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

sdk/lib/_internal/compiler/implementation/ssa/from_ir_inliner.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 SsaFromIrInliner extends IrNodesVisitor {
+
+  final SsaBuilder builder;
+
+  SsaFromIrInliner(this.builder);
+
+  final Map<IrNode, HInstruction> emitted = new Map<IrNode, HInstruction>();
+
+  Compiler get compiler => builder.compiler;
+
+  void visitIrReturn(IrReturn node) {
+    HInstruction hValue = emitted[node.value];
+    builder.localsHandler.updateLocal(builder.returnElement, hValue);
+  }
+
+  void visitIrConstant(IrConstant node) {
+    emitted[node] = builder.graph.addConstant(node.value, compiler);
+  }
+
+  void visitNode(IrNode node) {
+    compiler.internalError('Unexpected IrNode $node');
+  }
+}
+
+class IrInlineWeeder extends IrNodesVisitor {
+  static bool canBeInlined(IrFunction irFunction,
+                           int maxInliningNodes,
+                           bool useMaxInliningNodes) {
+    IrInlineWeeder weeder =
+        new IrInlineWeeder(maxInliningNodes, useMaxInliningNodes);
+    weeder.visitAll(irFunction.statements);
+    return !weeder.tooDifficult;
+  }
+
+  final int maxInliningNodes;
+  final bool useMaxInliningNodes;
+
+  IrInlineWeeder(this.maxInliningNodes, this.useMaxInliningNodes);
+
+  bool seenReturn = false;
+  bool tooDifficult = false;
+  int nodeCount = 0;
+
+  bool registerNode() {
+    if (!useMaxInliningNodes) return true;
+    if (nodeCount++ > maxInliningNodes) {
+      tooDifficult = true;
+      return false;
+    } else {
+      return true;
+    }
+  }
+
+  void visitNode(IrNode node) {
+    if (!registerNode()) return;
+    if (seenReturn) {
+      tooDifficult = true;
+    }
+  }
+
+  void visitIrReturn(IrReturn node) {
+    visitNode(node);
+    seenReturn = true;
+  }
+
+  void visitIrFunction(IrFunction node) {
+    tooDifficult = true;
+  }
+
+}