/* vim: set ts=4 sw=4 tw=99 et:
 *
 * Copyright (C) 2012 David Anderson
 *
 * This file is part of JITCraft.
 *
 * JITCraft is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option)
 * any later version.
 * 
 * Foobar is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * JITCraft. If not, see http://www.gnu.org/licenses/.
 */
#include "BytecodeCompiler.h"
#include "Scopes.h"
#include "Modules.h"
#include "Types.h"
#include "Array.h"
#include "Strings.h"
#include "Zone.h"
#include "Heap-inl.h"

using namespace ke;

typedef BytecodeEmitter::Label Label;

#define __ emitter_.

BytecodeCompiler::BytecodeCompiler(Zone *zone, ParseTree *tree, ModuleData *module)
  : zone_(zone),
    tree_(tree),
    emitter_(zone->pool()),
    moduleData_(module),
    locals_(NULL),
    scope_(NULL),
    loop_(NULL)
{
}

static inline TokenKind
ToCompare(Expression *expr)
{
    if (expr->isBinaryExpression()) {
        BinaryExpression *b = expr->toBinaryExpression();
        if (b->token() >= TOK_EQUALS && b->token() <= TOK_GE)
            return b->token();
    }
    return TOK_EOF;
}

static inline Opcode
CompareTokenToJump(TokenKind kind)
{
    switch (kind) {
      case TOK_EQUALS:
        return OP_JEQ;
      case TOK_NOTEQUALS:
        return OP_JNE;
      case TOK_GT:
        return OP_JG;
      case TOK_GE:
        return OP_JGE;
      case TOK_LT:
        return OP_JL;
      default:
        assert(kind == TOK_LE);
        return OP_JLE;
    }
}

static inline Opcode
TokenToOpcode(TokenKind kind)
{
    switch (kind) {
      case TOK_PLUS:
        return OP_ADD;
      case TOK_MINUS:
        return OP_SUB;
      case TOK_STAR:
        return OP_MUL;
      case TOK_SLASH:
        return OP_DIV;
      case TOK_SHR:
        return OP_SHR;
      case TOK_USHR:
        return OP_USHR;
      case TOK_SHL:
        return OP_SHL;
      case TOK_BITAND:
        return OP_BITAND;
      case TOK_BITOR:
        return OP_BITOR;
      default:
        assert(kind == TOK_BITXOR);
        return OP_BITXOR;
    }
}

void
BytecodeCompiler::recordLifoSlot(Scope *scope)
{
    if (!scope)
        return;

    if (Variable *var = scope->lifoSlot()) {
        locals_->set(zone_, var->slot(), var->type());
        __ savelifo(var->slot());
    }
}

void
BytecodeCompiler::unwindTo(Scope *scope)
{
    // Note: we only need to unwind to the outermost scope's LIFO slot.
    Variable *var = NULL;
    for (Scope *current = scope_; current != scope; current = current->enclosing()) {
        if (Variable *slot = current->lifoSlot())
            var = slot;
    }

    if (var)
        __ unwindlifo(var->slot());
}

void
BytecodeCompiler::visit(NameProxy *name)
{
    switch (name->binding()->kind()) {
      case BoundName::VARIABLE:
      {
        Variable *var = name->binding()->toVariable();

        if (var->location() == Variable::STACK) {
            __ getlocal(var);
            assert(!name->type()->isReference());
        } else {
            assert(var->location() == Variable::PARAMETER);
            __ getarg(var);

            // If this argument is actually a reference, dereference it now.
            if (var->type()->isReference())
                __ getref(var->type()->contained()->primitive());
        }
        break;
      }

      default:
      {
        NamedConstant *constant = name->binding()->toNamedConstant();
        __ int_(constant->value().toInt());
        break;
      }
    }
}

void
BytecodeCompiler::visit(ExpressionStatement *node)
{
    // Expressions leave their value on the top of the stack, so we make sure
    // to balance the stack if they're used as a statement.
    node->expression()->accept(this);
    __ pop();
}

void
BytecodeCompiler::visit(Assignment *node)
{
    // The first step is three sub-steps:
    //
    //   (1) Bind the left-hand side.
    //   -- If a cumulative operation (+=, etc):
    //   (2) Save a copy of the binding on the stack.
    //   (3) Dereference the binding to get a value.
    //
    if (node->lvalue()->isNameProxy()) {
        NameProxy *proxy = node->lvalue()->toNameProxy();
        Variable *var = proxy->binding()->toVariable();

