README.org

What is this?

This is a compiler. When you run it, it compiles ‘input.program’ and produces a binary a.out.

The frontend is written in clojure, and the back-end is LLVM.

How to Run

1. Install LLVM library.
2. lein deps
3. lein run

NOTE: The code assumes LLVM is at /opt/local/lib/libLLVM-2.9.dylib For different paths, update jna.library.path java property in native.clj.

Input Program

Here our toy language is used as input into compiler frontend.

func cos(Double) Double;
func printf(...) Integer;

func bar() Integer {
   printf("foo");
   return 3;
}

func main() Integer {
    printf("hello %d", 3);
    printf("bar ");
    bar();
    return 0;
}

Program Output

1. The intermediate representation is printed.
2. The object file and linked binary is created.
3. Binary is executed, output is shown at bottom.

How does it work?

• parser.clj is for transforming Input=>AST (using clarsec, a combinator parser)
• ast.clj is for transforming AST=>LLVM IR
• main.clj is for LLVM IR=>object file=>linking.
• llvm.clj contains needed llvm bindings for clojure.
• native.clj is a thin JNA wrapper. It’s like clj-native, but less efficient. (I couldn’t get arrays of pointers working in clj-native.)

If input program is this:

func main() Integer {
    printf("foo");
    printf("hello");
    return 1;
}

AST looks like this:

((:func main [] Integer
        (:call printf "foo")
        (:call printf "hello")
        (:return 1)))

LLVM IR looks like this:

@0 = internal constant [4 x i8] c"foo\00"
@1 = internal constant [9 x i8] c"hello %d\00"

define i32 @main() {
  %1 = call i32 (...)* @printf([9 x i8]* @1, i32 3)
  %2 = call i32 (...)* @printf([5 x i8]* @2)
  ret i32 1
}

x86 Disassembly looks like this:

0000000100000ef0 <_main>:
   100000ef0:	50                   	push   %rax
   100000ef1:	48 8d 3d 3c 00 00 00 	lea    0x3c(%rip),%rdi
   100000ef8:	be 03 00 00 00       	mov    $0x3,%esi
   100000efd:	30 c0                	xor    %al,%al
   100000eff:	e8 26 00 00 00       	callq  100000f2a <_printf$stub>
   100000f04:	48 8d 3d 32 00 00 00 	lea    0x32(%rip),%rdi
   100000f0b:	30 c0                	xor    %al,%al
   100000f0d:	e8 18 00 00 00       	callq  100000f2a <_printf$stub>
   100000f12:	48 8d 3d 17 00 00 00 	lea    0x17(%rip),%rdi
   100000f19:	30 c0                	xor    %al,%al
   100000f1b:	e8 0a 00 00 00       	callq  100000f2a <_printf$stub>
   100000f20:	31 c0                	xor    %eax,%eax
   100000f22:	5a                   	pop    %rdx
   100000f23:	c3                   	retq