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This way we avoid having to extract later, as we will never inline if the `isinst` argument if this could result in it being unrepresentable in C#. This commit also refactors inlining restrictions to avoid requiring special cases in ILInlining itself. But when making this change, I discovered that this broke our pattern-matching tests, and that the weird IL with double `isinst` is indeed generated by the C# compiler for `if (genericParam is StringComparison.Ordinal)` style code. So instead we also allow `isinst` with a `box(expr-without-side-effects)` argument to be represented with the `expr is T ? (T)expr : null` emulation.null-coalescing-assignment
Daniel Grunwald
4 months ago
10 changed files with 154 additions and 142 deletions
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#nullable enable |
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// Copyright (c) 2025 Daniel Grunwald
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this
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// software and associated documentation files (the "Software"), to deal in the Software
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// without restriction, including without limitation the rights to use, copy, modify, merge,
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// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
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// to whom the Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all copies or
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// substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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using System.Diagnostics; |
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using ICSharpCode.Decompiler.CSharp; |
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namespace ICSharpCode.Decompiler.IL; |
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partial class IsInst |
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{ |
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internal override bool SatisfiesSlotRestrictionForInlining(int childIndex, ILInstruction newChild) |
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{ |
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Debug.Assert(childIndex == 0); |
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Debug.Assert(base.SatisfiesSlotRestrictionForInlining(childIndex, newChild)); |
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if (this.Type.IsReferenceType == true) |
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{ |
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return true; // reference-type isinst is always supported
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} |
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if (SemanticHelper.IsPure(newChild.Flags)) |
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{ |
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return true; // emulated via "expr is T ? (T)expr : null"
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} |
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else if (newChild is Box box && SemanticHelper.IsPure(box.Argument.Flags)) |
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{ |
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// Also emulated via "expr is T ? (T)expr : null".
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// This duplicates the boxing side-effect, but that's harmless as one of the boxes is only
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// used in the `expr is T` type test where the object identity can never be observed.
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// This appears as part of C# pattern matching, inlining early makes those code patterns easier to detect.
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return true; |
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} |
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if (this.Parent is UnboxAny unboxAny && ExpressionBuilder.IsUnboxAnyWithIsInst(unboxAny, this.Type)) |
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{ |
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return true; // supported pattern "expr as T?"
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} |
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if (this.Parent != null && (this.Parent.MatchCompEqualsNull(out _) || this.Parent.MatchCompNotEqualsNull(out _))) |
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{ |
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return true; // supported pattern "expr is T"
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} |
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if (this.Parent is Block { Kind: BlockKind.ControlFlow }) |
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{ |
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return true; // supported via StatementBuilder.VisitIsInst
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} |
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return false; |
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} |
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} |
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@ -1,69 +0,0 @@
@@ -1,69 +0,0 @@
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// Copyright (c) 2020 Daniel Grunwald
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this
|
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// software and associated documentation files (the "Software"), to deal in the Software
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// without restriction, including without limitation the rights to use, copy, modify, merge,
|
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// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
|
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// to whom the Software is furnished to do so, subject to the following conditions:
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//
|
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// The above copyright notice and this permission notice shall be included in all copies or
|
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// substantial portions of the Software.
|
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//
|
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
|
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// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
|
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
|
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// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
|
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// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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using System.Collections.Generic; |
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using System.Linq; |
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using ICSharpCode.Decompiler.CSharp; |
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namespace ICSharpCode.Decompiler.IL.Transforms |
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{ |
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/// <summary>
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/// C# cannot represent `isinst T` directly for value-types.
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/// This transform un-inlines the argument of `isinst` instructions that can't be directly translated to C#,
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/// thus allowing the emulation via "expr is T ? (T)expr : null".
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/// </summary>
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public class FixLoneIsInst : IILTransform |
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{ |
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void IILTransform.Run(ILFunction function, ILTransformContext context) |
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{ |
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var instructionsToFix = new List<IsInst>(); |
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foreach (var isInst in function.Descendants.OfType<IsInst>()) |
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{ |
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if (isInst.Type.IsReferenceType == true) |
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{ |
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continue; // reference-type isinst is always supported
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} |
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if (SemanticHelper.IsPure(isInst.Argument.Flags)) |
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{ |
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continue; // emulated via "expr is T ? (T)expr : null"
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} |
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if (isInst.Parent is UnboxAny unboxAny && ExpressionBuilder.IsUnboxAnyWithIsInst(unboxAny, isInst)) |
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{ |
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continue; // supported pattern "expr as T?"
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} |
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if (isInst.Parent.MatchCompEqualsNull(out _) || isInst.Parent.MatchCompNotEqualsNull(out _)) |
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{ |
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continue; // supported pattern "expr is T"
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} |
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if (isInst.Parent is Block { Kind: BlockKind.ControlFlow }) |
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{ |
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continue; // supported via StatementBuilder.VisitIsInst
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} |
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instructionsToFix.Add(isInst); |
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} |
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// Need to delay fixing until we're done with iteration, because Extract() modifies parents
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foreach (var isInst in instructionsToFix) |
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{ |
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// Use extraction to turn isInst.Argument into a pure instruction, thus making the emulation possible
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context.Step("FixLoneIsInst", isInst); |
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isInst.Argument.Extract(context); |
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} |
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} |
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} |
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} |
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