);;finished auto generated .wasm code

Dependancies

• flex (>2.5)
• bison

Usage

jcc [INPUT_JMM_FILE]

The resulting WAT file will be saved to the current working directory.