// Copyright (c) Microsoft. All Rights Reserved. Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Immutable;
using System.Diagnostics;
using System.Reflection.Metadata;
using Microsoft.CodeAnalysis.CodeGen;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Roslyn.Utilities;
using static System.Linq.ImmutableArrayExtensions;
using static Microsoft.CodeAnalysis.CSharp.Binder;
namespace Microsoft.CodeAnalysis.CSharp.CodeGen
{
internal partial class CodeGenerator
{
private int _recursionDepth;
private class EmitCancelledException : Exception
{ }
private enum UseKind
{
Unused,
UsedAsValue,
UsedAsAddress
}
private void EmitExpression(BoundExpression expression, bool used)
{
if (expression == null)
{
return;
}
var constantValue = expression.ConstantValue;
if (constantValue != null)
{
if (!used)
{
// unused constants have no side-effects.
return;
}
if ((object)expression.Type == null || expression.Type.SpecialType != SpecialType.System_Decimal)
{
EmitConstantExpression(expression.Type, constantValue, used, expression.Syntax);
return;
}
}
_recursionDepth++;
if (_recursionDepth > 1)
{
StackGuard.EnsureSufficientExecutionStack(_recursionDepth);
EmitExpressionCore(expression, used);
}
else
{
EmitExpressionCoreWithStackGuard(expression, used);
}
_recursionDepth--;
}
private void EmitExpressionCoreWithStackGuard(BoundExpression expression, bool used)
{
Debug.Assert(_recursionDepth == 1);
try
{
EmitExpressionCore(expression, used);
Debug.Assert(_recursionDepth == 1);
}
catch (InsufficientExecutionStackException)
{
_diagnostics.Add(ErrorCode.ERR_InsufficientStack,
BoundTreeVisitor.CancelledByStackGuardException.GetTooLongOrComplexExpressionErrorLocation(expression));
throw new EmitCancelledException();
}
}
private void EmitExpressionCore(BoundExpression expression, bool used)
{
switch (expression.Kind)
{
case BoundKind.AssignmentOperator:
EmitAssignmentExpression((BoundAssignmentOperator)expression, used ? UseKind.UsedAsValue : UseKind.Unused);
break;
case BoundKind.Call:
EmitCallExpression((BoundCall)expression, used ? UseKind.UsedAsValue : UseKind.Unused);
break;
case BoundKind.ObjectCreationExpression:
EmitObjectCreationExpression((BoundObjectCreationExpression)expression, used);
break;
case BoundKind.DelegateCreationExpression:
EmitDelegateCreationExpression((BoundDelegateCreationExpression)expression, used);
break;
case BoundKind.ArrayCreation:
EmitArrayCreationExpression((BoundArrayCreation)expression, used);
break;
case BoundKind.ConvertedStackAllocExpression:
EmitConvertedStackAllocExpression((BoundConvertedStackAllocExpression)expression, used);
break;
case BoundKind.ReadOnlySpanFromArray:
EmitReadOnlySpanFromArrayExpression((BoundReadOnlySpanFromArray)expression, used);
break;
case BoundKind.Conversion:
EmitConversionExpression((BoundConversion)expression, used);
break;
case BoundKind.Local:
EmitLocalLoad((BoundLocal)expression, used);
break;
case BoundKind.Dup:
EmitDupExpression((BoundDup)expression, used);
break;
case BoundKind.PassByCopy:
EmitExpression(((BoundPassByCopy)expression).Expression, used);
break;
case BoundKind.Parameter:
if (used) // unused parameter has no side-effects
{
EmitParameterLoad((BoundParameter)expression);
}
break;
case BoundKind.FieldAccess:
EmitFieldLoad((BoundFieldAccess)expression, used);
break;
case BoundKind.ArrayAccess:
EmitArrayElementLoad((BoundArrayAccess)expression, used);
break;
case BoundKind.ArrayLength:
EmitArrayLength((BoundArrayLength)expression, used);
break;
case BoundKind.ThisReference:
if (used) // unused this has no side-effects
{
EmitThisReferenceExpression((BoundThisReference)expression);
}
break;
case BoundKind.PreviousSubmissionReference:
// Script references are lowered to a this reference and a field access.
throw ExceptionUtilities.UnexpectedValue(expression.Kind);
case BoundKind.BaseReference:
if (used) // unused base has no side-effects
{
var thisType = _method.ContainingType;
_builder.EmitOpCode(ILOpCode.Ldarg_0);
if (thisType.IsValueType)
{
EmitLoadIndirect(thisType, expression.Syntax);
EmitBox(thisType, expression.Syntax);
}
}
break;
case BoundKind.Sequence:
EmitSequenceExpression((BoundSequence)expression, used);
break;
case BoundKind.SequencePointExpression:
EmitSequencePointExpression((BoundSequencePointExpression)expression, used);
break;
case BoundKind.UnaryOperator:
EmitUnaryOperatorExpression((BoundUnaryOperator)expression, used);
break;
case BoundKind.BinaryOperator:
EmitBinaryOperatorExpression((BoundBinaryOperator)expression, used);
break;
case BoundKind.NullCoalescingOperator:
EmitNullCoalescingOperator((BoundNullCoalescingOperator)expression, used);
break;
case BoundKind.IsOperator:
EmitIsExpression((BoundIsOperator)expression, used);
break;
case BoundKind.AsOperator:
EmitAsExpression((BoundAsOperator)expression, used);
break;
case BoundKind.DefaultExpression:
EmitDefaultExpression((BoundDefaultExpression)expression, used);
break;
case BoundKind.TypeOfOperator:
if (used) // unused typeof has no side-effects
{
EmitTypeOfExpression((BoundTypeOfOperator)expression);
}
break;
case BoundKind.SizeOfOperator:
if (used) // unused sizeof has no side-effects
{
EmitSizeOfExpression((BoundSizeOfOperator)expression);
}
break;
case BoundKind.ModuleVersionId:
Debug.Assert(used);
EmitModuleVersionIdLoad((BoundModuleVersionId)expression);
break;
case BoundKind.ModuleVersionIdString:
Debug.Assert(used);
EmitModuleVersionIdStringLoad((BoundModuleVersionIdString)expression);
break;
case BoundKind.InstrumentationPayloadRoot:
Debug.Assert(used);
EmitInstrumentationPayloadRootLoad((BoundInstrumentationPayloadRoot)expression);
break;
case BoundKind.MethodDefIndex:
Debug.Assert(used);
EmitMethodDefIndexExpression((BoundMethodDefIndex)expression);
break;
case BoundKind.MaximumMethodDefIndex:
Debug.Assert(used);
EmitMaximumMethodDefIndexExpression((BoundMaximumMethodDefIndex)expression);
break;
case BoundKind.SourceDocumentIndex:
Debug.Assert(used);
EmitSourceDocumentIndex((BoundSourceDocumentIndex)expression);
break;
case BoundKind.MethodInfo:
if (used)
{
EmitMethodInfoExpression((BoundMethodInfo)expression);
}
break;
case BoundKind.FieldInfo:
if (used)
{
EmitFieldInfoExpression((BoundFieldInfo)expression);
}
break;
case BoundKind.ConditionalOperator:
EmitConditionalOperator((BoundConditionalOperator)expression, used);
break;
case BoundKind.AddressOfOperator:
EmitAddressOfExpression((BoundAddressOfOperator)expression, used);
break;
case BoundKind.PointerIndirectionOperator:
EmitPointerIndirectionOperator((BoundPointerIndirectionOperator)expression, used);
break;
case BoundKind.ArgList:
EmitArgList(used);
break;
case BoundKind.ArgListOperator:
Debug.Assert(used);
EmitArgListOperator((BoundArgListOperator)expression);
break;
case BoundKind.RefTypeOperator:
EmitRefTypeOperator((BoundRefTypeOperator)expression, used);
break;
case BoundKind.MakeRefOperator:
EmitMakeRefOperator((BoundMakeRefOperator)expression, used);
break;
case BoundKind.RefValueOperator:
EmitRefValueOperator((BoundRefValueOperator)expression, used);
break;
case BoundKind.LoweredConditionalAccess:
EmitLoweredConditionalAccessExpression((BoundLoweredConditionalAccess)expression, used);
break;
case BoundKind.ConditionalReceiver:
EmitConditionalReceiver((BoundConditionalReceiver)expression, used);
break;
case BoundKind.ComplexConditionalReceiver:
EmitComplexConditionalReceiver((BoundComplexConditionalReceiver)expression, used);
break;
case BoundKind.PseudoVariable:
EmitPseudoVariableValue((BoundPseudoVariable)expression, used);
break;
case BoundKind.ThrowExpression:
EmitThrowExpression((BoundThrowExpression)expression, used);
break;
default:
// Code gen should not be invoked if there are errors.
Debug.Assert(expression.Kind != BoundKind.BadExpression);
// node should have been lowered:
throw ExceptionUtilities.UnexpectedValue(expression.Kind);
}
}
private void EmitThrowExpression(BoundThrowExpression node, bool used)
{
this.EmitThrow(node.Expression);
// to satisfy invariants, we push a default value to pretend to adjust the stack height
EmitDefaultValue(node.Type, used, node.Syntax);
}
private void EmitComplexConditionalReceiver(BoundComplexConditionalReceiver expression, bool used)
{
Debug.Assert(!expression.Type.IsReferenceType);
Debug.Assert(!expression.Type.IsValueType);
var receiverType = expression.Type;
var whenValueTypeLabel = new object();
var doneLabel = new object();
EmitInitObj(receiverType, true, expression.Syntax);
EmitBox(receiverType, expression.Syntax);
_builder.EmitBranch(ILOpCode.Brtrue, whenValueTypeLabel);
EmitExpression(expression.ReferenceTypeReceiver, used);
_builder.EmitBranch(ILOpCode.Br, doneLabel);
_builder.AdjustStack(-1);
_builder.MarkLabel(whenValueTypeLabel);
EmitExpression(expression.ValueTypeReceiver, used);
_builder.MarkLabel(doneLabel);
}
private void EmitLoweredConditionalAccessExpression(BoundLoweredConditionalAccess expression, bool used)
{
var receiver = expression.Receiver;
var receiverType = receiver.Type;
LocalDefinition receiverTemp = null;
Debug.Assert(!receiverType.IsValueType ||
(receiverType.IsNullableType() && expression.HasValueMethodOpt != null), "conditional receiver cannot be a struct");
var receiverConstant = receiver.ConstantValue;
if (receiverConstant?.IsNull == false)
{
// const but not null, must be a reference type
Debug.Assert(receiverType.IsVerifierReference());
// receiver is a reference type, so addresskind does not matter, but we do not intend to write.
receiverTemp = EmitReceiverRef(receiver, AddressKind.ReadOnly);
EmitExpression(expression.WhenNotNull, used);
if (receiverTemp != null)
{
FreeTemp(receiverTemp);
}
return;
}
// labels
object whenNotNullLabel = new object();
object doneLabel = new object();
LocalDefinition cloneTemp = null;
var notConstrained = !receiverType.IsReferenceType && !receiverType.IsValueType;
// we need a copy if we deal with nonlocal value (to capture the value)
// or if we have a ref-constrained T (to do box just once)
// or if we deal with stack local (reads are destructive)
// or if we have default(T) (to do box just once)
var nullCheckOnCopy = LocalRewriter.CanChangeValueBetweenReads(receiver, localsMayBeAssignedOrCaptured: false) ||
(receiverType.IsReferenceType && receiverType.TypeKind == TypeKind.TypeParameter) ||
(receiver.Kind == BoundKind.Local && IsStackLocal(((BoundLocal)receiver).LocalSymbol));
// ===== RECEIVER
if (nullCheckOnCopy)
{
if (notConstrained)
{
// if T happens to be a value type, it could be a target of mutating calls.
receiverTemp = EmitReceiverRef(receiver, AddressKind.Constrained);
// unconstrained case needs to handle case where T is actually a struct.
// such values are never nulls
// we will emit a check for such case, but the check is really a JIT-time
// constant since JIT will know if T is a struct or not.
// if ((object)default(T) != null)
// {
// goto whenNotNull
// }
// else
// {
// temp = receiverRef
// receiverRef = ref temp
// }
EmitDefaultValue(receiverType, true, receiver.Syntax);
EmitBox(receiverType, receiver.Syntax);
_builder.EmitBranch(ILOpCode.Brtrue, whenNotNullLabel);
EmitLoadIndirect(receiverType, receiver.Syntax);
cloneTemp = AllocateTemp(receiverType, receiver.Syntax);
_builder.EmitLocalStore(cloneTemp);
_builder.EmitLocalAddress(cloneTemp);
_builder.EmitLocalLoad(cloneTemp);
EmitBox(receiver.Type, receiver.Syntax);
// here we have loaded a ref to a temp and its boxed value { &T, O }
}
else
{
// this does not need to be writeable
// we may call "HasValue" on this, but it is not mutating
var addressKind = AddressKind.ReadOnly;
receiverTemp = EmitReceiverRef(receiver, addressKind);
_builder.EmitOpCode(ILOpCode.Dup);
// here we have loaded two copies of a reference { O, O } or {&nub, &nub}
}
}
else
{
// this does not need to be writeable.
