//===-- StackerCompiler.cpp - Parser for llvm assembly files ----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by Reid Spencer and donated to the LLVM research
// group and is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file implements the compiler for the "Stacker" language.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "stacker"
#include "llvm/PassManager.h"
#include "llvm/Analysis/LoadValueNumbering.h"
#include "llvm/Analysis/Verifier.h"
#include "llvm/Assembly/Parser.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Instructions.h"
#include "llvm/ADT/Statistic.h"
#include "StackerCompiler.h"
#include "StackerParser.h"
#include <string>

// Lexer/Parser defined variables and functions
extern std::FILE *Stackerin;
extern int Stackerlineno;
extern char* Stackertext;
extern int Stackerleng;
extern int Stackerparse();

StackerCompiler* StackerCompiler::TheInstance = 0;

STATISTIC(NumDefinitions, "The number of definitions encountered");

StackerCompiler::StackerCompiler()
    : CurFilename("")
    , TheModule(0)
    , TheFunction(0)
    , DefinitionType(0)
    , TheStack(0)
    , TheIndex(0)
    , TheScanf(0)
    , ThePrintf(0)
    , TheExit(0)
    , StrFormat(0)
    , NumFormat(0)
    , ChrFormat(0)
    , InStrFormat(0)
    , InNumFormat(0)
    , InChrFormat(0)
    , Zero(0)
    , One(0)
    , Two(0)
    , Three(0)
    , Four(0)
    , Five(0)
    , no_arguments()
    , echo(false)
    , stack_size(256)
    , stack_type(0)
{
}

StackerCompiler::~StackerCompiler()
{
    // delete TheModule; << don't do this!
    // TheModule is passed to caller of the compile() method .. its their
    // problem.  Likewise for the other allocated objects (which become part
    // of TheModule.
    TheModule = 0;
    DefinitionType = 0;
    TheStack = 0;
    TheIndex = 0;
}

Module*
StackerCompiler::compile(
    const std::string& filename,
    bool should_echo,
    unsigned optLevel,
    size_t the_stack_size
)
{
    // TODO: Provide a global lock to protect the singled-threaded compiler
    // and its global variables. Should be in guard object on the stack so
    // that its destructor causes lock to be released (multiple exits from
    // this function).

    // Assign parameters
    CurFilename = filename;
    echo = should_echo;
    stack_size = the_stack_size;

    /// Default the file to read
    FILE *F = stdin;

    ///
    if (filename != "-")
    {
        F = fopen(filename.c_str(), "r");

        if (F == 0)
        {
          ParseError Err;
          Err.setError(filename, "Could not open file '" + filename + "'");
          throw Err;
        }
    }

    try
    {
        // Create the module we'll return
        TheModule = new Module( CurFilename );

        // Tell the module about our runtime library
        TheModule->addLibrary("stkr_runtime");

        // Create a type to represent the stack. This is the same as the LLVM
        // Assembly type [ 256 x long ]
        stack_type = ArrayType::get( Type::Int64Ty, stack_size );

        // Create a global variable for the stack. Note the use of appending
        // linkage linkage so that multiple modules will make the stack larger.
        // Also note that the last argument causes the global to be inserted
        // automatically into the module.
        TheStack = new GlobalVariable(
            /*type=*/ stack_type,
            /*isConstant=*/ false,
            /*Linkage=*/ GlobalValue::LinkOnceLinkage,
            /*initializer=*/ Constant::getNullValue(stack_type),
            /*name=*/ "_stack_",
            /*parent=*/ TheModule
        );

        // Create a global variable for indexing into the stack. Note the use
        // of LinkOnce linkage. Only one copy of _index_ will be retained
        // after linking
        TheIndex = new GlobalVariable(
            /*type=*/Type::Int64Ty,
            /*isConstant=*/false,
            /*Linkage=*/GlobalValue::LinkOnceLinkage,
            /*initializer=*/ Constant::getNullValue(Type::Int64Ty),
            /*name=*/"_index_",
            /*parent=*/TheModule
        );

        // Create a function prototype for definitions. No parameters, no
        // result.  This is used below any time a function is created.
        std::vector<const Type*> params; // No parameters
        DefinitionType = FunctionType::get( Type::VoidTy, params, false );

        // Create a function for printf(3)
        params.push_back( PointerType::get( Type::Int8Ty ) );
        FunctionType* printf_type =
            FunctionType::get( Type::Int32Ty, params, true );
        ThePrintf = new Function(
            printf_type, GlobalValue::ExternalLinkage, "printf", TheModule);

        // Create a function for scanf(3)
        TheScanf = new Function(
            printf_type, GlobalValue::ExternalLinkage, "scanf", TheModule);

        // Create a function for exit(3)
        params.clear();
        params.push_back( Type::Int32Ty );
        FunctionType* exit_type =
            FunctionType::get( Type::VoidTy, params, false );
        TheExit = new Function(
            exit_type, GlobalValue::ExternalLinkage, "exit", TheModule);

        Constant* str_format = ConstantArray::get("%s");
        StrFormat = new GlobalVariable(
            /*type=*/ArrayType::get( Type::Int8Ty,  3 ),
            /*isConstant=*/true,
            /*Linkage=*/GlobalValue::LinkOnceLinkage,
            /*initializer=*/str_format,
            /*name=*/"_str_format_",
            /*parent=*/TheModule
        );

        Constant* in_str_format = ConstantArray::get(" %as");
        InStrFormat = new GlobalVariable(
            /*type=*/ArrayType::get( Type::Int8Ty,  5 ),
            /*isConstant=*/true,
            /*Linkage=*/GlobalValue::LinkOnceLinkage,
            /*initializer=*/in_str_format,
            /*name=*/"_in_str_format_",
            /*parent=*/TheModule
        );

        Constant* num_format = ConstantArray::get("%d");
        NumFormat = new GlobalVariable(
            /*type=*/ArrayType::get( Type::Int8Ty,  3 ),
            /*isConstant=*/true,
            /*Linkage=*/GlobalValue::LinkOnceLinkage,
            /*initializer=*/num_format,
            /*name=*/"_num_format_",
            /*parent=*/TheModule
        );

        Constant* in_num_format = ConstantArray::get(" %d");
        InNumFormat = new GlobalVariable(
            /*type=*/ArrayType::get( Type::Int8Ty,  4 ),
            /*isConstant=*/true,
            /*Linkage=*/GlobalValue::LinkOnceLinkage,
            /*initializer=*/in_num_format,
            /*name=*/"_in_num_format_",
            /*parent=*/TheModule
        );

        Constant* chr_format = ConstantArray::get("%c");
        ChrFormat = new GlobalVariable(
            /*type=*/ArrayType::get( Type::Int8Ty,  3 ),
            /*isConstant=*/true,
            /*Linkage=*/GlobalValue::LinkOnceLinkage,
            /*initializer=*/chr_format,
            /*name=*/"_chr_format_",
            /*parent=*/TheModule
        );

        Constant* in_chr_format = ConstantArray::get(" %c");
        InChrFormat = new GlobalVariable(
            /*type=*/ArrayType::get( Type::Int8Ty,  4 ),
            /*isConstant=*/true,
            /*Linkage=*/GlobalValue::LinkOnceLinkage,
            /*initializer=*/in_chr_format,
            /*name=*/"_in_chr_format_",
            /*parent=*/TheModule
        );

        // Get some constants so we aren't always creating them
        Zero = ConstantInt::get( Type::Int64Ty, 0 );
        One = ConstantInt::get( Type::Int64Ty, 1 );
        Two = ConstantInt::get( Type::Int64Ty, 2 );
        Three = ConstantInt::get( Type::Int64Ty, 3 );
        Four = ConstantInt::get( Type::Int64Ty, 4 );
        Five = ConstantInt::get( Type::Int64Ty, 5 );

        // Reset the current line number
        Stackerlineno = 1;

        // Reset the parser's input to F
        Stackerin = F;          // Set the input file.

