// Copyright (c) 2015 Siegfried Pammer
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
using System;
using System.Diagnostics;
using System.Linq;
using System.Linq.Expressions;
using ICSharpCode.Decompiler.TypeSystem;
using ICSharpCode.Decompiler.Util;
namespace ICSharpCode.Decompiler.IL.Transforms
{
///
/// Constructs compound assignments and inline assignments.
///
///
/// This is a statement transform;
/// but some portions are executed as an expression transform instead
/// (with HandleCompoundAssign() as entry point)
///
public class TransformAssignment : IStatementTransform
{
StatementTransformContext context;
void IStatementTransform.Run(Block block, int pos, StatementTransformContext context)
{
this.context = context;
if (context.Settings.MakeAssignmentExpressions)
{
if (TransformInlineAssignmentStObjOrCall(block, pos) || TransformInlineAssignmentLocal(block, pos))
{
// both inline assignments create a top-level stloc which might affect inlining
context.RequestRerun();
return;
}
}
if (context.Settings.IntroduceIncrementAndDecrement)
{
if (TransformPostIncDecOperatorWithInlineStore(block, pos)
|| TransformPostIncDecOperator(block, pos))
{
// again, new top-level stloc might need inlining:
context.RequestRerun();
return;
}
}
}
///
/// stloc s(value)
/// stloc l(ldloc s)
/// stobj(..., ldloc s)
/// where ... is pure and does not use s or l,
/// and where neither the 'stloc s' nor the 'stobj' truncates
/// -->
/// stloc l(stobj (..., value))
///
/// e.g. used for inline assignment to instance field
///
/// -or-
///
///
/// stloc s(value)
/// stobj (..., ldloc s)
/// where ... is pure and does not use s, and where the 'stobj' does not truncate
/// -->
/// stloc s(stobj (..., value))
///
/// e.g. used for inline assignment to static field
///
/// -or-
///
///
/// stloc s(value)
/// call set_Property(..., ldloc s)
/// where the '...' arguments are pure and not using 's'
/// -->
/// stloc s(Block InlineAssign { call set_Property(..., stloc i(value)); final: ldloc i })
/// new temporary 'i' has type of the property; transform only valid if 'stloc i' doesn't truncate
///
bool TransformInlineAssignmentStObjOrCall(Block block, int pos)
{
var inst = block.Instructions[pos] as StLoc;
// in some cases it can be a compiler-generated local
if (inst == null || (inst.Variable.Kind != VariableKind.StackSlot && inst.Variable.Kind != VariableKind.Local))
return false;
if (IsImplicitTruncation(inst.Value, inst.Variable.Type, context.TypeSystem))
{
// 'stloc s' is implicitly truncating the value
return false;
}
ILVariable local;
int nextPos;
if (block.Instructions[pos + 1] is StLoc localStore)
{ // with extra local
if (localStore.Variable.Kind != VariableKind.Local || !localStore.Value.MatchLdLoc(inst.Variable))
return false;
// if we're using an extra local, we'll delete "s", so check that that doesn't have any additional uses
if (!(inst.Variable.IsSingleDefinition && inst.Variable.LoadCount == 2))
return false;
local = localStore.Variable;
nextPos = pos + 2;
}
else
{
local = inst.Variable;
localStore = null;
nextPos = pos + 1;
if (local.LoadCount == 1 && local.AddressCount == 0)
{
// inline assignment would produce a dead store in this case, which is ugly
// and causes problems with the deconstruction transform.
return false;
}
}
if (block.Instructions[nextPos] is StObj stobj)
{
if (!stobj.Value.MatchLdLoc(inst.Variable))
return false;
if (!SemanticHelper.IsPure(stobj.Target.Flags) || inst.Variable.IsUsedWithin(stobj.Target))
return false;
var pointerType = stobj.Target.InferType(context.TypeSystem);
IType newType = stobj.Type;
if (TypeUtils.IsCompatiblePointerTypeForMemoryAccess(pointerType, stobj.Type))
{
if (pointerType is ByReferenceType byref)
newType = byref.ElementType;
else if (pointerType is PointerType pointer)
newType = pointer.ElementType;
}
if (IsImplicitTruncation(inst.Value, newType, context.TypeSystem))
{
// 'stobj' is implicitly truncating the value
return false;
}
context.Step("Inline assignment stobj", stobj);
stobj.Type = newType;
block.Instructions.Remove(localStore);
block.Instructions.Remove(stobj);
stobj.Value = inst.Value;
inst.ReplaceWith(new StLoc(local, stobj));
// note: our caller will trigger a re-run, which will call HandleStObjCompoundAssign if applicable
return true;
}
else if (block.Instructions[nextPos] is CallInstruction call)
{
// call must be a setter call:
if (!(call.OpCode == OpCode.Call || call.OpCode == OpCode.CallVirt))
return false;
if (call.ResultType != StackType.Void || call.Arguments.Count == 0)
return false;
IProperty property = call.Method.AccessorOwner as IProperty;
if (property == null)
return false;
if (!call.Method.Equals(property.Setter))
return false;
if (!(property.IsIndexer || property.Setter.Parameters.Count == 1))
{
// this is a parameterized property, which cannot be expressed as C# code.