// we may call "HasValue" on this, but it is not mutating
// besides, since we are not making a copy, the receiver is not a field,
// so it cannot be readonly, in verifier sense, anyways.
receiverTemp = EmitReceiverRef(receiver, AddressKind.ReadOnly);
// here we have loaded just { O } or {&nub}
// we have the most trivial case where we can just reload receiver when needed again
}
// ===== CONDITION
var hasValueOpt = expression.HasValueMethodOpt;
if (hasValueOpt != null)
{
Debug.Assert(receiver.Type.IsNullableType());
_builder.EmitOpCode(ILOpCode.Call, stackAdjustment: 0);
EmitSymbolToken(hasValueOpt, expression.Syntax, null);
}
_builder.EmitBranch(ILOpCode.Brtrue, whenNotNullLabel);
// no longer need the temp if we are not holding a copy
if (receiverTemp != null && !nullCheckOnCopy)
{
FreeTemp(receiverTemp);
receiverTemp = null;
}
// ===== WHEN NULL
if (nullCheckOnCopy)
{
_builder.EmitOpCode(ILOpCode.Pop);
}
var whenNull = expression.WhenNullOpt;
if (whenNull == null)
{
EmitDefaultValue(expression.Type, used, expression.Syntax);
}
else
{
EmitExpression(whenNull, used);
}
_builder.EmitBranch(ILOpCode.Br, doneLabel);
// ===== WHEN NOT NULL
if (nullCheckOnCopy)
{
// notNull branch pops copy of receiver off the stack when nullCheckOnCopy
// however on the isNull branch we still have the stack as it was and need
// to adjust stack depth correspondingly.
_builder.AdjustStack(+1);
}
if (used)
{
// notNull branch pushes default on the stack when used
// however on the isNull branch we still have the stack as it was and need
// to adjust stack depth correspondingly.
_builder.AdjustStack(-1);
}
_builder.MarkLabel(whenNotNullLabel);
if (!nullCheckOnCopy)
{
Debug.Assert(receiverTemp == null);
// receiver may be used as target of a struct call (if T happens to be a struct)
receiverTemp = EmitReceiverRef(receiver, AddressKind.Constrained);
Debug.Assert(receiverTemp == null || receiver.IsDefaultValue());
}
EmitExpression(expression.WhenNotNull, used);
// ===== DONE
_builder.MarkLabel(doneLabel);
if (cloneTemp != null)
{
FreeTemp(cloneTemp);
}
if (receiverTemp != null)
{
FreeTemp(receiverTemp);
}
}
private void EmitConditionalReceiver(BoundConditionalReceiver expression, bool used)
{
Debug.Assert(!expression.Type.IsValueType);
if (!expression.Type.IsReferenceType)
{
EmitLoadIndirect(expression.Type, expression.Syntax);
}
EmitPopIfUnused(used);
}
private void EmitRefValueOperator(BoundRefValueOperator expression, bool used)
{
EmitRefValueAddress(expression);
EmitLoadIndirect(expression.Type, expression.Syntax);
EmitPopIfUnused(used);
}
private void EmitMakeRefOperator(BoundMakeRefOperator expression, bool used)
{
// push address of variable
// mkrefany [Type] -- takes address off stack, puts TypedReference on stack
var temp = EmitAddress(expression.Operand, AddressKind.Writeable);
Debug.Assert(temp == null, "makeref should not create temps");
_builder.EmitOpCode(ILOpCode.Mkrefany);
EmitSymbolToken(expression.Operand.Type, expression.Operand.Syntax);
EmitPopIfUnused(used);
}
private void EmitRefTypeOperator(BoundRefTypeOperator expression, bool used)
{
// push TypedReference
// refanytype -- takes TypedReference off stack, puts token on stack
// call GetTypeFromHandle -- takes token off stack, puts Type on stack
EmitExpression(expression.Operand, true);
_builder.EmitOpCode(ILOpCode.Refanytype);
_builder.EmitOpCode(ILOpCode.Call, stackAdjustment: 0);
var getTypeMethod = expression.GetTypeFromHandle;
Debug.Assert((object)getTypeMethod != null);
EmitSymbolToken(getTypeMethod, expression.Syntax, null);
EmitPopIfUnused(used);
}
private void EmitArgList(bool used)
{
_builder.EmitOpCode(ILOpCode.Arglist);
EmitPopIfUnused(used);
}
private void EmitArgListOperator(BoundArgListOperator expression)
{
for (int i = 0; i < expression.Arguments.Length; i++)
{
BoundExpression argument = expression.Arguments[i];
RefKind refKind = expression.ArgumentRefKindsOpt.IsDefaultOrEmpty ? RefKind.None : expression.ArgumentRefKindsOpt[i];
EmitArgument(argument, refKind);
}
}
private void EmitArgument(BoundExpression argument, RefKind refKind)
{
switch (refKind)
{
case RefKind.None:
EmitExpression(argument, true);
break;
case RefKind.In:
var temp = EmitAddress(argument, AddressKind.ReadOnly);
AddExpressionTemp(temp);
break;
default:
// NOTE: passing "ReadOnlyStrict" here.
// we should not get an address of a copy if at all possible
var unexpectedTemp = EmitAddress(argument, refKind == RefKindExtensions.StrictIn ? AddressKind.ReadOnlyStrict : AddressKind.Writeable);
if (unexpectedTemp != null)
{
// interestingly enough "ref dynamic" sometimes is passed via a clone
Debug.Assert(argument.Type.IsDynamic(), "passing args byref should not clone them into temps");
AddExpressionTemp(unexpectedTemp);
}
break;
}
}
private void EmitAddressOfExpression(BoundAddressOfOperator expression, bool used)
{
// NOTE: passing "ReadOnlyStrict" here.
// we should not get an address of a copy if at all possible
var temp = EmitAddress(expression.Operand, AddressKind.ReadOnlyStrict);
Debug.Assert(temp == null, "If the operand is addressable, then a temp shouldn't be required.");
if (used && !expression.IsManaged)
{
// When computing an address to be used to initialize a fixed-statement variable, we have to be careful
// not to convert the managed reference to an unmanaged pointer before storing it. Otherwise the GC might
// come along and move memory around, invalidating the pointer before it is pinned by being stored in
// the fixed variable. But elsewhere in the code we do use a conv.u instruction to convert the managed
// reference to the underlying type for unmanaged pointers, which is the type "unsigned int" (see CLI
// standard, Partition I section 12.1.1.1).
_builder.EmitOpCode(ILOpCode.Conv_u);
}
EmitPopIfUnused(used);
}
private void EmitPointerIndirectionOperator(BoundPointerIndirectionOperator expression, bool used)
{
EmitExpression(expression.Operand, used: true);
EmitLoadIndirect(expression.Type, expression.Syntax);
EmitPopIfUnused(used);
}
private void EmitDupExpression(BoundDup expression, bool used)
{
if (expression.RefKind == RefKind.None)
{
// unused dup is noop
if (used)
{
_builder.EmitOpCode(ILOpCode.Dup);
}
}
else
{
_builder.EmitOpCode(ILOpCode.Dup);
// must read in case if it is a null ref
EmitLoadIndirect(expression.Type, expression.Syntax);
EmitPopIfUnused(used);
}
}
private void EmitDelegateCreationExpression(BoundDelegateCreationExpression expression, bool used)
{
var mg = expression.Argument as BoundMethodGroup;
var receiver = mg != null ? mg.ReceiverOpt : expression.Argument;
var meth = expression.MethodOpt ?? receiver.Type.DelegateInvokeMethod();
Debug.Assert((object)meth != null);
EmitDelegateCreation(expression, receiver, expression.IsExtensionMethod, meth, expression.Type, used);
}
private void EmitThisReferenceExpression(BoundThisReference thisRef)
{
var thisType = thisRef.Type;
Debug.Assert(thisType.TypeKind != TypeKind.TypeParameter);
_builder.EmitOpCode(ILOpCode.Ldarg_0);
if (thisType.IsValueType)
{
EmitLoadIndirect(thisType, thisRef.Syntax);
}
}
private void EmitPseudoVariableValue(BoundPseudoVariable expression, bool used)
{
EmitExpression(expression.EmitExpressions.GetValue(expression, _diagnostics), used);
}
private void EmitSequencePointExpression(BoundSequencePointExpression node, bool used)
{
EmitSequencePoint(node);
// used is true to ensure that something is emitted
EmitExpression(node.Expression, used: true);
EmitPopIfUnused(used);
}
private void EmitSequencePoint(BoundSequencePointExpression node)
{
var syntax = node.Syntax;
if (_emitPdbSequencePoints)
{
if (syntax == null)
{
EmitHiddenSequencePoint();
}
else
{
EmitSequencePoint(syntax);
}
}
}
private void EmitSequenceExpression(BoundSequence sequence, bool used)
{
DefineLocals(sequence);
EmitSideEffects(sequence);
// CONSIDER: LocalRewriter.RewriteNestedObjectOrCollectionInitializerExpression may create a bound sequence with an unused BoundTypeExpression as the value,
// CONSIDER: which must be ignored by codegen. See comments in RewriteNestedObjectOrCollectionInitializerExpression for details and an example.
// CONSIDER: We may want to instead consider making the Value field of BoundSequence node optional to allow a sequence with
// CONSIDER: only side effects and no value. Note that VB's BoundSequence node has an optional value field.
// CONSIDER: This will allow us to remove the below check before emitting the value.
Debug.Assert(sequence.Value.Kind != BoundKind.TypeExpression || !used);
if (sequence.Value.Kind != BoundKind.TypeExpression)
{
EmitExpression(sequence.Value, used);
}
// sequence is used as a value, can release all locals
FreeLocals(sequence);
}
private void DefineLocals(BoundSequence sequence)
{
if (sequence.Locals.IsEmpty)
{
return;
}
_builder.OpenLocalScope();
foreach (var local in sequence.Locals)
{
DefineLocal(local, sequence.Syntax);
}
}
private void FreeLocals(BoundSequence sequence)
{
if (sequence.Locals.IsEmpty)
{
return;
}
_builder.CloseLocalScope();
foreach (var local in sequence.Locals)
{
FreeLocal(local);
}
}
///
/// Defines sequence locals and record them so that they could be retained for the duration of the encompassing expression
/// Use this when taking a reference of the sequence, which can indirectly refer to any of its locals.
///
private void DefineAndRecordLocals(BoundSequence sequence)
{
if (sequence.Locals.IsEmpty)
{
return;
}
_builder.OpenLocalScope();
foreach (var local in sequence.Locals)
{
var seqLocal = DefineLocal(local, sequence.Syntax);
AddExpressionTemp(seqLocal);
}
}
///
/// Closes the visibility/debug scopes for the sequence locals, but keep the local slots from reuse
/// for the duration of the encompassing expression.
/// Use this paired with DefineAndRecordLocals when taking a reference of the sequence, which can indirectly refer to any of its locals.
///
private void CloseScopeAndKeepLocals(BoundSequence sequence)
{
if (sequence.Locals.IsEmpty)
{
return;
}
_builder.CloseLocalScope();
}
private void EmitSideEffects(BoundSequence sequence)
{
var sideEffects = sequence.SideEffects;
if (!sideEffects.IsDefaultOrEmpty)
{
foreach (var se in sideEffects)
{
EmitExpression(se, false);
}
}
}
private void EmitArguments(ImmutableArray arguments, ImmutableArray parameters, ImmutableArray argRefKindsOpt)
{
// We might have an extra argument for the __arglist() of a varargs method.
Debug.Assert(arguments.Length == parameters.Length || arguments.Length == parameters.Length + 1, "argument count must match parameter count");
Debug.Assert(parameters.All(p => p.RefKind == RefKind.None) || !argRefKindsOpt.IsDefault, "there are nontrivial parameters, so we must have argRefKinds");
Debug.Assert(argRefKindsOpt.IsDefault || argRefKindsOpt.Length == arguments.Length, "if we have argRefKinds, we should have one for each argument");
for (int i = 0; i < arguments.Length; i++)
{
RefKind argRefKind = GetArgumentRefKind(arguments, parameters, argRefKindsOpt, i);
EmitArgument(arguments[i], argRefKind);
}
}
///
/// Computes the desired refkind of the argument.
/// Considers all the cases - where ref kinds are explicit, omitted, vararg cases.
