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merged 2 commits into from
Feb 6, 2024
Merged

Place vtable slots deemed final by analysis into sealed vtable #97951

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a5b2c10
Place vtable slots deemed final by analysis into sealed vtable
MichalStrehovsky Feb 4, 2024
2c3cf8d
Tweak to CanMethodBeInSealedVTable
MichalStrehovsky Feb 5, 2024
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45 changes: 34 additions & 11 deletions src/coreclr/tools/Common/Compiler/MethodExtensions.cs
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@@ -1,9 +1,13 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using ILCompiler.DependencyAnalysis;

using Internal.TypeSystem;
using Internal.TypeSystem.Ecma;

using Debug = System.Diagnostics.Debug;

namespace ILCompiler
{
public static class MethodExtensions
Expand Down Expand Up @@ -73,6 +77,7 @@ public static string GetUnmanagedCallersOnlyExportName(this EcmaMethod This)
return null;
}

#if !READYTORUN
/// <summary>
/// Determine whether a method can go into the sealed vtable of a type. Such method must be a sealed virtual
/// method that is not overriding any method on a base type.
Expand All @@ -82,25 +87,43 @@ public static string GetUnmanagedCallersOnlyExportName(this EcmaMethod This)
/// since all of their collection interface methods are sealed and implemented on the System.Array and
/// System.Array&lt;T&gt; base types, and therefore we can minimize the vtable sizes of all derived array types.
/// </summary>
public static bool CanMethodBeInSealedVTable(this MethodDesc method)
public static bool CanMethodBeInSealedVTable(this MethodDesc method, NodeFactory factory)
{
bool isInterfaceMethod = method.OwningType.IsInterface;
Debug.Assert(!method.OwningType.ContainsSignatureVariables(treatGenericParameterLikeSignatureVariable: true));

TypeDesc owningType = method.OwningType;

// Methods on interfaces never go into sealed vtable
// We would hit this code path for default implementations of interface methods (they are newslot+final).
// Interface types don't get physical slots, but they have logical slot numbers and that logic shouldn't
// attempt to place final+newslot methods differently.
if (method.IsFinal && method.IsNewSlot && !isInterfaceMethod)
// Interface types don't have physical slots so we never optimize to sealed slots
if (owningType.IsInterface)
return false;

// Implementations of static virtual methods go into the sealed vtable.
if (method.Signature.IsStatic)
return true;

// Implementations of static virtual method also go into the sealed vtable.
// Again, we don't let that happen for interface methods because the slot numbers are only logical,
// not physical.
if (method.Signature.IsStatic && !isInterfaceMethod)
// If the owning type is already considered sealed, there's little benefit in placing the slots
// in the sealed vtable: the sealed vtable has these properties:
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@jkotas jkotas Feb 5, 2024

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What are the downsides of keeping this simple and placing them in the sealed vtable? Are you trying to save the extra pointer to the sealed vtable?

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@MichalStrehovsky MichalStrehovsky Feb 5, 2024

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Yep, the extra pointer to the vtable. The old logic was just method.IsFinal && method.IsNewSlot so we didn't even look whether the type is sealed. Now we end up doing this for a lot more methods, often on valuetypes where it makes little sense.

//
// 1. We don't need to repeat them in derived classes.
// 2. The slots use 4-byte relative pointers, so they can be smaller.
// 3. The sealed vtable is shared among canonically-equivalent types.
//
// Benefit 1 doesn't apply to sealed types by definition. Benefit 2 doesn't manifest itself
// when data dehydration is enabled (which is the default) since pointers are compressed either way.
// Benefit 3 is still real, so we condition this opt out on type not having a canonical form.
if (factory.DevirtualizationManager.IsEffectivelySealed(owningType)
&& !owningType.ConvertToCanonForm(CanonicalFormKind.Specific).IsCanonicalSubtype(CanonicalFormKind.Any))
{
return false;
}

// Newslot final methods go into the sealed vtable.
if (method.IsNewSlot && factory.DevirtualizationManager.IsEffectivelySealed(method))
return true;

return false;
}
#endif

public static bool NotCallableWithoutOwningEEType(this MethodDesc method)
{
Expand Down
2 changes: 1 addition & 1 deletion src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/Compilation.cs
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Expand Up @@ -113,7 +113,7 @@ public DelegateCreationInfo GetDelegateCtor(TypeDesc delegateType, MethodDesc ta
// If we're creating a delegate to a virtual method that cannot be overridden, devirtualize.
// This is not just an optimization - it's required for correctness in the presence of sealed
// vtable slots.
if (followVirtualDispatch && (target.IsFinal || target.OwningType.IsSealed()))
if (followVirtualDispatch && NodeFactory.DevirtualizationManager.IsEffectivelySealed(target))
followVirtualDispatch = false;