        // Let the parse know about this instance
        TheInstance = this;

        // Parse the file. The parser (see StackParser.y) will call back to
        // the StackerCompiler via the "handle*" methods
        Stackerparse();

        // Avoid potential illegal use (TheInstance might be on the stack)
        TheInstance = 0;

        // Set up a pass manager
        PassManager Passes;
        // Add in the passes we want to execute
        Passes.add(new TargetData(TheModule));
        // Verify we start with valid
        Passes.add(createVerifierPass());

        if (optLevel > 0) {
            if (optLevel > 1) {
                // Clean up disgusting code
                Passes.add(createCFGSimplificationPass());
                // Remove unused globals
                Passes.add(createGlobalDCEPass());
                // IP Constant Propagation
                Passes.add(createIPConstantPropagationPass());
                // Clean up after IPCP
                Passes.add(createInstructionCombiningPass());
                // Clean up after IPCP
                Passes.add(createCFGSimplificationPass());
                // Inline small definitions (functions)
                Passes.add(createFunctionInliningPass());
                // Simplify cfg by copying code
                Passes.add(createTailDuplicationPass());
                if (optLevel > 2) {
                    // Merge & remove BBs
                    Passes.add(createCFGSimplificationPass());
                    // Compile silly sequences
                    Passes.add(createInstructionCombiningPass());
                    // Reassociate expressions
                    Passes.add(createReassociatePass());
                    // Combine silly seq's
                    Passes.add(createInstructionCombiningPass());
                    // Eliminate tail calls
                    Passes.add(createTailCallEliminationPass());
                    // Merge & remove BBs
                    Passes.add(createCFGSimplificationPass());
                    // Hoist loop invariants
                    Passes.add(createLICMPass());
                    // Clean up after the unroller
                    Passes.add(createInstructionCombiningPass());
                    // Canonicalize indvars
                    Passes.add(createIndVarSimplifyPass());
                    // Unroll small loops
                    Passes.add(createLoopUnrollPass());
                    // Clean up after the unroller
                    Passes.add(createInstructionCombiningPass());
                    // GVN for load instructions
                    Passes.add(createLoadValueNumberingPass());
                    // Remove common subexprs
                    Passes.add(createGCSEPass());
                    // Constant prop with SCCP
                    Passes.add(createSCCPPass());
                }
                if (optLevel > 3) {
                    // Run instcombine again after redundancy elimination
                    Passes.add(createInstructionCombiningPass());
                    // Delete dead stores
                    Passes.add(createDeadStoreEliminationPass());
                    // SSA based 'Aggressive DCE'
                    Passes.add(createAggressiveDCEPass());
                    // Merge & remove BBs
                    Passes.add(createCFGSimplificationPass());
                    // Merge dup global constants
                    Passes.add(createConstantMergePass());
                }
            }

            // Merge & remove BBs
            Passes.add(createCFGSimplificationPass());
            // Memory To Register
            Passes.add(createPromoteMemoryToRegisterPass());
            // Compile silly sequences
            Passes.add(createInstructionCombiningPass());
            // Make sure everything is still good.
            Passes.add(createVerifierPass());
        }

        // Run our queue of passes all at once now, efficiently.
        Passes.run(*TheModule);

    } catch (...) {
        if (F != stdin) fclose(F);      // Make sure to close file descriptor
        throw;                          // if an exception is thrown
    }

    // Close the file
    if (F != stdin) fclose(F);

    // Return the compiled module to the caller
    return TheModule;
}

//===----------------------------------------------------------------------===//
//            Internal Functions, used by handleXXX below.
//            These represent the basic stack operations.
//===----------------------------------------------------------------------===//

Instruction*
StackerCompiler::incr_stack_index( BasicBlock* bb, Value* ival = 0 )
{
    // Load the value from the TheIndex
    LoadInst* loadop = new LoadInst( TheIndex );
    bb->getInstList().push_back( loadop );

    // Increment the loaded index value
    if ( ival == 0 ) ival = One;
    CastInst* caster = CastInst::createSExtOrBitCast( ival, Type::Int64Ty );
    bb->getInstList().push_back( caster );
    BinaryOperator* addop = BinaryOperator::create( Instruction::Add,
            loadop, caster);
    bb->getInstList().push_back( addop );

    // Store the incremented value
    StoreInst* storeop = new StoreInst( addop, TheIndex );
    bb->getInstList().push_back( storeop );
    return storeop;
}

Instruction*
StackerCompiler::decr_stack_index( BasicBlock* bb, Value* ival = 0 )
{
    // Load the value from the TheIndex
    LoadInst* loadop = new LoadInst( TheIndex );
    bb->getInstList().push_back( loadop );

    // Decrement the loaded index value
    if ( ival == 0 ) ival = One;
    CastInst* caster = CastInst::createSExtOrBitCast( ival, Type::Int64Ty );
    bb->getInstList().push_back( caster );
    BinaryOperator* subop = BinaryOperator::create( Instruction::Sub,
            loadop, caster);
    bb->getInstList().push_back( subop );

    // Store the incremented value
    StoreInst* storeop = new StoreInst( subop, TheIndex );
    bb->getInstList().push_back( storeop );

    return storeop;
}

Instruction*
StackerCompiler::get_stack_pointer( BasicBlock* bb, Value* index = 0 )
{
    // Load the value of the Stack Index
    LoadInst* loadop = new LoadInst( TheIndex );
    bb->getInstList().push_back( loadop );

    // Index into the stack to get its address. NOTE the use of two
    // elements in this vector. The first de-references the pointer that
    // "TheStack" represents. The second indexes into the pointed to array.
    // Think of the first index as getting the address of the 0th element
    // of the array.
    std::vector<Value*> indexVec;
    indexVec.push_back( Zero );

    if ( index == 0 )
    {
        indexVec.push_back(loadop);
    }
    else
    {
        CastInst* caster = CastInst::createSExtOrBitCast( index, Type::Int64Ty );
        bb->getInstList().push_back( caster );
        BinaryOperator* subop = BinaryOperator::create(
            Instruction::Sub, loadop, caster );
        bb->getInstList().push_back( subop );
        indexVec.push_back(subop);
    }

    // Get the address of the indexed stack element
    GetElementPtrInst* gep = new GetElementPtrInst(TheStack, &indexVec[0], 
                                                   indexVec.size() );
    bb->getInstList().push_back( gep );         // Put GEP in Block

    return gep;
}

Instruction*
StackerCompiler::push_value( BasicBlock* bb, Value* val )
{
    // Get location of
    incr_stack_index(bb);

    // Get the stack pointer
    GetElementPtrInst* gep = cast<GetElementPtrInst>(
            get_stack_pointer( bb ) );

