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Add support for MCS 2.6.4 pinned region with array variable #3110

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Add support for MCS 2.6.4 pinned region with array variable #3110

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684a863
Add support for MCS 2.6.4 pinned region with array variable
ElektroKill Nov 4, 2023
c6cf74f
Enable `UnsafeCode` correctness test for MCS 2.6.4 compiler
ElektroKill Nov 4, 2023
0e64adc
Make the detection of the unpin `stloc` more strict
ElektroKill Nov 4, 2023
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4 changes: 0 additions & 4 deletions ICSharpCode.Decompiler.Tests/CorrectnessTestRunner.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -336,10 +336,6 @@ public async Task StackTypes([Values(false, true)] bool force32Bit)
[Test]
public async Task UnsafeCode([ValueSource(nameof(defaultOptions))] CompilerOptions options)
{
if (options.HasFlag(CompilerOptions.UseMcs2_6_4))
{
Assert.Ignore("Decompiler bug with mono!");
}
await RunCS(options: options);
}

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24 changes: 20 additions & 4 deletions ICSharpCode.Decompiler/IL/ControlFlow/DetectPinnedRegions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -614,14 +614,26 @@ bool CreatePinnedRegion(Block block, StLoc stLoc)
}
Branch br = innerBlock.Instructions.LastOrDefault() as Branch;
if (br != null && br.TargetBlock.IncomingEdgeCount == 1
&& br.TargetContainer == sourceContainer && reachedEdgesPerBlock[br.TargetBlock.ChildIndex] == 0)
&& br.TargetContainer == sourceContainer)
{
// branch that leaves body.
Block unpinBlock = null;
if (reachedEdgesPerBlock[br.TargetBlock.ChildIndex] == 0)
{
unpinBlock = br.TargetBlock;
}
else if (innerBlock.Instructions.Count == 2 &&
innerBlock.Instructions[0].MatchIfInstruction(out _, out var trueInstr) &&
trueInstr is Branch trueBr && trueBr.TargetContainer == sourceContainer &&
reachedEdgesPerBlock[trueBr.TargetBlock.ChildIndex] == 0)
{
unpinBlock = trueBr.TargetBlock;
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If I understand correctly, the point of this change is to check both outgoing edges for an if block?
Should innerBlock.Instructions.Count == 2 be innerBlock.Instructions.Count >= 2 instead?

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Yes, I used == 2 since in my testing there were always two instructions with one being an if and the second being the fallthrough br. If we were to extend the limit to more than 2 instructions I think it would be necessary to check other instructions for potential outgoing edges which would mean additional logic. though in my testing it seems that the current code is enough.

}

// The target block should have an instruction that resets the pin; delete that instruction:
StLoc unpin = br.TargetBlock.Instructions.First() as StLoc;
StLoc unpin = unpinBlock?.Instructions.First() as StLoc;
if (unpin != null && unpin.Variable == stLoc.Variable && IsNullOrZero(unpin.Value))
{
br.TargetBlock.Instructions.RemoveAt(0);
unpinBlock.Instructions.RemoveAt(0);
}
}
// move block into body
Expand Down Expand Up @@ -750,6 +762,10 @@ void ProcessPinnedRegion(PinnedRegion pinnedRegion)
// fixing a string
HandleStringToPointer(pinnedRegion);
}
else if (pinnedRegion.Init is Conv { Kind: ConversionKind.StopGCTracking, Argument: LdElema ldElema })
{
pinnedRegion.Init = ldElema;
}
// Detect nested pinned regions:
BlockContainer body = (BlockContainer)pinnedRegion.Body;
foreach (var block in body.Blocks)
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