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Speed up interface checking and casting #49257

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merged 5 commits into from
Mar 7, 2021
Merged

Speed up interface checking and casting #49257

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855430a
Reduce branches in IsInstanceOfInterface/ChkCastInterface
benaadams Mar 6, 2021
6617221
Drop extra var, lea; additional check for small counts
benaadams Mar 6, 2021
8670404
Feedback
benaadams Mar 7, 2021
ef16c9b
Undo IsInstanceOfClass change
benaadams Mar 7, 2021
c60450e
Tidy usings
benaadams Mar 7, 2021
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121 changes: 84 additions & 37 deletions src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/CastHelpers.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,11 +2,10 @@
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics;
using Internal.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Threading;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;

using Internal.Runtime.CompilerServices;

namespace System.Runtime.CompilerServices
{
Expand Down Expand Up @@ -207,34 +206,57 @@ private static CastResult TryGet(nuint source, nuint target)
[DebuggerStepThrough]
private static object? IsInstanceOfInterface(void* toTypeHnd, object? obj)
{
const int unrollSize = 4;

if (obj != null)
{
MethodTable* mt = RuntimeHelpers.GetMethodTable(obj);
nuint interfaceCount = mt->InterfaceCount;
nint interfaceCount = mt->InterfaceCount;
if (interfaceCount != 0)
{
MethodTable** interfaceMap = mt->InterfaceMap;
for (nuint i = 0; ; i += 4)
if (interfaceCount < unrollSize)
{
if (interfaceMap[i + 0] == toTypeHnd)
goto done;
if (--interfaceCount == 0)
break;
if (interfaceMap[i + 1] == toTypeHnd)
goto done;
if (--interfaceCount == 0)
break;
if (interfaceMap[i + 2] == toTypeHnd)
goto done;
if (--interfaceCount == 0)
break;
if (interfaceMap[i + 3] == toTypeHnd)
// If not enough for unrolled, jmp straight to small loop
// as we already know there is one or more interfaces so don't need to check again.
goto few;
}

do
{
if (interfaceMap[0] == toTypeHnd ||
interfaceMap[1] == toTypeHnd ||
interfaceMap[2] == toTypeHnd ||
interfaceMap[3] == toTypeHnd)
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{
goto done;
if (--interfaceCount == 0)
break;
}

interfaceMap += unrollSize;
interfaceCount -= unrollSize;
} while (interfaceCount >= unrollSize);

if (interfaceCount == 0)
{
// If none remaining, skip the short loop
goto extra;
}

few:
do
{
if (interfaceMap[0] == toTypeHnd)
{
goto done;
}

// Assign next offset
interfaceMap++;
interfaceCount--;
} while (interfaceCount > 0);
}

extra:
if (mt->NonTrivialInterfaceCast)
{
goto slowPath;
Expand Down Expand Up @@ -374,35 +396,60 @@ private static CastResult TryGet(nuint source, nuint target)
[DebuggerStepThrough]
private static object? ChkCastInterface(void* toTypeHnd, object? obj)
{
const int unrollSize = 4;

if (obj != null)
{
MethodTable* mt = RuntimeHelpers.GetMethodTable(obj);
nuint interfaceCount = mt->InterfaceCount;
nint interfaceCount = mt->InterfaceCount;
if (interfaceCount == 0)
{
goto slowPath;
}

MethodTable** interfaceMap = mt->InterfaceMap;
for (nuint i = 0; ; i += 4)
if (interfaceCount < unrollSize)
{
if (interfaceMap[i + 0] == toTypeHnd)
goto done;
if (--interfaceCount == 0)
goto slowPath;
if (interfaceMap[i + 1] == toTypeHnd)
goto done;
if (--interfaceCount == 0)
goto slowPath;
if (interfaceMap[i + 2] == toTypeHnd)
goto done;
if (--interfaceCount == 0)
goto slowPath;
if (interfaceMap[i + 3] == toTypeHnd)
// If not enough for unrolled, jmp straight to small loop
// as we already know there is one or more interfaces so don't need to check again.
goto few;
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If interface table is allocated as 4 elements aligned and zero-filled, we could remove the "few" case entirely. At least in Chk case which is expected to succeed.
That would come with size increase though, so does not seem worth it.

}

do
{
if (interfaceMap[0] == toTypeHnd ||
interfaceMap[1] == toTypeHnd ||
interfaceMap[2] == toTypeHnd ||
interfaceMap[3] == toTypeHnd)
{
goto done;
if (--interfaceCount == 0)
goto slowPath;
}

// Assign next offset
interfaceMap += unrollSize;
interfaceCount -= unrollSize;
} while (interfaceCount >= unrollSize);

if (interfaceCount == 0)
{
// If none remaining, skip the short loop
goto slowPath;
}

few:
do
{
if (interfaceMap[0] == toTypeHnd)
{
goto done;
}

// Assign next offset
interfaceMap++;
interfaceCount--;
} while (interfaceCount > 0);

goto slowPath;
}

done:
Expand Down