// setter calls are not valid in expression context, if property syntax cannot be used.
return false;
}
if (!call.Arguments.Last().MatchLdLoc(inst.Variable))
return false;
foreach (var arg in call.Arguments.SkipLast(1))
{
if (!SemanticHelper.IsPure(arg.Flags) || inst.Variable.IsUsedWithin(arg))
return false;
}
if (IsImplicitTruncation(inst.Value, call.Method.Parameters.Last().Type, context.TypeSystem))
{
// setter call is implicitly truncating the value
return false;
}
// stloc s(Block InlineAssign { call set_Property(..., stloc i(value)); final: ldloc i })
context.Step("Inline assignment call", call);
block.Instructions.Remove(localStore);
block.Instructions.Remove(call);
var newVar = context.Function.RegisterVariable(VariableKind.StackSlot, call.Method.Parameters.Last().Type);
call.Arguments[call.Arguments.Count - 1] = new StLoc(newVar, inst.Value);
var inlineBlock = new Block(BlockKind.CallInlineAssign) {
Instructions = { call },
FinalInstruction = new LdLoc(newVar)
};
inst.ReplaceWith(new StLoc(local, inlineBlock));
// because the ExpressionTransforms don't look into inline blocks, manually trigger HandleCallCompoundAssign
if (HandleCompoundAssign(call, context))
{
// if we did construct a compound assignment, it should have made our inline block redundant:
Debug.Assert(!inlineBlock.IsConnected);
}
return true;
}
else
{
return false;
}
}
static ILInstruction UnwrapSmallIntegerConv(ILInstruction inst, out Conv conv)
{
conv = inst as Conv;
if (conv != null && conv.Kind == ConversionKind.Truncate && conv.TargetType.IsSmallIntegerType())
{
// for compound assignments to small integers, the compiler emits a "conv" instruction
return conv.Argument;
}
else
{
return inst;
}
}
static bool ValidateCompoundAssign(BinaryNumericInstruction binary, Conv conv, IType targetType, DecompilerSettings settings)
{
if (!NumericCompoundAssign.IsBinaryCompatibleWithType(binary, targetType, settings))
return false;
if (conv != null && !(conv.TargetType == targetType.ToPrimitiveType() && conv.CheckForOverflow == binary.CheckForOverflow))
return false; // conv does not match binary operation
return true;
}
static bool MatchingGetterAndSetterCalls(CallInstruction getterCall, CallInstruction setterCall, out Action finalizeMatch)
{
finalizeMatch = null;
if (getterCall == null || setterCall == null || !IsSameMember(getterCall.Method.AccessorOwner, setterCall.Method.AccessorOwner))
return false;
if (setterCall.OpCode != getterCall.OpCode)
return false;
var owner = getterCall.Method.AccessorOwner as IProperty;
if (owner == null || !IsSameMember(getterCall.Method, owner.Getter) || !IsSameMember(setterCall.Method, owner.Setter))
return false;
if (setterCall.Arguments.Count != getterCall.Arguments.Count + 1)
return false;
// Ensure that same arguments are passed to getterCall and setterCall:
for (int j = 0; j < getterCall.Arguments.Count; j++)
{
if (setterCall.Arguments[j].MatchStLoc(out var v) && v.IsSingleDefinition && v.LoadCount == 1)
{
if (getterCall.Arguments[j].MatchLdLoc(v))
{
// OK, setter call argument is saved in temporary that is re-used for getter call
if (finalizeMatch == null)
{
finalizeMatch = AdjustArguments;
}
continue;
}
}
if (!SemanticHelper.IsPure(getterCall.Arguments[j].Flags))
return false;
if (!getterCall.Arguments[j].Match(setterCall.Arguments[j]).Success)
return false;
}
return true;
void AdjustArguments(ILTransformContext context)
{
Debug.Assert(setterCall.Arguments.Count == getterCall.Arguments.Count + 1);
for (int j = 0; j < getterCall.Arguments.Count; j++)
{
if (setterCall.Arguments[j].MatchStLoc(out var v, out var value))
{
Debug.Assert(v.IsSingleDefinition && v.LoadCount == 1);
Debug.Assert(getterCall.Arguments[j].MatchLdLoc(v));
getterCall.Arguments[j] = value;
}
}
}
}
///
/// Transform compound assignments where the return value is not being used,
/// or where there's an inlined assignment within the setter call.