if (followVirtualDispatch)
Expand Down
4 changes: 2 additions & 2 deletions src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/EETypeNode.cs
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Expand Up @@ -407,7 +407,7 @@ public sealed override IEnumerable<CombinedDependencyListEntry> GetConditionalSt
// We don't do this if the method can be placed in the sealed vtable since
// those can never be overriden by children anyway.
bool canUseTentativeMethod = isNonInterfaceAbstractType
&& !decl.CanMethodBeInSealedVTable()
&& !decl.CanMethodBeInSealedVTable(factory)
&& factory.CompilationModuleGroup.AllowVirtualMethodOnAbstractTypeOptimization(canonImpl);
IMethodNode implNode = canUseTentativeMethod ?
factory.TentativeMethodEntrypoint(canonImpl, impl.OwningType.IsValueType) :
Expand Down Expand Up @@ -1039,7 +1039,7 @@ private void OutputVirtualSlots(NodeFactory factory, ref ObjectDataBuilder objDa

// Final NewSlot methods cannot be overridden, and therefore can be placed in the sealed-vtable to reduce the size of the vtable
// of this type and any type that inherits from it.
if (declMethod.CanMethodBeInSealedVTable() && !declType.IsArrayTypeWithoutGenericInterfaces())
if (declMethod.CanMethodBeInSealedVTable(factory) && !declType.IsArrayTypeWithoutGenericInterfaces())
continue;

bool shouldEmitImpl = !implMethod.IsAbstract;
Expand Down
2 changes: 1 addition & 1 deletion ...reclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/NativeLayoutVertexNode.cs
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Expand Up @@ -1433,7 +1433,7 @@ private static void ProcessVTableEntriesForCallingConventionSignatureGeneration(

MethodDesc implMethod = closestDefType.FindVirtualFunctionTargetMethodOnObjectType(declMethod);

if (implMethod.CanMethodBeInSealedVTable() && !implType.IsArrayTypeWithoutGenericInterfaces())
if (implMethod.CanMethodBeInSealedVTable(factory) && !implType.IsArrayTypeWithoutGenericInterfaces())
{
// Sealed vtable entries on other types in the hierarchy should not be reported (types read entries
// from their own sealed vtables, and not from the sealed vtables of base types).
Expand Down
2 changes: 1 addition & 1 deletion src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ReflectedMethodNode.cs
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Expand Up @@ -68,7 +68,7 @@ public override IEnumerable<DependencyListEntry> GetStaticDependencies(NodeFacto
}
else
{
if (ReflectionVirtualInvokeMapNode.NeedsVirtualInvokeInfo(slotDefiningMethod) && !factory.VTable(slotDefiningMethod.OwningType).HasFixedSlots)
if (ReflectionVirtualInvokeMapNode.NeedsVirtualInvokeInfo(factory, slotDefiningMethod) && !factory.VTable(slotDefiningMethod.OwningType).HasFixedSlots)
dependencies.Add(factory.VirtualMethodUse(slotDefiningMethod), "Virtually callable reflectable method");
}
}
Expand Down
2 changes: 1 addition & 1 deletion ...eclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ReflectionInvokeMapNode.cs
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Expand Up @@ -156,7 +156,7 @@ public override ObjectData GetData(NodeFactory factory, bool relocsOnly = false)
if (method.IsDefaultConstructor)
flags |= InvokeTableFlags.IsDefaultConstructor;

if (ReflectionVirtualInvokeMapNode.NeedsVirtualInvokeInfo(method))
if (ReflectionVirtualInvokeMapNode.NeedsVirtualInvokeInfo(factory, method))
flags |= InvokeTableFlags.HasVirtualInvoke;

if (!method.IsAbstract)
Expand Down
11 changes: 4 additions & 7 deletions ...ols/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ReflectionVirtualInvokeMapNode.cs
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Expand Up @@ -39,15 +39,12 @@ public void AppendMangledName(NameMangler nameMangler, Utf8StringBuilder sb)
public override bool StaticDependenciesAreComputed => true;
protected override string GetName(NodeFactory factory) => this.GetMangledName(factory.NameMangler);

public static bool NeedsVirtualInvokeInfo(MethodDesc method)
public static bool NeedsVirtualInvokeInfo(NodeFactory factory, MethodDesc method)
{
if (!method.IsVirtual)
return false;

if (method.IsFinal)
return false;

if (method.OwningType.IsSealed())
if (factory.DevirtualizationManager.IsEffectivelySealed(method))
return false;

return true;
Expand Down Expand Up @@ -83,7 +80,7 @@ public static MethodDesc GetDeclaringVirtualMethodAndHierarchyDistance(MethodDes

public static void GetVirtualInvokeMapDependencies(ref DependencyList dependencies, NodeFactory factory, MethodDesc method)
{
if (NeedsVirtualInvokeInfo(method))
if (NeedsVirtualInvokeInfo(factory, method))
{
dependencies ??= new DependencyList();