    // Cast the value to a long .. hopefully it works
    Instruction::CastOps opcode = 
       (isa<PointerType>(val->getType()) ? Instruction::PtrToInt :
        (val->getType()->getPrimitiveSizeInBits() < 64 ? Instruction::SExt :
         Instruction::BitCast));
    CastInst* cast_inst = CastInst::create(opcode, val, Type::Int64Ty );
    bb->getInstList().push_back( cast_inst );

    // Store the value
    StoreInst* storeop = new StoreInst( cast_inst, gep );
    bb->getInstList().push_back( storeop );

    return storeop;
}

Instruction*
StackerCompiler::push_integer(BasicBlock* bb, int64_t value )
{
    // Just push a constant integer value
    return push_value( bb, ConstantInt::get( Type::Int64Ty, value ) );
}

Instruction*
StackerCompiler::pop_integer( BasicBlock*bb )
{
    // Get the stack pointer
    GetElementPtrInst* gep = cast<GetElementPtrInst>(
        get_stack_pointer( bb ));

    // Load the value
    LoadInst* load_inst = new LoadInst( gep );
    bb->getInstList().push_back( load_inst );

    // Decrement the stack index
    decr_stack_index( bb );

    // Return the value
    return load_inst;
}

Instruction*
StackerCompiler::push_string( BasicBlock* bb, const char* value )
{
    // Get length of the string
    size_t len = strlen( value );

    // Create a type for the string constant. Length is +1 for
    // the terminating 0.
    ArrayType* char_array = ArrayType::get( Type::Int8Ty, len + 1 );

    // Create an initializer for the value
    Constant* initVal = ConstantArray::get( value );

    // Create an internal linkage global variable to hold the constant.
    GlobalVariable* strconst = new GlobalVariable(
        char_array,
        /*isConstant=*/true,
        GlobalValue::InternalLinkage,
        /*initializer=*/initVal,
        "",
        TheModule
    );

    // Push the casted value
    return push_value( bb, strconst );
}

Instruction*
StackerCompiler::pop_string( BasicBlock* bb )
{
    // Get location of stack pointer
    GetElementPtrInst* gep = cast<GetElementPtrInst>(
        get_stack_pointer( bb ));

    // Load the value from the stack
    LoadInst* loader = new LoadInst( gep );
    bb->getInstList().push_back( loader );

    // Cast the integer to a sbyte*
    CastInst* caster = 
      new IntToPtrInst(loader, PointerType::get(Type::Int8Ty));
    bb->getInstList().push_back( caster );

    // Decrement stack index
    decr_stack_index( bb );

    // Return the value
    return caster;
}

Instruction*
StackerCompiler::replace_top( BasicBlock* bb, Value* new_top, Value* index = 0 )
{
    // Get the stack pointer
    GetElementPtrInst* gep = cast<GetElementPtrInst>(
            get_stack_pointer( bb, index ));

    // Store the value there
    StoreInst* store_inst = new StoreInst( new_top, gep );
    bb->getInstList().push_back( store_inst );

    // Return the value
    return store_inst;
}

Instruction*
StackerCompiler::stack_top( BasicBlock* bb, Value* index = 0 )
{
    // Get the stack pointer
    GetElementPtrInst* gep = cast<GetElementPtrInst>(
        get_stack_pointer( bb, index ));

    // Load the value
    LoadInst* load_inst = new LoadInst( gep );
    bb->getInstList().push_back( load_inst );

    // Return the value
    return load_inst;
}

Instruction*
StackerCompiler::stack_top_string( BasicBlock* bb, Value* index = 0 )
{
    // Get location of stack pointer
    GetElementPtrInst* gep = cast<GetElementPtrInst>(
        get_stack_pointer( bb, index ));

    // Load the value from the stack
    LoadInst* loader = new LoadInst( gep );
    bb->getInstList().push_back( loader );

    // Cast the integer to a sbyte*
    CastInst* caster = 
      new IntToPtrInst(loader, PointerType::get(Type::Int8Ty) );
    bb->getInstList().push_back( caster );

    // Return the value
    return caster;
}

static void
add_block( Function*f, BasicBlock* bb )
{
    if ( ! f->empty() && f->back().getTerminator() == 0 )
    {
        BranchInst* branch = new BranchInst(bb);
        f->back().getInstList().push_back( branch );
    }
    f->getBasicBlockList().push_back( bb );
}


//===----------------------------------------------------------------------===//
//            handleXXX - Handle semantics of parser productions
//===----------------------------------------------------------------------===//

Module*
StackerCompiler::handle_module_start( )
{
    // Return the newly created module
    return TheModule;
}

Module*
StackerCompiler::handle_module_end( Module* mod )
{
    // Return the module.
    return mod;
}

Module*
StackerCompiler::handle_definition_list_start()
{
    return TheModule;
}

Module*
StackerCompiler::handle_definition_list_end( Module* mod, Function* definition )
{
    if ( ! definition->empty() )
    {
        BasicBlock& last_block = definition->back();
        if ( last_block.getTerminator() == 0 )
        {
            last_block.getInstList().push_back( new ReturnInst() );
        }
    }
    // Insert the definition into the module
    mod->getFunctionList().push_back( definition );

    // Bump our (sample) statistic.
    ++NumDefinitions;
    return mod;
}

Function*
StackerCompiler::handle_main_definition( Function* func )
{
    // Set the name of the function defined as the Stacker main
    // This will get called by the "main" that is defined in
    // the runtime library.
    func->setName( "_MAIN_");

    // Turn "_stack_" into an initialized variable since this is the main
    // module. This causes it to not be "external" but defined in this module.
    TheStack->setInitializer( Constant::getNullValue(stack_type) );
    TheStack->setLinkage( GlobalValue::LinkOnceLinkage );

    // Turn "_index_" into an intialized variable for the same reason.
    TheIndex->setInitializer( Constant::getNullValue(Type::Int64Ty) );
    TheIndex->setLinkage( GlobalValue::LinkOnceLinkage );

    return func;
}

Function*
StackerCompiler::handle_forward( char * name )
{
    // Just create a placeholder function
    Function* the_function = new Function (
        DefinitionType,
        GlobalValue::ExternalLinkage,
        name );
    assert( the_function->isDeclaration() );

    free( name );
    return the_function;
}

Function*
StackerCompiler::handle_definition( char * name, Function* f )
{
    // Look up the function name in the module to see if it was forward
    // declared.
#if 0
    Function* existing_function = TheModule->getFunction( name );

    // If the function already exists...
    if ( existing_function )
    {
        // Just get rid of the placeholder
        existing_function->dropAllReferences();
        delete existing_function;
    }
#endif

    // Just set the name of the function now that we know what it is.
    f->setName( name );

    free( name );

    return f;
}

Function*
StackerCompiler::handle_word_list_start()
{
    TheFunction = new Function(DefinitionType, GlobalValue::ExternalLinkage);
    return TheFunction;
}

Function*
StackerCompiler::handle_word_list_end( Function* f, BasicBlock* bb )
{
    add_block( f, bb );
    return f;
}

BasicBlock*
StackerCompiler::handle_if( char* ifTrue, char* ifFalse )
{
    // Create a basic block for the preamble
    BasicBlock* bb = new BasicBlock((echo?"if":""));

    // Get the condition value
    LoadInst* cond = cast<LoadInst>( pop_integer(bb) );

    // Compare the condition against 0
    ICmpInst* cond_inst = new ICmpInst( ICmpInst::ICMP_NE, cond,
        ConstantInt::get( Type::Int64Ty, 0) );
    bb->getInstList().push_back( cond_inst );