///
/// Patterns handled:
/// 1.
/// callvirt set_Property(ldloc S_1, binary.op(callvirt get_Property(ldloc S_1), value))
/// ==> compound.op.new(callvirt get_Property(ldloc S_1), value)
/// 2.
/// callvirt set_Property(ldloc S_1, stloc v(binary.op(callvirt get_Property(ldloc S_1), value)))
/// ==> stloc v(compound.op.new(callvirt get_Property(ldloc S_1), value))
/// 3.
/// stobj(target, binary.op(ldobj(target), ...))
/// where target is pure
/// => compound.op(target, ...)
///
///
/// Called by ExpressionTransforms, or after the inline-assignment transform for setters.
///
internal static bool HandleCompoundAssign(ILInstruction compoundStore, StatementTransformContext context)
{
if (!context.Settings.MakeAssignmentExpressions || !context.Settings.IntroduceIncrementAndDecrement)
return false;
if (compoundStore is CallInstruction && compoundStore.SlotInfo != Block.InstructionSlot)
{
// replacing 'call set_Property' with a compound assignment instruction
// changes the return value of the expression, so this is only valid on block-level.
return false;
}
if (!IsCompoundStore(compoundStore, out var targetType, out var setterValue, context.TypeSystem))
return false;
// targetType = The type of the property/field/etc. being stored to.
// setterValue = The value being stored.
var storeInSetter = setterValue as StLoc;
if (storeInSetter != null)
{
// We'll move the stloc to top-level:
// callvirt set_Property(ldloc S_1, stloc v(binary.op(callvirt get_Property(ldloc S_1), value)))
// ==> stloc v(compound.op.new(callvirt get_Property(ldloc S_1), value))
setterValue = storeInSetter.Value;
if (storeInSetter.Variable.Type.IsSmallIntegerType())
{
// 'stloc v' implicitly truncates the value.
// Ensure that type of 'v' matches the type of the property:
if (storeInSetter.Variable.Type.GetSize() != targetType.GetSize())
return false;
if (storeInSetter.Variable.Type.GetSign() != targetType.GetSign())
return false;
}
}
ILInstruction newInst;
if (UnwrapSmallIntegerConv(setterValue, out var smallIntConv) is BinaryNumericInstruction binary)
{
if (compoundStore is StLoc)
{
// transform local variables only for user-defined operators
return false;
}
if (!IsMatchingCompoundLoad(binary.Left, compoundStore, out var target, out var targetKind, out var finalizeMatch, forbiddenVariable: storeInSetter?.Variable))
return false;
if (!ValidateCompoundAssign(binary, smallIntConv, targetType, context.Settings))
return false;
context.Step($"Compound assignment (binary.numeric)", compoundStore);
finalizeMatch?.Invoke(context);
newInst = new NumericCompoundAssign(
binary, target, targetKind, binary.Right,
targetType, CompoundEvalMode.EvaluatesToNewValue);
}
else if (setterValue is Call operatorCall && operatorCall.Method.IsOperator)
{
if (operatorCall.Arguments.Count == 0)
return false;
if (!IsMatchingCompoundLoad(operatorCall.Arguments[0], compoundStore, out var target, out var targetKind, out var finalizeMatch, forbiddenVariable: storeInSetter?.Variable))
return false;
ILInstruction rhs;
if (operatorCall.Arguments.Count == 2)
{
if (CSharp.ExpressionBuilder.GetAssignmentOperatorTypeFromMetadataName(operatorCall.Method.Name) == null)
return false;
rhs = operatorCall.Arguments[1];
}
else if (operatorCall.Arguments.Count == 1)
{
if (!(operatorCall.Method.Name == "op_Increment" || operatorCall.Method.Name == "op_Decrement"))
return false;
