/* 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_OR)

            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;

      case TOK_GT:

          return OP_GT;

      case TOK_GE:

          return OP_GE;

      case TOK_LT:

          return OP_LT;

      case TOK_LE:

          return OP_LE;

      case TOK_EQUALS:

          return OP_EQ;

      case TOK_NOTEQUALS:

          return OP_NE;

      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;

      }

      case BoundName::FUNCTION:

      {

        NamedFunction *fun = name->binding()->toNamedFunction();

        __ module();

        __ getmodule_fn(fun->slot());

        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);

    if (!node->expression()->type()->isVoid())

        __ 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_position(index->pos());

        // 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));

        __ note_position(node->pos());

        __ 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.

        __ note_position(node->pos());

        __ 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();

        __ note_position(index->pos());

        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);

    }

    __ note_position(node->pos());

    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());

}

static inline Type *

GetCoercionType(TokenKind tok, Type *left, Type *right)

{

    if (left->isFloat())

        return left;

    return right;

}

void

BytecodeCompiler::visit(BinaryExpression *node)

{

    if (node->token() == TOK_AND || node->token() == TOK_OR) {

        Label success, failure, done;

        visitForTest(node, &success, &failure, &success);

        __ bind(&success);

        __ int_(1);

        __ drop(1);         // Otherwise, the stack depth will be +1 too much.

        __ jump(&done);

        __ bind(&failure);

        __ int_(0);

        __ bind(&done);

        return;

    }

    Local<Type> leftType(zone_, node->left()->type());

    Local<Type> rightType(zone_, node->right()->type());

    Local<Type> coerce(zone_, GetCoercionType(node->token(), leftType, rightType));

    visitForALU(coerce, node->left());

    visitForALU(coerce, node->right());

    Opcode op = TokenToOpcode(node->token());

    if (node->type()->isFloat())

        op = (Opcode)(int(op) + (OP_ADD_F - OP_ADD));

    __ note_position(node->pos());

    __ binary(op);

}

void

BytecodeCompiler::visit(IndexExpression *node)

{

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

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

    __ note_position(node->pos());

    __ bounds();

    if (node->type()->isArray())

        __ getarray_o();

    else

        __ getarray(node->type()->primitive());

}

void

BytecodeCompiler::visit(ReturnStatement *node)

{

    if (node->expression()) {

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

        __ return_();

    } else {

        __ returnvoid();

    }

}

void

BytecodeCompiler::visitForTest(Expression *expression,

                               Label *trueBranch,

                               Label *falseBranch,

                               Label *fallthrough)

{

    TokenKind token = ToCompare(expression);

    if (token == TOK_EOF) {

        expression->accept(this);

        Opcode op = (fallthrough == trueBranch) ? OP_JF : OP_JT;

        if (expression->type()->isFloat())

            op = (Opcode)(int(op) + (OP_JL_F - OP_JL));

        if (fallthrough == trueBranch)

            __ j(op, falseBranch);

        else

            __ j(op, trueBranch);

        return;

    }

    BinaryExpression *binary = expression->toBinaryExpression();

    if (token == TOK_AND || token == TOK_OR) {

        Label next;

        if (token == TOK_AND)

            visitForTest(binary->left(), &next, falseBranch, &next);

        else

            visitForTest(binary->left(), trueBranch, &next, &next);

        __ bind(&next);

        visitForTest(binary->right(), trueBranch, falseBranch, fallthrough);

        return;

    }

    Opcode op = CompareTokenToJump(token);

    if (fallthrough == trueBranch)

        op = Invert(op);

    Local<Type> leftType(zone_, binary->left()->type());

    Local<Type> rightType(zone_, binary->right()->type());

    Local<Type> coerce(zone_, GetCoercionType(binary->token(), leftType, rightType));

    visitForALU(coerce, binary->left());

    visitForALU(coerce, binary->right());

    if (coerce->isFloat())

        op = (Opcode)(int(op) + (OP_JL_F - OP_JL));

    if (fallthrough == trueBranch)

        __ j(op, falseBranch);

    else

        __ j(op, trueBranch);

}

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, &join, &join);

    } 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) {

        Label body;

        visitForTest(node->condition(), &body, &join, &body);

        __ bind(&body);

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

        __ jump(&header);

    } else {

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

        visitForTest(node->condition(), &header, &join, &join);

    }

    __ bind(&join);

}

void

BytecodeCompiler::visit(BreakStatement *node)