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Add support for emitting finally regions in ILEmitter (#27109)
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This will be needed to properly do cleanups in marshalling stubs.

The usage goes like (I couldn't come up with anything better):

```
var b = codeStream.BeginTry();
//...
codeStream.EndTry(b);
codeStream.BeginHandler(b);
// ...
codeStream.EndHandler(b);

emit.NewFinallyRegion(b);
```
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@MichalStrehovsky @jkotas
MichalStrehovsky authored and jkotas committed Oct 11, 2019
1 parent d8bbcc4 commit a7ffbba
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Showing 2 changed files with 139 additions and 9 deletions.
39 changes: 37 additions & 2 deletions src/tools/crossgen2/Common/TypeSystem/IL/MethodILDebugView.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -92,10 +92,45 @@ public string Disassembly
}
sb.AppendLine();

// TODO: exception regions
const string pad = " ";

// TODO: pretty exception regions
foreach (ILExceptionRegion region in _methodIL.GetExceptionRegions())
{
sb.Append(pad);
sb.Append(".try ");
ILDisassembler.AppendOffset(sb, region.TryOffset);
sb.Append(" to ");
ILDisassembler.AppendOffset(sb, region.TryOffset + region.TryLength);

switch (region.Kind)
{
case ILExceptionRegionKind.Catch:
sb.Append(" catch ");
disasm.AppendType(sb, (TypeDesc)_methodIL.GetObject(region.ClassToken));
break;
case ILExceptionRegionKind.Fault:
sb.Append(" fault");
break;
case ILExceptionRegionKind.Filter:
sb.Append(" filter ");
ILDisassembler.AppendOffset(sb, region.FilterOffset);
break;
case ILExceptionRegionKind.Finally:
sb.Append(" finally");
break;
}

sb.Append(" handler ");
ILDisassembler.AppendOffset(sb, region.HandlerOffset);
sb.Append(" to ");
ILDisassembler.AppendOffset(sb, region.HandlerOffset + region.HandlerLength);
sb.AppendLine();
}

while (disasm.HasNextInstruction)
{
sb.Append(" ");
sb.Append(pad);
sb.AppendLine(disasm.GetNextInstruction());
}

Expand Down
109 changes: 102 additions & 7 deletions src/tools/crossgen2/Common/TypeSystem/IL/Stubs/ILEmitter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,8 @@ namespace Internal.IL.Stubs
{
public class ILCodeStream
{
private const int StartOffsetNotSet = -1;

private struct LabelAndOffset
{
public readonly ILCodeLabel Label;
Expand All @@ -37,10 +39,16 @@ public LabelAndOffset(ILCodeLabel label, int offset)
internal ILCodeStream(ILEmitter emitter)
{
_instructions = Array.Empty<byte>();
_startOffsetForLinking = -1;
_startOffsetForLinking = StartOffsetNotSet;
_emitter = emitter;
}

internal int RelativeToAbsoluteOffset(int relativeOffset)
{
Debug.Assert(_startOffsetForLinking != StartOffsetNotSet);
return _startOffsetForLinking + relativeOffset;
}

private void EmitByte(byte b)
{
if (_instructions.Length == _length)
Expand Down Expand Up @@ -417,14 +425,42 @@ public void EmitLabel(ILCodeLabel label)
label.Place(this, _length);
}

public void BeginTry(ILExceptionRegionBuilder builder)
{
Debug.Assert(builder._beginTryStream == null);
builder._beginTryStream = this;
builder._beginTryOffset = _length;
}

public void EndTry(ILExceptionRegionBuilder builder)
{
Debug.Assert(builder._endTryStream == null);
builder._endTryStream = this;
builder._endTryOffset = _length;
}

public void BeginHandler(ILExceptionRegionBuilder builder)
{
Debug.Assert(builder._beginHandlerStream == null);
builder._beginHandlerStream = this;
builder._beginHandlerOffset = _length;
}

public void EndHandler(ILExceptionRegionBuilder builder)
{
Debug.Assert(builder._endHandlerStream == null);
builder._endHandlerStream = this;
builder._endHandlerOffset = _length;
}

internal void PatchLabels()
{
for (int i = 0; i < _offsetsNeedingPatching.Count; i++)
{
LabelAndOffset patch = _offsetsNeedingPatching[i];

Debug.Assert(patch.Label.IsPlaced);
Debug.Assert(_startOffsetForLinking > -1);
Debug.Assert(_startOffsetForLinking != StartOffsetNotSet);

int offset = patch.Offset;