///
internal static RefKind GetArgumentRefKind(ImmutableArray arguments, ImmutableArray parameters, ImmutableArray argRefKindsOpt, int i)
{
RefKind argRefKind;
if (i < parameters.Length)
{
if (!argRefKindsOpt.IsDefault && i < argRefKindsOpt.Length)
{
// if we have an explicit refKind for the given argument, use that
argRefKind = argRefKindsOpt[i];
Debug.Assert(argRefKind == parameters[i].RefKind ||
argRefKind == RefKindExtensions.StrictIn && parameters[i].RefKind == RefKind.In,
"in Emit the argument RefKind must be compatible with the corresponding parameter");
}
else
{
// otherwise fallback to the refKind of the parameter
argRefKind = parameters[i].RefKind;
}
}
else
{
// vararg case
Debug.Assert(arguments[i].Kind == BoundKind.ArgListOperator);
argRefKind = RefKind.None;
}
return argRefKind;
}
private void EmitArrayElementLoad(BoundArrayAccess arrayAccess, bool used)
{
EmitExpression(arrayAccess.Expression, used: true);
EmitArrayIndices(arrayAccess.Indices);
if (((ArrayTypeSymbol)arrayAccess.Expression.Type).IsSZArray)
{
var elementType = arrayAccess.Type;
if (elementType.IsEnumType())
{
//underlying primitives do not need type tokens.
elementType = ((NamedTypeSymbol)elementType).EnumUnderlyingType;
}
switch (elementType.PrimitiveTypeCode)
{
case Microsoft.Cci.PrimitiveTypeCode.Int8:
_builder.EmitOpCode(ILOpCode.Ldelem_i1);
break;
case Microsoft.Cci.PrimitiveTypeCode.Boolean:
case Microsoft.Cci.PrimitiveTypeCode.UInt8:
_builder.EmitOpCode(ILOpCode.Ldelem_u1);
break;
case Microsoft.Cci.PrimitiveTypeCode.Int16:
_builder.EmitOpCode(ILOpCode.Ldelem_i2);
break;
case Microsoft.Cci.PrimitiveTypeCode.Char:
case Microsoft.Cci.PrimitiveTypeCode.UInt16:
_builder.EmitOpCode(ILOpCode.Ldelem_u2);
break;
case Microsoft.Cci.PrimitiveTypeCode.Int32:
_builder.EmitOpCode(ILOpCode.Ldelem_i4);
break;
case Microsoft.Cci.PrimitiveTypeCode.UInt32:
_builder.EmitOpCode(ILOpCode.Ldelem_u4);
break;
case Microsoft.Cci.PrimitiveTypeCode.Int64:
case Microsoft.Cci.PrimitiveTypeCode.UInt64:
_builder.EmitOpCode(ILOpCode.Ldelem_i8);
break;
case Microsoft.Cci.PrimitiveTypeCode.IntPtr:
case Microsoft.Cci.PrimitiveTypeCode.UIntPtr:
case Microsoft.Cci.PrimitiveTypeCode.Pointer:
_builder.EmitOpCode(ILOpCode.Ldelem_i);
break;
case Microsoft.Cci.PrimitiveTypeCode.Float32:
_builder.EmitOpCode(ILOpCode.Ldelem_r4);
break;
case Microsoft.Cci.PrimitiveTypeCode.Float64:
_builder.EmitOpCode(ILOpCode.Ldelem_r8);
break;
default:
if (elementType.IsVerifierReference())
{
_builder.EmitOpCode(ILOpCode.Ldelem_ref);
}
else
{
if (used)
{
_builder.EmitOpCode(ILOpCode.Ldelem);
}
else
{
// no need to read whole element of nontrivial type/size here
// just take a reference to an element for array access side-effects
if (elementType.TypeKind == TypeKind.TypeParameter)
{
_builder.EmitOpCode(ILOpCode.Readonly);
}
_builder.EmitOpCode(ILOpCode.Ldelema);
}
EmitSymbolToken(elementType, arrayAccess.Syntax);
}
break;
}
}
else
{
_builder.EmitArrayElementLoad(Emit.PEModuleBuilder.Translate((ArrayTypeSymbol)arrayAccess.Expression.Type), arrayAccess.Expression.Syntax, _diagnostics);
}
EmitPopIfUnused(used);
}
private void EmitFieldLoad(BoundFieldAccess fieldAccess, bool used)
{
var field = fieldAccess.FieldSymbol;
if (!used)
{
// fetching unused captured frame is a no-op (like reading "this")
if (field.IsCapturedFrame)
{
return;
}
// Accessing a volatile field is sideeffecting because it establishes an acquire fence.
// Otherwise, accessing an unused instance field on a struct is a noop. Just emit an unused receiver.
if (!field.IsVolatile && !field.IsStatic && fieldAccess.ReceiverOpt.Type.IsVerifierValue())
{
EmitExpression(fieldAccess.ReceiverOpt, used: false);
return;
}
}
Debug.Assert(!field.IsConst || field.ContainingType.SpecialType == SpecialType.System_Decimal,
"rewriter should lower constant fields into constant expressions");
// static field access is sideeffecting since it guarantees that ..ctor has run.
// we emit static accesses even if unused.
if (field.IsStatic)
{
if (field.IsVolatile)
{
_builder.EmitOpCode(ILOpCode.Volatile);
}
_builder.EmitOpCode(ILOpCode.Ldsfld);
EmitSymbolToken(field, fieldAccess.Syntax);
}
else
{
var receiver = fieldAccess.ReceiverOpt;
TypeSymbol fieldType = field.Type;
if (fieldType.IsValueType && (object)fieldType == (object)receiver.Type)
{
//Handle emitting a field of a self-containing struct (only possible in mscorlib)
//since "val.field" is the same as val, we only need to emit val.
EmitExpression(receiver, used);
}
else
{
var temp = EmitFieldLoadReceiver(receiver);
if (temp != null)
{
Debug.Assert(FieldLoadMustUseRef(receiver), "only clr-ambiguous structs use temps here");
FreeTemp(temp);
}
if (field.IsVolatile)
{
_builder.EmitOpCode(ILOpCode.Volatile);
}
_builder.EmitOpCode(ILOpCode.Ldfld);
EmitSymbolToken(field, fieldAccess.Syntax);
}
}
EmitPopIfUnused(used);
}
private LocalDefinition EmitFieldLoadReceiver(BoundExpression receiver)
{
// ldfld can work with structs directly or with their addresses
// accessing via address is typically same or cheaper, but not for homeless values, obviously
// there are also cases where we must emit receiver as a reference
if (FieldLoadMustUseRef(receiver) || FieldLoadPrefersRef(receiver))
{
return EmitFieldLoadReceiverAddress(receiver) ? null : EmitReceiverRef(receiver, AddressKind.ReadOnly);
}
EmitExpression(receiver, true);
return null;
}
// In special case of loading the sequence of field accesses we can perform all the
// necessary field loads using the following IL:
//
// .a.b...y.z
// |
// V
// Unbox -or- Load.Ref ()
// Ldflda a
// Ldflda b
// ...
// Ldflda y
// Ldfld z
//
// Returns 'true' if the receiver was actually emitted this way
private bool EmitFieldLoadReceiverAddress(BoundExpression receiver)
{
if (receiver == null || !receiver.Type.IsValueType)
{
return false;
}
else if (receiver.Kind == BoundKind.Conversion)
{
var conversion = (BoundConversion)receiver;
if (conversion.ConversionKind == ConversionKind.Unboxing)
{
EmitExpression(conversion.Operand, true);
_builder.EmitOpCode(ILOpCode.Unbox);
EmitSymbolToken(receiver.Type, receiver.Syntax);
return true;
}
}
else if (receiver.Kind == BoundKind.FieldAccess)
{
var fieldAccess = (BoundFieldAccess)receiver;
var field = fieldAccess.FieldSymbol;
if (!field.IsStatic && EmitFieldLoadReceiverAddress(fieldAccess.ReceiverOpt))
{
Debug.Assert(!field.IsVolatile, "volatile valuetype fields are unexpected");
_builder.EmitOpCode(ILOpCode.Ldflda);
EmitSymbolToken(field, fieldAccess.Syntax);
return true;
}
}
return false;
}
// ldfld can work with structs directly or with their addresses
// In some cases it results in same native code emitted, but in some cases JIT pushes values for real
// resulting in much worse code (on x64 in particular).
// So, we will always prefer references here except when receiver is a struct non-ref local or parameter.
private bool FieldLoadPrefersRef(BoundExpression receiver)
{
// only fields of structs can be accessed via value
if (!receiver.Type.IsVerifierValue())
{
return true;
}
// can unbox directly into a ref.
if (receiver.Kind == BoundKind.Conversion && ((BoundConversion)receiver).ConversionKind == ConversionKind.Unboxing)
{
return true;
}
// can we take address at all?
if (!HasHome(receiver, AddressKind.ReadOnly))
{
return false;
}
switch (receiver.Kind)
{
case BoundKind.Parameter:
// prefer ldarg over ldarga
return ((BoundParameter)receiver).ParameterSymbol.RefKind != RefKind.None;
case BoundKind.Local:
// prefer ldloc over ldloca
return ((BoundLocal)receiver).LocalSymbol.RefKind != RefKind.None;
case BoundKind.Sequence:
return FieldLoadPrefersRef(((BoundSequence)receiver).Value);
case BoundKind.FieldAccess:
var fieldAccess = (BoundFieldAccess)receiver;
if (fieldAccess.FieldSymbol.IsStatic)
{
return true;
}
if (DiagnosticsPass.IsNonAgileFieldAccess(fieldAccess, _module.Compilation))
{
return false;
}
return FieldLoadPrefersRef(fieldAccess.ReceiverOpt);
}
return true;
}
internal static bool FieldLoadMustUseRef(BoundExpression expr)
{
var type = expr.Type;
// type parameter values must be boxed to get access to fields
if (type.IsTypeParameter())
{
return true;
}
// From Dev12/symbol.cpp
//
// // Used by ILGEN to determine if the type of this AggregateSymbol is one that the CLR
// // will consider ambiguous to an unmanaged pointer when it is on the stack (see VSW #396011)
// bool AggregateSymbol::IsCLRAmbigStruct()
// . . .
switch (type.SpecialType)
{
// case PT_BYTE:
case SpecialType.System_Byte:
// case PT_SHORT:
case SpecialType.System_Int16:
// case PT_INT:
case SpecialType.System_Int32:
// case PT_LONG:
case SpecialType.System_Int64:
// case PT_CHAR:
case SpecialType.System_Char:
// case PT_BOOL:
case SpecialType.System_Boolean:
// case PT_SBYTE:
case SpecialType.System_SByte:
// case PT_USHORT:
case SpecialType.System_UInt16:
// case PT_UINT:
case SpecialType.System_UInt32:
// case PT_ULONG:
case SpecialType.System_UInt64:
// case PT_INTPTR:
case SpecialType.System_IntPtr:
// case PT_UINTPTR:
case SpecialType.System_UIntPtr:
// case PT_FLOAT:
case SpecialType.System_Single:
// case PT_DOUBLE:
case SpecialType.System_Double:
// case PT_TYPEHANDLE:
case SpecialType.System_RuntimeTypeHandle:
// case PT_FIELDHANDLE:
case SpecialType.System_RuntimeFieldHandle:
// case PT_METHODHANDLE:
case SpecialType.System_RuntimeMethodHandle:
//case PT_ARGUMENTHANDLE:
case SpecialType.System_RuntimeArgumentHandle:
return true;
}
// this is for value__
// I do not know how to hit this, since value__ is not bindable in C#, but Dev12 has code to handle this
return type.IsEnumType();
}
private static int ParameterSlot(BoundParameter parameter)
{
var sym = parameter.ParameterSymbol;
int slot = sym.Ordinal;
if (!sym.ContainingSymbol.IsStatic)
{
slot++; // skip "this"
}
return slot;
}
private void EmitLocalLoad(BoundLocal local, bool used)
{
if (IsStackLocal(local.LocalSymbol))
{
// local must be already on the stack
EmitPopIfUnused(used);
}
else
{
if (used)
{
LocalDefinition definition = GetLocal(local);
_builder.EmitLocalLoad(definition);
}
else
{
// do nothing. Unused local load has no side-effects.
return;
}
}
if (used && local.LocalSymbol.RefKind != RefKind.None)
{
EmitLoadIndirect(local.LocalSymbol.Type, local.Syntax);
}
}
private void EmitParameterLoad(BoundParameter parameter)
{
int slot = ParameterSlot(parameter);
_builder.EmitLoadArgumentOpcode(slot);
if (parameter.ParameterSymbol.RefKind != RefKind.None)
{
var parameterType = parameter.ParameterSymbol.Type;
EmitLoadIndirect(parameterType, parameter.Syntax);
}
}
private void EmitLoadIndirect(TypeSymbol type, SyntaxNode syntaxNode)
{
if (type.IsEnumType())
{
//underlying primitives do not need type tokens.
type = ((NamedTypeSymbol)type).EnumUnderlyingType;
}
switch (type.PrimitiveTypeCode)
{
case Microsoft.Cci.PrimitiveTypeCode.Int8:
_builder.EmitOpCode(ILOpCode.Ldind_i1);
break;
case Microsoft.Cci.PrimitiveTypeCode.Boolean:
case Microsoft.Cci.PrimitiveTypeCode.UInt8:
_builder.EmitOpCode(ILOpCode.Ldind_u1);
break;
case Microsoft.Cci.PrimitiveTypeCode.Int16:
_builder.EmitOpCode(ILOpCode.Ldind_i2);
break;
case Microsoft.Cci.PrimitiveTypeCode.Char:
case Microsoft.Cci.PrimitiveTypeCode.UInt16:
_builder.EmitOpCode(ILOpCode.Ldind_u2);
break;
case Microsoft.Cci.PrimitiveTypeCode.Int32:
_builder.EmitOpCode(ILOpCode.Ldind_i4);
break;
case Microsoft.Cci.PrimitiveTypeCode.UInt32:
_builder.EmitOpCode(ILOpCode.Ldind_u4);
break;
case Microsoft.Cci.PrimitiveTypeCode.Int64:
case Microsoft.Cci.PrimitiveTypeCode.UInt64:
_builder.EmitOpCode(ILOpCode.Ldind_i8);
break;
case Microsoft.Cci.PrimitiveTypeCode.IntPtr:
case Microsoft.Cci.PrimitiveTypeCode.UIntPtr:
case Microsoft.Cci.PrimitiveTypeCode.Pointer:
_builder.EmitOpCode(ILOpCode.Ldind_i);
break;
case Microsoft.Cci.PrimitiveTypeCode.Float32:
_builder.EmitOpCode(ILOpCode.Ldind_r4);
break;
case Microsoft.Cci.PrimitiveTypeCode.Float64:
_builder.EmitOpCode(ILOpCode.Ldind_r8);
break;
default:
if (type.IsVerifierReference())
{
_builder.EmitOpCode(ILOpCode.Ldind_ref);
}
else
{
_builder.EmitOpCode(ILOpCode.Ldobj);
EmitSymbolToken(type, syntaxNode);
}
break;
}
}
///
/// Used to decide if we need to emit call or callvirt.
/// It basically checks if the receiver expression cannot be null, but it is not 100% precise.
/// There are cases where it really can be null, but we do not care.
