RyuJIT: Optimize `obj.GetType() != typeof(X)` for sealed classes #32790

EgorBo · 2020-02-25T13:30:43Z

impIsClassExact now returns true for arrays of sealed classes, e.g. String[] (but returns false for arrays of other things including primitives and enums).

Also, optimizes obj.GetType() == typeof(X) to a const + nullcheck (can be eliminated later by Jit) if we can prove both types are sealed, e.g.:

public static bool Check<T>(T[] array)
{
    // co-variance check, e.g. see Span<T>'s ctor
    return array.GetType() != typeof(T[]);
}

Old codegen for `Check<string>`:

       mov      rax, 0xD1FFAB1E
       cmp      qword ptr [rcx], rax 
       setne    al
       movzx    rax, al
       ret

New codegen for `Check<string>`:

       cmp      dword ptr [rcx], ecx  ;; null-check for array
       xor      eax, eax
       ret

Jit-diff (-f -pmi):

(Correct me if I am wrong but the diff should be way bigger once jit learns how to inline generics into shared methods -- because Span<T> uses that check a lot)

Found 5 files with textual diffs.

Summary of Code Size diffs:
(Lower is better)

Total bytes of diff: -363 (-0.00% of base)
    diff is an improvement.

Top file improvements (bytes):
        -135 : System.Private.CoreLib.dasm (-0.00% of base)
        -129 : System.IO.FileSystem.Watcher.dasm (-0.84% of base)
         -75 : System.Net.Http.dasm (-0.01% of base)
         -24 : System.Text.RegularExpressions.dasm (-0.01% of base)

4 total files with Code Size differences (4 improved, 0 regressed), 158 unchanged.

Top method improvements (bytes):
         -87 (-55.41% of base) : System.Private.CoreLib.dasm - System.Text.UTF32Encoding:get_Preamble():System.ReadOnlySpan`1[Byte]:this
         -65 (-10.38% of base) : System.IO.FileSystem.Watcher.dasm - ImmutableStringList:Insert(int,System.String):this
         -64 (-10.83% of base) : System.IO.FileSystem.Watcher.dasm - ImmutableStringList:RemoveAt(int):this
         -48 (-3.48% of base) : System.Private.CoreLib.dasm - System.Threading.WaitHandle:WaitMultiple(System.ReadOnlySpan`1[[System.Threading.WaitHandle, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]],bool,int):int
         -25 (-2.34% of base) : System.Net.Http.dasm - System.Net.Http.Http2Connection:WriteHeaderCollection(System.Net.Http.Headers.HttpHeaders):this
         -25 (-1.43% of base) : System.Net.Http.dasm - System.Net.Http.Http3RequestStream:BufferHeaderCollection(System.Net.Http.Headers.HttpHeaders):this
         -25 (-5.94% of base) : System.Net.Http.dasm - System.Net.Http.Headers.HttpHeaders:GetValuesAsStrings(System.Net.Http.Headers.HeaderDescriptor,HeaderStoreItemInfo,System.Object):System.String[]
         -24 (-9.80% of base) : System.Text.RegularExpressions.dasm - System.Text.RegularExpressions.Regex:GetGroupNames():System.String[]:this

Top method improvements (percentages):
         -87 (-55.41% of base) : System.Private.CoreLib.dasm - System.Text.UTF32Encoding:get_Preamble():System.ReadOnlySpan`1[Byte]:this
         -64 (-10.83% of base) : System.IO.FileSystem.Watcher.dasm - ImmutableStringList:RemoveAt(int):this
         -65 (-10.38% of base) : System.IO.FileSystem.Watcher.dasm - ImmutableStringList:Insert(int,System.String):this
         -24 (-9.80% of base) : System.Text.RegularExpressions.dasm - System.Text.RegularExpressions.Regex:GetGroupNames():System.String[]:this
         -25 (-5.94% of base) : System.Net.Http.dasm - System.Net.Http.Headers.HttpHeaders:GetValuesAsStrings(System.Net.Http.Headers.HeaderDescriptor,HeaderStoreItemInfo,System.Object):System.String[]
         -48 (-3.48% of base) : System.Private.CoreLib.dasm - System.Threading.WaitHandle:WaitMultiple(System.ReadOnlySpan`1[[System.Threading.WaitHandle, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]],bool,int):int
         -25 (-2.34% of base) : System.Net.Http.dasm - System.Net.Http.Http2Connection:WriteHeaderCollection(System.Net.Http.Headers.HttpHeaders):this
         -25 (-1.43% of base) : System.Net.Http.dasm - System.Net.Http.Http3RequestStream:BufferHeaderCollection(System.Net.Http.Headers.HttpHeaders):this

8 total methods with Code Size differences (8 improved, 0 regressed), 305673 unchanged.

