Here are bits and pieces of the operator processing:

    case OpK:
        // process lhs
	codegen_expression(currnode->child[0]);

        // process rhs if binary operator
	if (currnode->child[1]) {
	    emitRM("ST", AC, toff--, FP, "Save left side");
	    codegen_expression(currnode->child[1]);
	    emitRM("LD", AC1, ++toff, FP, "Load left into ac1");
	}

        // do operator
	switch (currnode->attr.op) {
	case '+':
	    emitRO("ADD", AC, AC1, AC, "Op +");
	    break;


----------------------------------------------------------------------


Here is doing a while-statement:

    case WhileK:
	emitComment("WHILE");
	currloc = emitSkip(0);             // return to here to do the test
	codegen_expression(currnode->child[0]);

	emitRM("LDC", AC1, 1, 6, "Load constant 1");
	emitRO("SUB", AC, AC, AC1, "While cond check");
	emitRM("JGE", AC, 1, PC, "Jump to while part");
	emitComment("DO");
	skiploc = emitSkip(1);            // addr of instr that jumps to end of loop

        skiploc2 = breakloc;              // save for break statement
        breakloc = skiploc;
	codegen_next(currnode->child[1]);
        breakloc = skiploc2;

	emitRMAbs("LDA", PC, currloc, "go to beginning of loop");

	currloc = emitSkip(0);
	emitBackup(skiploc);
	emitRMAbs("LDA", PC, currloc, "No more loop");   // backpatch jump to end of loop
	emitBackup(currloc);

	emitComment("ENDWHILE");
	break;

----------------------------------------------------------------------

Here is the return statement:
    case ReturnK:
        emitComment("RETURN");
        if (currnode->child[0]) {
            codegen_expression(currnode->child[0]);
        }

        emitRM("LDA", RT, 0, AC, "Copy result to rt register");
        emitRM("LD", AC, RETURN_OFFSET, FP, "Load return address");
        emitRM("LD", FP, OFPOFF, FP, "Adjust fp");
        emitRM("LDA", PC, 0, AC, "Return");
        break;



----------------------------------------------------------------------

int backPatchJumpToHere(int addr, char *comment)
{
    int currloc;

    currloc = emitSkip(0);
    emitBackup(addr);
    emitRMAbs("LDA", PC, currloc, "Jump around the THEN");
    emitBackup(currloc);
}

----------------------------------------------------------------------


void codegen(FILE *codeFile,         // where the code should be written
             char *srcFile,          // name of file compiled
             TreeNode *syntaxTree,   // the internal representation of the program
	     SymTab *globalsIn,      // globals so function info can be found
	     int globalOffset)       // size of the global frame
{
    int init_jump;

    code = codeFile;
    globals = globalsIn;
    breakloc = 0;

    init_jump = emitSkip(1);         // save a place for the jump to init
    codegen_header(srcFile);         // nice comments describing what is compiled
    codegen_general(syntaxTree);     // general code generation including I/O library 
    codegen_init(init_jump, globalOffset);      // generation of initialization for run
}