Jit: Remove bounds checks with tests against length.

[nathan-moore]

Look through assertions when trying to get the array length if we don't have a better way.

This removes bounds checks in this form:

if(arr.Length>5){arr[4]=1;arr[i%5]=1;}if(arr.Length!=0){arr[0]=1;}

fixes#11623

Total bytes of diff: -12616 (-0.039% of base)
diff is an improvement.
Top file improvements (bytes):
-4356 : System.Private.CoreLib.dasm (-0.134% of base)
-898 : System.Private.Xml.dasm (-0.028% of base)
-582 : Microsoft.VisualBasic.Core.dasm (-0.137% of base)
-500 : System.Data.Common.dasm (-0.045% of base)
-394 : Microsoft.CodeAnalysis.VisualBasic.dasm (-0.017% of base)
-381 : Microsoft.CodeAnalysis.CSharp.dasm (-0.018% of base)
-378 : Microsoft.CodeAnalysis.dasm (-0.049% of base)
-321 : FSharp.Core.dasm (-0.034% of base)
-278 : System.Private.DataContractSerialization.dasm (-0.038% of base)
-278 : System.Linq.Expressions.dasm (-0.010% of base)
-249 : Newtonsoft.Json.dasm (-0.040% of base)
-239 : System.Text.Json.dasm (-0.079% of base)
-206 : Microsoft.Diagnostics.Tracing.TraceEvent.dasm (-0.006% of base)
-201 : System.Runtime.Numerics.dasm (-0.291% of base)
-199 : System.Reflection.Metadata.dasm (-0.061% of base)
-198 : System.Net.Security.dasm (-0.072% of base)
-162 : System.Net.Http.dasm (-0.027% of base)
-148 : System.ComponentModel.TypeConverter.dasm (-0.066% of base)
-136 : System.ComponentModel.Composition.dasm (-0.063% of base)
-132 : System.Memory.dasm (-0.150% of base)
72 total files with Code Size differences (72 improved, 0 regressed), 195 unchanged.
Top method regressions (bytes):
8 (0.163% of base) : System.Data.Common.dasm - XSDSchema:LoadSchema(XmlSchemaSet,DataSet):this
2 (0.015% of base) : System.Data.Common.dasm - XmlTreeGen:HandleTable(DataTable,XmlDocument,XmlElement,bool):XmlElement:this
Top method improvements (bytes):
-366 (-23.033% of base) : System.Private.CoreLib.dasm - Utf8Parser:TryParseDateTimeOffsetO(ReadOnlySpan`1,byref,byref,byref):bool
-308 (-20.995% of base) : System.Private.CoreLib.dasm - Utf8Parser:TryParseDateTimeOffsetR(ReadOnlySpan`1,int,byref,byref):bool
-295 (-15.784% of base) : System.Private.CoreLib.dasm - DateTimeParse:ParseFormatR(ReadOnlySpan`1,byref,byref):bool
-199 (-24.121% of base) : System.Private.CoreLib.dasm - Utf8Parser:TryParseDateTimeG(ReadOnlySpan`1,byref,byref,byref):bool
-198 (-2.402% of base) : System.Private.CoreLib.dasm - Vector256`1:ToString():String:this (11 methods)
-198 (-2.492% of base) : System.Private.CoreLib.dasm - Vector64`1:ToString():String:this (11 methods)
-174 (-2.257% of base) : System.Private.CoreLib.dasm - Vector128`1:ToString():String:this (11 methods)
-86 (-23.056% of base) : System.Private.CoreLib.dasm - Rune:TryEncodeToUtf8(Span`1,byref):bool:this
-86 (-9.317% of base) : Microsoft.VisualBasic.Core.dasm - Strings:Format(Object,String):String
-83 (-20.048% of base) : System.Private.CoreLib.dasm - Utf8Parser:TryParseDateTimeOffsetDefault(ReadOnlySpan`1,byref,byref):bool