1 files had text diffs but no metric diffs.
System.Runtime.Serialization.Formatters.dasm had 66 diffs

Will add tests later.

cc @AndyAyersMS

AndyAyersMS

Thanks for looking at this.

src/coreclr/src/jit/importer.cpp

src/coreclr/src/jit/gentree.cpp

src/coreclr/src/jit/importer.cpp

src/coreclr/src/jit/gentree.cpp

EgorBo · 2020-02-25T17:05:44Z

src/coreclr/src/jit/importer.cpp

@@ -20742,7 +20756,7 @@ bool Compiler::impCanSkipCovariantStoreCheck(GenTree* value, GenTree* array)
 }

 // Check for T[] with T exact.
- if (!impIsClassExact(arrayElementHandle))
+ if (!impIsClassExact(arrayElementHandle, false))
 {


if I enable impIsClassExact for arrays by default this call will cause ~400bytes regression. Example: https://www.diffchecker.com/nKWlHaG7

That's a size regression but quite likely a perf improvement -- the code no longer needs the covariant store check, it just needs a write barrier.

The store check helper also does bounds checking, which now must be done in the jitted code, and is what causes the size growth.

If all the "bad" diffs are like that, I'm ok with a small size regression.

Github acting weird.

ah, ok, I thought it introduced a new bound check. Will post the new diff later then.

EgorBo · 2020-02-25T23:17:12Z

@AndyAyersMS
New diff is:

Found 13 files with textual diffs.

Summary of Code Size diffs:
(Lower is better)

Total bytes of diff: 22 (0.00% of base)
    diff is a regression.

Top file regressions (bytes):
         147 : System.Linq.Parallel.dasm (0.01% of base)
          55 : Microsoft.Diagnostics.FastSerialization.dasm (0.05% of base)
          26 : Microsoft.Diagnostics.Tracing.TraceEvent.dasm (0.00% of base)
          14 : System.Private.CoreLib.dasm (0.00% of base)
          13 : System.Private.Xml.dasm (0.00% of base)

Top file improvements (bytes):
        -129 : System.IO.FileSystem.Watcher.dasm (-0.84% of base)
         -75 : System.Net.Http.dasm (-0.01% of base)
         -24 : System.Text.RegularExpressions.dasm (-0.01% of base)
          -5 : Microsoft.CodeAnalysis.CSharp.dasm (-0.00% of base)

9 total files with Code Size differences (4 improved, 5 regressed), 153 unchanged.

Top method regressions (bytes):
          74 (81.32% of base) : System.Linq.Parallel.dasm - System.Linq.Parallel.JaggedArray`1[Vector`1][System.Numerics.Vector`1[System.Single]]:Allocate(int,int):System.Numerics.Vector`1[System.Single][][]
          70 ( 3.43% of base) : System.Private.CoreLib.dasm - System.Buffers.TlsOverPerCoreLockedStacksArrayPool`1[ReadOnlyMemory`1][System.ReadOnlyMemory`1[System.Char]]:Return(System.ReadOnlyMemory`1[System.Char][],bool):this (2 methods)
          35 ( 9.11% of base) : Microsoft.Diagnostics.FastSerialization.dasm - System.Collections.Generic.SegmentedList`1[Vector`1][System.Numerics.Vector`1[System.Single]]:EnsureCapacity(int):this
          32 ( 1.20% of base) : System.Linq.Parallel.dasm - System.Linq.Parallel.SortHelper`2[Vector`1,Int64][System.Numerics.Vector`1[System.Single],System.Int64]:MergeSortCooperatively():this
          31 ( 2.82% of base) : System.Private.CoreLib.dasm - System.Buffers.TlsOverPerCoreLockedStacksArrayPool`1[Vector`1][System.Numerics.Vector`1[System.Single]]:Return(System.Numerics.Vector`1[System.Single][],bool):this
          22 ( 5.13% of base) : System.Linq.Parallel.dasm - System.Linq.Parallel.SortHelper`2[Vector`1,Int64][System.Numerics.Vector`1[System.Single],System.Int64]:QuickSortIndicesInPlace(System.Linq.Parallel.GrowingArray`1[Int64],System.Collections.Generic.List`1[Vector`1],ubyte):this
          20 ( 8.23% of base) : Microsoft.Diagnostics.FastSerialization.dasm - System.Collections.Generic.SegmentedList`1[Vector`1][System.Numerics.Vector`1[System.Single]]:.ctor(int,int):this
          19 (16.10% of base) : System.Linq.Parallel.dasm - System.Linq.Parallel.AsynchronousChannel`1[Vector`1][System.Numerics.Vector`1[System.Single]]:EnqueueChunk(System.Numerics.Vector`1[System.Single][]):this
          19 ( 4.59% of base) : System.Private.CoreLib.dasm - Bucket[Vector`1][System.Numerics.Vector`1[System.Single]]:Return(System.Numerics.Vector`1[System.Single][]):this
          17 (16.50% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - Microsoft.Diagnostics.Tracing.Analysis.GC.TraceGC:EnsureBGCRevisitInfoAlloc():this
          17 (13.71% of base) : System.Private.CoreLib.dasm - LockedStack[Vector`1][System.Numerics.Vector`1[System.Single]]:TryPush(System.Numerics.Vector`1[System.Single][]):bool:this
          13 ( 0.75% of base) : System.Private.Xml.dasm - System.Xml.Xsl.Runtime.XmlQueryStaticData:.ctor(System.Byte[],System.Type[]):this
          12 ( 5.17% of base) : System.Private.CoreLib.dasm - PerCoreLockedStacks[Vector`1][System.Numerics.Vector`1[System.Single]]:TryPush(System.Numerics.Vector`1[System.Single][]):this
           9 ( 2.81% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - Microsoft.Diagnostics.Tracing.Etlx.TraceCodeAddresses:get_Item(int):Microsoft.Diagnostics.Tracing.Etlx.TraceCodeAddress:this