Expand Down Expand Up @@ -137,7 +134,7 @@ public override ObjectData GetData(NodeFactory factory, bool relocsOnly = false)
continue;

// Only virtual methods are interesting
if (!NeedsVirtualInvokeInfo(method))
if (!NeedsVirtualInvokeInfo(factory, method))
continue;

//
Expand Down
8 changes: 4 additions & 4 deletions src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/SealedVTableNode.cs
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Expand Up @@ -125,7 +125,7 @@ public bool BuildSealedVTableSlots(NodeFactory factory, bool relocsOnly)

MethodDesc implMethod = declType.FindVirtualFunctionTargetMethodOnObjectType(virtualSlots[i]);

if (implMethod.CanMethodBeInSealedVTable())
if (implMethod.CanMethodBeInSealedVTable(factory))
_sealedVTableEntries.Add(SealedVTableEntry.FromVirtualMethod(implMethod));
}

Expand Down Expand Up @@ -162,8 +162,7 @@ public bool BuildSealedVTableSlots(NodeFactory factory, bool relocsOnly)
// dispatch will walk the inheritance chain).
if (implMethod != null)
{
if (implMethod.Signature.IsStatic ||
(implMethod.CanMethodBeInSealedVTable() && !implMethod.OwningType.HasSameTypeDefinition(declType)))
if (implMethod.Signature.IsStatic || !implMethod.OwningType.HasSameTypeDefinition(declType))
{
TypeDesc implType = declType;
while (!implType.HasSameTypeDefinition(implMethod.OwningType))
Expand All @@ -173,7 +172,8 @@ public bool BuildSealedVTableSlots(NodeFactory factory, bool relocsOnly)
if (!implType.IsTypeDefinition)
targetMethod = factory.TypeSystemContext.GetMethodForInstantiatedType(implMethod.GetTypicalMethodDefinition(), (InstantiatedType)implType);

_sealedVTableEntries.Add(SealedVTableEntry.FromVirtualMethod(targetMethod));
if (targetMethod.CanMethodBeInSealedVTable(factory) || implMethod.Signature.IsStatic)
_sealedVTableEntries.Add(SealedVTableEntry.FromVirtualMethod(targetMethod));
}
}
else
Expand Down
6 changes: 3 additions & 3 deletions ...aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_ARM/ARMReadyToRunHelperNode.cs
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Expand Up @@ -22,7 +22,7 @@ protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bo
MethodDesc targetMethod = (MethodDesc)Target;

Debug.Assert(!targetMethod.OwningType.IsInterface);
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable(factory));

int pointerSize = factory.Target.PointerSize;

Expand Down Expand Up @@ -126,7 +126,7 @@ protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bo

if (target.TargetNeedsVTableLookup)
{
Debug.Assert(!target.TargetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!target.TargetMethod.CanMethodBeInSealedVTable(factory));

encoder.EmitLDR(encoder.TargetRegister.Arg2, encoder.TargetRegister.Arg1);

Expand Down Expand Up @@ -175,7 +175,7 @@ protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bo

encoder.EmitLDR(encoder.TargetRegister.Result, encoder.TargetRegister.Arg0);

Debug.Assert(!targetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable(factory));

int slot = VirtualMethodSlotHelper.GetVirtualMethodSlot(factory, targetMethod, targetMethod.OwningType);
Debug.Assert(slot != -1);
Expand Down
6 changes: 3 additions & 3 deletions ...ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_ARM64/ARM64ReadyToRunHelperNode.cs
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Expand Up @@ -23,7 +23,7 @@ protected override void EmitCode(NodeFactory factory, ref ARM64Emitter encoder,
MethodDesc targetMethod = (MethodDesc)Target;

Debug.Assert(!targetMethod.OwningType.IsInterface);
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable(factory));

int pointerSize = factory.Target.PointerSize;

Expand Down Expand Up @@ -161,7 +161,7 @@ protected override void EmitCode(NodeFactory factory, ref ARM64Emitter encoder,

if (target.TargetNeedsVTableLookup)
{
Debug.Assert(!target.TargetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!target.TargetMethod.CanMethodBeInSealedVTable(factory));

encoder.EmitLDR(encoder.TargetRegister.Arg2, encoder.TargetRegister.Arg1);

Expand Down Expand Up @@ -210,7 +210,7 @@ protected override void EmitCode(NodeFactory factory, ref ARM64Emitter encoder,

encoder.EmitLDR(encoder.TargetRegister.Result, encoder.TargetRegister.Arg0);

