TIGER

The Tiger compiler. Copyright (C) 2013-2015, SSE of USTC.

Tiger is a MiniJava lanuage(see Tiger book Appendix MiniJava Language Reference Manual) compile. Just for fun, it has a garbage collector using copy collection algorithm.

##Getting Start

compile to C programming language

use

java -jar tiger test/LinkedList.java -codegen C

compile to jasmin programming language

use

java -jar tiger test/LinkedList.java -codegen bytecode

and is will translate .java to .j(jasmin).

##GC Support

In tiger, we use a gc named Gimple garbage collector, whitch means gc is simple. And we use the algorithm called Cheney's algorithm which uses a breadth-first strategy.

###Object Model

An object model is the strategy that how an object can be laid out in memory (the heap). A good object model should support all kinds of possible operations efficiently on an object: virtual method dispatching, locking, garbage collection, etc., whereas at the same time be as compact as possible to save storage.

There are two different forms of objects in MiniJava: normal objects and (integer) array objects. So, to support virtual method dispatching on normal objects, each object is represented as a sequence of its fields plus a unique virtual method table pointer at the zero offset as a header. And to support array length operations on array objects, arrays contain a length field as a header.

// "new" a new object, do necessary initializations, and
// return the pointer (reference).

	  ----------------
      | vptr      ---|----> (points to the virtual method table)
      |--------------|
      | isObjOrArray | (0: for normal objects)
      |--------------|
      | length       | (this field should be empty for normal objects)
      |--------------|
      | forwarding   |
      |--------------|\
p---->| v_0          | \
      |--------------|  s
      | ...          |  i
      |--------------|  z
      | v_{size-1}   | /e
      ----------------/


// "new" an array of size "length", do necessary
// initializations. And each array comes with an
// extra "header" storing the array length and other information.
	  ----------------
	  | vptr         | (this field should be empty for an array)
	  |--------------|
	  | isObjOrArray | (1: for array)
	  |--------------|
	  | length       |
	  |--------------|
      | forwarding   |
	  |--------------|\
p---->| e_0          | \
  	  |--------------|  s
  	  | ...          |  i
  	  |--------------|  z
  	  | e_{length-1} | /e
  	  ----------------/

###Play In Runtime

Since the evaluation order of the argument list, when using clang, need add the compile options __CLANG__

tiger-comp/runtime$ clang test/Test_GC3.java.c runtime.c -D__CLANG__

###command-line

-heapSize <n>            set the Java heap size (in bytes)
-verbose {0|1|2|3}       trace method execuated
-gcLog                   generate GClog
-help                    help

##Caveats & Limitations

Too many...

##More

dog-comp is a MiniJava compiler implements in Golang which has dataflow optimazation.