// use a dummy node so that we don't need a dedicated instruction for user-defined unary operator calls
rhs = new LdcI4(1);
}
else
{
return false;
}
if (operatorCall.IsLifted)
return false; // TODO: add tests and think about whether nullables need special considerations
context.Step($"Compound assignment (user-defined binary)", compoundStore);
finalizeMatch?.Invoke(context);
newInst = new UserDefinedCompoundAssign(operatorCall.Method, CompoundEvalMode.EvaluatesToNewValue,
target, targetKind, rhs);
}
else if (setterValue is DynamicBinaryOperatorInstruction dynamicBinaryOp)
{
if (!IsMatchingCompoundLoad(dynamicBinaryOp.Left, compoundStore, out var target, out var targetKind, out var finalizeMatch, forbiddenVariable: storeInSetter?.Variable))
return false;
context.Step($"Compound assignment (dynamic binary)", compoundStore);
finalizeMatch?.Invoke(context);
newInst = new DynamicCompoundAssign(ToCompound(dynamicBinaryOp.Operation), dynamicBinaryOp.BinderFlags, target, dynamicBinaryOp.LeftArgumentInfo, dynamicBinaryOp.Right, dynamicBinaryOp.RightArgumentInfo, targetKind);
static ExpressionType ToCompound(ExpressionType from)
{
return from switch {
ExpressionType.Add => ExpressionType.AddAssign,
ExpressionType.AddChecked => ExpressionType.AddAssignChecked,
ExpressionType.And => ExpressionType.AndAssign,
ExpressionType.Divide => ExpressionType.DivideAssign,
ExpressionType.ExclusiveOr => ExpressionType.ExclusiveOrAssign,
ExpressionType.LeftShift => ExpressionType.LeftShiftAssign,
ExpressionType.Modulo => ExpressionType.ModuloAssign,
ExpressionType.Multiply => ExpressionType.MultiplyAssign,
ExpressionType.MultiplyChecked => ExpressionType.MultiplyAssignChecked,
ExpressionType.Or => ExpressionType.OrAssign,
ExpressionType.Power => ExpressionType.PowerAssign,
ExpressionType.RightShift => ExpressionType.RightShiftAssign,
ExpressionType.Subtract => ExpressionType.SubtractAssign,
ExpressionType.SubtractChecked => ExpressionType.SubtractAssignChecked,
_ => from
};
}
}
else if (setterValue is Call concatCall && UserDefinedCompoundAssign.IsStringConcat(concatCall.Method))
{
// setterValue is a string.Concat() invocation
if (compoundStore is StLoc)
{
// transform local variables only for user-defined operators
return false;
}
if (concatCall.Arguments.Count != 2)
return false; // for now we only support binary compound assignments
if (!targetType.IsKnownType(KnownTypeCode.String))
return false;
if (!IsMatchingCompoundLoad(concatCall.Arguments[0], compoundStore, out var target, out var targetKind, out var finalizeMatch, forbiddenVariable: storeInSetter?.Variable))
return false;
context.Step($"Compound assignment (string concatenation)", compoundStore);
finalizeMatch?.Invoke(context);
newInst = new UserDefinedCompoundAssign(concatCall.Method, CompoundEvalMode.EvaluatesToNewValue,
target, targetKind, concatCall.Arguments[1]);
}
else
{
return false;
}
newInst.AddILRange(setterValue);
if (storeInSetter != null)
{
storeInSetter.Value = newInst;
newInst = storeInSetter;
context.RequestRerun(); // moving stloc to top-level might trigger inlining
}
compoundStore.ReplaceWith(newInst);
if (newInst.Parent is Block inlineAssignBlock && inlineAssignBlock.Kind == BlockKind.CallInlineAssign)
{
// It's possible that we first replaced the instruction in an inline-assign helper block.
// In such a situation, we know from the block invariant that we're have a storeInSetter.
