// -classpath .:/home/apt/software/bcel/bcel-5.0rc1/bcel.jar
import java.io.*;
import java.util.*;
import org.apache.bcel.classfile.*;
import org.apache.bcel.generic.*;
import org.apache.bcel.*;
/**
* Read a class file and generate the corresponding MIPS assembly code to stdout.
* The command line usage is:
*
*
java compile1 foo.class > foo.s
*/
public class compile1{
// these variables are fixed for a given class file
static ConstantPool cp;
static ConstantPoolGen cpg;
public static void main(String[] argv) throws IOException {
JavaClass java_class = new ClassParser(argv[0]).parse(); // May throw IOException
cp = java_class.getConstantPool();
cpg = new ConstantPoolGen(cp);
Method[] methods = java_class.getMethods();
// Process each method
for (int j = 0; j < methods.length; j++)
emit_method(methods[j]);
// Emit exception handlers
emit0(".text");
emitlab("NASexception");
emit2("la","$a0","NASmessage");
emit1("b","_issue_exception");
emitlab("NPexception");
emit2("la","$a0","NPmessage");
emit1("b","_issue_exception");
emitlab("AIOOBexception");
emit2("la","$a0","AIOOBmessage");
emitlab("_issue_exception");
emit2("li","$v0","4"); // magic SPIM code for print_string
emit0("syscall");
emit2("li","$v0","10"); // magic SPIM code for exit
emit0("syscall");
emit0(".data");
emitlab("NASmessage");
emit1(".asciiz","\"Uncaught NegativeArraySizeException\n\"");
emitlab("NPmessage");
emit1(".asciiz","\"Uncaught NullPointerException\n\"");
emitlab("AIOOBmessage");
emit1(".asciiz","\"Uncaught ArrayIndexOutOfBoundsException\n\"");
}
// these variables change per-method
static String name;
static int string_label = 0;
static int max_locals = 0;
// tos is index of top of stack.
// so number of stack slots in use = tos + 1.
static int tos = -1;
static void emit_method(Method m) {
name = m.getName();
if (name.equals(""))
return; // hack to skip constructors
Code code = m.getCode();
byte method_bytes[] = code.getCode();
max_locals = code.getMaxLocals(); // includes arguments
// int max_stack = code.getMaxStack(); -- we don't actually use this
// emit header
emit0(".text");
emit1(".globl", name);
emitlab(name);
InstructionHandle[] instrhandles = new InstructionList(method_bytes).getInstructionHandles();
tos = -1;
EmitVisitor emitter = new EmitVisitor();
for (int i = 0; i < instrhandles.length; i ++) {
InstructionHandle ih = instrhandles[i];
if (ih.hasTargeters()) // if this is a branch target
emitlab(llab(ih.getPosition())); // emit a label
Instruction inst = ih.getInstruction();
inst.accept(emitter); // emit the code corresponding to instruction
if (inst instanceof BranchInstruction && tos != -1)
System.err.println("Compiler invariant violated: stack not empty at branch from " + ih.getPosition());
}
// all returns are explicit in instruction list, so nothing to do at the end
}
// Code emission utilities
// We use the following MIPS/SPIM register assignments:
// $2 = $v0 return values from methods; call code for syscalls
// $4 = $a0 argument value for syscalls
// $5-$14 locals (local i = $(5+i)
// $15 temporary (for use within code for a single JVM instruction)
// $16-$25 stack slots (slot i = $(16+i))
// $31 = $ra return address
// others unused
// Register representing stack slot (10 from $16-$25)
