coolc

(Yet another) Cool compiler

Note: This is not the coolc that outputs BIT. This coolc outputs 32-bit x86 assembly with AT&T (GNU as) syntax.

Calling convention

• The reciever is pushed onto the stack first, followed by the arguments in the same order that they are listed in the source code. That is, 8(%ebp) is the last argument, 12(%ebp) is the second-last, and so on.
• The return value is in the AX register.

Memory layout

• Heap consists of objects end to end.
• Objects have a tag, a size, and a garbage collector tag, followed by the data of the object. The 3-word header is not included in the size.
• The tag is either -2 for raw memory (managed by something other than the garbage collector), -1 for garbage, 0 for the end of the heap, or a number from 1 to max_tag, inclusive, for a class type.
• Each positive tag number has an associated method table, name, and pointer coount.
• GC tags are negative for certain special cases like permanent objects and garbage, and otherwise contain the number of stack references to the object. Non-garbage objects with a non-zero GC tag are considered roots of the heap.