Fold bound checks for static readonly arrays/strings

[EgorBo]

Closes#76578
Closes#42087

This PR folds obj.Length into a constant for static readonly initialized arrays/strings - as a side effect - it removes bound checks. Example:

staticreadonlyint[]MyArr={1,2,3,4,5};staticreadonlystringMyStr=(42).ToString();intTest1()=>MyArr[3];intTest2()=>MyStr.Length;

Codegen diff:

; Assembly listing for method Program:Test1():int:this
- sub rsp, 40
mov rax, 0xD1FFAB1E
mov rax, gword ptr [rax]
- cmp dword ptr [rax+08H], 3- jbe SHORT G_M18247_IG04
mov eax, dword ptr [rax+1CH]
- add rsp, 40
ret -G_M18247_IG04:- call CORINFO_HELP_RNGCHKFAIL- int3 -; Total bytes of code 37+; Total bytes of code 17
; Assembly listing for method Program:Test2():int:this
- mov rax, 0xD1FFAB1E- mov rax, gword ptr [rax]- mov eax, dword ptr [rax+08H]+ mov eax, 2 ;; folded to just 2
ret -; Total bytes of code 17+; Total bytes of code 6

Jit-diffs (-f -pmi --cctors):

Total bytes of base: 63327742
Total bytes of diff: 63313731
Total bytes of delta: -14011 (-0.02 % of base)
Total relative delta: -35.61
diff is an improvement.
relative diff is an improvement.
Total byte diff includes -206 bytes from reconciling methods
Base had 2 unique methods, 206 unique bytes
Diff had 0 unique methods, 0 unique bytes
Top file regressions (bytes):
21 : System.Resources.Extensions.dasm (0.06% of base)
16 : System.Security.Cryptography.Pkcs.dasm (0.00% of base)
7 : System.IO.Hashing.dasm (0.03% of base)
2 : System.IO.Compression.dasm (0.00% of base)
2 : System.ComponentModel.Composition.Registration.dasm (0.00% of base)
2 : Microsoft.Extensions.FileProviders.Physical.dasm (0.01% of base)
2 : Microsoft.Win32.Registry.dasm (0.01% of base)
Top file improvements (bytes):
-5357 : System.Private.Xml.dasm (-0.13% of base)
-1634 : System.Private.DataContractSerialization.dasm (-0.18% of base)
-1160 : System.Private.CoreLib.dasm (-0.02% of base)
-872 : System.ComponentModel.TypeConverter.dasm (-0.30% of base)
-536 : Microsoft.CSharp.dasm (-0.13% of base)
-429 : Microsoft.CodeAnalysis.dasm (-0.02% of base)
-336 : System.Net.Mail.dasm (-0.19% of base)
-305 : System.Linq.Expressions.dasm (-0.04% of base)
-277 : System.Net.Http.dasm (-0.03% of base)
-266 : System.Data.Common.dasm (-0.02% of base)
-254 : System.ComponentModel.Composition.dasm (-0.07% of base)
-213 : System.Diagnostics.DiagnosticSource.dasm (-0.11% of base)
-191 : System.Text.Json.dasm (-0.02% of base)
-191 : System.Configuration.ConfigurationManager.dasm (-0.05% of base)
-146 : Newtonsoft.Json.dasm (-0.02% of base)
62 total files with Code Size differences (55 improved, 7 regressed), 212 unchanged.
Top method regressions (bytes):
39 (12.00% of base) : System.Private.CoreLib.dasm - System.Threading.Timer:.ctor(System.Threading.TimerCallback,System.Object,uint,uint):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[double]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[int]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[long]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[short]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[System.Nullable`1[int]]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[System.Numerics.Vector`1[float]]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[ubyte]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
32 ( 3.82% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[System.__Canon]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
32 ( 5.88% of base) : System.Private.CoreLib.dasm - System.Threading.Timer:.ctor(System.Threading.TimerCallback,System.Object,int,int):this
