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/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation.
*
* This source code is subject to terms and conditions of the Apache License, Version 2.0. A
* copy of the license can be found in the License.html file at the root of this distribution. If
* you cannot locate the Apache License, Version 2.0, please send an email to
* dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound
* by the terms of the Apache License, Version 2.0.
*
* You must not remove this notice, or any other, from this software.
*
*
* ***************************************************************************/
using System;
using System.Diagnostics;
using System.Collections.Generic;
using Microsoft.Scripting.Utils;
namespace Microsoft.Scripting.Interpreter {
internal struct RuntimeLabel {
public readonly int Index;
public readonly int StackDepth;
public readonly int ContinuationStackDepth;
public RuntimeLabel(int index, int continuationStackDepth, int stackDepth) {
Index = index;
ContinuationStackDepth = continuationStackDepth;
StackDepth = stackDepth;
}
public override string ToString() {
return String.Format("->{0} C({1}) S({2})", Index, ContinuationStackDepth, StackDepth);
}
}
public sealed class BranchLabel {
internal const int UnknownIndex = Int32.MinValue;
internal const int UnknownDepth = Int32.MinValue;
internal int _labelIndex = UnknownIndex;
internal int _targetIndex = UnknownIndex;
internal int _stackDepth = UnknownDepth;
internal int _continuationStackDepth = UnknownDepth;
// Offsets of forward branching instructions targetting this label
// that need to be updated after we emit the label.
private List<int> _forwardBranchFixups;
public BranchLabel() {
}
internal int LabelIndex {
get { return _labelIndex; }
set { _labelIndex = value; }
}
internal bool HasRuntimeLabel {
get { return _labelIndex != UnknownIndex; }
}
internal int TargetIndex {
get { return _targetIndex; }
}
internal RuntimeLabel ToRuntimeLabel() {
Debug.Assert(_targetIndex != UnknownIndex && _stackDepth != UnknownDepth && _continuationStackDepth != UnknownDepth);
return new RuntimeLabel(_targetIndex, _continuationStackDepth, _stackDepth);
}
internal void Mark(InstructionList instructions) {
ContractUtils.Requires(_targetIndex == UnknownIndex && _stackDepth == UnknownDepth && _continuationStackDepth == UnknownDepth);
_stackDepth = instructions.CurrentStackDepth;
_continuationStackDepth = instructions.CurrentContinuationsDepth;
_targetIndex = instructions.Count;
if (_forwardBranchFixups != null) {
foreach (var branchIndex in _forwardBranchFixups) {
FixupBranch(instructions, branchIndex);
}
_forwardBranchFixups = null;
}
}
internal void AddBranch(InstructionList instructions, int branchIndex) {
Debug.Assert(((_targetIndex == UnknownIndex) == (_stackDepth == UnknownDepth)));
Debug.Assert(((_targetIndex == UnknownIndex) == (_continuationStackDepth == UnknownDepth)));
if (_targetIndex == UnknownIndex) {
if (_forwardBranchFixups == null) {
_forwardBranchFixups = new List<int>();
}
_forwardBranchFixups.Add(branchIndex);
} else {
FixupBranch(instructions, branchIndex);
}
}
internal void FixupBranch(InstructionList instructions, int branchIndex) {
Debug.Assert(_targetIndex != UnknownIndex);
instructions.FixupBranch(branchIndex, _targetIndex - branchIndex);
}
}
}
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