///
private bool CanUseCallOnRefTypeReceiver(BoundExpression receiver)
{
// It seems none of the ways that could produce a receiver typed as a type param
// can guarantee that it is not null.
if (receiver.Type.IsTypeParameter())
{
return false;
}
Debug.Assert(receiver.Type.IsVerifierReference(), "this is not a reference");
Debug.Assert(receiver.Kind != BoundKind.BaseReference, "base should always use call");
var constVal = receiver.ConstantValue;
if (constVal != null)
{
// only when this is a constant Null, we need a callvirt
return !constVal.IsNull;
}
switch (receiver.Kind)
{
case BoundKind.ArrayCreation:
return true;
case BoundKind.ObjectCreationExpression:
// NOTE: there are cases involving ProxyAttribute
// where newobj may produce null
return true;
case BoundKind.Conversion:
var conversion = (BoundConversion)receiver;
switch (conversion.ConversionKind)
{
case ConversionKind.Boxing:
// NOTE: boxing can produce null for Nullable, but any call through that
// will result in null reference exceptions anyways.
return true;
case ConversionKind.MethodGroup:
case ConversionKind.AnonymousFunction:
return true;
case ConversionKind.ExplicitReference:
case ConversionKind.ImplicitReference:
return CanUseCallOnRefTypeReceiver(conversion.Operand);
}
break;
case BoundKind.ThisReference:
// NOTE: these actually can be null if called from a different language
// however, we assume it is responsibility of the caller to nullcheck "this"
// if we already have access to "this", we must be in a member and should
// not redo the check
return true;
case BoundKind.FieldAccess:
// same reason as for "ThisReference"
return ((BoundFieldAccess)receiver).FieldSymbol.IsCapturedFrame;
case BoundKind.Local:
// same reason as for "ThisReference"
return ((BoundLocal)receiver).LocalSymbol.SynthesizedKind == SynthesizedLocalKind.FrameCache;
case BoundKind.DelegateCreationExpression:
return true;
case BoundKind.Sequence:
var seqValue = ((BoundSequence)(receiver)).Value;
return CanUseCallOnRefTypeReceiver(seqValue);
case BoundKind.AssignmentOperator:
var rhs = ((BoundAssignmentOperator)receiver).Right;
return CanUseCallOnRefTypeReceiver(rhs);
case BoundKind.TypeOfOperator:
return true;
case BoundKind.ConditionalReceiver:
return true;
//TODO: there could be more cases where we can be sure that receiver is not a null.
}
return false;
}
///
/// checks if receiver is effectively ldarg.0
///
private bool IsThisReceiver(BoundExpression receiver)
{
switch (receiver.Kind)
{
case BoundKind.ThisReference:
return true;
case BoundKind.Sequence:
var seqValue = ((BoundSequence)(receiver)).Value;
return IsThisReceiver(seqValue);
}
return false;
}
private enum CallKind
{
Call,
CallVirt,
ConstrainedCallVirt,
}
private void EmitCallExpression(BoundCall call, UseKind useKind)
{
var method = call.Method;
var receiver = call.ReceiverOpt;
LocalDefinition tempOpt = null;
// Calls to the default struct constructor are emitted as initobj, rather than call.
// NOTE: constructor invocations are represented as BoundObjectCreationExpressions,
// rather than BoundCalls. This is why we can be confident that if we see a call to a
// constructor, it has this very specific form.
if (method.IsDefaultValueTypeConstructor())
{
Debug.Assert(method.IsImplicitlyDeclared);
Debug.Assert(TypeSymbol.Equals(method.ContainingType, receiver.Type, TypeCompareKind.ConsiderEverything2));
Debug.Assert(receiver.Kind == BoundKind.ThisReference);
tempOpt = EmitReceiverRef(receiver, AddressKind.Writeable);
_builder.EmitOpCode(ILOpCode.Initobj); // initobj
EmitSymbolToken(method.ContainingType, call.Syntax);
FreeOptTemp(tempOpt);
return;
}
var arguments = call.Arguments;
CallKind callKind;
if (!method.RequiresInstanceReceiver)
{
callKind = CallKind.Call;
}
else
{
var receiverType = receiver.Type;
if (receiverType.IsVerifierReference())
{
EmitExpression(receiver, used: true);
// In some cases CanUseCallOnRefTypeReceiver returns true which means that
// null check is unnecessary and we can use "call"
if (receiver.SuppressVirtualCalls ||
(!method.IsMetadataVirtual() && CanUseCallOnRefTypeReceiver(receiver)))
{
callKind = CallKind.Call;
}
else
{
callKind = CallKind.CallVirt;
}
}
else if (receiverType.IsVerifierValue())
{
NamedTypeSymbol methodContainingType = method.ContainingType;
if (methodContainingType.IsVerifierValue())
{
// if method is defined in the struct itself it is assumed to be mutating, unless
// it is a member of a readonly struct and is not a constructor
var receiverAddresskind = IsReadOnlyCall(method, methodContainingType) ?
AddressKind.ReadOnly :
AddressKind.Writeable;
if (MayUseCallForStructMethod(method))
{
// NOTE: this should be either a method which overrides some abstract method or
// does not override anything (with few exceptions, see MayUseCallForStructMethod);
// otherwise we should not use direct 'call' and must use constrained call;
// calling a method defined in a value type
Debug.Assert(TypeSymbol.Equals(receiverType, methodContainingType, TypeCompareKind.ObliviousNullableModifierMatchesAny));
tempOpt = EmitReceiverRef(receiver, receiverAddresskind);
callKind = CallKind.Call;
}
else
{
tempOpt = EmitReceiverRef(receiver, receiverAddresskind);
callKind = CallKind.ConstrainedCallVirt;
}
}
else
{
// calling a method defined in a base class.
// When calling a method that is virtual in metadata on a struct receiver,
// we use a constrained virtual call. If possible, it will skip boxing.
if (method.IsMetadataVirtual())
{
// NB: all methods that a struct could inherit from bases are non-mutating
// treat receiver as ReadOnly
tempOpt = EmitReceiverRef(receiver, AddressKind.ReadOnly);
callKind = CallKind.ConstrainedCallVirt;
}
else
{
EmitExpression(receiver, used: true);
EmitBox(receiverType, receiver.Syntax);
callKind = CallKind.Call;
}
}
}
else
{
// receiver is generic and method must come from the base or an interface or a generic constraint
// if the receiver is actually a value type it would need to be boxed.
// let .constrained sort this out.
callKind = receiverType.IsReferenceType && !IsRef(receiver) ?
CallKind.CallVirt :
CallKind.ConstrainedCallVirt;
tempOpt = EmitReceiverRef(receiver, callKind == CallKind.ConstrainedCallVirt ? AddressKind.Constrained : AddressKind.Writeable);
}
}
// When emitting a callvirt to a virtual method we always emit the method info of the
// method that first declared the virtual method, not the method info of an
// overriding method. It would be a subtle breaking change to change that rule;
// see bug 6156 for details.
MethodSymbol actualMethodTargetedByTheCall = method;
if (method.IsOverride && callKind != CallKind.Call)
{
actualMethodTargetedByTheCall = method.GetConstructedLeastOverriddenMethod(_method.ContainingType);
}
if (callKind == CallKind.ConstrainedCallVirt && actualMethodTargetedByTheCall.ContainingType.IsValueType)
{
// special case for overridden methods like ToString(...) called on
// value types: if the original method used in emit cannot use callvirt in this
// case, change it to Call.
callKind = CallKind.Call;
}
// Devirtualizing of calls to effectively sealed methods.
if (callKind == CallKind.CallVirt)
{
// NOTE: we check that we call method in same module just to be sure
// that it cannot be recompiled as not final and make our call not verifiable.
// such change by adversarial user would arguably be a compat break, but better be safe...
// In reality we would typically have one method calling another method in the same class (one GetEnumerator calling another).
// Other scenarios are uncommon since base class cannot be sealed and
// referring to a derived type in a different module is not an easy thing to do.
if (IsThisReceiver(receiver) && actualMethodTargetedByTheCall.ContainingType.IsSealed &&
(object)actualMethodTargetedByTheCall.ContainingModule == (object)_method.ContainingModule)
{
// special case for target is in a sealed class and "this" receiver.
Debug.Assert(receiver.Type.IsVerifierReference());
callKind = CallKind.Call;
}
// NOTE: we do not check that we call method in same module.
// Because of the "GetOriginalConstructedOverriddenMethod" above, the actual target
// can only be final when it is "newslot virtual final".
// In such case Dev11 emits "call" and we will just replicate the behavior. (see DevDiv: 546853 )
else if (actualMethodTargetedByTheCall.IsMetadataFinal && CanUseCallOnRefTypeReceiver(receiver))
{
// special case for calling 'final' virtual method on reference receiver
Debug.Assert(receiver.Type.IsVerifierReference());
callKind = CallKind.Call;
}
}
EmitArguments(arguments, method.Parameters, call.ArgumentRefKindsOpt);
int stackBehavior = GetCallStackBehavior(call);
switch (callKind)
{
case CallKind.Call:
_builder.EmitOpCode(ILOpCode.Call, stackBehavior);
break;
case CallKind.CallVirt:
_builder.EmitOpCode(ILOpCode.Callvirt, stackBehavior);
break;
case CallKind.ConstrainedCallVirt:
_builder.EmitOpCode(ILOpCode.Constrained);
EmitSymbolToken(receiver.Type, receiver.Syntax);
_builder.EmitOpCode(ILOpCode.Callvirt, stackBehavior);
break;
}
EmitSymbolToken(actualMethodTargetedByTheCall, call.Syntax,
actualMethodTargetedByTheCall.IsVararg ? (BoundArgListOperator)call.Arguments[call.Arguments.Length - 1] : null);
if (!method.ReturnsVoid)
{
EmitPopIfUnused(useKind != UseKind.Unused);
}
else if (_ilEmitStyle == ILEmitStyle.Debug)
{
// The only void methods with usable return values are constructors and we represent those
// as BoundObjectCreationExpressions, not BoundCalls.
Debug.Assert(useKind == UseKind.Unused, "Using the return value of a void method.");
Debug.Assert(_method.GenerateDebugInfo, "Implied by this.emitSequencePoints");
// DevDiv #15135. When a method like System.Diagnostics.Debugger.Break() is called, the
// debugger sees an event indicating that a user break (vs a breakpoint) has occurred.
// When this happens, it uses ICorDebugILFrame.GetIP(out uint, out CorDebugMappingResult)
// to determine the current instruction pointer. This method returns the instruction
// *after* the call. The source location is then given by the last sequence point before
// or on this instruction. As a result, if the instruction after the call has its own
// sequence point, then that sequence point will be used to determine the source location
// and the debugging experience will be disrupted. The easiest way to ensure that the next
// instruction does not have a sequence point is to insert a nop. Obviously, we only do this
// if debugging is enabled and optimization is disabled.
// From ILGENREC::genCall:
// We want to generate a NOP after CALL opcodes that end a statement so the debugger
// has better stepping behavior
// CONSIDER: In the native compiler, there's an additional restriction on when this nop is
// inserted. It is quite complicated, but it basically seems to say that, if we thought
// we could omit the temp-and-copy for a struct construction and it turned out that we
// couldn't (perhaps because the assigned local was captured by a lambda), and if we're
// not using the result of the constructor call (how can this even happen?), then we don't
// want to insert the nop. Since the consequence of not implementing this complicated logic
// is an extra nop in debug code, this is likely not a priority.
// CONSIDER: The native compiler also checks !(tree->flags & EXF_NODEBUGINFO). We don't have
// this mutable bit on our bound nodes, so we can't exactly match the behavior. We might be
// able to approximate the native behavior by inspecting call.WasCompilerGenerated, but it is
// not in a reliable state after lowering.
_builder.EmitOpCode(ILOpCode.Nop);
}
if (useKind == UseKind.UsedAsValue && method.RefKind != RefKind.None)
{
EmitLoadIndirect(method.ReturnType, call.Syntax);
}
else if (useKind == UseKind.UsedAsAddress)
{
Debug.Assert(method.RefKind != RefKind.None);
}
FreeOptTemp(tempOpt);
}
private bool IsReadOnlyCall(MethodSymbol method, NamedTypeSymbol methodContainingType)
{
Debug.Assert(methodContainingType.IsVerifierValue(), "only struct calls can be readonly");
if (method.IsEffectivelyReadOnly && method.MethodKind != MethodKind.Constructor)
{
return true;
}
if (methodContainingType.IsNullableType())
{
var originalMethod = method.OriginalDefinition;
if ((object)originalMethod == this._module.Compilation.GetSpecialTypeMember(SpecialMember.System_Nullable_T_GetValueOrDefault) ||
(object)originalMethod == this._module.Compilation.GetSpecialTypeMember(SpecialMember.System_Nullable_T_get_Value) ||
(object)originalMethod == this._module.Compilation.GetSpecialTypeMember(SpecialMember.System_Nullable_T_get_HasValue))
{
return true;
}
}
return false;
}
// returns true when receiver is already a ref.