32 ( 4.22% of base) : System.Private.CoreLib.dasm - System.Threading.Timer:.ctor(System.Threading.TimerCallback,System.Object,long,long):this
32 ( 3.67% of base) : System.Private.CoreLib.dasm - System.Threading.Timer:.ctor(System.Threading.TimerCallback,System.Object,System.TimeSpan,System.TimeSpan):this
30 (10.49% of base) : System.Private.CoreLib.dasm - System.Threading.Timer:.ctor(System.Threading.TimerCallback):this
30 (13.57% of base) : System.Private.CoreLib.dasm - System.Threading.TimerQueueTimer:.ctor(System.Threading.TimerCallback,System.Object,uint,uint,bool):this
26 ( 6.91% of base) : System.Private.CoreLib.dasm - DelayPromise:.ctor(uint):this
Top method improvements (bytes):
-358 (-38.96% of base) : System.Private.CoreLib.dasm - System.Text.EncodingTable:GetEncodings(System.Collections.Generic.Dictionary`2[int,System.Text.EncodingInfo]):System.Text.EncodingInfo[]
-324 (-45.70% of base) : System.Private.CoreLib.dasm - System.Text.EncodingTable:GetEncodings():System.Text.EncodingInfo[]
-215 (-8.61% of base) : System.Private.Xml.dasm - System.Xml.Serialization.XmlSerializationReaderILGen:WriteArray(System.String,System.String,System.Xml.Serialization.ArrayMapping,bool,bool,int,int):this
-213 (-5.32% of base) : System.Private.Xml.dasm - System.Xml.Serialization.XmlSerializationWriterILGen:WriteEnumAndArrayTypes():this
-204 (-6.00% of base) : System.Private.Xml.dasm - System.Xml.Schema.XmlAnyConverter:ChangeType(System.Object,System.Type,System.Xml.IXmlNamespaceResolver):System.Object:this
-170 (-12.72% of base) : System.Private.CoreLib.dasm - System.Convert:ChangeType(System.Object,System.Type,System.IFormatProvider):System.Object
-167 (-6.38% of base) : System.Private.Xml.dasm - System.Xml.Serialization.XmlSerializationReaderILGen:WriteEnumAndArrayTypes():this
-166 (-11.44% of base) : System.Private.CoreLib.dasm - System.Convert:DefaultToType(System.IConvertible,System.Type,System.IFormatProvider):System.Object
-165 (-3.06% of base) : System.Private.DataContractSerialization.dasm - CriticalHelper:ReadCollection(System.Runtime.Serialization.DataContracts.CollectionDataContract):this (2 methods)
-160 (-9.16% of base) : System.Private.Xml.dasm - System.Xml.Serialization.XmlSerializationReaderILGen:WriteText(Member):this
-155 (-18.32% of base) : System.Private.CoreLib.dasm - System.Reflection.Emit.TypeBuilder:DefineDefaultConstructorNoLock(int):System.Reflection.Emit.ConstructorBuilder:this
-140 (-23.53% of base) : System.Private.DataContractSerialization.dasm - System.Xml.XmlUTF8NodeWriter:WriteDeclaration():this
-133 (-13.96% of base) : System.Private.Xml.dasm - System.Xml.Serialization.XmlSerializationReaderILGen:WriteXmlNodeEqual(System.String,System.String,System.String,bool):this
-123 (-9.81% of base) : System.Data.Common.dasm - System.Data.Common.ObjectStorage:GetXmlSerializer(System.Type,System.Xml.Serialization.XmlRootAttribute):System.Xml.Serialization.XmlSerializer
-121 (-11.33% of base) : System.Private.Xml.dasm - System.Xml.Serialization.XmlSerializationILGen:GenerateBaseSerializer(System.String,System.String,System.String,System.Xml.Serialization.CodeIdentifiers):System.String:this
Top method regressions (percentages):
30 (13.57% of base) : System.Private.CoreLib.dasm - System.Threading.TimerQueueTimer:.ctor(System.Threading.TimerCallback,System.Object,uint,uint,bool):this
39 (12.00% of base) : System.Private.CoreLib.dasm - System.Threading.Timer:.ctor(System.Threading.TimerCallback,System.Object,uint,uint):this
30 (10.49% of base) : System.Private.CoreLib.dasm - System.Threading.Timer:.ctor(System.Threading.TimerCallback):this
3 ( 7.14% of base) : System.Drawing.Primitives.dasm - System.Drawing.KnownColorNames:KnownColorToName(int):System.String