Debug.Assert(storeInSetter != null);
Debug.Assert(storeInSetter.Variable.IsSingleDefinition && storeInSetter.Variable.LoadCount == 1);
Debug.Assert(inlineAssignBlock.Instructions.Single() == storeInSetter);
Debug.Assert(inlineAssignBlock.FinalInstruction.MatchLdLoc(storeInSetter.Variable));
// Block CallInlineAssign { stloc I_0(compound.op(...)); final: ldloc I_0 }
// --> compound.op(...)
inlineAssignBlock.ReplaceWith(storeInSetter.Value);
}
return true;
}
///
/// stloc s(value)
/// stloc l(ldloc s)
/// where neither 'stloc s' nor 'stloc l' truncates the value
/// -->
/// stloc s(stloc l(value))
///
bool TransformInlineAssignmentLocal(Block block, int pos)
{
var inst = block.Instructions[pos] as StLoc;
var nextInst = block.Instructions.ElementAtOrDefault(pos + 1) as StLoc;
if (inst == null || nextInst == null)
return false;
if (inst.Variable.Kind != VariableKind.StackSlot)
return false;
if (!(nextInst.Variable.Kind == VariableKind.Local || nextInst.Variable.Kind == VariableKind.Parameter))
return false;
if (!nextInst.Value.MatchLdLoc(inst.Variable))
return false;
if (IsImplicitTruncation(inst.Value, inst.Variable.Type, context.TypeSystem))
{
// 'stloc s' is implicitly truncating the stack value
return false;
}
if (IsImplicitTruncation(inst.Value, nextInst.Variable.Type, context.TypeSystem))
{
// 'stloc l' is implicitly truncating the stack value
return false;
}
if (nextInst.Variable.StackType == StackType.Ref)
{
// ref locals need to be initialized when they are declared, so
// we can only use inline assignments when we know that the
// ref local is definitely assigned.
// We don't have an easy way to check for that in this transform,
// so avoid inline assignments to ref locals for now.
return false;
}
context.Step("Inline assignment to local variable", inst);
var value = inst.Value;
var var = nextInst.Variable;
var stackVar = inst.Variable;
block.Instructions.RemoveAt(pos);
nextInst.ReplaceWith(new StLoc(stackVar, new StLoc(var, value)));
return true;
}
///
/// Gets whether 'stobj type(..., value)' would evaluate to a different value than 'value'
/// due to implicit truncation.
///
static internal bool IsImplicitTruncation(ILInstruction value, IType type, ICompilation compilation, bool allowNullableValue = false)
{
if (!type.IsSmallIntegerType())
{
// Implicit truncation in ILAst only happens for small integer types;
// other types of implicit truncation in IL cause the ILReader to insert
// conv instructions.
return false;
}
// With small integer types, test whether the value might be changed by
// truncation (based on type.GetSize()) followed by sign/zero extension (based on type.GetSign()).
// (it's OK to have false-positives here if we're unsure)
if (value.MatchLdcI4(out int val))
{
switch (type.GetEnumUnderlyingType().GetDefinition()?.KnownTypeCode)
{
case KnownTypeCode.Boolean:
return !(val == 0 || val == 1);
case KnownTypeCode.Byte:
return !(val >= byte.MinValue && val <= byte.MaxValue);
case KnownTypeCode.SByte:
return !(val >= sbyte.MinValue && val <= sbyte.MaxValue);
case KnownTypeCode.Int16:
return !(val >= short.MinValue && val <= short.MaxValue);
case KnownTypeCode.UInt16:
case KnownTypeCode.Char:
return !(val >= ushort.MinValue && val <= ushort.MaxValue);
}
}
else if (value is Conv conv)
{
return conv.TargetType != type.ToPrimitiveType();
}
else if (value is Comp)
{
return false; // comp returns 0 or 1, which always fits
}
else if (value is BinaryNumericInstruction bni)
{
switch (bni.Operator)
{
case BinaryNumericOperator.BitAnd:
case BinaryNumericOperator.BitOr:
case BinaryNumericOperator.BitXor:
// If both input values fit into the type without truncation,
// the result of a binary operator will also fit.
return IsImplicitTruncation(bni.Left, type, compilation, allowNullableValue)
|| IsImplicitTruncation(bni.Right, type, compilation, allowNullableValue);
}
}
else if (value is IfInstruction ifInst)
{
return IsImplicitTruncation(ifInst.TrueInst, type, compilation, allowNullableValue)
|| IsImplicitTruncation(ifInst.FalseInst, type, compilation, allowNullableValue);
}
else
{
IType inferredType = value.InferType(compilation);
if (allowNullableValue)
{
inferredType = NullableType.GetUnderlyingType(inferredType);
}
if (inferredType.Kind != TypeKind.Unknown)
{
return !(inferredType.GetSize() <= type.GetSize() && inferredType.GetSign() == type.GetSign());
}
}
return true;
}
///
/// Gets whether 'inst' is a possible store for use as a compound store.