Top method improvements (bytes):
         -87 (-55.41% of base) : System.Private.CoreLib.dasm - System.Text.UTF32Encoding:get_Preamble():System.ReadOnlySpan`1[Byte]:this
         -65 (-10.38% of base) : System.IO.FileSystem.Watcher.dasm - ImmutableStringList:Insert(int,System.String):this
         -64 (-10.83% of base) : System.IO.FileSystem.Watcher.dasm - ImmutableStringList:RemoveAt(int):this
         -48 (-3.48% of base) : System.Private.CoreLib.dasm - System.Threading.WaitHandle:WaitMultiple(System.ReadOnlySpan`1[[System.Threading.WaitHandle, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]],bool,int):int
         -25 (-2.34% of base) : System.Net.Http.dasm - System.Net.Http.Http2Connection:WriteHeaderCollection(System.Net.Http.Headers.HttpHeaders):this
         -25 (-1.43% of base) : System.Net.Http.dasm - System.Net.Http.Http3RequestStream:BufferHeaderCollection(System.Net.Http.Headers.HttpHeaders):this
         -25 (-5.94% of base) : System.Net.Http.dasm - System.Net.Http.Headers.HttpHeaders:GetValuesAsStrings(System.Net.Http.Headers.HeaderDescriptor,HeaderStoreItemInfo,System.Object):System.String[]
         -24 (-9.80% of base) : System.Text.RegularExpressions.dasm - System.Text.RegularExpressions.Regex:GetGroupNames():System.String[]:this
          -5 (-0.23% of base) : Microsoft.CodeAnalysis.CSharp.dasm - Microsoft.CodeAnalysis.CSharp.BuiltInOperators:GetSimpleBuiltInOperators(int,Microsoft.CodeAnalysis.ArrayBuilder`1[BinaryOperatorSignature]):this