// in such cases calling through a ref could be preferred over
// calling through indirectly loaded value.
private bool IsRef(BoundExpression receiver)
{
switch (receiver.Kind)
{
case BoundKind.Local:
return ((BoundLocal)receiver).LocalSymbol.RefKind != RefKind.None;
case BoundKind.Parameter:
return ((BoundParameter)receiver).ParameterSymbol.RefKind != RefKind.None;
case BoundKind.Call:
return ((BoundCall)receiver).Method.RefKind != RefKind.None;
case BoundKind.Dup:
return ((BoundDup)receiver).RefKind != RefKind.None;
case BoundKind.Sequence:
return IsRef(((BoundSequence)receiver).Value);
}
return false;
}
private static int GetCallStackBehavior(BoundCall call)
{
int stack = 0;
if (!call.Method.ReturnsVoid)
{
// The call puts the return value on the stack.
stack += 1;
}
if (call.Method.RequiresInstanceReceiver)
{
// The call pops the receiver off the stack.
stack -= 1;
}
if (call.Method.IsVararg)
{
// The call pops all the arguments, fixed and variadic.
int fixedArgCount = call.Arguments.Length - 1;
int varArgCount = ((BoundArgListOperator)call.Arguments[fixedArgCount]).Arguments.Length;
stack -= fixedArgCount;
stack -= varArgCount;
}
else
{
// The call pops all the arguments.
stack -= call.Arguments.Length;
}
return stack;
}
private static int GetObjCreationStackBehavior(BoundObjectCreationExpression objCreation)
{
int stack = 0;
// Constructor puts the return value on the stack.
stack += 1;
if (objCreation.Constructor.IsVararg)
{
// Constructor pops all the arguments, fixed and variadic.
int fixedArgCount = objCreation.Arguments.Length - 1;
int varArgCount = ((BoundArgListOperator)objCreation.Arguments[fixedArgCount]).Arguments.Length;
stack -= fixedArgCount;
stack -= varArgCount;
}
else
{
// Constructor pops all the arguments.
stack -= objCreation.Arguments.Length;
}
return stack;
}
///
/// Used to decide if we need to emit 'call' or 'callvirt' for structure method.
/// It basically checks if the method overrides any other and method's defining type
/// is not a 'special' or 'special-by-ref' type.
///
internal static bool MayUseCallForStructMethod(MethodSymbol method)
{
Debug.Assert(method.ContainingType.IsVerifierValue(), "this is not a value type");
if (!method.IsMetadataVirtual())
{
return true;
}
var overriddenMethod = method.OverriddenMethod;
if ((object)overriddenMethod == null || overriddenMethod.IsAbstract)
{
return true;
}
var containingType = method.ContainingType;
// overrides in structs that are special types can be called directly.
// we can assume that special types will not be removing overrides
return containingType.SpecialType != SpecialType.None;
}
///
/// When array operation get long or ulong arguments the args should be
/// cast to native int.
/// Note that the cast is always checked.
///
private void TreatLongsAsNative(Microsoft.Cci.PrimitiveTypeCode tc)
{
if (tc == Microsoft.Cci.PrimitiveTypeCode.Int64)
{
_builder.EmitOpCode(ILOpCode.Conv_ovf_i);
}
else if (tc == Microsoft.Cci.PrimitiveTypeCode.UInt64)
{
_builder.EmitOpCode(ILOpCode.Conv_ovf_i_un);
}
}
private void EmitArrayLength(BoundArrayLength expression, bool used)
{
// The binder recognizes Array.Length and Array.LongLength and creates BoundArrayLength for them.
//
// ArrayLength can be either
// int32 for Array.Length
// int64 for Array.LongLength
// UIntPtr for synthetic code that needs just check if length != 0 -
// this is used in "fixed(int* ptr = arr)"
Debug.Assert(expression.Type.SpecialType == SpecialType.System_Int32 ||
expression.Type.SpecialType == SpecialType.System_Int64 ||
expression.Type.SpecialType == SpecialType.System_UIntPtr);
// ldlen will null-check the expression so it must be "used"
EmitExpression(expression.Expression, used: true);
_builder.EmitOpCode(ILOpCode.Ldlen);
var typeTo = expression.Type.PrimitiveTypeCode;
// NOTE: ldlen returns native uint, but newarr takes native int, so the length value is always
// a positive native int. We can treat it as either signed or unsigned.
// We will use whatever typeTo says so we do not need to convert because of sign.
var typeFrom = typeTo.IsUnsigned() ? Microsoft.Cci.PrimitiveTypeCode.UIntPtr : Microsoft.Cci.PrimitiveTypeCode.IntPtr;
// NOTE: In Dev10 C# this cast is unchecked.
// That seems to be wrong since that would cause silent truncation on 64bit platform if that implements large arrays.
//
// Emitting checked conversion however results in redundant overflow checks on 64bit and also inhibits range check hoisting in loops.
// Therefore we will emit unchecked conversion here as C# compiler always did.
_builder.EmitNumericConversion(typeFrom, typeTo, @checked: false);
EmitPopIfUnused(used);
}
private void EmitArrayCreationExpression(BoundArrayCreation expression, bool used)
{
var arrayType = (ArrayTypeSymbol)expression.Type;
EmitArrayIndices(expression.Bounds);
if (arrayType.IsSZArray)
{
_builder.EmitOpCode(ILOpCode.Newarr);
EmitSymbolToken(arrayType.ElementType, expression.Syntax);
}
else
{
_builder.EmitArrayCreation(Emit.PEModuleBuilder.Translate(arrayType), expression.Syntax, _diagnostics);
}
if (expression.InitializerOpt != null)
{
EmitArrayInitializers(arrayType, expression.InitializerOpt);
}
// newarr has side-effects (negative bounds etc) so always emitted.
EmitPopIfUnused(used);
}
private void EmitConvertedStackAllocExpression(BoundConvertedStackAllocExpression expression, bool used)
{
EmitExpression(expression.Count, used);
// the only sideeffect of a localloc is a nondeterministic and generally fatal StackOverflow.
// we can ignore that if the actual result is unused
if (used)
{
_sawStackalloc = true;
_builder.EmitOpCode(ILOpCode.Localloc);
}
var initializer = expression.InitializerOpt;
if (initializer != null)
{
if (used)
{
EmitStackAllocInitializers(expression.Type, initializer);
}
else
{
// If not used, just emit initializer elements to preserve possible sideeffects
foreach (var init in initializer.Initializers)
{
EmitExpression(init, used: false);
}
}
}
}
private void EmitObjectCreationExpression(BoundObjectCreationExpression expression, bool used)
{
MethodSymbol constructor = expression.Constructor;
if (constructor.IsDefaultValueTypeConstructor())
{
EmitInitObj(expression.Type, used, expression.Syntax);
}
else
{
// check if need to construct at all
if (!used && ConstructorNotSideEffecting(constructor))
{
// ctor has no side-effects, so we will just evaluate the arguments
foreach (var arg in expression.Arguments)
{
EmitExpression(arg, used: false);
}
return;
}
// ReadOnlySpan may just refer to the blob, if possible.
if (this._module.Compilation.IsReadOnlySpanType(expression.Type) &&
expression.Arguments.Length == 1)
{
if (TryEmitReadonlySpanAsBlobWrapper((NamedTypeSymbol)expression.Type, expression.Arguments[0], used, inPlace: false))
{
return;
}
}
// none of the above cases, so just create an instance
EmitArguments(expression.Arguments, constructor.Parameters, expression.ArgumentRefKindsOpt);
var stackAdjustment = GetObjCreationStackBehavior(expression);
_builder.EmitOpCode(ILOpCode.Newobj, stackAdjustment);
// for variadic ctors emit expanded ctor token
EmitSymbolToken(constructor, expression.Syntax,
constructor.IsVararg ? (BoundArgListOperator)expression.Arguments[expression.Arguments.Length - 1] : null);
EmitPopIfUnused(used);
}
}
///
/// Recognizes constructors known to not have side-effects (which means they can be skipped unless the constructed object is used)
///
private bool ConstructorNotSideEffecting(MethodSymbol constructor)
{
var originalDef = constructor.OriginalDefinition;
var compilation = _module.Compilation;
if (originalDef == compilation.GetSpecialTypeMember(SpecialMember.System_Nullable_T__ctor))
{
return true;
}
if (originalDef.ContainingType.Name == NamedTypeSymbol.ValueTupleTypeName &&
(originalDef == compilation.GetWellKnownTypeMember(WellKnownMember.System_ValueTuple_T2__ctor) ||
originalDef == compilation.GetWellKnownTypeMember(WellKnownMember.System_ValueTuple_T3__ctor) ||
originalDef == compilation.GetWellKnownTypeMember(WellKnownMember.System_ValueTuple_T4__ctor) ||
originalDef == compilation.GetWellKnownTypeMember(WellKnownMember.System_ValueTuple_T5__ctor) ||
originalDef == compilation.GetWellKnownTypeMember(WellKnownMember.System_ValueTuple_T6__ctor) ||
originalDef == compilation.GetWellKnownTypeMember(WellKnownMember.System_ValueTuple_T7__ctor) ||
originalDef == compilation.GetWellKnownTypeMember(WellKnownMember.System_ValueTuple_TRest__ctor) ||
originalDef == compilation.GetWellKnownTypeMember(WellKnownMember.System_ValueTuple_T1__ctor)))
{
return true;
}
return false;
}
private void EmitAssignmentExpression(BoundAssignmentOperator assignmentOperator, UseKind useKind)
{
if (TryEmitAssignmentInPlace(assignmentOperator, useKind != UseKind.Unused))
{
Debug.Assert(!assignmentOperator.IsRef);
return;
}
// Assignment expression codegen has the following parts:
//
// * PreRHS: We need to emit instructions before the load of the right hand side if:
// - If the left hand side is a ref local or ref formal parameter and the right hand
// side is a value then we must put the ref on the stack early so that we can store
// indirectly into it.
// - If the left hand side is an array slot then we must evaluate the array and indices
// before we evaluate the right hand side. We ensure that the array and indices are
// on the stack when the store is executed.
// - Similarly, if the left hand side is a non-static field then its receiver must be
// evaluated before the right hand side.
//
// * RHS: There are three possible ways to do an assignment with respect to "refness",
// and all are found in the lowering of:
//
// N().s += 10;
//
// That expression is realized as
//
// ref int addr = ref N().s; // Assign a ref on the right hand side to the left hand side.
// int sum = addr + 10; // No refs at all; assign directly to sum.
// addr = sum; // Assigns indirectly through the address.
//
// - If we are in the first case then assignmentOperator.RefKind is Ref and the left hand side is a
// ref local temporary. We simply assign the ref on the RHS to the storage on the LHS with no indirection.
//
// - If we are in the second case then nothing is ref; we have a value on one side an a local on the other.
// Again, there is no indirection.
//
// - If we are in the third case then we have a ref on the left and a value on the right. We must compute the
// value of the right hand side and then store it into the left hand side.
//
// * Duplication: The result of an assignment operation is the value that was assigned. It is possible that
// later codegen is expecting this value to be on the stack when we're done here. This is controlled by
// the "used" formal parameter. There are two possible cases:
// - If the preamble put stuff on the stack for the usage of the store, then we must not put an extra copy
// of the right hand side value on the stack; that will be between the value and the stuff needed to
// do the storage. In that case we put the right hand side value in a temporary and restore it later.
// - Otherwise we can just do a dup instruction; there's nothing before the dup on the stack that we'll need.
//
// * Storage: Either direct or indirect, depending. See the RHS section above for details.
//
// * Post-storage: If we stashed away the duplicated value in the temporary, we need to restore it back to the stack.
bool lhsUsesStack = EmitAssignmentPreamble(assignmentOperator);
EmitAssignmentValue(assignmentOperator);
LocalDefinition temp = EmitAssignmentDuplication(assignmentOperator, useKind, lhsUsesStack);
EmitStore(assignmentOperator);
EmitAssignmentPostfix(assignmentOperator, temp, useKind);
}
// sometimes it is possible and advantageous to get an address of the lHS and
// perform assignment as an in-place initialization via initobj or constructor invocation.
//
// 1) initobj
// is used when assigning default value to T that is not a verifier reference.
//
// 2) in-place ctor call
// is used when assigning a freshly created struct. "x = new S(arg)" can be
// replaced by x.S(arg) as long as partial assignment cannot be observed -
// i.e. target must not be on the heap and we should not be in a try block.
private bool TryEmitAssignmentInPlace(BoundAssignmentOperator assignmentOperator, bool used)
{
var left = assignmentOperator.Left;
// if result is used, and lives on heap, we must keep RHS value on the stack.
// otherwise we can try conjuring up the RHS value directly where it belongs.
if (used && !TargetIsNotOnHeap(left))
{
return false;
}
if (!SafeToGetWriteableReference(left))
{
// cannot take a ref
return false;
}
var right = assignmentOperator.Right;
var rightType = right.Type;
// in-place is not advantageous for reference types or constants
if (!rightType.IsTypeParameter())
{
if (rightType.IsReferenceType || (right.ConstantValue != null && rightType.SpecialType != SpecialType.System_Decimal))
{
return false;
}
}
if (right.IsDefaultValue())
{
InPlaceInit(left, used);
return true;
}
if (right is BoundObjectCreationExpression objCreation)
{
// If we are creating a Span from a stackalloc, which is a particular pattern of code
// produced by lowering, we must use the constructor in its standard form because the stack
// is required to contain nothing more than stackalloc's argument.
if (objCreation.Arguments.Length > 0 && objCreation.Arguments[0].Kind == BoundKind.ConvertedStackAllocExpression)
{
return false;
}
// It is desirable to do in-place ctor call if possible.
