CS322 Winter’09: Languages and Compiler Design I I 2/24/09
Prof. Jingke Li (FAB 120-06, [email protected]), Classes: TTh 2-3:50pm, URBAN 304, Office Hours: TTh 10-11am.
Project #5: SPARC Assembly Code Generation
(Due Tuesday 3/10/09 @ 5pm)
This (last) project is to implement the final component of the MINI compiler, a SPARC assembly code
generator for the IR Tree language. This codegen module should be implemented as a self-contained Java
class (like the interpreter in Project 4), Codegen, with the following interface:
public Codegen(PROG p) {...} --- the constructor takes an IR program as input
public void go() {...} --- the main trigger for the codegen module
Operand Representation
In the codegen, all operands, including constants, addresses, and intermediate results, are stored in ob jects
of the class Operand. For each kind of operands, there is a subclass for representing it:
abstract class Operand {}
public class Reg extends Operand // register
{ static final int RESERVED=-1, FREE=0, USE=1, TEMP=2;
String name; int status; }
public class RegOffset extends Operand { Reg r; int o; } // Stack location
public class Imm13 extends Operand { int i; } // 13-bit immed value
public class Imm32 extends Operand { int i; } // 32-bit immed value
public class AddrName extends Operand { String s; } // global address name
Register Management
The codegen uses a simple register allocation scheme. The register allo cator keeps track of each register’s
status: reserved,free,used, or temp. Upon an allocation request, the allocator simply allocates the next
available register. If there is no more registers available, it just throws an exception. When a temp is assigned
to a register, it will stay there until the end of the program. A special status, temp, is used to prevent the
register from being freed. The register allocator routines are:
// requesting an arbitrary free register;
// throws an exception if none is free
// (Note that the status of the reg will be set to ’use’;
// if it is to be used for a temp, the status needs to be
// changed to ’temp’ after the call is returned.)
private Reg getReg() throws CodegenException { ... }
// requesting a specific register r;
// throws an exception if r is not free
private void getReg(Reg r) throws CodegenException { ... }
// freeing a register, skipping if it holds a temp
void freeReg(Reg r) { ... }
// freeing all used registers, including those holding temps
void freeAllRegs() { ... }
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