        // Bind.
        if (var->type()->isReference() || var->type()->isArray())
            __ get(var);

        // Get the value if needed.
        if (node->token() != TOK_ASSIGN) {
            // += etc is not allowed on arrays.
            assert(!var->type()->isArray());

            if (var->type()->isReference()) {
                __ dup();
                __ getref(var->type()->contained()->primitive());
            } else {
                __ get(var);
            }
        }
    } else {
        IndexExpression *index = node->lvalue()->toIndexExpression();

        // Note: Eventually, watch out for a whole here. An expression like:
        //
        //   (a[4] = (5, a = []))
        //
        // Could shrink array, so we need to either bind a[i] to a Reference,
        // or keep the bounds check near the set. This is just a semantic
        // decision.
        index->left()->accept(this);
        index->right()->accept(this);

        if (node->token() != TOK_ASSIGN) {
            __ dup2();
            __ bounds();
            if (node->type()->isArray())
                __ getarray_o();
            else
                __ getarray(node->type()->primitive());
        }
    }

    if (node->token() == TOK_ASSIGN) {
        node->expression()->accept(this);
    } else {
        visitForALU(node->type(), node->expression());

        TokenKind alu = TokenKind(int(node->token()) - (TOK_ASSIGN_ADD - TOK_PLUS));
        __ binary(TokenToOpcode(alu));
    }

    // Emit the store.
    if (node->expression()->type()->isArray()) {
        // Unlike references, which can only be computed from a NamePRoxy,
        // arrays can be computed from multiple lvalue types.
        __ arraycopy();
    } else if (node->lvalue()->isNameProxy()) {
        NameProxy *proxy = node->lvalue()->toNameProxy();
        Variable *var = proxy->binding()->toVariable();

        if (var->type()->isReference())
            __ setref(var->type()->contained()->primitive());
        else
            __ set(var);
    } else {
        IndexExpression *index = node->lvalue()->toIndexExpression();
        // :TODO: get rid of the BOUNDS instruction, embed it in g/setarray*?
        // We can't emit it here because the stack is slightly out of position.
        // __ bounds();
        __ setarray(index->left()->type()->contained()->primitive());
    }
}

void
BytecodeCompiler::visit(IncDecExpression *node)
{
    // In the postfix case, the logic looks like:
    //      (1) Bind       -> REF
    //      (2) Dup        -> REF REF
    //      (3) Fetch      -> REF VAL
    //      (4) Swap       -> VAL REF
    //      (5) Pick       -> VAL REF VAL
    //      (6) Add        -> VAL REF VAL+1
    //      (7) Store      -> VAL VAL+1
    //      (8) Drop       -> VAL
    //
    // In the prefix case, the logic looks like:
    //      (1) Bind       -> REF
    //      (2) Dup        -> REF REF
    //      (3) Fetch      -> REF VAL
    //      --
    //      --
    //      (6) Add        -> REF VAL+1
    //      (7) Store      -> VAL+1
    //      --
    //
    // This is squirrely enough such that we don't bother sharing too much
    // with the above.
    // 
    // Note: We simulate a "Pick" operation with a dup2+pop.

    // This is steps (1) to (5).
    Expression *expr = node->expression();
    if (expr->isNameProxy()) {
        NameProxy *proxy = expr->toNameProxy();
        Variable *var = proxy->binding()->toVariable();

        // Bind.
        if (var->type()->isReference() || var->type()->isArray())
            __ get(var);

        // Dup and fetch.
        if (var->type()->isReference()) {
            __ dup();
            __ getref(node->type()->primitive());
            if (node->postfix()) {
                __ swap();
                __ pick2();
            }
        } else {
            assert(!var->type()->isArray());
            __ get(var);
            if (node->postfix())
                __ dup();
        }
    } else {
        IndexExpression *index = expr->toIndexExpression();
        index->left()->accept(this);
        index->right()->accept(this);

        assert(!node->type()->isArray());
        __ bounds();
        __ dup2();
        __ getarray(node->type()->primitive());

        if (node->postfix()) {
            // The stack looks like this now:
            // ARRAY INDEX VALUE
            //
            // So we must use a PICK operation to rotate the stack into position.
            __ roll3();         // INDEX VALUE ARRAY
            __ roll3();         // VALUE ARRAY INDEX
            __ pick3();         // VALUE ARRAY INDEX VALUE
        }
    }