    // Create an exit block
    BasicBlock* exit_bb = new BasicBlock((echo?"endif":""));

    // Create the true_block
    BasicBlock* true_bb = new BasicBlock((echo?"then":""));

    // Create the false_block
    BasicBlock* false_bb = 0;
    if ( ifFalse ) false_bb = new BasicBlock((echo?"else":""));

    // Create a branch on the ICmp
    BranchInst* br_inst = new BranchInst( true_bb,
        ( ifFalse ? false_bb : exit_bb ), cond_inst );
    bb->getInstList().push_back( br_inst );

    // Fill the true block
    std::vector<Value*> args;
    if ( Function* true_func = TheModule->getFunction(ifTrue) )
    {
        true_bb->getInstList().push_back(
                new CallInst( true_func, &args[0], args.size() ) );
        true_bb->getInstList().push_back(
                new BranchInst( exit_bb ) );
    }
    else
    {
        ThrowException(std::string("Function '") + ifTrue +
            "' must be declared first.'");
    }

    free( ifTrue );

    // Fill the false block
    if ( false_bb )
    {
        if ( Function* false_func = TheModule->getFunction(ifFalse) )
        {
            false_bb->getInstList().push_back(
                    new CallInst( false_func, &args[0], args.size() ) );
            false_bb->getInstList().push_back(
                    new BranchInst( exit_bb ) );
        }
        else
        {
            ThrowException(std::string("Function '") + ifFalse +
                    "' must be declared first.'");
        }
        free( ifFalse );
    }

    // Add the blocks to the function
    add_block( TheFunction, bb );
    add_block( TheFunction, true_bb );
    if ( false_bb ) add_block( TheFunction, false_bb );

    return exit_bb;
}

BasicBlock*
StackerCompiler::handle_while( char* todo )
{

    // Create a basic block for the loop test
    BasicBlock* test = new BasicBlock((echo?"while":""));

    // Create an exit block
    BasicBlock* exit = new BasicBlock((echo?"end":""));

    // Create a loop body block
    BasicBlock* body = new BasicBlock((echo?"do":""));

    // Create a root node
    BasicBlock* bb = new BasicBlock((echo?"root":""));
    BranchInst* root_br_inst = new BranchInst( test );
    bb->getInstList().push_back( root_br_inst );

    // Examine the condition value
    LoadInst* cond = cast<LoadInst>( stack_top(test) );

    // Compare the condition against 0
    ICmpInst* cond_inst = new ICmpInst(
        ICmpInst::ICMP_NE, cond, ConstantInt::get( Type::Int64Ty, 0));
    test->getInstList().push_back( cond_inst );

    // Add the branch instruction
    BranchInst* br_inst = new BranchInst( body, exit, cond_inst );
    test->getInstList().push_back( br_inst );

    // Fill in the body
    std::vector<Value*> args;
    if ( Function* body_func = TheModule->getFunction(todo) )
    {
        body->getInstList().push_back( new CallInst( body_func, &args[0], 
                                                     args.size() ) );
        body->getInstList().push_back( new BranchInst( test ) );
    }
    else
    {
        ThrowException(std::string("Function '") + todo +
            "' must be declared first.'");
    }

    free( todo );

    // Add the blocks
    add_block( TheFunction, bb );
    add_block( TheFunction, test );
    add_block( TheFunction, body );

    return exit;
}

BasicBlock*
StackerCompiler::handle_identifier( char * name )
{
    Function* func = TheModule->getFunction( name );
    BasicBlock* bb = new BasicBlock((echo?"call":""));
    if ( func )
    {
        CallInst* call_def = new CallInst( func );
        bb->getInstList().push_back( call_def );
    }
    else
    {
        ThrowException(std::string("Definition '") + name +
            "' must be defined before it can be used.");
    }

    free( name );
    return bb;
}

BasicBlock*
StackerCompiler::handle_string( char * value )
{
    // Create a new basic block for the push operation
    BasicBlock* bb = new BasicBlock((echo?"string":""));

    // Push the string onto the stack
    push_string(bb, value);

    // Free the strdup'd string
    free( value );

    return bb;
}

BasicBlock*
StackerCompiler::handle_integer( const int64_t value )
{
    // Create a new basic block for the push operation
    BasicBlock* bb = new BasicBlock((echo?"int":""));

    // Push the integer onto the stack
    push_integer(bb, value );

    return bb;
}

BasicBlock*
StackerCompiler::handle_word( int tkn )
{
    // Create a new basic block to hold the instruction(s)
    BasicBlock* bb = new BasicBlock();

    /* Fill the basic block with the appropriate instructions */
    switch ( tkn )
    {
    case DUMP :  // Dump the stack (debugging aid)
    {
        if (echo) bb->setName("DUMP");
        Constant * f = TheModule->getOrInsertFunction(
            "_stacker_dump_stack_", DefinitionType);
        std::vector<Value*> args;
        bb->getInstList().push_back( new CallInst( f, &args[0], args.size()));
        break;
    }

    // Logical Operations
    case TRUETOK :  // -- -1
    {
        if (echo) bb->setName("TRUE");
        push_integer(bb,-1);
        break;
    }
    case FALSETOK : // -- 0
    {
        if (echo) bb->setName("FALSE");
        push_integer(bb,0);
        break;
    }
    case LESS : // w1 w2 -- w2<w1
    {
        if (echo) bb->setName("LESS");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        ICmpInst* cond_inst =
            new ICmpInst( ICmpInst::ICMP_SLT, op1, op2 );
        bb->getInstList().push_back( cond_inst );
        push_value( bb, cond_inst );
        break;
    }
    case MORE : // w1 w2 -- w2>w1
    {
        if (echo) bb->setName("MORE");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        ICmpInst* cond_inst =
            new ICmpInst( ICmpInst::ICMP_SGT, op1, op2 );
        bb->getInstList().push_back( cond_inst );
        push_value( bb, cond_inst );
        break;
    }
    case LESS_EQUAL : // w1 w2 -- w2<=w1
    {
        if (echo) bb->setName("LE");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        ICmpInst* cond_inst =
            new ICmpInst( ICmpInst::ICMP_SLE, op1, op2 );
        bb->getInstList().push_back( cond_inst );
        push_value( bb, cond_inst );
        break;
    }
    case MORE_EQUAL : // w1 w2 -- w2>=w1
    {
        if (echo) bb->setName("GE");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        ICmpInst* cond_inst =
            new ICmpInst( ICmpInst::ICMP_SGE, op1, op2 );
        bb->getInstList().push_back( cond_inst );
        push_value( bb, cond_inst );
        break;
    }
    case NOT_EQUAL : // w1 w2 -- w2!=w1
    {
        if (echo) bb->setName("NE");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        ICmpInst* cond_inst =
            new ICmpInst( ICmpInst::ICMP_NE, op1, op2 );
        bb->getInstList().push_back( cond_inst );
        push_value( bb, cond_inst );
        break;
    }
    case EQUAL : // w1 w2 -- w1==w2
    {
        if (echo) bb->setName("EQ");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        ICmpInst* cond_inst =
            new ICmpInst( ICmpInst::ICMP_EQ, op1, op2 );
        bb->getInstList().push_back( cond_inst );
        push_value( bb, cond_inst );
        break;
    }