Top method regressions (percentages):
          74 (81.32% of base) : System.Linq.Parallel.dasm - System.Linq.Parallel.JaggedArray`1[Vector`1][System.Numerics.Vector`1[System.Single]]:Allocate(int,int):System.Numerics.Vector`1[System.Single][][]
          17 (16.50% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - Microsoft.Diagnostics.Tracing.Analysis.GC.TraceGC:EnsureBGCRevisitInfoAlloc():this
          19 (16.10% of base) : System.Linq.Parallel.dasm - System.Linq.Parallel.AsynchronousChannel`1[Vector`1][System.Numerics.Vector`1[System.Single]]:EnqueueChunk(System.Numerics.Vector`1[System.Single][]):this
          17 (13.71% of base) : System.Private.CoreLib.dasm - LockedStack[Vector`1][System.Numerics.Vector`1[System.Single]]:TryPush(System.Numerics.Vector`1[System.Single][]):bool:this
          35 ( 9.11% of base) : Microsoft.Diagnostics.FastSerialization.dasm - System.Collections.Generic.SegmentedList`1[Vector`1][System.Numerics.Vector`1[System.Single]]:EnsureCapacity(int):this
          20 ( 8.23% of base) : Microsoft.Diagnostics.FastSerialization.dasm - System.Collections.Generic.SegmentedList`1[Vector`1][System.Numerics.Vector`1[System.Single]]:.ctor(int,int):this
          12 ( 5.17% of base) : System.Private.CoreLib.dasm - PerCoreLockedStacks[Vector`1][System.Numerics.Vector`1[System.Single]]:TryPush(System.Numerics.Vector`1[System.Single][]):this
          22 ( 5.13% of base) : System.Linq.Parallel.dasm - System.Linq.Parallel.SortHelper`2[Vector`1,Int64][System.Numerics.Vector`1[System.Single],System.Int64]:QuickSortIndicesInPlace(System.Linq.Parallel.GrowingArray`1[Int64],System.Collections.Generic.List`1[Vector`1],ubyte):this
          19 ( 4.59% of base) : System.Private.CoreLib.dasm - Bucket[Vector`1][System.Numerics.Vector`1[System.Single]]:Return(System.Numerics.Vector`1[System.Single][]):this
          70 ( 3.43% of base) : System.Private.CoreLib.dasm - System.Buffers.TlsOverPerCoreLockedStacksArrayPool`1[ReadOnlyMemory`1][System.ReadOnlyMemory`1[System.Char]]:Return(System.ReadOnlyMemory`1[System.Char][],bool):this (2 methods)
          31 ( 2.82% of base) : System.Private.CoreLib.dasm - System.Buffers.TlsOverPerCoreLockedStacksArrayPool`1[Vector`1][System.Numerics.Vector`1[System.Single]]:Return(System.Numerics.Vector`1[System.Single][],bool):this
           9 ( 2.81% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - Microsoft.Diagnostics.Tracing.Etlx.TraceCodeAddresses:get_Item(int):Microsoft.Diagnostics.Tracing.Etlx.TraceCodeAddress:this
          32 ( 1.20% of base) : System.Linq.Parallel.dasm - System.Linq.Parallel.SortHelper`2[Vector`1,Int64][System.Numerics.Vector`1[System.Single],System.Int64]:MergeSortCooperatively():this
          13 ( 0.75% of base) : System.Private.Xml.dasm - System.Xml.Xsl.Runtime.XmlQueryStaticData:.ctor(System.Byte[],System.Type[]):this

Top method improvements (percentages):
         -87 (-55.41% of base) : System.Private.CoreLib.dasm - System.Text.UTF32Encoding:get_Preamble():System.ReadOnlySpan`1[Byte]:this
         -64 (-10.83% of base) : System.IO.FileSystem.Watcher.dasm - ImmutableStringList:RemoveAt(int):this
         -65 (-10.38% of base) : System.IO.FileSystem.Watcher.dasm - ImmutableStringList:Insert(int,System.String):this
         -24 (-9.80% of base) : System.Text.RegularExpressions.dasm - System.Text.RegularExpressions.Regex:GetGroupNames():System.String[]:this
         -25 (-5.94% of base) : System.Net.Http.dasm - System.Net.Http.Headers.HttpHeaders:GetValuesAsStrings(System.Net.Http.Headers.HeaderDescriptor,HeaderStoreItemInfo,System.Object):System.String[]
         -48 (-3.48% of base) : System.Private.CoreLib.dasm - System.Threading.WaitHandle:WaitMultiple(System.ReadOnlySpan`1[[System.Threading.WaitHandle, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]],bool,int):int
         -25 (-2.34% of base) : System.Net.Http.dasm - System.Net.Http.Http2Connection:WriteHeaderCollection(System.Net.Http.Headers.HttpHeaders):this
         -25 (-1.43% of base) : System.Net.Http.dasm - System.Net.Http.Http3RequestStream:BufferHeaderCollection(System.Net.Http.Headers.HttpHeaders):this
          -5 (-0.23% of base) : Microsoft.CodeAnalysis.CSharp.dasm - Microsoft.CodeAnalysis.CSharp.BuiltInOperators:GetSimpleBuiltInOperators(int,Microsoft.CodeAnalysis.ArrayBuilder`1[BinaryOperatorSignature]):this

23 total methods with Code Size differences (9 improved, 14 regressed), 305658 unchanged.