    // Perform step (6).
    if (node->type()->isFloat()) {
        __ float_(1.0);
    } else {
        assert(node->type()->isInt32());
        __ int_(1);
    }

    if (node->token() == TOK_INCREMENT)
        __ binary(OP_ADD);
    else
        __ binary(OP_SUB);

    // Perform step (7).
    if (expr->isNameProxy()) {
        NameProxy *proxy = expr->toNameProxy();
        Variable *var = proxy->binding()->toVariable();

        if (var->type()->isReference())
            __ setref(node->type()->primitive());
        else
            __ set(var);
    } else {
        __ setarray(node->type()->primitive());
    }

    // Perform step (8).
    if (node->postfix())
        __ pop();
}

void
BytecodeCompiler::visitForALU(Type *needed, Expression *node)
{
    node->accept(this);
    if (needed->isFloat() && !node->type()->isFloat())
        __ cvt_i2f();
    else
        assert(needed->primitive() == node->type()->primitive());
}

void
BytecodeCompiler::visit(BinaryExpression *node)
{
    visitForALU(node->type(), node->left());
    visitForALU(node->type(), node->right());

    Opcode op = TokenToOpcode(node->token());
    if (node->type()->isFloat())
        op = (Opcode)(int(op) + (OP_ADD_F - OP_ADD));
    __ binary(op);
}

void
BytecodeCompiler::visit(IndexExpression *node)
{
    node->left()->accept(this);
    node->right()->accept(this);
    __ bounds();

    if (node->type()->isArray())
        __ getarray_o();
    else
        __ getarray(node->type()->primitive());
}

void
BytecodeCompiler::visit(ReturnStatement *node)
{
    if (node->expression())
        node->expression()->accept(this);
    else
        __ int_(0);

    __ return_();
}

void
BytecodeCompiler::visitForTest(Expression *expression, Label *label, bool onTrue)
{
    TokenKind token = ToCompare(expression);
    if (token == TOK_EOF) {
        expression->accept(this);
        if (onTrue)
            __ j(OP_JT, label);
        else
            __ j(OP_JF, label);
        return;
    }

    Opcode op = CompareTokenToJump(token);
    if (!onTrue)
        op = Invert(op);

    assert(expression->isBinaryExpression());
    BinaryExpression *binary = expression->toBinaryExpression();
    binary->left()->accept(this);
    binary->right()->accept(this);
    __ j(op, label);
}

void
BytecodeCompiler::visit(ForStatement *node)
{
    AutoEnterScope forScope(this, node->scope());

    recordLifoSlot(node->scope());

    Label join, update;
    LoopScope loop(scope_, &join, &update, &loop_);

    if (node->initialization())
        node->initialization()->accept(this);

    Label header, test;
    if (node->condition())
        __ jump(&test);

    __ bind(&header);
    node->body()->accept(this);

    __ bind(&update);
    if (node->update())
        node->update()->accept(this);

    if (node->condition()) {
        __ bind(&test);
        visitForTest(node->condition(), &header, true);
    } else {
        __ jump(&header);
    }

    __ bind(&join);

    if (node->scope())
        unwindTo(node->scope()->enclosing());
    assert(__ stackDepth() == 0);
}

void
BytecodeCompiler::visit(WhileStatement *node)
{
    Label header, join;

    __ bind(&header);

    LoopScope loop(scope_, &join, &header, &loop_);

    if (node->token() == TOK_WHILE) {
        visitForTest(node->condition(), &join, false);
        node->body()->accept(this);
        __ jump(&header);
    } else {
        node->body()->accept(this);
        visitForTest(node->condition(), &header, true);
    }

    __ bind(&join);
}

void
BytecodeCompiler::visit(BreakStatement *node)
{
    unwindTo(loop_->scope());
    __ jump(loop_->break_());
}

void
BytecodeCompiler::visit(ContinueStatement *node)
{
    unwindTo(loop_->scope());
    __ jump(loop_->continue_());
}

void
BytecodeCompiler::visit(BlockStatement *node)
{
    AutoEnterScope blockScope(this, node->scope());

    recordLifoSlot(node->scope());

    for (size_t i = 0; i < node->statements()->length(); i++) {
        Statement *statement = node->statements()->at(i);
        statement->accept(this);
        assert(__ stackDepth() == 0);
    }