3 ( 6.98% of base) : Microsoft.CodeAnalysis.VisualBasic.dasm - Microsoft.CodeAnalysis.VisualBasic.SyntaxFacts:IsNarrowIdentifierCharacter(ushort):bool
3 ( 6.98% of base) : Microsoft.CodeAnalysis.dasm - Microsoft.CodeAnalysis.WellKnownTypes:GetMetadataName(int):System.String
26 ( 6.91% of base) : System.Private.CoreLib.dasm - DelayPromise:.ctor(uint):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[double]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[int]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[long]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[short]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[System.Nullable`1[int]]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[System.Numerics.Vector`1[float]]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
38 ( 6.02% of base) : System.Private.CoreLib.dasm - CancellationPromise`1[ubyte]:.ctor(System.Threading.Tasks.Task,uint,System.Threading.CancellationToken):this
32 ( 5.88% of base) : System.Private.CoreLib.dasm - System.Threading.Timer:.ctor(System.Threading.TimerCallback,System.Object,int,int):this
Top method improvements (percentages):
-103 (-100.00% of base) : Microsoft.CodeAnalysis.dasm - Microsoft.CodeAnalysis.SmallDictionary`2[System.__Canon,int]:LeftComplex(AvlNode[System.__Canon,int]):AvlNode[System.__Canon,int] (1 base, 0 diff methods)
-103 (-100.00% of base) : Microsoft.CodeAnalysis.dasm - Microsoft.CodeAnalysis.SmallDictionary`2[System.__Canon,int]:RightComplex(AvlNode[System.__Canon,int]):AvlNode[System.__Canon,int] (1 base, 0 diff methods)
-11 (-64.71% of base) : System.Net.Http.dasm - System.Net.Http.HPack.H2StaticTable:get_Count():int
-20 (-52.63% of base) : System.Private.CoreLib.dasm - NullStreamReader:ReadAsync(ushort[],int,int):System.Threading.Tasks.Task`1[int]:this
-20 (-52.63% of base) : System.Private.CoreLib.dasm - NullStreamReader:ReadBlockAsync(ushort[],int,int):System.Threading.Tasks.Task`1[int]:this
-324 (-45.70% of base) : System.Private.CoreLib.dasm - System.Text.EncodingTable:GetEncodings():System.Text.EncodingInfo[]
-74 (-44.58% of base) : System.Private.Xml.dasm - System.Xml.Serialization.ReflectionXmlSerializationReader:GetDefaultConstructor(System.Type):System.Reflection.ConstructorInfo
-23 (-41.82% of base) : System.Net.Http.dasm - System.Net.Http.HttpRuleParser:IsTokenChar(ushort):bool
-89 (-41.20% of base) : System.ComponentModel.TypeConverter.dasm - System.ComponentModel.TypeDescriptor:GetAttributes(System.Type):System.ComponentModel.AttributeCollection
-70 (-40.94% of base) : System.Private.DataContractSerialization.dasm - System.Runtime.Serialization.XmlFormatGeneratorStatics:get_HashtableCtor():System.Reflection.ConstructorInfo
-19 (-39.58% of base) : System.Diagnostics.DiagnosticSource.dasm - System.Diagnostics.Metrics.Instrument`1[System.Numerics.Vector`1[float]]:RecordMeasurement(System.Numerics.Vector`1[float]):this
-358 (-38.96% of base) : System.Private.CoreLib.dasm - System.Text.EncodingTable:GetEncodings(System.Collections.Generic.Dictionary`2[int,System.Text.EncodingInfo]):System.Text.EncodingInfo[]
-113 (-37.79% of base) : System.Private.Xml.dasm - System.Xml.Serialization.XmlSerializer:.ctor(System.Type,System.Xml.Serialization.XmlRootAttribute):this
-89 (-37.55% of base) : Newtonsoft.Json.Bson.dasm - Newtonsoft.Json.Bson.BsonDataReader:BytesInSequence(ubyte):int:this
-89 (-37.55% of base) : Newtonsoft.Json.dasm - Newtonsoft.Json.Bson.BsonReader:BytesInSequence(ubyte):int:this
607 total methods with Code Size differences (428 improved, 179 regressed), 391602 unchanged.