///
///
/// Output parameters:
/// storeType: The type of the value being stored.
/// value: The value being stored (will be analyzed further to detect compound assignments)
///
/// Every IsCompoundStore() call should be followed by an IsMatchingCompoundLoad() call.
///
static bool IsCompoundStore(ILInstruction inst, out IType storeType,
out ILInstruction value, ICompilation compilation)
{
value = null;
storeType = null;
if (inst is StObj stobj)
{
// stobj.Type may just be 'int' (due to stind.i4) when we're actually operating on a 'ref MyEnum'.
// Try to determine the real type of the object we're modifying:
storeType = stobj.Target.InferType(compilation);
if (storeType is ByReferenceType refType)
{
if (TypeUtils.IsCompatibleTypeForMemoryAccess(refType.ElementType, stobj.Type))
{
storeType = refType.ElementType;
}
else
{
storeType = stobj.Type;
}
}
else if (storeType is PointerType pointerType)
{
if (TypeUtils.IsCompatibleTypeForMemoryAccess(pointerType.ElementType, stobj.Type))
{
storeType = pointerType.ElementType;
}
else
{
storeType = stobj.Type;
}
}
else
{
storeType = stobj.Type;
}
value = stobj.Value;
return SemanticHelper.IsPure(stobj.Target.Flags);
}
else if (inst is CallInstruction call && (call.OpCode == OpCode.Call || call.OpCode == OpCode.CallVirt))
{
if (call.Method.Parameters.Count == 0)
{
return false;
}
foreach (var arg in call.Arguments.SkipLast(1))
{
if (arg.MatchStLoc(out var v) && v.IsSingleDefinition && v.LoadCount == 1)
{
continue; // OK, IsMatchingCompoundLoad can perform an adjustment in this special case
}
if (!SemanticHelper.IsPure(arg.Flags))
{
return false;
}
}
storeType = call.Method.Parameters.Last().Type;
value = call.Arguments.Last();
return IsSameMember(call.Method, (call.Method.AccessorOwner as IProperty)?.Setter);
}
else if (inst is StLoc stloc && (stloc.Variable.Kind == VariableKind.Local || stloc.Variable.Kind == VariableKind.Parameter))
{
storeType = stloc.Variable.Type;
value = stloc.Value;
return true;
}
else
{
return false;
}
}
///
/// Checks whether 'load' and 'store' both access the same store, and can be combined to a compound assignment.
///
/// The load instruction to test.
/// The compound store to test against. Must have previously been tested via IsCompoundStore()
/// The target to use for the compound assignment instruction.
/// The target kind to use for the compound assignment instruction.
/// If set to a non-null value, call this delegate to fix up minor mismatches between getter and setter.
///
/// If given a non-null value, this function returns false if the forbiddenVariable is used in the load/store instructions.
/// Some transforms effectively move a store around,
/// which is only valid if the variable stored to does not occur in the compound load/store.
///
///
/// Instruction preceding the load.
///
static bool IsMatchingCompoundLoad(ILInstruction load, ILInstruction store,
out ILInstruction target, out CompoundTargetKind targetKind,
out Action finalizeMatch,
ILVariable forbiddenVariable = null,
ILInstruction previousInstruction = null)
{
target = null;
targetKind = 0;
finalizeMatch = null;
if (load is LdObj ldobj && store is StObj stobj)
{
Debug.Assert(SemanticHelper.IsPure(stobj.Target.Flags));
if (!SemanticHelper.IsPure(ldobj.Target.Flags))
return false;
if (forbiddenVariable != null && forbiddenVariable.IsUsedWithin(ldobj.Target))
return false;
target = ldobj.Target;
targetKind = CompoundTargetKind.Address;
if (ldobj.Target.Match(stobj.Target).Success)
{
return true;
}
else if (IsDuplicatedAddressComputation(stobj.Target, ldobj.Target))
{
// Use S_0 as target, so that S_0 can later be eliminated by inlining.