    // Arithmetic Operations
    case PLUS : // w1 w2 -- w2+w1
    {
        if (echo) bb->setName("ADD");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        BinaryOperator* addop =
            BinaryOperator::create( Instruction::Add, op1, op2);
        bb->getInstList().push_back( addop );
        push_value( bb, addop );
        break;
    }
    case MINUS : // w1 w2 -- w2-w1
    {
        if (echo) bb->setName("SUB");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        BinaryOperator* subop =
            BinaryOperator::create( Instruction::Sub, op1, op2);
        bb->getInstList().push_back( subop );
        push_value( bb, subop );
        break;
    }
    case INCR :  // w1 -- w1+1
    {
        if (echo) bb->setName("INCR");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        BinaryOperator* addop =
            BinaryOperator::create( Instruction::Add, op1, One );
        bb->getInstList().push_back( addop );
        push_value( bb, addop );
        break;
    }
    case DECR : // w1 -- w1-1
    {
        if (echo) bb->setName("DECR");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        BinaryOperator* subop = BinaryOperator::create( Instruction::Sub, op1,
            ConstantInt::get( Type::Int64Ty, 1 ) );
        bb->getInstList().push_back( subop );
        push_value( bb, subop );
        break;
    }
    case MULT : // w1 w2 -- w2*w1
    {
        if (echo) bb->setName("MUL");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        BinaryOperator* multop =
            BinaryOperator::create( Instruction::Mul, op1, op2);
        bb->getInstList().push_back( multop );
        push_value( bb, multop );
        break;
    }
    case DIV :// w1 w2 -- w2/w1
    {
        if (echo) bb->setName("DIV");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        BinaryOperator* divop =
            BinaryOperator::create( Instruction::SDiv, op1, op2);
        bb->getInstList().push_back( divop );
        push_value( bb, divop );
        break;
    }
    case MODULUS : // w1 w2 -- w2%w1
    {
        if (echo) bb->setName("MOD");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        BinaryOperator* divop =
            BinaryOperator::create( Instruction::SRem, op1, op2);
        bb->getInstList().push_back( divop );
        push_value( bb, divop );
        break;
    }
    case STAR_SLASH : // w1 w2 w3 -- (w3*w2)/w1
    {
        if (echo) bb->setName("STAR_SLASH");
        // Get the operands
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op3 = cast<LoadInst>(pop_integer(bb));

        // Multiply the first two
        BinaryOperator* multop =
            BinaryOperator::create( Instruction::Mul, op1, op2);
        bb->getInstList().push_back( multop );

        // Divide by the third operand
        BinaryOperator* divop =
            BinaryOperator::create( Instruction::SDiv, multop, op3);
        bb->getInstList().push_back( divop );

        // Push the result
        push_value( bb, divop );

        break;
    }
    case NEGATE : // w1 -- -w1
    {
        if (echo) bb->setName("NEG");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        // APPARENTLY, the following doesn't work:
        // BinaryOperator* negop = BinaryOperator::createNeg( op1 );
        // bb->getInstList().push_back( negop );
        // So we'll multiply by -1 (ugh)
        BinaryOperator* multop = BinaryOperator::create( Instruction::Mul, op1,
            ConstantInt::get( Type::Int64Ty, -1 ) );
        bb->getInstList().push_back( multop );
        push_value( bb, multop );
        break;
    }
    case ABS : // w1 -- |w1|
    {
        if (echo) bb->setName("ABS");
        // Get the top of stack value
        LoadInst* op1 = cast<LoadInst>(stack_top(bb));

        // Determine if its negative
        ICmpInst* cond_inst =
            new ICmpInst( ICmpInst::ICMP_SLT, op1, Zero );
        bb->getInstList().push_back( cond_inst );

        // Create a block for storing the result
        BasicBlock* exit_bb = new BasicBlock((echo?"exit":""));

        // Create a block for making it a positive value
        BasicBlock* pos_bb = new BasicBlock((echo?"neg":""));

        // Create the branch on the ICmp
        BranchInst* br_inst = new BranchInst( pos_bb, exit_bb, cond_inst );
        bb->getInstList().push_back( br_inst );

        // Fill out the negation block
        LoadInst* pop_op = cast<LoadInst>( pop_integer(pos_bb) );
        BinaryOperator* neg_op = BinaryOperator::createNeg( pop_op );
        pos_bb->getInstList().push_back( neg_op );
        push_value( pos_bb, neg_op );
        pos_bb->getInstList().push_back( new BranchInst( exit_bb ) );

        // Add the new blocks in the correct order
        add_block( TheFunction, bb );
        add_block( TheFunction, pos_bb );
        bb = exit_bb;
        break;
    }
    case MIN : // w1 w2 -- (w2<w1?w2:w1)
    {
        if (echo) bb->setName("MIN");

        // Create the three blocks
        BasicBlock* exit_bb  = new BasicBlock((echo?"exit":""));
        BasicBlock* op1_block = new BasicBlock((echo?"less":""));
        BasicBlock* op2_block = new BasicBlock((echo?"more":""));

        // Get the two operands
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));

        // Compare them
        ICmpInst* cond_inst =
            new ICmpInst( ICmpInst::ICMP_SLT, op1, op2);
        bb->getInstList().push_back( cond_inst );

        // Create a branch on the ICmp
        BranchInst* br_inst =
            new BranchInst( op1_block, op2_block, cond_inst );
        bb->getInstList().push_back( br_inst );

        // Create a block for pushing the first one
        push_value(op1_block, op1);
        op1_block->getInstList().push_back( new BranchInst( exit_bb ) );

        // Create a block for pushing the second one
        push_value(op2_block, op2);
        op2_block->getInstList().push_back( new BranchInst( exit_bb ) );

        // Add the blocks
        add_block( TheFunction, bb );
        add_block( TheFunction, op1_block );
        add_block( TheFunction, op2_block );
        bb = exit_bb;
        break;
    }
    case MAX : // w1 w2 -- (w2>w1?w2:w1)
    {
        if (echo) bb->setName("MAX");
        // Get the two operands
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));

        // Compare them
        ICmpInst* cond_inst =
            new ICmpInst( ICmpInst::ICMP_SGT, op1, op2);
        bb->getInstList().push_back( cond_inst );

        // Create an exit block
        BasicBlock* exit_bb = new BasicBlock((echo?"exit":""));

        // Create a block for pushing the larger one
        BasicBlock* op1_block = new BasicBlock((echo?"more":""));
        push_value(op1_block, op1);
        op1_block->getInstList().push_back( new BranchInst( exit_bb ) );

        // Create a block for pushing the smaller or equal one
        BasicBlock* op2_block = new BasicBlock((echo?"less":""));
        push_value(op2_block, op2);
        op2_block->getInstList().push_back( new BranchInst( exit_bb ) );

        // Create a banch on the ICmp
        BranchInst* br_inst =
            new BranchInst( op1_block, op2_block, cond_inst );
        bb->getInstList().push_back( br_inst );