Expand Down Expand Up @@ -456,6 +492,34 @@ public void DefineSequencePoint(string document, int lineNumber)
}
}

public class ILExceptionRegionBuilder
{
internal ILCodeStream _beginTryStream;
internal int _beginTryOffset;

internal ILCodeStream _endTryStream;
internal int _endTryOffset;

internal ILCodeStream _beginHandlerStream;
internal int _beginHandlerOffset;

internal ILCodeStream _endHandlerStream;
internal int _endHandlerOffset;

internal ILExceptionRegionBuilder()
{
}

internal int TryOffset => _beginTryStream.RelativeToAbsoluteOffset(_beginTryOffset);
internal int TryLength => _endTryStream.RelativeToAbsoluteOffset(_endTryOffset) - TryOffset;
internal int HandlerOffset => _beginHandlerStream.RelativeToAbsoluteOffset(_beginHandlerOffset);
internal int HandlerLength => _endHandlerStream.RelativeToAbsoluteOffset(_endHandlerOffset) - HandlerOffset;

internal bool IsDefined =>
_beginTryStream != null && _endTryStream != null
&& _beginHandlerStream != null && _endHandlerStream != null;
}

/// <summary>
/// Represent a token. Use one of the overloads of <see cref="ILEmitter.NewToken"/>
/// to create a new token.
Expand All @@ -473,19 +537,24 @@ public class ILStubMethodIL : MethodIL
private readonly LocalVariableDefinition[] _locals;
private readonly Object[] _tokens;
private readonly MethodDesc _method;
private readonly ILExceptionRegion[] _exceptionRegions;
private readonly MethodDebugInformation _debugInformation;

private const int MaxStackNotSet = -1;
private int _maxStack;

public ILStubMethodIL(MethodDesc owningMethod, byte[] ilBytes, LocalVariableDefinition[] locals, Object[] tokens, MethodDebugInformation debugInfo = null)
public ILStubMethodIL(MethodDesc owningMethod, byte[] ilBytes, LocalVariableDefinition[] locals, Object[] tokens, ILExceptionRegion[] exceptionRegions = null, MethodDebugInformation debugInfo = null)
{
_ilBytes = ilBytes;
_locals = locals;
_tokens = tokens;
_method = owningMethod;
_maxStack = MaxStackNotSet;

if (exceptionRegions == null)
exceptionRegions = Array.Empty<ILExceptionRegion>();
_exceptionRegions = exceptionRegions;

if (debugInfo == null)
debugInfo = MethodDebugInformation.None;
_debugInformation = debugInfo;
Expand Down Expand Up @@ -531,7 +600,7 @@ public override int MaxStack

public override ILExceptionRegion[] GetExceptionRegions()
{
return Array.Empty<ILExceptionRegion>();
return _exceptionRegions;
}
public override bool IsInitLocals
{
Expand Down Expand Up @@ -569,8 +638,7 @@ internal int AbsoluteOffset
get
{
Debug.Assert(IsPlaced);
Debug.Assert(_codeStream._startOffsetForLinking >= 0);
return _codeStream._startOffsetForLinking + _offsetWithinCodeStream;
return _codeStream.RelativeToAbsoluteOffset(_offsetWithinCodeStream);
}
}

Expand All @@ -591,6 +659,7 @@ public class ILEmitter
private ArrayBuilder<ILCodeStream> _codeStreams;
private ArrayBuilder<LocalVariableDefinition> _locals;
private ArrayBuilder<Object> _tokens;
private ArrayBuilder<ILExceptionRegionBuilder> _finallyRegions;

public ILEmitter()
{
Expand Down Expand Up @@ -648,6 +717,13 @@ public ILCodeLabel NewCodeLabel()
return newLabel;
}

public ILExceptionRegionBuilder NewFinallyRegion()
{
var region = new ILExceptionRegionBuilder();
_finallyRegions.Add(region);
return region;
}

public MethodIL Link(MethodDesc owningMethod)
{
int totalLength = 0;
Expand Down Expand Up @@ -694,7 +770,26 @@ public MethodIL Link(MethodDesc owningMethod)
debugInfo = new EmittedMethodDebugInformation(sequencePoints);
}

var result = new ILStubMethodIL(owningMethod, ilInstructions, _locals.ToArray(), _tokens.ToArray(), debugInfo);
ILExceptionRegion[] exceptionRegions = null;

int numberOfExceptionRegions = _finallyRegions.Count;
if (numberOfExceptionRegions > 0)
{
exceptionRegions = new ILExceptionRegion[numberOfExceptionRegions];

for (int i = 0; i < _finallyRegions.Count; i++)
{
ILExceptionRegionBuilder region = _finallyRegions[i];

Debug.Assert(region.IsDefined);

exceptionRegions[i] = new ILExceptionRegion(ILExceptionRegionKind.Finally,
region.TryOffset, region.TryLength, region.HandlerOffset, region.HandlerLength,
classToken: 0, filterOffset: 0);
}
}

var result = new ILStubMethodIL(owningMethod, ilInstructions, _locals.ToArray(), _tokens.ToArray(), exceptionRegions, debugInfo);
result.CheckStackBalance();
return result;
}
Expand Down

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