// we could do newobj/stloc, but in-place call
// produces the same or better code in current JITs
if (PartialCtorResultCannotEscape(left))
{
var ctor = objCreation.Constructor;
// ctor can possibly see its own assignments indirectly if there are ref parameters or __arglist
if (System.Linq.ImmutableArrayExtensions.All(ctor.Parameters, p => p.RefKind == RefKind.None) &&
!ctor.IsVararg)
{
InPlaceCtorCall(left, objCreation, used);
return true;
}
}
}
return false;
}
private bool SafeToGetWriteableReference(BoundExpression left)
{
if (!HasHome(left, AddressKind.Writeable))
{
return false;
}
// because of array covariance, taking a reference to an element of
// generic array may fail even though assignment "arr[i] = default(T)" would always succeed.
if (left.Kind == BoundKind.ArrayAccess && left.Type.TypeKind == TypeKind.TypeParameter && !left.Type.IsValueType)
{
return false;
}
if (left.Kind == BoundKind.FieldAccess)
{
var fieldAccess = (BoundFieldAccess)left;
if (fieldAccess.FieldSymbol.IsVolatile ||
DiagnosticsPass.IsNonAgileFieldAccess(fieldAccess, _module.Compilation))
{
return false;
}
}
return true;
}
private void InPlaceInit(BoundExpression target, bool used)
{
var temp = EmitAddress(target, AddressKind.Writeable);
Debug.Assert(temp == null, "in-place init target should not create temps");
_builder.EmitOpCode(ILOpCode.Initobj); // initobj
EmitSymbolToken(target.Type, target.Syntax);
if (used)
{
Debug.Assert(TargetIsNotOnHeap(target), "cannot read-back the target since it could have been modified");
EmitExpression(target, used);
}
}
private void InPlaceCtorCall(BoundExpression target, BoundObjectCreationExpression objCreation, bool used)
{
Debug.Assert(TargetIsNotOnHeap(target), "in-place construction target should not be on heap");
var temp = EmitAddress(target, AddressKind.Writeable);
Debug.Assert(temp == null, "in-place ctor target should not create temps");
// ReadOnlySpan may just refer to the blob, if possible.
if (this._module.Compilation.IsReadOnlySpanType(objCreation.Type) && objCreation.Arguments.Length == 1)
{
if (TryEmitReadonlySpanAsBlobWrapper((NamedTypeSymbol)objCreation.Type, objCreation.Arguments[0], used, inPlace: true))
{
if (used)
{
EmitExpression(target, used: true);
}
return;
}
}
var constructor = objCreation.Constructor;
EmitArguments(objCreation.Arguments, constructor.Parameters, objCreation.ArgumentRefKindsOpt);
// -2 to adjust for consumed target address and not produced value.
var stackAdjustment = GetObjCreationStackBehavior(objCreation) - 2;
_builder.EmitOpCode(ILOpCode.Call, stackAdjustment);
// for variadic ctors emit expanded ctor token
EmitSymbolToken(constructor, objCreation.Syntax,
constructor.IsVararg ? (BoundArgListOperator)objCreation.Arguments[objCreation.Arguments.Length - 1] : null);
if (used)
{
EmitExpression(target, used: true);
}
}
// partial ctor results are not observable when target is not on the heap.
// we also must not be in a try, otherwise if ctor throws
// partially assigned value may be observed in the handler.
private bool PartialCtorResultCannotEscape(BoundExpression left)
{
if (TargetIsNotOnHeap(left))
{
if (_tryNestingLevel != 0)
{
var local = left as BoundLocal;
if (local != null && !_builder.PossiblyDefinedOutsideOfTry(GetLocal(local)))
{
// local defined inside immediate Try - cannot escape
return true;
}
// local defined outside of immediate try or it is a parameter - can escape
return false;
}
// we are not in a try - locals, parameters cannot escape
return true;
}
// left is a reference, partial initializations can escape.
return false;
}
// returns True when assignment target is definitely not on the heap
private static bool TargetIsNotOnHeap(BoundExpression left)
{
switch (left.Kind)
{
case BoundKind.Parameter:
return ((BoundParameter)left).ParameterSymbol.RefKind == RefKind.None;
case BoundKind.Local:
// NOTE: stack locals are either homeless or refs, no need to special case them
// they will never be assigned in-place.
return ((BoundLocal)left).LocalSymbol.RefKind == RefKind.None;
}
return false;
}
private bool EmitAssignmentPreamble(BoundAssignmentOperator assignmentOperator)
{
var assignmentTarget = assignmentOperator.Left;
bool lhsUsesStack = false;
switch (assignmentTarget.Kind)
{
case BoundKind.RefValueOperator:
EmitRefValueAddress((BoundRefValueOperator)assignmentTarget);
break;
case BoundKind.FieldAccess:
{
var left = (BoundFieldAccess)assignmentTarget;
if (!left.FieldSymbol.IsStatic)
{
var temp = EmitReceiverRef(left.ReceiverOpt, AddressKind.Writeable);
Debug.Assert(temp == null, "temp is unexpected when assigning to a field");
lhsUsesStack = true;
}
}
break;
case BoundKind.Parameter:
{
var left = (BoundParameter)assignmentTarget;
if (left.ParameterSymbol.RefKind != RefKind.None &&
!assignmentOperator.IsRef)
{
_builder.EmitLoadArgumentOpcode(ParameterSlot(left));
lhsUsesStack = true;
}
}
break;
case BoundKind.Local:
{
var left = (BoundLocal)assignmentTarget;
// Again, consider our earlier case:
//
// ref int addr = ref N().s;
// int sum = addr + 10;
// addr = sum;
//
// There are three different ways we could be assigning to a local.
//
// In the first case, we want to simply call N(), take the address
// of s, and then store that address in addr.
//
// In the second case again we simply want to compute the sum and
// store the result in sum.
//
// In the third case however we want to first load the contents of
// addr -- the address of field s -- then put the sum on the stack,
// and then do an indirect store. In that case we need to have the
// contents of addr on the stack.
if (left.LocalSymbol.RefKind != RefKind.None && !assignmentOperator.IsRef)
{
if (!IsStackLocal(left.LocalSymbol))
{
LocalDefinition localDefinition = GetLocal(left);
_builder.EmitLocalLoad(localDefinition);
}
else
{
// this is a case of indirect assignment to a stack temp.
// currently byref temp can only be a stack local in scenarios where
// there is only one assignment and it is the last one.
// I do not yet know how to support cases where we assign more than once.
// That where Dup of LHS would be needed, but as a general scenario
// it is not always possible to handle. Fortunately all the cases where we
// indirectly assign to a byref temp come from rewriter and all
// they all are write-once cases.
//
// For now analyzer asserts that indirect writes are final reads of
// a ref local. And we never need a dup here.
// builder.EmitOpCode(ILOpCode.Dup);
}
lhsUsesStack = true;
}
}
break;
case BoundKind.ArrayAccess:
{
var left = (BoundArrayAccess)assignmentTarget;
EmitExpression(left.Expression, used: true);
EmitArrayIndices(left.Indices);
lhsUsesStack = true;
}
break;
case BoundKind.ThisReference:
{
var left = (BoundThisReference)assignmentTarget;
var temp = EmitAddress(left, AddressKind.Writeable);
Debug.Assert(temp == null, "taking ref of this should not create a temp");
lhsUsesStack = true;
}
break;
case BoundKind.Dup:
{
var left = (BoundDup)assignmentTarget;
var temp = EmitAddress(left, AddressKind.Writeable);
Debug.Assert(temp == null, "taking ref of Dup should not create a temp");
lhsUsesStack = true;
}
break;
case BoundKind.ConditionalOperator:
{
var left = (BoundConditionalOperator)assignmentTarget;
Debug.Assert(left.IsRef);
var temp = EmitAddress(left, AddressKind.Writeable);
Debug.Assert(temp == null, "taking ref of this should not create a temp");
lhsUsesStack = true;
}
break;
case BoundKind.PointerIndirectionOperator:
{
var left = (BoundPointerIndirectionOperator)assignmentTarget;
EmitExpression(left.Operand, used: true);
lhsUsesStack = true;
}
break;
case BoundKind.Sequence:
{
var sequence = (BoundSequence)assignmentTarget;
// NOTE: not releasing sequence locals right away.
// Since sequence is used as a variable, we will keep the locals for the extent of the containing expression
DefineAndRecordLocals(sequence);
EmitSideEffects(sequence);
lhsUsesStack = EmitAssignmentPreamble(assignmentOperator.Update(sequence.Value, assignmentOperator.Right, assignmentOperator.IsRef, assignmentOperator.Type));
CloseScopeAndKeepLocals(sequence);
}
break;
case BoundKind.Call:
{
var left = (BoundCall)assignmentTarget;
Debug.Assert(left.Method.RefKind != RefKind.None);
EmitCallExpression(left, UseKind.UsedAsAddress);
lhsUsesStack = true;
}
break;
case BoundKind.PropertyAccess:
case BoundKind.IndexerAccess:
// Property access should have been rewritten.
case BoundKind.PreviousSubmissionReference:
// Script references are lowered to a this reference and a field access.
throw ExceptionUtilities.UnexpectedValue(assignmentTarget.Kind);
case BoundKind.PseudoVariable:
EmitPseudoVariableAddress((BoundPseudoVariable)assignmentTarget);
lhsUsesStack = true;
break;
case BoundKind.ModuleVersionId:
case BoundKind.InstrumentationPayloadRoot:
break;
case BoundKind.AssignmentOperator:
var assignment = (BoundAssignmentOperator)assignmentTarget;
if (!assignment.IsRef)
{
goto default;
}
EmitAssignmentExpression(assignment, UseKind.UsedAsAddress);
break;
default:
throw ExceptionUtilities.UnexpectedValue(assignmentTarget.Kind);
}
return lhsUsesStack;
}
private void EmitAssignmentValue(BoundAssignmentOperator assignmentOperator)
{
if (!assignmentOperator.IsRef)
{
EmitExpression(assignmentOperator.Right, used: true);
}
else
{
int exprTempsBefore = _expressionTemps?.Count ?? 0;
BoundExpression lhs = assignmentOperator.Left;
// NOTE: passing "ReadOnlyStrict" here.
// we should not get an address of a copy if at all possible
LocalDefinition temp = EmitAddress(assignmentOperator.Right, lhs.GetRefKind() == RefKind.RefReadOnly ? AddressKind.ReadOnlyStrict : AddressKind.Writeable);
// Generally taking a ref for the purpose of ref assignment should not be done on homeless values
// however, there are very rare cases when we need to get a ref off a temp in synthetic code.
// Retain those temps for the extent of the encompassing expression.
AddExpressionTemp(temp);
var exprTempsAfter = _expressionTemps?.Count ?? 0;
// are we, by the way, ref-assigning to something that lives longer than encompassing expression?
Debug.Assert(lhs.Kind != BoundKind.Parameter || exprTempsAfter <= exprTempsBefore);
if (lhs.Kind == BoundKind.Local && ((BoundLocal)lhs).LocalSymbol.SynthesizedKind.IsLongLived())
{
// This situation is extremely rare. We are assigning a ref to a local with unknown lifetime
// while computing that ref required expression temps.
//
// We cannot reuse any of those temps and must leak them from the retained set.
// Any of them could be directly or indirectly referred by the LHS after the assignment.
// and we do not know the scope of the LHS - could be the whole method.
if (exprTempsAfter > exprTempsBefore)
{
_expressionTemps.Count = exprTempsBefore;
}
}
}
}
private LocalDefinition EmitAssignmentDuplication(BoundAssignmentOperator assignmentOperator, UseKind useKind, bool lhsUsesStack)
{
LocalDefinition temp = null;
if (useKind != UseKind.Unused)
{
_builder.EmitOpCode(ILOpCode.Dup);
if (lhsUsesStack)
{
// Today we sometimes have a case where we assign a ref directly to a temporary of ref type:
//
// ref int addr = ref N().y; <-- copies the address by value; no indirection
// int sum = addr + 10;
// addr = sum;
//
// If we have something like:
//
// ref int t1 = (ref int t2 = ref M().s);
//
// or the even more odd:
//
// int t1 = (ref int t2 = ref M().s);
//
// We need to figure out which of the situations above we are in, and ensure that the
// correct kind of temporary is created here. And also that either its value or its
// indirected value is read out after the store, in EmitAssignmentPostfix, below.
temp = AllocateTemp(
assignmentOperator.Left.Type,
assignmentOperator.Left.Syntax,
assignmentOperator.IsRef ? LocalSlotConstraints.ByRef : LocalSlotConstraints.None);
_builder.EmitLocalStore(temp);
}
}
return temp;
}
private void EmitStore(BoundAssignmentOperator assignment)
{
BoundExpression expression = assignment.Left;
switch (expression.Kind)
{
case BoundKind.FieldAccess:
EmitFieldStore((BoundFieldAccess)expression);
break;
case BoundKind.Local:
// If we are doing a 'normal' local assignment like 'int t = 10;', or
// if we are initializing a temporary like 'ref int t = ref M().s;' then
// we just emit a local store. If we are doing an assignment through
// a ref local temporary then we assume that the instruction to load
// the address is already on the stack, and we must indirect through it.
// See the comments in EmitAssignmentExpression above for details.
