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Add support for exception regions #62

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merged 3 commits into from
Oct 14, 2021
Merged

Add support for exception regions #62

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0bc0805
Add support for exception regions
Oct 14, 2021
fdcc634
Use small exception regions when possible
Oct 14, 2021
2f0ba6d
Add test
Oct 14, 2021
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52 changes: 52 additions & 0 deletions src/coreclr/tools/ILTrim/ILTrim.Tests.Cases/Basic/ExceptionRegions.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,52 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using Mono.Linker.Tests.Cases.Expectations.Assertions;

namespace Mono.Linker.Tests.Cases.Basic
{
[Kept]
public class ExceptionRegions
{
[Kept]
static void Main()
{
try
{
A();
}
catch (CustomException ce)
{
Console.WriteLine(ce.Message);
try
{
B();
}
catch (Exception e) when (e.InnerException != null)
{
Console.WriteLine(e.Message);
}
}
finally
{
C();
}
}

[Kept]
static void A() { }

[Kept]
static void B() { }

[Kept]
static void C() { }
}

[Kept]
[KeptBaseType(typeof(Exception))]
class CustomException : Exception
{
}
}
69 changes: 64 additions & 5 deletions src/coreclr/tools/ILTrim/ILTrim/DependencyAnalysis/MethodBodyNode.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,18 @@ public override IEnumerable<DependencyListEntry> GetStaticDependencies(NodeFacto
if (!bodyBlock.LocalSignature.IsNil)
yield return new DependencyListEntry(factory.StandaloneSignature(_module, bodyBlock.LocalSignature), "Signatures of local variables");

var exceptionRegions = bodyBlock.ExceptionRegions;
if (!bodyBlock.ExceptionRegions.IsEmpty)
{
foreach (var exceptionRegion in exceptionRegions)
{
if (exceptionRegion.Kind != ExceptionRegionKind.Catch)
continue;

yield return new DependencyListEntry(factory.GetNodeForToken(_module, exceptionRegion.CatchType), "Catch type of exception region");
}
}

ILReader ilReader = new(bodyBlock.GetILBytes());
while (ilReader.HasNext)
{
Expand Down Expand Up @@ -123,10 +135,23 @@ public int Write(ModuleWritingContext writeContext)
return -1;

MethodBodyBlock bodyBlock = _module.PEReader.GetMethodBody(rva);
var exceptionRegions = bodyBlock.ExceptionRegions;

// TODO: need to rewrite token references in the exception regions
// This would need ControlFlowBuilder and setting up labels and such.
// All doable, just more code.
// Use small exception regions when the code size of the try block and
// the handler code are less than 256 bytes and offsets smaller than 65536 bytes.
bool useSmallExceptionRegions = ExceptionRegionEncoder.IsSmallRegionCount(exceptionRegions.Length);
if (useSmallExceptionRegions)
{
foreach (var exceptionRegion in exceptionRegions)
{
if (!ExceptionRegionEncoder.IsSmallExceptionRegion(exceptionRegion.TryOffset, exceptionRegion.TryLength) ||
!ExceptionRegionEncoder.IsSmallExceptionRegion(exceptionRegion.HandlerOffset, exceptionRegion.HandlerLength))
{
useSmallExceptionRegions = false;
break;
}
}
}

BlobBuilder outputBodyBuilder = writeContext.GetSharedBlobBuilder();
byte[] bodyBytes = bodyBlock.GetILBytes();
Expand Down Expand Up @@ -201,11 +226,45 @@ public int Write(ModuleWritingContext writeContext)
MethodBodyStreamEncoder.MethodBody bodyEncoder = writeContext.MethodBodyEncoder.AddMethodBody(
outputBodyBuilder.Count,
bodyBlock.MaxStack,
exceptionRegionCount: 0,
hasSmallExceptionRegions: false,
exceptionRegionCount: exceptionRegions.Length,
hasSmallExceptionRegions: useSmallExceptionRegions,
(StandaloneSignatureHandle)writeContext.TokenMap.MapToken(bodyBlock.LocalSignature),
bodyBlock.LocalVariablesInitialized ? MethodBodyAttributes.InitLocals : MethodBodyAttributes.None);
BlobWriter instructionsWriter = new(bodyEncoder.Instructions);

ExceptionRegionEncoder exceptionRegionEncoder = bodyEncoder.ExceptionRegions;
foreach (var exceptionRegion in exceptionRegions)
{
switch (exceptionRegion.Kind)
{
case ExceptionRegionKind.Catch:
exceptionRegionEncoder.AddCatch(
exceptionRegion.TryOffset,
exceptionRegion.TryLength,
exceptionRegion.HandlerOffset,
exceptionRegion.HandlerLength,
writeContext.TokenMap.MapToken(exceptionRegion.CatchType));
break;

case ExceptionRegionKind.Filter:
exceptionRegionEncoder.AddFilter(
exceptionRegion.TryOffset,
exceptionRegion.TryLength,
exceptionRegion.HandlerOffset,
exceptionRegion.HandlerLength,
exceptionRegion.FilterOffset);
break;

case ExceptionRegionKind.Finally:
exceptionRegionEncoder.AddFinally(
exceptionRegion.TryOffset,
exceptionRegion.TryLength,
exceptionRegion.HandlerOffset,
exceptionRegion.HandlerLength);
break;
}
}

outputBodyBuilder.WriteContentTo(ref instructionsWriter);

return bodyEncoder.Offset;
Expand Down