        // Add the blocks
        add_block( TheFunction, bb );
        add_block( TheFunction, op1_block );
        add_block( TheFunction, op2_block );

        bb = exit_bb;
        break;
    }

    // Bitwise Operators
    case AND : // w1 w2 -- w2&w1
    {
        if (echo) bb->setName("AND");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        BinaryOperator* andop =
            BinaryOperator::create( Instruction::And, op1, op2);
        bb->getInstList().push_back( andop );
        push_value( bb, andop );
        break;
    }
    case OR : // w1 w2 -- w2|w1
    {
        if (echo) bb->setName("OR");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        BinaryOperator* orop =
            BinaryOperator::create( Instruction::Or, op1, op2);
        bb->getInstList().push_back( orop );
        push_value( bb, orop );
        break;
    }
    case XOR : // w1 w2 -- w2^w1
    {
        if (echo) bb->setName("XOR");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        BinaryOperator* xorop =
            BinaryOperator::create( Instruction::Xor, op1, op2);
        bb->getInstList().push_back( xorop );
        push_value( bb, xorop );
        break;
    }
    case LSHIFT : // w1 w2 -- w1<<w2
    {
        if (echo) bb->setName("SHL");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        CastInst* castop = new TruncInst( op1, Type::Int8Ty );
        bb->getInstList().push_back( castop );
        BinaryOperator* shlop = 
          BinaryOperator::create( Instruction::Shl, op2, castop );
        bb->getInstList().push_back( shlop );
        push_value( bb, shlop );
        break;
    }
    case RSHIFT :  // w1 w2 -- w1>>w2
    {
        if (echo) bb->setName("SHR");
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));
        LoadInst* op2 = cast<LoadInst>(pop_integer(bb));
        CastInst* castop = new TruncInst( op1, Type::Int8Ty );
        bb->getInstList().push_back( castop );
        BinaryOperator* shrop = 
          BinaryOperator::create( Instruction::AShr, op2, castop );
        bb->getInstList().push_back( shrop );
        push_value( bb, shrop );
        break;
    }

    // Stack Manipulation Operations
    case DROP:          // w --
    {
        if (echo) bb->setName("DROP");
        decr_stack_index(bb, One);
        break;
    }
    case DROP2: // w1 w2 --
    {
        if (echo) bb->setName("DROP2");
        decr_stack_index( bb, Two );
        break;
    }
    case NIP:   // w1 w2 -- w2
    {
        if (echo) bb->setName("NIP");
        LoadInst* w2 = cast<LoadInst>( stack_top( bb ) );
        decr_stack_index( bb  );
        replace_top( bb, w2 );
        break;
    }
    case NIP2:  // w1 w2 w3 w4 -- w3 w4
    {
        if (echo) bb->setName("NIP2");
        LoadInst* w4 = cast<LoadInst>( stack_top( bb ) );
        LoadInst* w3 = cast<LoadInst>( stack_top( bb, One ) );
        decr_stack_index( bb, Two );
        replace_top( bb, w4 );
        replace_top( bb, w3, One );
        break;
    }
    case DUP:   // w -- w w
    {
        if (echo) bb->setName("DUP");
        LoadInst* w = cast<LoadInst>( stack_top( bb ) );
        push_value( bb, w );
        break;
    }
    case DUP2:  // w1 w2 -- w1 w2 w1 w2
    {
        if (echo) bb->setName("DUP2");
        LoadInst* w2 = cast<LoadInst>( stack_top(bb) );
        LoadInst* w1 = cast<LoadInst>( stack_top(bb, One ) );
        incr_stack_index( bb, Two );
        replace_top( bb, w1, One );
        replace_top( bb, w2 );
        break;
    }
    case SWAP:  // w1 w2 -- w2 w1
    {
        if (echo) bb->setName("SWAP");
        LoadInst* w2 = cast<LoadInst>( stack_top( bb ) );
        LoadInst* w1 = cast<LoadInst>( stack_top( bb, One ) );
        replace_top( bb, w1 );
        replace_top( bb, w2, One );
        break;
    }
    case SWAP2: // w1 w2 w3 w4 -- w3 w4 w1 w2
    {
        if (echo) bb->setName("SWAP2");
        LoadInst* w4 = cast<LoadInst>( stack_top( bb ) );
        LoadInst* w3 = cast<LoadInst>( stack_top( bb, One ) );
        LoadInst* w2 = cast<LoadInst>( stack_top( bb, Two ) );
        LoadInst* w1 = cast<LoadInst>( stack_top( bb, Three ) );
        replace_top( bb, w2 );
        replace_top( bb, w1, One );
        replace_top( bb, w4, Two );
        replace_top( bb, w3, Three );
        break;
    }
    case OVER:  // w1 w2 -- w1 w2 w1
    {
        if (echo) bb->setName("OVER");
        LoadInst* w1 = cast<LoadInst>( stack_top( bb, One ) );
        push_value( bb, w1 );
        break;
    }
    case OVER2: // w1 w2 w3 w4 -- w1 w2 w3 w4 w1 w2
    {
        if (echo) bb->setName("OVER2");
        LoadInst* w2 = cast<LoadInst>( stack_top( bb, Two ) );
        LoadInst* w1 = cast<LoadInst>( stack_top( bb, Three ) );
        incr_stack_index( bb, Two );
        replace_top( bb, w2 );
        replace_top( bb, w1, One );
        break;
    }
    case ROT:   // w1 w2 w3 -- w2 w3 w1
    {
        if (echo) bb->setName("ROT");
        LoadInst* w3 = cast<LoadInst>( stack_top( bb ) );
        LoadInst* w2 = cast<LoadInst>( stack_top( bb, One ) );
        LoadInst* w1 = cast<LoadInst>( stack_top( bb, Two ) );
        replace_top( bb, w1 );
        replace_top( bb, w3, One );
        replace_top( bb, w2, Two );
        break;
    }
    case ROT2:  // w1 w2 w3 w4 w5 w6 -- w3 w4 w5 w6 w1 w2
    {
        if (echo) bb->setName("ROT2");
        LoadInst* w6 = cast<LoadInst>( stack_top( bb ) );
        LoadInst* w5 = cast<LoadInst>( stack_top( bb, One ) );
        LoadInst* w4 = cast<LoadInst>( stack_top( bb, Two ) );
        LoadInst* w3 = cast<LoadInst>( stack_top( bb, Three) );
        LoadInst* w2 = cast<LoadInst>( stack_top( bb, Four ) );
        LoadInst* w1 = cast<LoadInst>( stack_top( bb, Five ) );
        replace_top( bb, w2 );
        replace_top( bb, w1, One );
        replace_top( bb, w6, Two );
        replace_top( bb, w5, Three );
        replace_top( bb, w4, Four );
        replace_top( bb, w3, Five );
        break;
    }
    case RROT:  // w1 w2 w3 -- w3 w1 w2
    {
        if (echo) bb->setName("RROT2");
        LoadInst* w3 = cast<LoadInst>( stack_top( bb ) );
        LoadInst* w2 = cast<LoadInst>( stack_top( bb, One ) );
        LoadInst* w1 = cast<LoadInst>( stack_top( bb, Two ) );
        replace_top( bb, w2 );
        replace_top( bb, w1, One );
        replace_top( bb, w3, Two );
        break;
    }
    case RROT2: // w1 w2 w3 w4 w5 w6 -- w5 w6 w1 w2 w3 w4
    {
        if (echo) bb->setName("RROT2");
        LoadInst* w6 = cast<LoadInst>( stack_top( bb ) );
        LoadInst* w5 = cast<LoadInst>( stack_top( bb, One ) );
        LoadInst* w4 = cast<LoadInst>( stack_top( bb, Two ) );
        LoadInst* w3 = cast<LoadInst>( stack_top( bb, Three) );
        LoadInst* w2 = cast<LoadInst>( stack_top( bb, Four ) );
        LoadInst* w1 = cast<LoadInst>( stack_top( bb, Five ) );
        replace_top( bb, w4 );
        replace_top( bb, w3, One );
        replace_top( bb, w2, Two );
        replace_top( bb, w1, Three );
        replace_top( bb, w6, Four );
        replace_top( bb, w5, Five );
        break;
    }
    case TUCK:  // w1 w2 -- w2 w1 w2
    {
        if (echo) bb->setName("TUCK");
        LoadInst* w2 = cast<LoadInst>( stack_top( bb ) );
        LoadInst* w1 = cast<LoadInst>( stack_top( bb, One ) );
        incr_stack_index( bb );
        replace_top( bb, w2 );
        replace_top( bb, w1, One );
        replace_top( bb, w2, Two );
        break;
    }
    case TUCK2: // w1 w2 w3 w4 -- w3 w4 w1 w2 w3 w4
    {
        if (echo) bb->setName("TUCK2");
        LoadInst* w4 = cast<LoadInst>( stack_top( bb ) );
        LoadInst* w3 = cast<LoadInst>( stack_top( bb, One ) );
        LoadInst* w2 = cast<LoadInst>( stack_top( bb, Two ) );
        LoadInst* w1 = cast<LoadInst>( stack_top( bb, Three) );
        incr_stack_index( bb, Two );
        replace_top( bb, w4 );
        replace_top( bb, w3, One );
        replace_top( bb, w2, Two );
        replace_top( bb, w1, Three );
        replace_top( bb, w4, Four );
        replace_top( bb, w3, Five );
        break;
    }
    case ROLL:  // x0 x1 .. xn n -- x1 .. xn x0
    {
        /// THIS OEPRATOR IS OMITTED PURPOSEFULLY AND IS LEFT TO THE
        /// READER AS AN EXERCISE. THIS IS ONE OF THE MORE COMPLICATED
        /// OPERATORS. IF YOU CAN GET THIS ONE RIGHT, YOU COMPLETELY
        /// UNDERSTAND HOW BOTH LLVM AND STACKER WOR.
        /// HINT: LOOK AT PICK AND SELECT. ROLL IS SIMILAR.
        if (echo) bb->setName("ROLL");
        break;
    }
    case PICK:  // x0 ... Xn n -- x0 ... Xn x0
    {
        if (echo) bb->setName("PICK");
        LoadInst* n = cast<LoadInst>( stack_top( bb ) );
        BinaryOperator* addop =
            BinaryOperator::create( Instruction::Add, n, One );
        bb->getInstList().push_back( addop );
        LoadInst* x0 = cast<LoadInst>( stack_top( bb, addop ) );
        replace_top( bb, x0 );
        break;
    }
    case SELECT:        // m n X0..Xm Xm+1 .. Xn -- Xm
    {
        if (echo) bb->setName("SELECT");
        LoadInst* m = cast<LoadInst>( stack_top(bb) );
        LoadInst* n = cast<LoadInst>( stack_top(bb, One) );
        BinaryOperator* index =
            BinaryOperator::create( Instruction::Add, m, One );
        bb->getInstList().push_back( index );
        LoadInst* Xm = cast<LoadInst>( stack_top(bb, index ) );
        BinaryOperator* n_plus_1 =
            BinaryOperator::create( Instruction::Add, n, One );
        bb->getInstList().push_back( n_plus_1 );
        decr_stack_index( bb, n_plus_1 );
        replace_top( bb, Xm );
        break;
    }
    case MALLOC : // n -- p
    {
        if (echo) bb->setName("MALLOC");
        // Get the number of bytes to mallocate
        LoadInst* op1 = cast<LoadInst>( pop_integer(bb) );