BoundLocal local = (BoundLocal)expression;
if (local.LocalSymbol.RefKind != RefKind.None && !assignment.IsRef)
{
EmitIndirectStore(local.LocalSymbol.Type, local.Syntax);
}
else
{
if (IsStackLocal(local.LocalSymbol))
{
// assign to stack var == leave original value on stack
break;
}
else
{
_builder.EmitLocalStore(GetLocal(local));
}
}
break;
case BoundKind.ArrayAccess:
var array = ((BoundArrayAccess)expression).Expression;
var arrayType = (ArrayTypeSymbol)array.Type;
EmitArrayElementStore(arrayType, expression.Syntax);
break;
case BoundKind.ThisReference:
EmitThisStore((BoundThisReference)expression);
break;
case BoundKind.Parameter:
EmitParameterStore((BoundParameter)expression, assignment.IsRef);
break;
case BoundKind.Dup:
Debug.Assert(((BoundDup)expression).RefKind != RefKind.None);
EmitIndirectStore(expression.Type, expression.Syntax);
break;
case BoundKind.ConditionalOperator:
Debug.Assert(((BoundConditionalOperator)expression).IsRef);
EmitIndirectStore(expression.Type, expression.Syntax);
break;
case BoundKind.RefValueOperator:
case BoundKind.PointerIndirectionOperator:
case BoundKind.PseudoVariable:
EmitIndirectStore(expression.Type, expression.Syntax);
break;
case BoundKind.Sequence:
{
var sequence = (BoundSequence)expression;
EmitStore(assignment.Update(sequence.Value, assignment.Right, assignment.IsRef, assignment.Type));
}
break;
case BoundKind.Call:
Debug.Assert(((BoundCall)expression).Method.RefKind != RefKind.None);
EmitIndirectStore(expression.Type, expression.Syntax);
break;
case BoundKind.ModuleVersionId:
EmitModuleVersionIdStore((BoundModuleVersionId)expression);
break;
case BoundKind.InstrumentationPayloadRoot:
EmitInstrumentationPayloadRootStore((BoundInstrumentationPayloadRoot)expression);
break;
case BoundKind.AssignmentOperator:
var nested = (BoundAssignmentOperator)expression;
if (!nested.IsRef)
{
goto default;
}
EmitIndirectStore(nested.Type, expression.Syntax);
break;
case BoundKind.PreviousSubmissionReference:
// Script references are lowered to a this reference and a field access.
default:
throw ExceptionUtilities.UnexpectedValue(expression.Kind);
}
}
private void EmitAssignmentPostfix(BoundAssignmentOperator assignment, LocalDefinition temp, UseKind useKind)
{
if (temp != null)
{
if (useKind == UseKind.UsedAsAddress)
{
_builder.EmitLocalAddress(temp);
}
else
{
_builder.EmitLocalLoad(temp);
}
FreeTemp(temp);
}
if (useKind == UseKind.UsedAsValue && assignment.IsRef)
{
EmitLoadIndirect(assignment.Type, assignment.Syntax);
}
}
private void EmitThisStore(BoundThisReference thisRef)
{
Debug.Assert(thisRef.Type.IsValueType);
_builder.EmitOpCode(ILOpCode.Stobj);
EmitSymbolToken(thisRef.Type, thisRef.Syntax);
}
private void EmitArrayElementStore(ArrayTypeSymbol arrayType, SyntaxNode syntaxNode)
{
if (arrayType.IsSZArray)
{
EmitVectorElementStore(arrayType, syntaxNode);
}
else
{
_builder.EmitArrayElementStore(Emit.PEModuleBuilder.Translate(arrayType), syntaxNode, _diagnostics);
}
}
///
/// Emit an element store instruction for a single dimensional array.
///
private void EmitVectorElementStore(ArrayTypeSymbol arrayType, SyntaxNode syntaxNode)
{
var elementType = arrayType.ElementType;
if (elementType.IsEnumType())
{
//underlying primitives do not need type tokens.
elementType = ((NamedTypeSymbol)elementType).EnumUnderlyingType;
}
switch (elementType.PrimitiveTypeCode)
{
case Microsoft.Cci.PrimitiveTypeCode.Boolean:
case Microsoft.Cci.PrimitiveTypeCode.Int8:
case Microsoft.Cci.PrimitiveTypeCode.UInt8:
_builder.EmitOpCode(ILOpCode.Stelem_i1);
break;
case Microsoft.Cci.PrimitiveTypeCode.Char:
case Microsoft.Cci.PrimitiveTypeCode.Int16:
case Microsoft.Cci.PrimitiveTypeCode.UInt16:
_builder.EmitOpCode(ILOpCode.Stelem_i2);
break;
case Microsoft.Cci.PrimitiveTypeCode.Int32:
case Microsoft.Cci.PrimitiveTypeCode.UInt32:
_builder.EmitOpCode(ILOpCode.Stelem_i4);
break;
case Microsoft.Cci.PrimitiveTypeCode.Int64:
case Microsoft.Cci.PrimitiveTypeCode.UInt64:
_builder.EmitOpCode(ILOpCode.Stelem_i8);
break;
case Microsoft.Cci.PrimitiveTypeCode.IntPtr:
case Microsoft.Cci.PrimitiveTypeCode.UIntPtr:
case Microsoft.Cci.PrimitiveTypeCode.Pointer:
_builder.EmitOpCode(ILOpCode.Stelem_i);
break;
case Microsoft.Cci.PrimitiveTypeCode.Float32:
_builder.EmitOpCode(ILOpCode.Stelem_r4);
break;
case Microsoft.Cci.PrimitiveTypeCode.Float64:
_builder.EmitOpCode(ILOpCode.Stelem_r8);
break;
default:
if (elementType.IsVerifierReference())
{
_builder.EmitOpCode(ILOpCode.Stelem_ref);
}
else
{
_builder.EmitOpCode(ILOpCode.Stelem);
EmitSymbolToken(elementType, syntaxNode);
}
break;
}
}
private void EmitFieldStore(BoundFieldAccess fieldAccess)
{
var field = fieldAccess.FieldSymbol;
if (field.IsVolatile)
{
_builder.EmitOpCode(ILOpCode.Volatile);
}
_builder.EmitOpCode(field.IsStatic ? ILOpCode.Stsfld : ILOpCode.Stfld);
EmitSymbolToken(field, fieldAccess.Syntax);
}
private void EmitParameterStore(BoundParameter parameter, bool refAssign)
{
int slot = ParameterSlot(parameter);
if (parameter.ParameterSymbol.RefKind != RefKind.None && !refAssign)
{
//NOTE: we should have the actual parameter already loaded,
//now need to do a store to where it points to
EmitIndirectStore(parameter.ParameterSymbol.Type, parameter.Syntax);
}
else
{
_builder.EmitStoreArgumentOpcode(slot);
}
}
private void EmitIndirectStore(TypeSymbol type, SyntaxNode syntaxNode)
{
if (type.IsEnumType())
{
//underlying primitives do not need type tokens.
type = ((NamedTypeSymbol)type).EnumUnderlyingType;
}
switch (type.PrimitiveTypeCode)
{
case Microsoft.Cci.PrimitiveTypeCode.Boolean:
case Microsoft.Cci.PrimitiveTypeCode.Int8:
case Microsoft.Cci.PrimitiveTypeCode.UInt8:
_builder.EmitOpCode(ILOpCode.Stind_i1);
break;
case Microsoft.Cci.PrimitiveTypeCode.Char:
case Microsoft.Cci.PrimitiveTypeCode.Int16:
case Microsoft.Cci.PrimitiveTypeCode.UInt16:
_builder.EmitOpCode(ILOpCode.Stind_i2);
break;
case Microsoft.Cci.PrimitiveTypeCode.Int32:
case Microsoft.Cci.PrimitiveTypeCode.UInt32:
_builder.EmitOpCode(ILOpCode.Stind_i4);
break;
case Microsoft.Cci.PrimitiveTypeCode.Int64:
case Microsoft.Cci.PrimitiveTypeCode.UInt64:
_builder.EmitOpCode(ILOpCode.Stind_i8);
break;
case Microsoft.Cci.PrimitiveTypeCode.IntPtr:
case Microsoft.Cci.PrimitiveTypeCode.UIntPtr:
case Microsoft.Cci.PrimitiveTypeCode.Pointer:
_builder.EmitOpCode(ILOpCode.Stind_i);
break;
case Microsoft.Cci.PrimitiveTypeCode.Float32:
_builder.EmitOpCode(ILOpCode.Stind_r4);
break;
case Microsoft.Cci.PrimitiveTypeCode.Float64:
_builder.EmitOpCode(ILOpCode.Stind_r8);
break;
default:
if (type.IsVerifierReference())
{
_builder.EmitOpCode(ILOpCode.Stind_ref);
}
else
{
_builder.EmitOpCode(ILOpCode.Stobj);
EmitSymbolToken(type, syntaxNode);
}
break;
}
}
private void EmitPopIfUnused(bool used)
{
if (!used)
{
_builder.EmitOpCode(ILOpCode.Pop);
}
}
private void EmitIsExpression(BoundIsOperator isOp, bool used)
{
var operand = isOp.Operand;
EmitExpression(operand, used);
if (used)
{
Debug.Assert((object)operand.Type != null);
if (!operand.Type.IsVerifierReference())
{
// box the operand for isinst if it is not a verifier reference
EmitBox(operand.Type, operand.Syntax);
}
_builder.EmitOpCode(ILOpCode.Isinst);
EmitSymbolToken(isOp.TargetType.Type, isOp.Syntax);
_builder.EmitOpCode(ILOpCode.Ldnull);
_builder.EmitOpCode(ILOpCode.Cgt_un);
}
}
private void EmitAsExpression(BoundAsOperator asOp, bool used)
{
Debug.Assert(!asOp.Conversion.Kind.IsImplicitConversion());
var operand = asOp.Operand;
EmitExpression(operand, used);
if (used)
{
var operandType = operand.Type;
var targetType = asOp.Type;
Debug.Assert((object)targetType != null);
if ((object)operandType != null && !operandType.IsVerifierReference())
{
// box the operand for isinst if it is not a verifier reference
EmitBox(operandType, operand.Syntax);
}
_builder.EmitOpCode(ILOpCode.Isinst);
EmitSymbolToken(targetType, asOp.Syntax);
if (!targetType.IsVerifierReference())
{
// We need to unbox if the target type is not a reference type
_builder.EmitOpCode(ILOpCode.Unbox_any);
EmitSymbolToken(targetType, asOp.Syntax);
}
}
}
private void EmitDefaultValue(TypeSymbol type, bool used, SyntaxNode syntaxNode)
{
if (used)
{
// default type parameter values must be emitted as 'initobj' regardless of constraints
if (!type.IsTypeParameter() && type.SpecialType != SpecialType.System_Decimal)
{
var constantValue = type.GetDefaultValue();
if (constantValue != null)
{
_builder.EmitConstantValue(constantValue);
return;
}
}
if (type.IsPointerType() || type.SpecialType == SpecialType.System_UIntPtr)
{
// default(whatever*) and default(UIntPtr) can be emitted as:
_builder.EmitOpCode(ILOpCode.Ldc_i4_0);
_builder.EmitOpCode(ILOpCode.Conv_u);
}
else if (type.SpecialType == SpecialType.System_IntPtr)
{
_builder.EmitOpCode(ILOpCode.Ldc_i4_0);
_builder.EmitOpCode(ILOpCode.Conv_i);
}
else
{
EmitInitObj(type, true, syntaxNode);
}
}
}
private void EmitDefaultExpression(BoundDefaultExpression expression, bool used)
{
Debug.Assert(expression.Type.SpecialType == SpecialType.System_Decimal ||
expression.Type.GetDefaultValue() == null, "constant should be set on this expression");
// Default value for the given default expression is not a constant
// Expression must be of type parameter type or a non-primitive value type
// Emit an initobj instruction for these cases
EmitDefaultValue(expression.Type, used, expression.Syntax);
}
private void EmitConstantExpression(TypeSymbol type, ConstantValue constantValue, bool used, SyntaxNode syntaxNode)
{
if (used) // unused constant has no side-effects
{
// Null type parameter values must be emitted as 'initobj' rather than 'ldnull'.
if (((object)type != null) && (type.TypeKind == TypeKind.TypeParameter) && constantValue.IsNull)
{
EmitInitObj(type, used, syntaxNode);
}
else
{
_builder.EmitConstantValue(constantValue);
}
}
}
private void EmitInitObj(TypeSymbol type, bool used, SyntaxNode syntaxNode)
{
if (used)
{
var temp = this.AllocateTemp(type, syntaxNode);
_builder.EmitLocalAddress(temp); // ldloca temp
_builder.EmitOpCode(ILOpCode.Initobj); // initobj
EmitSymbolToken(type, syntaxNode);
_builder.EmitLocalLoad(temp); // ldloc temp
FreeTemp(temp);
}
}
private void EmitGetTypeFromHandle(BoundTypeOf boundTypeOf)
{
_builder.EmitOpCode(ILOpCode.Call, stackAdjustment: 0); //argument off, return value on
var getTypeMethod = boundTypeOf.GetTypeFromHandle;
Debug.Assert((object)getTypeMethod != null); // Should have been checked during binding
EmitSymbolToken(getTypeMethod, boundTypeOf.Syntax, null);
}
private void EmitTypeOfExpression(BoundTypeOfOperator boundTypeOfOperator)
{
TypeSymbol type = boundTypeOfOperator.SourceType.Type;
_builder.EmitOpCode(ILOpCode.Ldtoken);
EmitSymbolToken(type, boundTypeOfOperator.SourceType.Syntax);
EmitGetTypeFromHandle(boundTypeOfOperator);
}
private void EmitSizeOfExpression(BoundSizeOfOperator boundSizeOfOperator)
{
TypeSymbol type = boundSizeOfOperator.SourceType.Type;
_builder.EmitOpCode(ILOpCode.Sizeof);
EmitSymbolToken(type, boundSizeOfOperator.SourceType.Syntax);
}
private void EmitMethodDefIndexExpression(BoundMethodDefIndex node)
{
Debug.Assert(node.Method.IsDefinition);
Debug.Assert(node.Type.SpecialType == SpecialType.System_Int32);
_builder.EmitOpCode(ILOpCode.Ldtoken);
// For partial methods, we emit pseudo token based on the symbol for the partial
// definition part as opposed to the symbol for the partial implementation part.
