// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

part of ssa;

class SsaFromIrBuilderTask extends CompilerTask {
  SsaFromIrBuilderTask(Compiler compiler) : super(compiler);

  HGraph build(CodegenWorkItem work) {
    return measure(() {
      Element element = work.element.implementation;
      return compiler.withCurrentElement(element, () {
        HInstruction.idCounter = 0;
        SsaFromIrBuilder builder = new SsaFromIrBuilder(compiler, element);

        HGraph graph;
        ElementKind kind = element.kind;
        if (kind == ElementKind.GENERATIVE_CONSTRUCTOR) {
          throw "Build HGraph for constructor from IR";
//          graph = compileConstructor(builder, work);
        } else if (kind == ElementKind.GENERATIVE_CONSTRUCTOR_BODY ||
                   kind == ElementKind.FUNCTION ||
                   kind == ElementKind.GETTER ||
                   kind == ElementKind.SETTER) {
          graph = builder.buildMethod();
        } else if (kind == ElementKind.FIELD) {
          throw "Build HGraph for field from IR";
//          assert(!element.isInstanceMember());
//          graph = builder.buildLazyInitializer(element);
        } else {
          compiler.internalErrorOnElement(element,
                                          'unexpected element kind $kind');
        }
        assert(graph.isValid());
        // TODO(lry): for default arguments, register constants in backend.
        // TODO(lry): tracing (factor out code in SsaBuilderTask).
        return graph;
      });
    });
  }
}

/**
 * This builder generates SSA nodes for elements that have an IR representation.
 * It mixes in [SsaGraphBuilderMixin] to share functionality with the
 * [SsaBuilder] that creates SSA nodes from trees.
 */
class SsaFromIrBuilder
    extends IrNodesVisitor<HInstruction> with SsaGraphBuilderMixin {
  final Compiler compiler;

  final Element sourceElement;

  SsaFromIrBuilder(this.compiler, this.sourceElement);

  /**
   * Maps IR nodes ot the generated [HInstruction]. Because the IR is itself
   * in an SSA form, the arguments of an [IrNode] have already been visited
   * prior to the node. This map is used to obtain the corresponding generated
   * SSA node.
   */
  final Map<IrNode, HInstruction> generated = new Map<IrNode, HInstruction>();

  HInstruction recordGenerated(IrNode irNode, HInstruction ssaNode) {
    return generated[irNode] = ssaNode;
  }

  HInstruction attachPosition(HInstruction target, IrNode node) {
    target.sourcePosition = sourceFileLocation(node);
    return target;
  }

  SourceFileLocation sourceFileLocation(IrNode node) {
    Element element = sourceElement;
    // TODO(johnniwinther): remove the 'element.patch' hack.
    if (element is FunctionElement) {
      FunctionElement functionElement = element;
      if (functionElement.patch != null) element = functionElement.patch;
    }
    Script script = element.getCompilationUnit().script;
    SourceFile sourceFile = script.file;
    SourceFileLocation location =
        new OffsetSourceFileLocation(sourceFile, node.offset, node.sourceName);
    if (!location.isValid()) {
      throw MessageKind.INVALID_SOURCE_FILE_LOCATION.message(
          {'offset': node.offset,
           'fileName': sourceFile.filename,
           'length': sourceFile.length});
    }
    return location;
  }

  HGraph buildMethod() {
    graph.calledInLoop = compiler.world.isCalledInLoop(sourceElement);

    open(graph.entry);
    HBasicBlock block = graph.addNewBlock();
    close(new HGoto()).addSuccessor(block);
    open(block);

    IrFunction function = compiler.irBuilder.getIr(sourceElement);
    visitAll(function.statements);
    if (!isAborted()) closeAndGotoExit(new HGoto());
    graph.finalize();
    return graph;
  }

  HInstruction visitIrConstant(IrConstant node) {
    return recordGenerated(node, graph.addConstant(node.value, compiler));
  }

  HInstruction visitIrReturn(IrReturn node) {
    assert(isReachable);
    HInstruction value = generated[node.value];
    // TODO(lry): add code for dynamic type check.
    // value = potentiallyCheckType(value, returnType);
    closeAndGotoExit(attachPosition(new HReturn(value), node));
  }

  HInstruction visitNode(IrNode node) {
    abort(node);
  }

  void abort(IrNode node) {
    throw 'Cannot build SSA from IR for $node';
  }
}