Size regressions are actually improvements, e.g.:
https://www.diffchecker.com/rJTFoUpk (mov reg, imm vs mov reg, [reg])
https://www.diffchecker.com/Rt1IPpnb (idiv is expanded to mul + magic constants)

[ghost]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
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Issue Details

---

Closes #76578

This PR fold obj.Length into a constant for static readonly initialized arrays/strings - it removes bound checks. Example:

staticreadonlyint[]MyArr={1,2,3,4,5};staticreadonlystringMyStr=(42).ToString();intTest1()=>MyArr[3];intTest2()=>MyStr.Length;

Old codegen:

; Assembly listing for method Program:Test1():int:thissubrsp,40movrax,0xD1FFAB1Emovrax, gword ptr [rax]cmp dword ptr [rax+08H],3jbe SHORT G_M18247_IG04moveax, dword ptr [rax+1CH]addrsp,40retG_M18247_IG04:call CORINFO_HELP_RNGCHKFAILint3; Total bytes of code 37; Assembly listing for method Program:Test2():int:thismovrax,0xD1FFAB1Emovrax, gword ptr [rax]moveax, dword ptr [rax+08H]ret; Total bytes of code 17

New codegen:

; Assembly listing for method Program:Test1():int:thismovrax,0xD1FFAB1Emovrax, gword ptr [rax]moveax, dword ptr [rax+1CH]ret; Total bytes of code 17; Assembly listing for method Program:Test2():int:thismoveax,2ret; Total bytes of code 6

Author:	EgorBo
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[hez2010]

Would like to see the codegen of method Test1 being optimized to just

mov eax, 4
ret

;)

[EgorBo]

Would like to see the codegen of method Test1 being optimized to just

mov eax, 4
ret

;)

Unfortunately it's not legal, array is mutable 😞

[EgorBo]

@dotnet/jit-contrib @jakobbotsch PTAL
(and @jkotas for vm side)

[jakobbotsch]

LGTM. The encoding of field sequence in VNF_InvariantNonNullLoad/VNF_InvariantLoad still feels a bit unfortunate to me, but seems ok to be pragmatic about it for now, we can always try to clean this up later. @SingleAccretion do you have an opinion on this?

[SingleAccretion]

It does look suboptimal; how much more code would using VNF_PtrToStatic imply?

[EgorBo]

It does look suboptimal; how much more code would using VNF_PtrToStatic imply?

@jakobbotsch@SingleAccretion just for my understanding - what exactly we try to avoid by using that?
Do you mean to use VNF_PtrToStatic encoded into VNF_InvariantLoad? so the unpack will be like

if (GetVNFunc())
{
if (GetVNFunc()..
}

?

[SingleAccretion]

Do you mean to use VNF_PtrToStatic encoded into VNF_InvariantLoad?

Yes.

Q: what's the advantage:
A:
- Not using two args for invariant loads where most of them don't use the second argument.
- Naturally extends to more complex load patterns (e. g. readonlyStruct.Field).

[SingleAccretion]

Although, actually, thinking a bit more about it, I realize this is not currently possible due to how the addresses are constant handles (and "renumbering" them in invariant load numbering defeats the purpose).

So my actual suggestion is to encode the addresses for invariant loads as field sequence VNs (GTF_ICON_FIELD_SEQ handles) (given the offset of the implicit struct fields is zero).

[AndyAyersMS]

Couldn't we do this in early prop? Or do we somehow get a lot more cases running it later?

[EgorBo]

Couldn't we do this in early prop? Or do we somehow get a lot more cases running it later?

Do you mind if I do it separately, once we get SPMI collection for this and it will be easier to determinate if it's profitable or not to do it in the early prop. This OPT handles ARR_LEN(tmplcl) where tmplcl is either a const frozen handle or IND to a static field

[AndyAyersMS]

Couldn't we do this in early prop? Or do we somehow get a lot more cases running it later?

Do you mind if I do it separately, once we get SPMI collection for this and it will be easier to determinate if it's profitable or not to do it in the early prop. This OPT handles ARR_LEN(tmplcl) where tmplcl is either a const frozen handle or IND to a static field

Fine by me. I was mostly curious why you chose VN over early prop, since early prop already does similar things, and the transformation is probably simpler there.

[EgorBo]

improvements on arm64 dotnet/perf-autofiling-issues#9676