    // We don't bother emitting an "unwind" instruction for function scopes,
    // since this is taken care of by the calling convention.
    if (node->scope() && node->scope()->enclosing()->kind() != Scope::FUNCTION)
        unwindTo(node->scope()->enclosing());
}

void
BytecodeCompiler::visit(IntegerLiteral *node)
{
    __ int_(node->value());
}

void
BytecodeCompiler::visit(FloatLiteral *node)
{
    __ float_((float)node->value());
}

static inline ArrayMap *
BuildArrayMap(Zone *zone, Handle<Type> type)
{
    Local<ArrayMap> contained(zone);
    if (type->levels() > 1) {
        Local<Type> containedType(zone, type->contained());
        contained = BuildArrayMap(zone, containedType);
        if (!contained)
            return NULL;
    }

    return ArrayMap::New(zone, type, contained);
}

void
BytecodeCompiler::visit(StringLiteral *node)
{
    Local<Type> type(zone_, node->type());
    Local<ArrayMap> map(zone_, BuildArrayMap(zone_, type));
    if (!map)
        return;

    Local<Array> array(zone_, Array::New(zone_, map, node->string()->length(), Heap::Tenure_Old));
    if (!array)
        return;

    assert(array->nelements() >= node->string()->length());
    memcpy(array->chars(), node->string()->raw(), node->string()->length() * sizeof(char));

    __ object(array);
}

void
BytecodeCompiler::visit(VariableDeclaration *node)
{
    Variable *var = node->variable();
    assert(var->location() == Variable::STACK);
    
    Local<Type> type(zone_, var->type());
    if (type->isArray()) {
        Local<ArrayMap> map(zone_, BuildArrayMap(zone_, type));
        __ newarray_lifo(map);

        if (node->initialization()) {
            node->initialization()->accept(this);
            __ arraycopy();
        }
    } else {
        if (node->initialization()) {
            node->initialization()->accept(this);
        } else {
            if (!node->postDimensions())
                __ int_(0);
        }
    }
    __ setlocal(var);
    __ pop();

    locals_->set(zone_, var->slot(), var->type());
}

void
BytecodeCompiler::visit(CallExpression *node)
{
    Local<Type> funType(zone_, node->callee()->type());

    for (size_t i = 0; i < node->arguments()->length(); i++) {
        Expression *arg = node->arguments()->at(i);

        Local<Type> given(zone_, arg->type());
        Local<Type> actual(zone_, Type::cast(funType->parameters()->at(i)));
        if (actual->isReference()) {
            if (given->isReference()) {
                // The input type is already a reference, so we're just passing
                // it on to the callee.
                arg->accept(this);
            } else if (arg->isNameProxy()) {
                // :TODO: test with functions and globals
                // Compute a reference to the name.
                Variable *var = arg->toNameProxy()->binding()->toVariable();
                __ newref(var);
            } else if (arg->isIndexExpression()) {
                IndexExpression *expr = arg->toIndexExpression();
                expr->left()->accept(this);
                expr->right()->accept(this);
                __ bounds();
                __ arrayref_lifo();
            } else {
                // We don't know how to, or can't, build a direct reference to
                // this type. Make an indirect one, by taking the top of the
                // stack and boxing it up.
                arg->accept(this);
                __ slotref_lifo();
            }
        } else {
            arg->accept(this);
        }
    }

    __ callglobal(node->callee()->toNameProxy()->binding()->toNamedFunction()->slot());
    __ drop(node->arguments()->length());
}

void
BytecodeCompiler::visit(IfStatement *node)
{
    if (!node->ifFalse()) {
        Label fail;
        visitForTest(node->condition(), &fail, false);
        node->ifTrue()->accept(this);
        __ bind(&fail);
    } else {
        Label fail, join;
        visitForTest(node->condition(), &fail, false);
        node->ifTrue()->accept(this);
        __ jump(&join);
        __ bind(&fail);
        node->ifFalse()->accept(this);
        __ bind(&join);
    }
}

void
BytecodeCompiler::visit(FunctionStatement *node)
{
    // If the function has no body, then it's just a declaration.
    if (!node->body()) {
        assert(node->fun()->isForward() || node->fun()->isPublic());
        return;
    }

    BytecodeCompiler child(zone_, tree_, moduleData_);
    Local<Function> fun(zone_, child.compileFunction(moduleData_, node));
    if (!fun)
        return;
    
    assert(!moduleData_->module->getFunction(node->fun()->slot()));
    moduleData_->module->setFunction(zone_, node->fun()->slot(), fun);
}

void
BytecodeCompiler::visit(EnumStatement *node)
{
    // :TODO: eventually, we'll export these.
}