static String stack(int i) {
if (i < 0 || i > 9)
System.err.println("Can't handle stack slot " + i);
return "$" + (16 + i);
}
// Register representing local (10 from $5-$14)
static String lvar(int i) {
if (i < 0 || i > 9)
System.err.println("Can't handle local number " + i);
return "$" + (5 + i);
}
// Temporary register ($15)
static String temp = "$15";
// Local label
static String llab(int i) {
return name + "_" + i;
}
static void unimplemented(Object obj) {
System.err.println("Can't handle instruction " + obj);
}
// Code emission
static void emitlab(String lab) {
System.out.println(lab + ":");
}
static void emit0(String op) {
System.out.println("\t" + op);
}
static void emit1(String op, String a1) {
System.out.println("\t" + op + " " + a1);
}
static void emit2(String op, String a1, String a2) {
System.out.println("\t" + op + " " + a1 + ", " + a2);
}
static void emit3(String op, String a1, String a2, String a3) {
System.out.println("\t" + op + " " + a1 + ", " + a2 + ", " + a3);
}
// Store return address register, lvar registers and operand stack registers onto machine stack
static void emit_caller_save(int stack_slots) {
emit3("sub", "$sp", "$sp", Integer.toString(4*(1+max_locals+stack_slots)));
emit2("sw", "$ra", "($sp)");
for (int i = 0; i < max_locals; i++)
emit2("sw", lvar(i), "" + (4*(1+i)) + "($sp)");
for (int i = 0; i < stack_slots; i++)
emit2("sw", stack(i), "" + (4*(1+max_locals+i)) + "($sp)");
}
// Restore return address register, lvar registers and operand stack registers from machine stack
static void emit_caller_restore(int stack_slots) {
emit2("lw","$ra","($sp)");
for (int i = 0; i < max_locals; i++)
emit2("lw", lvar(i),"" + (4*(1+i)) + "($sp)");
for (int i = 0; i < stack_slots; i++)
emit2("lw", stack(i),"" + (4*(1+max_locals+i)) + "($sp)");
emit3("add", "$sp", "$sp", Integer.toString(4*(1+max_locals+stack_slots)));
}
// Utilities for conditional branch instructions
static void emit_branch(String op,BranchInstruction obj) {
int target = obj.getTarget().getPosition();
emit3("b" + op,stack(tos-1),stack(tos),llab(target));
tos -= 2;
}
static void emit_branch_zero(String op,BranchInstruction obj) {
int target = obj.getTarget().getPosition();
emit2("b" + op + "z",stack(tos),llab(target));
tos -= 1;
}
// Per-instruction code generator is done using the visitor pattern,
// because that's how bcel is set up.
static class EmitVisitor extends org.apache.bcel.generic.EmptyVisitor
implements org.apache.bcel.generic.Visitor {
EmitVisitor() {
}
// Emit MIPS code for JVM instructions we know how to deal with; complain about others
public void visitAALOAD(AALOAD obj) { unimplemented(obj); }
public void visitAASTORE(AASTORE obj) { unimplemented(obj);}
public void visitACONST_NULL(ACONST_NULL obj) {
emit2("li",stack(tos+1),"0");
tos += 1;
}
public void visitALOAD(ALOAD obj) {
emit2("move",stack(tos+1),lvar(obj.getIndex()));
tos+=1;
}
public void visitANEWARRAY(ANEWARRAY obj) { unimplemented(obj);}
public void visitARETURN(ARETURN obj) {
emit2("move", "$v0",stack(tos));
emit1("jr","$ra");
tos -= 1;
}
public void visitARRAYLENGTH(ARRAYLENGTH obj) {
emit2("beqz",stack(tos),"NPexception"); // check for null pointer
emit2("lw",stack(tos),"(" + stack(tos) + ")");
