mirror of https://github.com/icsharpcode/ILSpy.git
Daniel Grunwald
7 years ago
9 changed files with 287 additions and 58 deletions
@ -0,0 +1,84 @@
@@ -0,0 +1,84 @@
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using System; |
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using System.Collections.Generic; |
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using System.Text; |
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using ICSharpCode.Decompiler.TypeSystem; |
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namespace ICSharpCode.Decompiler.IL |
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{ |
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/// <summary>
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/// Analyses the RHS of a 'ptr + int' or 'ptr - int' operation.
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/// </summary>
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struct PointerArithmeticOffset |
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{ |
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/// <summary>
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/// Given an instruction that computes a pointer arithmetic offset in bytes,
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/// returns an instruction that computes the same offset in number of elements.
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///
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/// Returns null if no such instruction can be found.
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/// </summary>
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/// <param name="byteOffsetInst">Input instruction.</param>
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/// <param name="pointerType">The pointer type.</param>
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/// <param name="checkForOverflow">Whether the pointer arithmetic operation checks for overflow.</param>
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/// <param name="unwrapZeroExtension">Whether to allow zero extensions in the mul argument.</param>
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public static ILInstruction Detect(ILInstruction byteOffsetInst, PointerType pointerType, |
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bool checkForOverflow, |
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bool unwrapZeroExtension = false) |
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{ |
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if (byteOffsetInst is Conv conv && conv.InputType == StackType.I8 && conv.ResultType == StackType.I) { |
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byteOffsetInst = conv.Argument; |
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} |
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int? elementSize = ComputeSizeOf(pointerType.ElementType); |
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if (elementSize == 1) { |
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return byteOffsetInst; |
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} else if (byteOffsetInst is BinaryNumericInstruction mul && mul.Operator == BinaryNumericOperator.Mul) { |
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if (mul.IsLifted) |
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return null; |
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if (mul.CheckForOverflow != checkForOverflow) |
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return null; |
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if (elementSize > 0 && mul.Right.MatchLdcI(elementSize.Value) |
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|| mul.Right.UnwrapConv(ConversionKind.SignExtend) is SizeOf sizeOf && sizeOf.Type.Equals(pointerType.ElementType)) { |
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var countOffsetInst = mul.Left; |
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if (unwrapZeroExtension) { |
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countOffsetInst = countOffsetInst.UnwrapConv(ConversionKind.ZeroExtend); |
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} |
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return countOffsetInst; |
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} |
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} else if (byteOffsetInst.UnwrapConv(ConversionKind.SignExtend) is SizeOf sizeOf && sizeOf.Type.Equals(pointerType.ElementType)) { |
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return new LdcI4(1) { ILRange = byteOffsetInst.ILRange }; |
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} else if (byteOffsetInst.MatchLdcI(out long val)) { |
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// If the offset is a constant, it's possible that the compiler
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// constant-folded the multiplication.
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if (elementSize > 0 && (val % elementSize == 0) && val > 0) { |
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val /= elementSize.Value; |
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if (val <= int.MaxValue) { |
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return new LdcI4((int)val) { ILRange = byteOffsetInst.ILRange }; |
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} |
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} |
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} |
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return null; |
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} |
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public static int? ComputeSizeOf(IType type) |
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{ |
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switch (type.GetEnumUnderlyingType().GetDefinition()?.KnownTypeCode) { |
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case KnownTypeCode.Boolean: |
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case KnownTypeCode.SByte: |
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case KnownTypeCode.Byte: |
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return 1; |
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case KnownTypeCode.Char: |
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case KnownTypeCode.Int16: |
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case KnownTypeCode.UInt16: |
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return 2; |
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case KnownTypeCode.Int32: |
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case KnownTypeCode.UInt32: |
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case KnownTypeCode.Single: |
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return 4; |
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case KnownTypeCode.Int64: |
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case KnownTypeCode.UInt64: |
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case KnownTypeCode.Double: |
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return 8; |
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} |
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return null; |
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} |
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} |
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} |
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