Function *
BytecodeCompiler::compileFunction(ModuleData *module, FunctionStatement *node)
{
    // Note: No need to record a life slot here, since it's part of the Frame.
    AutoEnterScope functionScope(this, node->scope());

    locals_ = FixedArray::New(zone_, node->scope()->maxContainedLocals(), Heap::Tenure_Old);

    node->body()->accept(this);

    __ stop();

    if (__ oom())
        return NULL;

    Local<ByteArray> bytes(zone_, ByteArray::New(zone_, __ length() * sizeof(bytecode), Heap::Tenure_Old));
    if (!bytes)
        return NULL;
    memcpy(bytes->raw(), __ buffer(), __ length());

    unsigned nargs = node->scope()->numArguments();
    Local<FixedArray> args(zone_, FixedArray::New(zone_, nargs, Heap::Tenure_Old));
    if (!args)
        return NULL;

    for (size_t i = 0; i < node->scope()->numArguments(); i++)
        args->set(zone_, i, node->scope()->getArgument(i)->type());

    for (size_t i = 0; i < node->scope()->maxContainedLocals(); i++)
        assert(locals_->at(i));

    Local<FixedArray> objects(zone_, FixedArray::New(zone_, __ objects()->length(), Heap::Tenure_Old));
    if (!objects)
        return NULL;

    for (size_t i = 0; i < __ objects()->length(); i++)
        objects->set(zone_, i, *(__ objects()->at(i)));

    Local<ByteArray> safepoints(zone_);

    // If any stack slots hold gc pointers at potential failure points in the
    // bytecode, record them now. We do this by building a list of tuples;
    // each tuple contains the pc offset, and a bitset containing which stack
    // slots must be scanned by the gc.
    if (__ oopRecords()->length()) {
        size_t bytesPerSafepoint = Code::BytesPerSafepoint(__ maxStackDepth());
        size_t gcmapSize = bytesPerSafepoint * __ oopRecords()->length();
        safepoints = ByteArray::New(zone_, gcmapSize, Heap::Tenure_Old);
        if (!safepoints)
            return NULL;

        Address cursor = safepoints->raw();
        for (size_t i = 0; i < __ oopRecords()->length(); i++) {
            OopRecord *record = __ oopRecords()->at(i);
            assert(record->depth <= __ maxStackDepth());

            *reinterpret_cast<unsigned *>(cursor) = record->offset;

            unsigned char *bits = reinterpret_cast<unsigned char *>(cursor + sizeof(unsigned));
            for (unsigned i = 0; i < record->depth; i++)
                bits[i / 8] |= (1 << (i % 8));

            cursor += bytesPerSafepoint;
        }

        assert(cursor == safepoints->raw() + gcmapSize);
    }

    Local<Code> code(zone_, Code::New(zone_, bytes, locals_, objects, __ maxStackDepth(),
                     moduleData_->module, safepoints));
    if (!code)
        return NULL;

    Local<Type> type(zone_, node->fun()->type());
    Local<String> name(zone_, node->fun()->name());
    Local<Function> fun(zone_, Function::New(zone_, code, type, name, node->pos()));
    if (!fun)
        return NULL;

    // If this function had a forward, export it as a named public.
    if (node->fun()->isPublic()) {
        assert(node->fun()->isPublic());
        ScopedRoot<Function> root(fun);
        if (!root)
            return NULL;
        if (!moduleData_->publics.append(root))
            return NULL;
    }

    Disassemble(code, stdout);
    
    return fun;
}

Module *
BytecodeCompiler::compile()
{
    ModuleData moduleData;

    moduleData_ = &moduleData;
    moduleData_->module = Module::New(zone_, tree_->scope()->numFunctions());

    if (!moduleData_)
        return NULL;

    for (size_t i = 0; i < tree_->statements()->length(); i++) {
        Statement *statement = tree_->statements()->at(i);
        statement->accept(this);
    }

#ifndef NDEBUG
    for (size_t i = 0; i < tree_->scope()->numFunctions(); i++)
        assert(moduleData_->module->getFunction(i));
#endif

    if (moduleData_->publics.length()) {
        Local<Function> fun(zone_);
        Local<FixedArray> list(zone_, FixedArray::New(zone_, moduleData_->publics.length(),
                               Heap::Tenure_Old));
        if (!list)
            return NULL;

        for (size_t i = 0; i < moduleData_->publics.length(); i++)
            list->set(zone_, i, moduleData_->publics[i]);

        moduleData_->module->setPublics(list);
    }

    return moduleData_->module;
}