}
public void visitASTORE(ASTORE obj) {
emit2("move",lvar(obj.getIndex()),stack(tos));
tos -= 1;
}
public void visitATHROW(ATHROW obj) { unimplemented(obj); }
public void visitBALOAD(BALOAD obj) { unimplemented(obj);}
public void visitBASTORE(BASTORE obj) { unimplemented(obj); }
public void visitBIPUSH(BIPUSH obj) {
emit2("li", stack(tos+1), obj.getValue().toString());
tos += 1;
}
public void visitBREAKPOINT(BREAKPOINT obj) { unimplemented(obj);}
public void visitCALOAD(CALOAD obj) { unimplemented(obj);}
public void visitCASTORE(CASTORE obj) { unimplemented(obj);}
public void visitCHECKCAST(CHECKCAST obj) { unimplemented(obj); }
public void visitD2F(D2F obj) { unimplemented(obj);}
public void visitD2I(D2I obj) { unimplemented(obj);}
public void visitD2L(D2L obj) { unimplemented(obj);}
public void visitDADD(DADD obj) { unimplemented(obj);}
public void visitDALOAD(DALOAD obj) { unimplemented(obj); }
public void visitDASTORE(DASTORE obj) { unimplemented(obj); }
public void visitDCONST(DCONST obj) { unimplemented(obj);}
public void visitDCMPG(DCMPG obj) {unimplemented(obj); }
public void visitDCMPL(DCMPL obj) { unimplemented(obj); }
public void visitDDIV(DDIV obj) { unimplemented(obj); }
public void visitDLOAD(DLOAD obj) { unimplemented(obj);}
public void visitDMUL(DMUL obj) { unimplemented(obj);}
public void visitDNEG(DNEG obj) { unimplemented(obj);}
public void visitDREM(DREM obj) { unimplemented(obj); }
public void visitDRETURN(DRETURN obj) { unimplemented(obj);}
public void visitDSTORE(DSTORE obj) { unimplemented(obj); }
public void visitDSUB(DSUB obj) { unimplemented(obj);}
public void visitDUP(DUP obj) {
emit2("move",stack(tos+1),stack(tos));
tos+=1;
}
public void visitDUP_X1(DUP_X1 obj) { unimplemented(obj);}
public void visitDUP_X2(DUP_X2 obj) { unimplemented(obj);}
public void visitDUP2(DUP2 obj) { unimplemented(obj); }
public void visitDUP2_X1(DUP2_X1 obj) { unimplemented(obj);}
public void visitDUP2_X2(DUP2_X2 obj) { unimplemented(obj); }
public void visitF2D(F2D obj) { unimplemented(obj);}
public void visitF2I(F2I obj) { unimplemented(obj);}
public void visitF2L(F2L obj) { unimplemented(obj); }
public void visitFADD(FADD obj) { unimplemented(obj);}
public void visitFALOAD(FALOAD obj) { unimplemented(obj);}
public void visitFASTORE(FASTORE obj) { unimplemented(obj);}
public void visitFCMPG(FCMPG obj) { unimplemented(obj); }
public void visitFCMPL(FCMPL obj) { unimplemented(obj);}
public void visitFCONST(FCONST obj) { unimplemented(obj);}
public void visitFDIV(FDIV obj) { unimplemented(obj);}
public void visitFLOAD(FLOAD obj) { unimplemented(obj);}
public void visitFMUL(FMUL obj) { unimplemented(obj); }
public void visitFNEG(FNEG obj) { unimplemented(obj);}
public void visitFREM(FREM obj) { unimplemented(obj); }
public void visitFRETURN(FRETURN obj) { unimplemented(obj);}
public void visitFSTORE(FSTORE obj) { unimplemented(obj); }
public void visitFSUB(FSUB obj) { unimplemented(obj); }
public void visitGETFIELD(GETFIELD obj) { unimplemented(obj);}
public void visitGETSTATIC(GETSTATIC obj) {
// hack to quietly handle fetches of System.out
if (obj.getClassName(cpg).equals("java.lang.System") &&
obj.getFieldName(cpg).equals("out"))
