* Feel free to change this code in any way that you find useful, * or to ignore it completely and roll your own code generator from * scratch. *
* This code assumes that your top-level AST node is called * Program. You may need to change this to match your own AST * hierarchy. Usage: * *
* CodeGenerator cg = new CodeGenerator("file.ic", program);
* cg.generate();
*
*/
public class CodeGenerator {
/** The name of the assembly file being generated */
protected final String asmFile;
/** The writer used to print the assembly file */
protected final PrintWriter out;
/** The program being translated into assembly */
protected final Program program;
/**
* Given a file name "file.ic" and a program AST, construct a
* code generator to print "file.s", the assembly code version
* of the program.
*/
public CodeGenerator(String icFileName, Program program) throws IOException {
asmFile = icFileName.substring(0, icFileName.indexOf('.')) + ".s";
out = new PrintWriter(new FileWriter(asmFile));
this.program = program;
}
/**
* The main method to call when you wish to perform the
* translation.
*/
public void generate() {
out.println("# Compiled from " + asmFile);
out.println();
out.println();
generateVTables();
generateCode();
generateErrorHandlers();
// TODO: Provide the real information for main.
String classForMain = "Simple";
int sizeOfMainObject = 4;
int offsetOfMainInDV = 0;
generateMain(classForMain, sizeOfMainObject, offsetOfMainInDV);
generateStringConstants();
out.close();
}
/**
* Print the VTable for all the classes. You'll need to change this.
*
*/
protected void generateVTables() {
// TODO: You must implement this method
out.println("# ----------------------------");
out.println("# VTables");
out.println();
out.println(".data");
out.println(".align 4");
out.println();
out.println("_Simple_DV:");
out.println(" .long _Simple_main");
out.println("");
out.println("");
out.println("");
}
/**
* Generate Simple.main method. You'll need to change this.
*/
protected void generateCode() {
// TODO: You must implement this method
out.println("# ----------------------------");
out.println("# Code. Just the Simple main method for now...");
out.println("");
out.println(".text");
out.println(".align 4");
out.println("_Simple_main:");
out.println("");
out.println(" # prologue");
out.println(" pushl %ebp ");
out.println(" mov %esp, %ebp ");
out.println(" subl $4, %esp ");
out.println("");
out.println(" # store 1234 into a local variable.");
out.println(" movl $1234, %ecx ");
out.println(" movl %ecx, -4(%ebp)");
out.println("");
out.println(" # print that local var...");
out.println(" pushl -4(%ebp)");
out.println(" call __LIB_printi");
out.println(" addl $4, %esp");
out.println("");
out.println(" # ... and a new line");
out.printf (" pushl $%s\n",
labelForStringConstant("\na string \n containing \t\t quotes and escape characters: \"moo\"\n"));
out.println(" call __LIB_println");
out.println(" addl $4, %esp ");
out.println(" ");
out.println(" # epilogue");
out.println(" mov %ebp, %esp ");
out.println(" pop %ebp ");
out.println(" ret ");
out.println("");
out.println("");
out.println("");
}
/**
* Print out the assembly code to print run-time errors and
* exit gracefully. You should jump to these labels on
* run-time check failure. You should not need to change this
* method.
*/
protected void generateErrorHandlers() {
out.println("# ----------------------------");
out.println("# Error handling. Jump to these procedures when a run-time check fails.");
out.println("");
out.println(".data");
out.println(".long 23");
out.println("strNullPtrError: .ascii \"Null pointer violation.\"");
out.println(".long 23");
out.println("strArrayBoundsError: .ascii \"Array bounds violation.\"");
out.println(".long 21");
out.println("strArraySizeError: .ascii \"Array size violation.\"");
out.println("");
out.println(".text");
out.println(".align 4");
out.println("labelNullPtrError:");
out.println(" push $strNullPtrError");
out.println(" call __LIB_println");
out.println(" push $1");
out.println(" call __LIB_exit");
out.println("");
out.println(".align 4");
out.println("labelArrayBoundsError:");
out.println(" push $strArrayBoundsError");
out.println(" call __LIB_println");
out.println(" push $1");
out.println(" call __LIB_exit");
out.println("");
out.println(".align 4");
out.println("labelArraySizeError:");
out.println(" push $strArraySizeError");
out.println(" call __LIB_println");
out.println(" push $1");
out.println(" call __LIB_exit");
out.println("");
out.println("");
out.println("");
}
/**
* Generate the __ic_main stub that creates and calls main on
* the right object. You should not need to change this
* method.
* @param className name of the class containing main
* @param objectSize size of objects of that class
* @param indexOfMainInVTable index on that class's vtable for main
*/
protected void generateMain(String className, int objectSize, int indexOfMainInVTable) {
out.println("# The main entry point. Allocate object and invoke main on it.");
out.println("");
out.println(".text");
out.println(".align 4");
out.println(".globl __ic_main");
out.println("__ic_main:");
out.println(" pushl %ebp # prologue");
out.println(" movl %esp,%ebp ");
out.println("");
out.printf (" pushl $%-4d # o = new %s\n",
objectSize, className);
out.println(" call __LIB_allocateObject ");
out.println(" addl $4, %esp ");
out.printf (" movl $_%s_DV, (%%eax) \n",
className);
out.println(" pushl 8(%ebp) # o.main(args)");
out.println(" pushl %eax ");
out.println(" movl (%eax), %eax ");
out.printf (" call *%d(%%eax) # main is at offset %d in vtable\n",
indexOfMainInVTable * 4, indexOfMainInVTable);
out.println(" addl $8, %esp ");
out.println(" movl $0, %eax # __ic_main always returns 0");
out.println("");
out.println(" movl %ebp,%esp # epilogue");
out.println(" popl %ebp ");
out.println(" ret ");
out.println("");
out.println("");
out.println("");
}
/********************** String Constants *********************/
/** A map from string constant to the assembly code label in
* the data segment where that constant is stored. See the
* labelForStringConstant method.
*/
protected final HashMap