Debug.Assert(!targetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable(factory));

int slot = VirtualMethodSlotHelper.GetVirtualMethodSlot(factory, targetMethod, targetMethod.OwningType);
Debug.Assert(slot != -1);
Expand Down
6 changes: 3 additions & 3 deletions ...ompiler/Compiler/DependencyAnalysis/Target_LoongArch64/LoongArch64ReadyToRunHelperNode.cs
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Expand Up @@ -23,7 +23,7 @@ protected override void EmitCode(NodeFactory factory, ref LoongArch64Emitter enc
MethodDesc targetMethod = (MethodDesc)Target;

Debug.Assert(!targetMethod.OwningType.IsInterface);
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable(factory));

int pointerSize = factory.Target.PointerSize;

Expand Down Expand Up @@ -133,7 +133,7 @@ protected override void EmitCode(NodeFactory factory, ref LoongArch64Emitter enc

if (target.TargetNeedsVTableLookup)
{
Debug.Assert(!target.TargetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!target.TargetMethod.CanMethodBeInSealedVTable(factory));

encoder.EmitLD(encoder.TargetRegister.Arg2, encoder.TargetRegister.Arg1, 0);

Expand Down Expand Up @@ -182,7 +182,7 @@ protected override void EmitCode(NodeFactory factory, ref LoongArch64Emitter enc

encoder.EmitLD(encoder.TargetRegister.Result, encoder.TargetRegister.Arg0, 0);

Debug.Assert(!targetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable(factory));

int slot = VirtualMethodSlotHelper.GetVirtualMethodSlot(factory, targetMethod, targetMethod.OwningType);
Debug.Assert(slot != -1);
Expand Down
6 changes: 3 additions & 3 deletions ...mpiler.Compiler/Compiler/DependencyAnalysis/Target_RiscV64/RiscV64ReadyToRunHelperNode.cs
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Expand Up @@ -23,7 +23,7 @@ protected override void EmitCode(NodeFactory factory, ref RiscV64Emitter encoder
MethodDesc targetMethod = (MethodDesc)Target;

Debug.Assert(!targetMethod.OwningType.IsInterface);
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable(factory));

int pointerSize = factory.Target.PointerSize;

Expand Down Expand Up @@ -130,7 +130,7 @@ protected override void EmitCode(NodeFactory factory, ref RiscV64Emitter encoder

if (target.TargetNeedsVTableLookup)
{
Debug.Assert(!target.TargetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!target.TargetMethod.CanMethodBeInSealedVTable(factory));

encoder.EmitLD(encoder.TargetRegister.Arg2, encoder.TargetRegister.Arg1, 0);

Expand Down Expand Up @@ -179,7 +179,7 @@ protected override void EmitCode(NodeFactory factory, ref RiscV64Emitter encoder

encoder.EmitLD(encoder.TargetRegister.Result, encoder.TargetRegister.Arg0, 0);

Debug.Assert(!targetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable(factory));

int slot = VirtualMethodSlotHelper.GetVirtualMethodSlot(factory, targetMethod, targetMethod.OwningType);
Debug.Assert(slot != -1);
Expand Down
6 changes: 3 additions & 3 deletions ...aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_X64/X64ReadyToRunHelperNode.cs
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Expand Up @@ -23,7 +23,7 @@ protected override void EmitCode(NodeFactory factory, ref X64Emitter encoder, bo
MethodDesc targetMethod = (MethodDesc)Target;

Debug.Assert(!targetMethod.OwningType.IsInterface);
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable(factory));

AddrMode loadFromThisPtr = new AddrMode(encoder.TargetRegister.Arg0, null, 0, 0, AddrModeSize.Int64);
encoder.EmitMOV(encoder.TargetRegister.Result, ref loadFromThisPtr);
Expand Down Expand Up @@ -162,7 +162,7 @@ protected override void EmitCode(NodeFactory factory, ref X64Emitter encoder, bo

if (target.TargetNeedsVTableLookup)
{
Debug.Assert(!target.TargetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!target.TargetMethod.CanMethodBeInSealedVTable(factory));

AddrMode loadFromThisPtr = new AddrMode(encoder.TargetRegister.Arg1, null, 0, 0, AddrModeSize.Int64);
encoder.EmitMOV(encoder.TargetRegister.Arg2, ref loadFromThisPtr);
Expand Down Expand Up @@ -210,7 +210,7 @@ protected override void EmitCode(NodeFactory factory, ref X64Emitter encoder, bo
AddrMode loadFromThisPtr = new AddrMode(encoder.TargetRegister.Arg0, null, 0, 0, AddrModeSize.Int64);
encoder.EmitMOV(encoder.TargetRegister.Result, ref loadFromThisPtr);

Debug.Assert(!targetMethod.CanMethodBeInSealedVTable());
Debug.Assert(!targetMethod.CanMethodBeInSealedVTable(factory));

int slot = VirtualMethodSlotHelper.GetVirtualMethodSlot(factory, targetMethod, targetMethod.OwningType);
Debug.Assert(slot != -1);
Expand Down
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