        // Make sure its a UIntTy
        CastInst* caster = CastInst::createTruncOrBitCast( op1, Type::Int32Ty );
        bb->getInstList().push_back( caster );

        // Allocate the bytes
        MallocInst* mi = new MallocInst( Type::Int8Ty, caster );
        bb->getInstList().push_back( mi );

        // Push the pointer
        push_value( bb, mi );
        break;
    }
    case FREE :  // p --
    {
        if (echo) bb->setName("FREE");
        // Pop the value off the stack
        CastInst* ptr = cast<CastInst>( pop_string(bb) );

        // Free the memory
        FreeInst* fi = new FreeInst( ptr );
        bb->getInstList().push_back( fi );

        break;
    }
    case GET : // p w1 -- p w2
    {
        if (echo) bb->setName("GET");
        // Get the character index
        LoadInst* op1 = cast<LoadInst>( stack_top(bb) );
        CastInst* chr_idx = CastInst::createSExtOrBitCast( op1, Type::Int64Ty );
        bb->getInstList().push_back( chr_idx );

        // Get the String pointer
        CastInst* ptr = cast<CastInst>( stack_top_string(bb,One) );

        // Get address of op1'th element of the string
        std::vector<Value*> indexVec;
        indexVec.push_back( chr_idx );
        GetElementPtrInst* gep = new GetElementPtrInst( ptr, &indexVec[0], 
                                                        indexVec.size() );
        bb->getInstList().push_back( gep );

        // Get the value and push it
        LoadInst* loader = new LoadInst( gep );
        bb->getInstList().push_back( loader );
        CastInst* caster = CastInst::createTruncOrBitCast(loader, Type::Int32Ty);
        bb->getInstList().push_back( caster );

        // Push the result back on stack
        replace_top( bb, caster );

        break;
    }
    case PUT : // p w2 w1  -- p
    {
        if (echo) bb->setName("PUT");

        // Get the value to put
        LoadInst* w1 = cast<LoadInst>( pop_integer(bb) );

        // Get the character index
        LoadInst* w2 = cast<LoadInst>( pop_integer(bb) );
        CastInst* chr_idx = CastInst::createSExtOrBitCast( w2, Type::Int64Ty );
        bb->getInstList().push_back( chr_idx );

        // Get the String pointer
        CastInst* ptr = cast<CastInst>( stack_top_string(bb) );

        // Get address of op2'th element of the string
        std::vector<Value*> indexVec;
        indexVec.push_back( chr_idx );
        GetElementPtrInst* gep = new GetElementPtrInst( ptr, &indexVec[0], 
                                                        indexVec.size());
        bb->getInstList().push_back( gep );

        // Cast the value and put it
        CastInst* caster = new TruncInst( w1, Type::Int8Ty );
        bb->getInstList().push_back( caster );
        StoreInst* storer = new StoreInst( caster, gep );
        bb->getInstList().push_back( storer );

        break;
    }
    case RECURSE :
    {
        if (echo) bb->setName("RECURSE");
        std::vector<Value*> params;
        CallInst* call_inst = new CallInst(TheFunction, &params[0], 
                                           params.size());
        bb->getInstList().push_back( call_inst );
        break;
    }
    case RETURN :
    {
        if (echo) bb->setName("RETURN");
        bb->getInstList().push_back( new ReturnInst() );
        break;
    }
    case EXIT :
    {
        if (echo) bb->setName("EXIT");
        // Get the result value
        LoadInst* op1 = cast<LoadInst>(pop_integer(bb));

        // Cast down to an integer
        CastInst* caster = new TruncInst( op1, Type::Int32Ty );
        bb->getInstList().push_back( caster );