// (we can't eliminate previousInstruction right now, because it's before the transform's starting instruction)
target = stobj.Target;
return true;
}
else
{
return false;
}
}
else if (MatchingGetterAndSetterCalls(load as CallInstruction, store as CallInstruction, out finalizeMatch))
{
if (forbiddenVariable != null && forbiddenVariable.IsUsedWithin(load))
return false;
target = load;
targetKind = CompoundTargetKind.Property;
return true;
}
else if (load is LdLoc ldloc && store is StLoc stloc && ILVariableEqualityComparer.Instance.Equals(ldloc.Variable, stloc.Variable))
{
if (ILVariableEqualityComparer.Instance.Equals(ldloc.Variable, forbiddenVariable))
return false;
target = new LdLoca(ldloc.Variable).WithILRange(ldloc);
targetKind = CompoundTargetKind.Address;
finalizeMatch = context => context.Function.RecombineVariables(ldloc.Variable, stloc.Variable);
return true;
}
else
{
return false;
}
bool IsDuplicatedAddressComputation(ILInstruction storeTarget, ILInstruction loadTarget)
{
// Sometimes roslyn duplicates the address calculation:
// stloc S_0(ldloc refParam)
// stloc V_0(ldobj System.Int32(ldloc refParam))
// stobj System.Int32(ldloc S_0, binary.add.i4(ldloc V_0, ldc.i4 1))
while (storeTarget is LdFlda storeLdFlda && loadTarget is LdFlda loadLdFlda)
{
if (!storeLdFlda.Field.Equals(loadLdFlda.Field))
return false;
storeTarget = storeLdFlda.Target;
loadTarget = loadLdFlda.Target;
}
if (!storeTarget.MatchLdLoc(out var s))
return false;
if (!(s.Kind == VariableKind.StackSlot && s.IsSingleDefinition && s != forbiddenVariable))
return false;
if (s.StoreInstructions.SingleOrDefault() != previousInstruction)
return false;
return previousInstruction is StLoc addressStore && addressStore.Value.Match(loadTarget).Success;
}
}
///
/// stobj(target, binary.add(stloc l(ldobj(target)), ldc.i4 1))
/// where target is pure and does not use 'l', and the 'stloc l' does not truncate
/// -->
/// stloc l(compound.op.old(ldobj(target), ldc.i4 1))
///
/// -or-
///
/// call set_Prop(args..., binary.add(stloc l(call get_Prop(args...)), ldc.i4 1))
/// where args.. are pure and do not use 'l', and the 'stloc l' does not truncate
/// -->
/// stloc l(compound.op.old(call get_Prop(target), ldc.i4 1))
///
///
/// This pattern is used for post-increment by legacy csc.
///
/// Even though this transform operates only on a single expression, it's not an expression transform
/// as the result value of the expression changes (this is OK only for statements in a block).
///
bool TransformPostIncDecOperatorWithInlineStore(Block block, int pos)
{
var store = block.Instructions[pos];
if (!IsCompoundStore(store, out var targetType, out var value, context.TypeSystem))
{
return false;
}
StLoc stloc;
var binary = UnwrapSmallIntegerConv(value, out var conv) as BinaryNumericInstruction;
if (binary != null && (binary.Right.MatchLdcI(1) || binary.Right.MatchLdcF4(1) || binary.Right.MatchLdcF8(1)))
{
if (!(binary.Operator == BinaryNumericOperator.Add || binary.Operator == BinaryNumericOperator.Sub))
return false;
if (!ValidateCompoundAssign(binary, conv, targetType, context.Settings))
return false;
stloc = binary.Left as StLoc;
}
else if (value is Call operatorCall && operatorCall.Method.IsOperator && operatorCall.Arguments.Count == 1)
{
if (!(operatorCall.Method.Name == "op_Increment" || operatorCall.Method.Name == "op_Decrement"))
return false;
if (operatorCall.IsLifted)
return false; // TODO: add tests and think about whether nullables need special considerations
stloc = operatorCall.Arguments[0] as StLoc;
}
else
{
return false;
}
if (stloc == null)
return false;
if (!(stloc.Variable.Kind == VariableKind.Local || stloc.Variable.Kind == VariableKind.StackSlot))
return false;
if (!IsMatchingCompoundLoad(stloc.Value, store, out var target, out var targetKind, out var finalizeMatch, forbiddenVariable: stloc.Variable))
return false;
if (IsImplicitTruncation(stloc.Value, stloc.Variable.Type, context.TypeSystem))
return false;
context.Step("TransformPostIncDecOperatorWithInlineStore", store);
finalizeMatch?.Invoke(context);
if (binary != null)
{
block.Instructions[pos] = new StLoc(stloc.Variable, new NumericCompoundAssign(
binary, target, targetKind, binary.Right, targetType, CompoundEvalMode.EvaluatesToOldValue));
}
else
{
Call operatorCall = (Call)value;
block.Instructions[pos] = new StLoc(stloc.Variable, new UserDefinedCompoundAssign(
operatorCall.Method, CompoundEvalMode.EvaluatesToOldValue, target, targetKind, new LdcI4(1)));
}
return true;
}
///
/// stloc tmp(ldobj(target))
/// stobj(target, binary.op(ldloc tmp, ldc.i4 1))
/// target is pure and does not use 'tmp', 'stloc does not truncate'
/// -->
/// stloc tmp(compound.op.old(ldobj(target), ldc.i4 1))
///
/// This is usually followed by inlining or eliminating 'tmp'.
