Revert "Revert "Build new IR for functions returning a constant.""

sdk/lib/_internal/compiler/implementation/ssa/from_ir_builder.dart

+// 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';
+  }
+}