tos += 1; // just leave an empty slot
else
unimplemented(obj); }
public void visitGOTO(GOTO obj) {
emit1("b",llab(obj.getTarget().getPosition()));
}
public void visitGOTO_W(GOTO_W obj) {
emit1("b",llab(obj.getTarget().getPosition()));
}
public void visitI2B(I2B obj) { unimplemented(obj);}
public void visitI2C(I2C obj) { unimplemented(obj);}
public void visitI2D(I2D obj) { unimplemented(obj);}
public void visitI2F(I2F obj) { unimplemented(obj); }
public void visitI2L(I2L obj) { unimplemented(obj);}
public void visitI2S(I2S obj) { unimplemented(obj);}
public void visitIADD(IADD obj) {
emit3("add",stack(tos-1),stack(tos-1),stack(tos));
tos -=1;
}
public void visitIALOAD(IALOAD obj) {
emit2("beqz",stack(tos-1),"NPexception"); // check for null pointer
emit2("lw",temp,"(" + stack(tos-1) + ")"); // fetch length
emit3("bgeu",stack(tos),temp,"AIOOBexception"); // check bounds
emit3("sll",temp,stack(tos),"2"); // cheap multiply of index by 4
emit3("add",temp,temp,stack(tos-1));
emit2("lw",stack(tos-1),"4(" + temp + ")"); // add 4 to skip length as we go
tos -= 1;
}
public void visitIAND(IAND obj) {
emit3("and",stack(tos-1),stack(tos-1),stack(tos));
tos-=1;
}
public void visitIASTORE(IASTORE obj) { // without checking
emit2("beqz",stack(tos-2),"NPexception"); // check for null pointer
emit2("lw",temp,"(" + stack(tos-2) + ")"); // fetch length
emit3("bgeu",stack(tos-1),temp,"AIOOBexception"); // check bounds
emit3("sll",temp,stack(tos-1),"2"); // cheap multiply of index by 4
emit3("add",temp,temp,stack(tos-2));
emit2("sw",stack(tos),"4(" + temp + ")"); // add 4 to skip length as we go
tos -= 3;
}
public void visitICONST(ICONST obj) {
emit2("li", stack(tos+1), obj.getValue().toString());
tos+= 1;
}
public void visitIDIV(IDIV obj) {
emit3("div",stack(tos-1),stack(tos-1),stack(tos));
tos-=1;
}
public void visitIF_ACMPEQ(IF_ACMPEQ obj) {
emit_branch("eq",obj);
}
public void visitIF_ACMPNE(IF_ACMPNE obj) {
emit_branch("ne",obj);
}
public void visitIF_ICMPEQ(IF_ICMPEQ obj) {
emit_branch("eq",obj);
}
public void visitIF_ICMPGE(IF_ICMPGE obj) {
emit_branch("ge",obj);
}
public void visitIF_ICMPGT(IF_ICMPGT obj) {
emit_branch("gt",obj);
}
public void visitIF_ICMPLE(IF_ICMPLE obj) {
emit_branch("le",obj);
}
public void visitIF_ICMPLT(IF_ICMPLT obj) {
emit_branch("lt",obj);
}
public void visitIF_ICMPNE(IF_ICMPNE obj) {
emit_branch("ne",obj);
}
public void visitIFEQ(IFEQ obj) {
emit_branch_zero("eq",obj);
}
public void visitIFGE(IFGE obj) {
emit_branch_zero("ge",obj);
}
public void visitIFGT(IFGT obj) {
emit_branch_zero("gt",obj);
}
public void visitIFLE(IFLE obj) {
emit_branch_zero("le",obj);
}
public void visitIFLT(IFLT obj) {
emit_branch_zero("lt",obj);
}
public void visitIFNE(IFNE obj) {
emit_branch_zero("ne",obj);
}
public void visitIFNONNULL(IFNONNULL obj) {
emit_branch_zero("ne",obj);
}
public void visitIFNULL(IFNULL obj) {
emit_branch_zero("eq",obj);
}
public void visitIINC(IINC obj) {
emit3("add",lvar(obj.getIndex()),lvar(obj.getIndex()), Integer.toString(obj.getIncrement()));
}
public void visitILOAD(ILOAD obj) {
emit2("move",stack(tos+1),lvar(obj.getIndex()));
tos+=1;
}
public void visitIMPDEP1(IMPDEP1 obj) { unimplemented(obj);}
public void visitIMPDEP2(IMPDEP2 obj) {unimplemented(obj); }