///
/// Local variables use a similar pattern, also detected by this function:
///
/// stloc tmp(ldloc target)
/// stloc target(binary.op(ldloc tmp, ldc.i4 1))
/// -->
/// stloc tmp(compound.op.old(ldloca target, ldc.i4 1))
///
///
/// This pattern occurs with legacy csc for static fields, and with Roslyn for most post-increments.
///
bool TransformPostIncDecOperator(Block block, int i)
{
var inst = block.Instructions[i] as StLoc;
var store = block.Instructions.ElementAtOrDefault(i + 1);
if (inst == null || store == null)
return false;
var tmpVar = inst.Variable;
if (!IsCompoundStore(store, out var targetType, out var value, context.TypeSystem))
return false;
if (IsImplicitTruncation(inst.Value, targetType, context.TypeSystem))
{
// 'stloc tmp' is implicitly truncating the value
return false;
}
if (!IsMatchingCompoundLoad(inst.Value, store, out var target, out var targetKind, out var finalizeMatch,
forbiddenVariable: inst.Variable,
previousInstruction: block.Instructions.ElementAtOrDefault(i - 1)))
{
return false;
}
if (UnwrapSmallIntegerConv(value, out var conv) is BinaryNumericInstruction binary)
{
if (!binary.Left.MatchLdLoc(tmpVar) || !(binary.Right.MatchLdcI(1) || binary.Right.MatchLdcF4(1) || binary.Right.MatchLdcF8(1)))
return false;
if (!(binary.Operator == BinaryNumericOperator.Add || binary.Operator == BinaryNumericOperator.Sub))
return false;
if (!ValidateCompoundAssign(binary, conv, targetType, context.Settings))
return false;
context.Step("TransformPostIncDecOperator (builtin)", inst);
finalizeMatch?.Invoke(context);
inst.Value = new NumericCompoundAssign(binary, target, targetKind, binary.Right,
targetType, CompoundEvalMode.EvaluatesToOldValue);
}
else if (value is Call operatorCall && operatorCall.Method.IsOperator && operatorCall.Arguments.Count == 1)
{
if (!operatorCall.Arguments[0].MatchLdLoc(tmpVar))
return false;
if (!(operatorCall.Method.Name == "op_Increment" || operatorCall.Method.Name == "op_Decrement"))
return false;
if (operatorCall.IsLifted)
return false; // TODO: add tests and think about whether nullables need special considerations
context.Step("TransformPostIncDecOperator (user-defined)", inst);
finalizeMatch?.Invoke(context);
inst.Value = new UserDefinedCompoundAssign(operatorCall.Method,
CompoundEvalMode.EvaluatesToOldValue, target, targetKind, new LdcI4(1));
}
else
{
return false;
}
block.Instructions.RemoveAt(i + 1);
if (inst.Variable.IsSingleDefinition && inst.Variable.LoadCount == 0)
{
// dead store -> it was a statement-level post-increment
inst.ReplaceWith(inst.Value);
}
return true;
}
static bool IsSameMember(IMember a, IMember b)
{
if (a == null || b == null)
return false;
a = a.MemberDefinition;
b = b.MemberDefinition;
return a.Equals(b);
}
}
}