3 files had text diffs but no metric diffs.
System.Runtime.Serialization.Formatters.dasm had 66 diffs
System.Net.Requests.dasm had 28 diffs
Microsoft.CSharp.dasm had 6 diffs

Asm diffs for top3 regressions:

the first one looks a bit suspicious (see code), others are the optimized covariance check case. JaggedArray + Vector as T -- doesn't sound like a real world application, so I guess it's pmi.

AndyAyersMS · 2020-02-25T23:41:08Z

In Allocate the explicit IR for the array address triggers loop cloning, so you get two copies of the loop and so a larger size impact. This is a known "feature" of the loop cloner; it is very touchy. On the upside you've now likely eliminated a bounds check from the hot path.

What does the diff in System.Text.UTF32Encoding:get_Preamble():System.ReadOnlySpan`1[Byte]:thislook like?

EgorBo · 2020-02-26T10:21:45Z

What does the diff in System.Text.UTF32Encoding:get_Preamble():System.ReadOnlySpan`1[Byte]:thislook like?

Diff: https://www.diffchecker.com/cMI34jXb
Code:

runtime/src/libraries/System.Private.CoreLib/src/System/Text/UTF32Encoding.cs

Lines 1141 to 1145 in 7855aa3

                           
                              public override ReadOnlySpan<byte> Preamble =>
                             
                              GetType() != typeof(UTF32Encoding) ? new ReadOnlySpan<byte>(GetPreamble()) : // in case a derived UTF32Encoding overrode GetPreamble
                             
                              !_emitUTF32ByteOrderMark ? default :
                             
                              _bigEndian ? (ReadOnlySpan<byte>)new byte[4] { 0x00, 0x00, 0xFE, 0xFF } : // uses C# compiler's optimization for static byte[] data
                             
                              (ReadOnlySpan<byte>)new byte[4] { 0xFF, 0xFE, 0x00, 0x00 };

Eliminated that check.

AndyAyersMS

This looks good. Thanks!

EgorBo · 2020-02-26T16:16:50Z

With this PR, the following snippet:

static Span<string> ToSpan(string[] a)
{
    return a;
}

Asm diff: https://www.diffchecker.com/KtZmiPvY (new codegen is on the right)
cc @GrabYourPitchforks

AndyAyersMS · 2020-02-26T17:51:02Z

cc @dotnet/jit-contrib

erozenfeld

LGTM

EgorBo added 2 commits February 25, 2020 15:04

Optimize arrOfStrings.GetType() == typeof(string[])

0141547

handle more cases

1bc8f2e

Dotnet-GitSync-Bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Feb 25, 2020

Minor cleanup

fd10775

AndyAyersMS reviewed Feb 25, 2020

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Clean up

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EgorBo force-pushed the opt-arr-gettype branch from a32fe1e to 14f66a4 Compare February 25, 2020 19:19

Clean up

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BruceForstall changed the title ~~RuyJIT: Optimize obj.GetType() != typeof(X) for sealed classes~~ RyuJIT: Optimize obj.GetType() != typeof(X) for sealed classes Feb 26, 2020

AndyAyersMS merged commit 366a4d6 into dotnet:master Feb 27, 2020

EgorBo mentioned this pull request Feb 28, 2020

Span<ReferenceType>.CopyTo is 10-20% slower than Array<ReferenceType>.CopyTo #29093

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This was referenced Mar 4, 2020

Investigate optimizing away Span<class> type checks #7646

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JIT crash caused by late GetType() optimizations #33333

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Fix JIT crash caused by GetType() == typeof(SealedClass) optimization #33337

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JIT: fgLateDevirtualization should try and simplify type compares #11436

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RyuJIT: Optimize `obj.GetType() != typeof(X)` for sealed classes #32790

RyuJIT: Optimize `obj.GetType() != typeof(X)` for sealed classes #32790

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RyuJIT: Optimize obj.GetType() != typeof(X) for sealed classes #32790

RyuJIT: Optimize obj.GetType() != typeof(X) for sealed classes #32790

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EgorBo commented Feb 25, 2020 • edited

Old codegen for Check<string>:

New codegen for Check<string>:

Jit-diff (-f -pmi):

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RyuJIT: Optimize `obj.GetType() != typeof(X)` for sealed classes #32790

RyuJIT: Optimize `obj.GetType() != typeof(X)` for sealed classes #32790

EgorBo commented Feb 25, 2020 •

edited

Old codegen for `Check<string>`:

New codegen for `Check<string>`:

EgorBo commented Feb 25, 2020 •

edited

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edited