public void visitIMUL(IMUL obj) {
emit3("mul",stack(tos-1),stack(tos-1),stack(tos));
tos -=1;
}
public void visitINEG(INEG obj) {
emit2("neg",stack(tos),stack(tos));
}
public void visitINSTANCEOF(INSTANCEOF obj) { unimplemented(obj);}
public void visitINVOKEINTERFACE(INVOKEINTERFACE obj) { unimplemented(obj); }
public void visitINVOKESPECIAL(INVOKESPECIAL obj) { unimplemented(obj); }
public void visitINVOKESTATIC(INVOKESTATIC obj) {
int arg_count = obj.getArgumentTypes(cpg).length;
int stack_slots = 1+tos-arg_count;
emit_caller_save(stack_slots);
// move arguments from stack regs to lvar regs
for (int i = 0; i < arg_count; i++)
emit2("move",lvar(arg_count-1-i),stack(tos-i));
tos -= arg_count;
// do call
emit1("jal",obj.getMethodName(cpg));
emit_caller_restore(stack_slots);
// if there was a return value, push it onto operand stack
if (!obj.getReturnType(cpg).equals(Type.VOID)) {
emit2("move",stack(tos+1),"$v0");
tos +=1;
}
}
public void visitINVOKEVIRTUAL(INVOKEVIRTUAL obj) {
// hack to support printing ints or strings to stdout
if (obj.getClassName(cpg).equals("java.io.PrintStream") &&
obj.getName(cpg).equals("print")) {
if (obj.getSignature(cpg).equals("(Ljava/lang/String;)V")) {
emit2("li","$v0","4"); // magic SPIM code for print_string
emit2("move","$a0",stack(tos));
emit0("syscall");
tos -= 2; // consume the value and the placeholder for the PrintStream object
} else if (obj.getSignature(cpg).equals("(I)V")) {
emit2("li","$v0","1"); // magic SPIM code for print_int
emit2("move","$a0",stack(tos));
emit0("syscall");
tos -= 2; // consume the value and the placeholder for the PrintStream object
}
else
unimplemented(obj);
} else
unimplemented(obj);
}
public void visitIOR(IOR obj) {
emit3("or",stack(tos-1),stack(tos-1),stack(tos));
tos -=1;
}
public void visitIREM(IREM obj) {
emit3("rem",stack(tos-1),stack(tos-1),stack(tos));
tos -=1;
}
public void visitIRETURN(IRETURN obj) {
emit2("move", "$v0",stack(tos));
emit1("jr","$ra");
tos -=1;
}
public void visitISHL(ISHL obj) {
emit3("and",stack(tos),stack(tos),"0x1f");
emit3("sllv",stack(tos-1),stack(tos-1),stack(tos));
tos -=1;
}
public void visitISHR(ISHR obj) {
emit3("and",stack(tos),stack(tos),"0x1f");
emit3("srav",stack(tos-1),stack(tos-1),stack(tos));
tos -=1;
}
public void visitISTORE(ISTORE obj) {
emit2("move",lvar(obj.getIndex()),stack(tos));
tos -= 1;
}
public void visitISUB(ISUB obj) {
emit3("sub",stack(tos-1),stack(tos-1),stack(tos));
tos -=1;
}
public void visitIUSHR(IUSHR obj) { unimplemented(obj);}
public void visitIXOR(IXOR obj) {
emit3("xor",stack(tos-1),stack(tos-1),stack(tos));
tos -=1;
}
public void visitJSR(JSR obj) { unimplemented(obj); }
public void visitJSR_W(JSR_W obj) { unimplemented(obj);}
public void visitL2D(L2D obj) { unimplemented(obj);}
public void visitL2F(L2F obj) { unimplemented(obj);}
public void visitL2I(L2I obj) { unimplemented(obj);}
public void visitLADD(LADD obj) { unimplemented(obj);}
public void visitLAND(LAND obj) { unimplemented(obj); }
public void visitLALOAD(LALOAD obj) { unimplemented(obj);}
public void visitLASTORE(LASTORE obj) { unimplemented(obj);}
public void visitLCMP(LCMP obj) { unimplemented(obj);}
public void visitLCONST(LCONST obj) { unimplemented(obj); }
