mcs/class/dlr/Runtime/Microsoft.Dynamic/Interpreter/BranchLabel.cs

   1 /* ****************************************************************************
   2  *
   3  * Copyright (c) Microsoft Corporation.
   4  *
   5  * This source code is subject to terms and conditions of the Apache License, Version 2.0. A
   6  * copy of the license can be found in the License.html file at the root of this distribution. If
   7  * you cannot locate the  Apache License, Version 2.0, please send an email to
   8  * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound
   9  * by the terms of the Apache License, Version 2.0.
  10  *
  11  * You must not remove this notice, or any other, from this software.
  12  *
  13  *
  14  * ***************************************************************************/
  15
  16 using System;
  17 using System.Diagnostics;
  18 using System.Collections.Generic;
  19 using Microsoft.Scripting.Utils;
  20
  21 namespace Microsoft.Scripting.Interpreter {
  22     internal struct RuntimeLabel {
  23         public readonly int Index;
  24         public readonly int StackDepth;
  25         public readonly int ContinuationStackDepth;
  26
  27         public RuntimeLabel(int index, int continuationStackDepth, int stackDepth) {
  28             Index = index;
  29             ContinuationStackDepth = continuationStackDepth;
  30             StackDepth = stackDepth;
  31         }
  32
  33         public override string ToString() {
  34             return String.Format("->{0} C({1}) S({2})", Index, ContinuationStackDepth, StackDepth);
  35         }
  36     }
  37
  38     public sealed class BranchLabel {
  39         internal const int UnknownIndex = Int32.MinValue;
  40         internal const int UnknownDepth = Int32.MinValue;
  41
  42         internal int _labelIndex = UnknownIndex;
  43         internal int _targetIndex = UnknownIndex;
  44         internal int _stackDepth = UnknownDepth;
  45         internal int _continuationStackDepth = UnknownDepth;
  46
  47         // Offsets of forward branching instructions targetting this label
  48         // that need to be updated after we emit the label.
  49         private List<int> _forwardBranchFixups;
  50
  51         public BranchLabel() {
  52         }
  53
  54         internal int LabelIndex {
  55             get { return _labelIndex; }
  56             set { _labelIndex = value; }
  57         }
  58
  59         internal bool HasRuntimeLabel {
  60             get { return _labelIndex != UnknownIndex; }
  61         }
  62
  63         internal int TargetIndex {
  64             get { return _targetIndex; }
  65         }
  66
  67         internal RuntimeLabel ToRuntimeLabel() {
  68             Debug.Assert(_targetIndex != UnknownIndex && _stackDepth != UnknownDepth && _continuationStackDepth != UnknownDepth);
  69             return new RuntimeLabel(_targetIndex, _continuationStackDepth, _stackDepth);
  70         }
  71
  72         internal void Mark(InstructionList instructions) {
  73             ContractUtils.Requires(_targetIndex == UnknownIndex && _stackDepth == UnknownDepth && _continuationStackDepth == UnknownDepth);
  74
  75             _stackDepth = instructions.CurrentStackDepth;
  76             _continuationStackDepth = instructions.CurrentContinuationsDepth;
  77             _targetIndex = instructions.Count;
  78
  79             if (_forwardBranchFixups != null) {
  80                 foreach (var branchIndex in _forwardBranchFixups) {
  81                     FixupBranch(instructions, branchIndex);
  82                 }
  83                 _forwardBranchFixups = null;
  84             }
  85         }
  86
  87         internal void AddBranch(InstructionList instructions, int branchIndex) {
  88             Debug.Assert(((_targetIndex == UnknownIndex) == (_stackDepth == UnknownDepth)));
  89             Debug.Assert(((_targetIndex == UnknownIndex) == (_continuationStackDepth == UnknownDepth)));
  90
  91             if (_targetIndex == UnknownIndex) {
  92                 if (_forwardBranchFixups == null) {
  93                     _forwardBranchFixups = new List<int>();
  94                 }
  95                 _forwardBranchFixups.Add(branchIndex);
  96             } else {
  97                 FixupBranch(instructions, branchIndex);
  98             }
  99         }
 100
 101         internal void FixupBranch(InstructionList instructions, int branchIndex) {
 102             Debug.Assert(_targetIndex != UnknownIndex);
 103             instructions.FixupBranch(branchIndex, _targetIndex - branchIndex);
 104         }
 105     }
 106
 107
 108 }