        // Call exit(3)
        std::vector<Value*> params;
        params.push_back(caster);
        CallInst* call_inst = new CallInst( TheExit, &params[0], params.size());
        bb->getInstList().push_back( call_inst );
        break;
    }
    case TAB :
    {
        if (echo) bb->setName("TAB");
        // Get the format string for a character
        std::vector<Value*> indexVec;
        indexVec.push_back( Zero );
        indexVec.push_back( Zero );
        GetElementPtrInst* format_gep =
            new GetElementPtrInst( ChrFormat, &indexVec[0], indexVec.size() );
        bb->getInstList().push_back( format_gep );

        // Get the character to print (a tab)
        ConstantInt* newline = ConstantInt::get(Type::Int32Ty,
            static_cast<int>('\t'));

        // Call printf
        std::vector<Value*> args;
        args.push_back( format_gep );
        args.push_back( newline );
        bb->getInstList().push_back( new CallInst(ThePrintf, &args[0], 
                                                  args.size()));
        break;
    }
    case SPACE :
    {
        if (echo) bb->setName("SPACE");
        // Get the format string for a character
        std::vector<Value*> indexVec;
        indexVec.push_back( Zero );
        indexVec.push_back( Zero );
        GetElementPtrInst* format_gep =
            new GetElementPtrInst( ChrFormat, &indexVec[0], indexVec.size() );
        bb->getInstList().push_back( format_gep );

        // Get the character to print (a space)
        ConstantInt* newline = ConstantInt::get(Type::Int32Ty,
            static_cast<int>(' '));

        // Call printf
        std::vector<Value*> args;
        args.push_back( format_gep );
        args.push_back( newline );
        bb->getInstList().push_back( new CallInst(ThePrintf, &args[0], 
                                                  args.size()));
        break;
    }
    case CR :
    {
        if (echo) bb->setName("CR");
        // Get the format string for a character
        std::vector<Value*> indexVec;
        indexVec.push_back( Zero );
        indexVec.push_back( Zero );
        GetElementPtrInst* format_gep =
            new GetElementPtrInst( ChrFormat, &indexVec[0], indexVec.size() );
        bb->getInstList().push_back( format_gep );

        // Get the character to print (a newline)
        ConstantInt* newline = ConstantInt::get(Type::Int32Ty,
            static_cast<int>('\n'));

        // Call printf
        std::vector<Value*> args;
        args.push_back( format_gep );
        args.push_back( newline );
        bb->getInstList().push_back( new CallInst(ThePrintf, &args[0], 
                                                  args.size()));
        break;
    }
    case IN_STR :
    {
        if (echo) bb->setName("IN_STR");
        // Make room for the value result
        incr_stack_index(bb);
        GetElementPtrInst* gep_value =
          cast<GetElementPtrInst>(get_stack_pointer(bb));
        CastInst* caster = 
          new BitCastInst(gep_value, PointerType::get(Type::Int8Ty));

        // Make room for the count result
        incr_stack_index(bb);
        GetElementPtrInst* gep_count =
            cast<GetElementPtrInst>(get_stack_pointer(bb));

        // Call scanf(3)
        std::vector<Value*> args;
        args.push_back( InStrFormat );
        args.push_back( caster );
        CallInst* scanf = new CallInst( TheScanf, &args[0], args.size());
        bb->getInstList().push_back( scanf );

        // Store the result
        bb->getInstList().push_back( new StoreInst( scanf, gep_count ) );
        break;
    }
    case IN_NUM :
    {
        if (echo) bb->setName("IN_NUM");
        // Make room for the value result
        incr_stack_index(bb);
        GetElementPtrInst* gep_value =
            cast<GetElementPtrInst>(get_stack_pointer(bb));

        // Make room for the count result
        incr_stack_index(bb);
        GetElementPtrInst* gep_count =
            cast<GetElementPtrInst>(get_stack_pointer(bb));

        // Call scanf(3)
        std::vector<Value*> args;
        args.push_back( InStrFormat );
        args.push_back( gep_value );
        CallInst* scanf = new CallInst( TheScanf, &args[0], args.size());
        bb->getInstList().push_back( scanf );

        // Store the result
        bb->getInstList().push_back( new StoreInst( scanf, gep_count ) );
        break;
    }
    case IN_CHAR :
    {
        if (echo) bb->setName("IN_CHAR");
        // Make room for the value result
        incr_stack_index(bb);
        GetElementPtrInst* gep_value =
            cast<GetElementPtrInst>(get_stack_pointer(bb));

        // Make room for the count result
        incr_stack_index(bb);
        GetElementPtrInst* gep_count =
            cast<GetElementPtrInst>(get_stack_pointer(bb));

        // Call scanf(3)
        std::vector<Value*> args;
        args.push_back( InChrFormat );
        args.push_back( gep_value );
        CallInst* scanf = new CallInst( TheScanf, &args[0], args.size());
        bb->getInstList().push_back( scanf );

        // Store the result
        bb->getInstList().push_back( new StoreInst( scanf, gep_count ) );
        break;
    }
    case OUT_STR :
    {
        if (echo) bb->setName("OUT_STR");
        LoadInst* op1 = cast<LoadInst>(stack_top(bb));

        // Get the address of the format string
        std::vector<Value*> indexVec;
        indexVec.push_back( Zero );
        indexVec.push_back( Zero );
        GetElementPtrInst* format_gep =
            new GetElementPtrInst( StrFormat, &indexVec[0], indexVec.size() );
        bb->getInstList().push_back( format_gep );
        // Build function call arguments
        std::vector<Value*> args;
        args.push_back( format_gep );
        args.push_back( op1 );
        // Call printf
        bb->getInstList().push_back( new CallInst(ThePrintf, &args[0], 
                                                  args.size()));
        break;
    }
    case OUT_NUM :
    {
        if (echo) bb->setName("OUT_NUM");
        // Pop the numeric operand off the stack
        LoadInst* op1 = cast<LoadInst>(stack_top(bb));

        // Get the address of the format string
        std::vector<Value*> indexVec;
        indexVec.push_back( Zero );
        indexVec.push_back( Zero );
        GetElementPtrInst* format_gep =
            new GetElementPtrInst( NumFormat, &indexVec[0], indexVec.size() );
        bb->getInstList().push_back( format_gep );

        // Build function call arguments
        std::vector<Value*> args;
        args.push_back( format_gep );
        args.push_back( op1 );

        // Call printf
        bb->getInstList().push_back( new CallInst(ThePrintf, &args[0],
                                                  args.size()));
        break;
    }
    case OUT_CHAR :
    {
        if (echo) bb->setName("OUT_CHAR");
        // Pop the character operand off the stack
        LoadInst* op1 = cast<LoadInst>(stack_top(bb));

        // Get the address of the format string
        std::vector<Value*> indexVec;
        indexVec.push_back( Zero );
        indexVec.push_back( Zero );
        GetElementPtrInst* format_gep =
            new GetElementPtrInst( ChrFormat, &indexVec[0], indexVec.size() );
        bb->getInstList().push_back( format_gep );

        // Build function call arguments
        std::vector<Value*> args;
        args.push_back( format_gep );
        args.push_back( op1 );
        // Call printf
        bb->getInstList().push_back( new CallInst(ThePrintf, &args[0],
                                                  args.size()));
        break;
    }
    default :
    {
        ThrowException(std::string("Compiler Error: Unhandled token #"));
    }
    }

    // Return the basic block
    return bb;
}