public void visitLDC(LDC obj) {
Constant c = cpg.getConstant(obj.getIndex());
if (c instanceof ConstantInteger) {
int i = ((ConstantInteger) c).getBytes();
if ((i & 0xffff0000) != 0) {
emit2 ("lui",stack(tos+1),Integer.toString(i >> 16));
emit3 ("or",stack(tos+1),stack(tos+1),Integer.toString(i & 0xffff));
} else
emit2 ("li",stack(tos),Integer.toString(i));
tos += 1;
} else if (c instanceof ConstantString) {
String s = ((ConstantString) c).getBytes(cp);
emit0(".data");
string_label += 1;
emitlab("string_" + string_label);
emit1(".asciiz","\"" + s + "\""); // a bit lazy: should handle embedded non-printing characters, but this works ok
emit0(".text");
emit2 ("la", stack(tos+1),"string_" + string_label);
tos += 1;
} else
unimplemented(obj);
}
public void visitLDC2_W(LDC2_W obj) { unimplemented(obj);}
public void visitLDIV(LDIV obj) { unimplemented(obj);}
public void visitLLOAD(LLOAD obj) { unimplemented(obj); }
public void visitLMUL(LMUL obj) { unimplemented(obj);}
public void visitLNEG(LNEG obj) { unimplemented(obj);}
public void visitLOOKUPSWITCH(LOOKUPSWITCH obj) { unimplemented(obj);}
public void visitLOR(LOR obj) { unimplemented(obj);}
public void visitLREM(LREM obj) { unimplemented(obj);}
public void visitLRETURN(LRETURN obj) { unimplemented(obj);}
public void visitLSHL(LSHL obj) { unimplemented(obj);}
public void visitLSHR(LSHR obj) { unimplemented(obj);}
public void visitLSTORE(LSTORE obj) { unimplemented(obj); }
public void visitLSUB(LSUB obj) { unimplemented(obj);}
public void visitLUSHR(LUSHR obj) { unimplemented(obj);}
public void visitLXOR(LXOR obj) { unimplemented(obj);}
public void visitMONITORENTER(MONITORENTER obj) { unimplemented(obj);}
public void visitMONITOREXIT(MONITOREXIT obj) { unimplemented(obj); }
public void visitMULTIANEWARRAY(MULTIANEWARRAY obj) { unimplemented(obj);}
public void visitNEW(NEW obj) { unimplemented(obj);}
public void visitNEWARRAY(NEWARRAY obj) {
if (obj.getType().equals(new ArrayType(Type.INT,1))) {
// check argument
emit2("bltz",stack(tos),"NASexception");
// allocate space for integer array (4*size + 4 bytes)
emit2("li","$v0","9"); // magic SPIM code for sbrk
emit3("sll","$a0",stack(tos),"2"); // cheap multiply by 4
emit3("add","$a0","$a0","4");
emit0("syscall"); // new memory comes back zeroed
emit2("sw",stack(tos),"($v0)"); // store length
emit2("move",stack(tos),"$v0");
} else
unimplemented(obj);
}
public void visitNOP(NOP obj) {
/* nothing to do !! */
}
public void visitPOP(POP obj) {
tos--;
}
public void visitPOP2(POP2 obj) {
tos -=2;
}
public void visitPUTFIELD(PUTFIELD obj) { unimplemented(obj);}
public void visitPUTSTATIC(PUTSTATIC obj) { unimplemented(obj);}
public void visitRET(RET obj) { unimplemented(obj);}
public void visitRETURN(RETURN obj) {
emit1("jr","$ra");
}
public void visitSALOAD(SALOAD obj) { unimplemented(obj);}
public void visitSASTORE(SASTORE obj) { unimplemented(obj); }
public void visitSIPUSH(SIPUSH obj) {
emit2("li", stack(tos+1), obj.getValue().toString());
tos+= 1;
}
public void visitSWAP(SWAP obj) {
emit2("move",temp,stack(tos));
emit2("move",stack(tos),stack(tos-1));
emit2("move",stack(tos),temp);
}
public void visitTABLESWITCH(TABLESWITCH obj) { unimplemented(obj); }
}
}