// We will need to resolve the symbol associated with each pseudo token in order
// to compute the real method definition tokens later. For partial methods, this
// resolution can only succeed if the associated symbol is the symbol for the
// partial definition and not the symbol for the partial implementation (see
// MethodSymbol.ResolvedMethodImpl()).
var symbol = node.Method.PartialDefinitionPart ?? node.Method;
EmitSymbolToken(symbol, node.Syntax, null, encodeAsRawDefinitionToken: true);
}
private void EmitMaximumMethodDefIndexExpression(BoundMaximumMethodDefIndex node)
{
Debug.Assert(node.Type.SpecialType == SpecialType.System_Int32);
_builder.EmitOpCode(ILOpCode.Ldtoken);
_builder.EmitGreatestMethodToken();
}
private void EmitModuleVersionIdLoad(BoundModuleVersionId node)
{
_builder.EmitOpCode(ILOpCode.Ldsfld);
EmitModuleVersionIdToken(node);
}
private void EmitModuleVersionIdStore(BoundModuleVersionId node)
{
_builder.EmitOpCode(ILOpCode.Stsfld);
EmitModuleVersionIdToken(node);
}
private void EmitModuleVersionIdToken(BoundModuleVersionId node)
{
_builder.EmitToken(_module.GetModuleVersionId(_module.Translate(node.Type, node.Syntax, _diagnostics), node.Syntax, _diagnostics), node.Syntax, _diagnostics);
}
private void EmitModuleVersionIdStringLoad(BoundModuleVersionIdString node)
{
_builder.EmitOpCode(ILOpCode.Ldstr);
_builder.EmitModuleVersionIdStringToken();
}
private void EmitInstrumentationPayloadRootLoad(BoundInstrumentationPayloadRoot node)
{
_builder.EmitOpCode(ILOpCode.Ldsfld);
EmitInstrumentationPayloadRootToken(node);
}
private void EmitInstrumentationPayloadRootStore(BoundInstrumentationPayloadRoot node)
{
_builder.EmitOpCode(ILOpCode.Stsfld);
EmitInstrumentationPayloadRootToken(node);
}
private void EmitInstrumentationPayloadRootToken(BoundInstrumentationPayloadRoot node)
{
_builder.EmitToken(_module.GetInstrumentationPayloadRoot(node.AnalysisKind, _module.Translate(node.Type, node.Syntax, _diagnostics), node.Syntax, _diagnostics), node.Syntax, _diagnostics);
}
private void EmitSourceDocumentIndex(BoundSourceDocumentIndex node)
{
Debug.Assert(node.Type.SpecialType == SpecialType.System_Int32);
_builder.EmitOpCode(ILOpCode.Ldtoken);
_builder.EmitSourceDocumentIndexToken(node.Document);
}
private void EmitMethodInfoExpression(BoundMethodInfo node)
{
_builder.EmitOpCode(ILOpCode.Ldtoken);
EmitSymbolToken(node.Method, node.Syntax, null);
MethodSymbol getMethod = node.GetMethodFromHandle;
Debug.Assert((object)getMethod != null);
if (getMethod.ParameterCount == 1)
{
_builder.EmitOpCode(ILOpCode.Call, stackAdjustment: 0); //argument off, return value on
}
else
{
Debug.Assert(getMethod.ParameterCount == 2);
_builder.EmitOpCode(ILOpCode.Ldtoken);
EmitSymbolToken(node.Method.ContainingType, node.Syntax);
_builder.EmitOpCode(ILOpCode.Call, stackAdjustment: -1); //2 arguments off, return value on
}
EmitSymbolToken(getMethod, node.Syntax, null);
if (!TypeSymbol.Equals(node.Type, getMethod.ReturnType, TypeCompareKind.ConsiderEverything2))
{
_builder.EmitOpCode(ILOpCode.Castclass);
EmitSymbolToken(node.Type, node.Syntax);
}
}
private void EmitFieldInfoExpression(BoundFieldInfo node)
{
_builder.EmitOpCode(ILOpCode.Ldtoken);
EmitSymbolToken(node.Field, node.Syntax);
MethodSymbol getField = node.GetFieldFromHandle;
Debug.Assert((object)getField != null);
if (getField.ParameterCount == 1)
{
_builder.EmitOpCode(ILOpCode.Call, stackAdjustment: 0); //argument off, return value on
}
else
{
Debug.Assert(getField.ParameterCount == 2);
_builder.EmitOpCode(ILOpCode.Ldtoken);
EmitSymbolToken(node.Field.ContainingType, node.Syntax);
_builder.EmitOpCode(ILOpCode.Call, stackAdjustment: -1); //2 arguments off, return value on
}
EmitSymbolToken(getField, node.Syntax, null);
if (!TypeSymbol.Equals(node.Type, getField.ReturnType, TypeCompareKind.ConsiderEverything2))
{
_builder.EmitOpCode(ILOpCode.Castclass);
EmitSymbolToken(node.Type, node.Syntax);
}
}
///
/// Emit code for a conditional (aka ternary) operator.
///
///
/// (b ? x : y) becomes
/// push b
/// if pop then goto CONSEQUENCE
/// push y
/// goto DONE
/// CONSEQUENCE:
/// push x
/// DONE:
///
private void EmitConditionalOperator(BoundConditionalOperator expr, bool used)
{
Debug.Assert(expr.ConstantValue == null, "Constant value should have been emitted directly");
object consequenceLabel = new object();
object doneLabel = new object();
EmitCondBranch(expr.Condition, ref consequenceLabel, sense: true);
EmitExpression(expr.Alternative, used);
//
// III.1.8.1.3 Merging stack states
// . . .
// Let T be the type from the slot on the newly computed state and S
// be the type from the corresponding slot on the previously stored state. The merged type, U, shall
// be computed as follows (recall that S := T is the compatibility function defined
// in §III.1.8.1.2.2):
// 1. if S := T then U=S
// 2. Otherwise, if T := S then U=T
// 3. Otherwise, if S and T are both object types, then let V be the closest common supertype of S and T then U=V.
// 4. Otherwise, the merge shall fail.
//
// When the target merge type is an interface that one or more classes implement, we emit static casts
// from any class to the target interface.
// You may think that it's possible to elide one of the static casts and have the CLR recognize
// that merging a class and interface should succeed if the class implements the interface. Unfortunately,
// it seems that either PEVerify or the runtime/JIT verifier will complain at you if you try to remove
// either of the casts.
//
var mergeTypeOfAlternative = StackMergeType(expr.Alternative);
if (used)
{
if (IsVarianceCast(expr.Type, mergeTypeOfAlternative))
{
EmitStaticCast(expr.Type, expr.Syntax);
mergeTypeOfAlternative = expr.Type;
}
else if (expr.Type.IsInterfaceType() && !TypeSymbol.Equals(expr.Type, mergeTypeOfAlternative, TypeCompareKind.ConsiderEverything2))
{
EmitStaticCast(expr.Type, expr.Syntax);
}
}
_builder.EmitBranch(ILOpCode.Br, doneLabel);
if (used)
{
// If we get to consequenceLabel, we should not have Alternative on stack, adjust for that.
_builder.AdjustStack(-1);
}
_builder.MarkLabel(consequenceLabel);
EmitExpression(expr.Consequence, used);
if (used)
{
var mergeTypeOfConsequence = StackMergeType(expr.Consequence);
if (IsVarianceCast(expr.Type, mergeTypeOfConsequence))
{
EmitStaticCast(expr.Type, expr.Syntax);
mergeTypeOfConsequence = expr.Type;
}
else if (expr.Type.IsInterfaceType() && !TypeSymbol.Equals(expr.Type, mergeTypeOfConsequence, TypeCompareKind.ConsiderEverything2))
{
EmitStaticCast(expr.Type, expr.Syntax);
}
}
_builder.MarkLabel(doneLabel);
}
///
/// Emit code for a null-coalescing operator.
///
///
/// x ?? y becomes
/// push x
/// dup x
/// if pop != null goto LEFT_NOT_NULL
/// pop
/// push y
/// LEFT_NOT_NULL:
///
private void EmitNullCoalescingOperator(BoundNullCoalescingOperator expr, bool used)
{
Debug.Assert(expr.LeftConversion.IsIdentity, "coalesce with nontrivial left conversions are lowered into conditional.");
Debug.Assert(expr.Type.IsReferenceType);
EmitExpression(expr.LeftOperand, used: true);
// See the notes about verification type merges in EmitConditionalOperator
var mergeTypeOfLeftValue = StackMergeType(expr.LeftOperand);
if (used)
{
if (IsVarianceCast(expr.Type, mergeTypeOfLeftValue))
{
EmitStaticCast(expr.Type, expr.Syntax);
mergeTypeOfLeftValue = expr.Type;
}
else if (expr.Type.IsInterfaceType() && !TypeSymbol.Equals(expr.Type, mergeTypeOfLeftValue, TypeCompareKind.ConsiderEverything2))
{
EmitStaticCast(expr.Type, expr.Syntax);
}
_builder.EmitOpCode(ILOpCode.Dup);
}
if (expr.Type.IsTypeParameter())
{
EmitBox(expr.Type, expr.LeftOperand.Syntax);
}
object ifLeftNotNullLabel = new object();
_builder.EmitBranch(ILOpCode.Brtrue, ifLeftNotNullLabel);
if (used)
{
_builder.EmitOpCode(ILOpCode.Pop);
}
EmitExpression(expr.RightOperand, used);
if (used)
{
var mergeTypeOfRightValue = StackMergeType(expr.RightOperand);
if (IsVarianceCast(expr.Type, mergeTypeOfRightValue))
{
EmitStaticCast(expr.Type, expr.Syntax);
mergeTypeOfRightValue = expr.Type;
}
}
_builder.MarkLabel(ifLeftNotNullLabel);
}
// Implicit casts are not emitted. As a result verifier may operate on a different
// types from the types of operands when performing stack merges in coalesce/conditional.
// Such differences are in general irrelevant since merging rules work the same way
// for base and derived types.
//
// Situation becomes more complicated with delegates, arrays and interfaces since they
// allow implicit casts from types that do not derive from them. In such cases
// we may need to introduce static casts in the code to prod the verifier to the
// right direction
//
// This helper returns actual type of array|interface|delegate expression ignoring implicit
// casts. This would be the effective stack merge type in the verifier.
//
// NOTE: In cases where stack merge type cannot be determined, we just return null.
// We still must assume that it can be an array, delegate or interface though.
private TypeSymbol StackMergeType(BoundExpression expr)
{
// these cases are not interesting. Merge type is the same or derived. No difference.
if (!(expr.Type.IsInterfaceType() || expr.Type.IsDelegateType()))
{
return expr.Type;
}
// Dig through casts. We only need to check for expressions that -
// 1) implicit casts
// 2) transparently return operands, so we need to dig deeper
// 3) stack values
switch (expr.Kind)
{
case BoundKind.Conversion:
var conversion = (BoundConversion)expr;
var conversionKind = conversion.ConversionKind;
Debug.Assert(conversionKind != ConversionKind.NullLiteral && conversionKind != ConversionKind.DefaultLiteral);
if (conversionKind.IsImplicitConversion() &&
conversionKind != ConversionKind.MethodGroup &&
conversionKind != ConversionKind.NullLiteral &&
conversionKind != ConversionKind.DefaultLiteral)
{
return StackMergeType(conversion.Operand);
}
break;
case BoundKind.AssignmentOperator:
var assignment = (BoundAssignmentOperator)expr;
return StackMergeType(assignment.Right);
case BoundKind.Sequence:
var sequence = (BoundSequence)expr;
return StackMergeType(sequence.Value);
case BoundKind.Local:
var local = (BoundLocal)expr;
if (this.IsStackLocal(local.LocalSymbol))
{
// stack value, we cannot be sure what it is
return null;
}
break;
case BoundKind.Dup:
// stack value, we cannot be sure what it is
return null;
}
return expr.Type;
}
// Although III.1.8.1.3 seems to imply that verifier understands variance casts.
// It appears that verifier/JIT gets easily confused.
// So to not rely on whether that should work or not we will flag potentially
// "complicated" casts and make them static casts to ensure we are all on
// the same page with what type should be tracked.
private static bool IsVarianceCast(TypeSymbol to, TypeSymbol from)
{
if (TypeSymbol.Equals(to, from, TypeCompareKind.ConsiderEverything2))
{
return false;
}
if ((object)from == null)
{
// from unknown type - this could be a variance conversion.
return true;
}
// while technically variance casts, array conversions do not seem to be a problem
// unless the element types are converted via variance.
if (to.IsArray())
{
return IsVarianceCast(((ArrayTypeSymbol)to).ElementType, ((ArrayTypeSymbol)from).ElementType);
}
return (to.IsDelegateType() && !TypeSymbol.Equals(to, from, TypeCompareKind.ConsiderEverything2)) ||
(to.IsInterfaceType() && from.IsInterfaceType() && !from.InterfacesAndTheirBaseInterfacesNoUseSiteDiagnostics.ContainsKey((NamedTypeSymbol)to));
}
private void EmitStaticCast(TypeSymbol to, SyntaxNode syntax)
{
Debug.Assert(to.IsVerifierReference());
// From ILGENREC::GenQMark
// See VSWhidbey Bugs #49619 and 108643. If the destination type is an interface we need
// to force a static cast to be generated for any cast result expressions. The static cast
// should be done before the unifying jump so the code is verifiable and to allow the JIT to
// optimize it away. NOTE: Since there is no staticcast instruction, we implement static cast
// with a stloc / ldloc to a temporary.
// Bug: VSWhidbey/49619
// Bug: VSWhidbey/108643
// Bug: Devdiv/42645
var temp = AllocateTemp(to, syntax);
_builder.EmitLocalStore(temp);
_builder.EmitLocalLoad(temp);
FreeTemp(temp);
}
private void EmitBox(TypeSymbol type, SyntaxNode syntaxNode)
{
Debug.Assert(!type.IsRefLikeType);
_builder.EmitOpCode(ILOpCode.Box);
EmitSymbolToken(type, syntaxNode);
}
}
}