-78 (-16.810% of base) : System.Net.Security.dasm - SslStream:DetectFraming(ReadOnlySpan`1):int:this
-70 (-0.489% of base) : Microsoft.VisualBasic.Core.dasm - VBBinder:BindToMethod(int,ref,byref,ref,CultureInfo,ref,byref):MethodBase:this
-67 (-3.851% of base) : System.Memory.dasm - SequenceReader`1:TryReadToAnyInternal(byref,ReadOnlySpan`1,bool,int):bool:this (2 methods)
-66 (-2.891% of base) : System.Private.CoreLib.dasm - GenericArraySortHelper`1:HeapSort(Span`1) (13 methods)
-65 (-7.096% of base) : System.Memory.dasm - SequenceReader`1:TryReadToAny(byref,ReadOnlySpan`1,bool):bool:this (4 methods)
-60 (-1.823% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - TraceEvent:PayloadString(int,IFormatProvider):String:this
-59 (-7.403% of base) : System.Net.HttpListener.dasm - HttpListenerRequest:SetRequestLine(String):this
-55 (-5.765% of base) : System.Private.CoreLib.dasm - DateTimeFormatInfo:SetAllDateTimePatterns(ref,ushort):this
-55 (-18.395% of base) : System.Net.Security.dasm - SslStream:GetFrameSize(ReadOnlySpan`1):int:this
-52 (-17.162% of base) : Microsoft.CodeAnalysis.dasm - PathUtilities:GetPathKind(String):int
Top method regressions (percentages):
8 (0.163% of base) : System.Data.Common.dasm - XSDSchema:LoadSchema(XmlSchemaSet,DataSet):this
2 (0.015% of base) : System.Data.Common.dasm - XmlTreeGen:HandleTable(DataTable,XmlDocument,XmlElement,bool):XmlElement:this
Top method improvements (percentages):
-17 (-53.125% of base) : System.Collections.Immutable.dasm - ImmutableArrayExtensions:FirstOrDefault(ImmutableArray`1):__Canon
-17 (-43.590% of base) : System.Private.Xml.dasm - Compiler:IsPhantomNamespace(String):bool:this
-28 (-41.791% of base) : Microsoft.CodeAnalysis.CSharp.dasm - ExplicitInterfaceMethodTypeParameterMap:GetOverriddenMethod(SourceMemberMethodSymbol):MethodSymbol:this
-17 (-40.476% of base) : Microsoft.CodeAnalysis.CSharp.dasm - CodeGenerator:IsMultidimensionalInitializer(ImmutableArray`1):bool
-17 (-40.476% of base) : Microsoft.CodeAnalysis.VisualBasic.dasm - CodeGenerator:IsMultidimensionalInitializer(ImmutableArray`1):bool:this
-17 (-39.535% of base) : Newtonsoft.Json.Bson.dasm - StringUtils:StartsWith(String,ushort):bool
-17 (-39.535% of base) : Newtonsoft.Json.dasm - StringUtils:StartsWith(String,ushort):bool
-17 (-39.535% of base) : System.Private.Xml.dasm - Compiler:IsPhantomName(QilName):bool:this
-17 (-33.333% of base) : System.Data.Common.dasm - XmlDataDocument:GetNestedParentRelation(DataRow):DataRelation
-27 (-32.927% of base) : System.Collections.Immutable.dasm - ImmutableArrayExtensions:First(ImmutableArray`1):__Canon
-21 (-30.882% of base) : System.Private.Xml.dasm - CSharpHelpers:IsPrefixTwoUnderscore(String):bool
-21 (-30.882% of base) : System.CodeDom.dasm - CSharpHelpers:IsPrefixTwoUnderscore(String):bool
-11 (-29.730% of base) : Microsoft.VisualBasic.Core.dasm - CharType:FromString(String):ushort
-11 (-29.730% of base) : Microsoft.VisualBasic.Core.dasm - Conversions:ToChar(String):ushort
-16 (-29.630% of base) : Microsoft.CodeAnalysis.dasm - PathUtilities:IsDriveRootedAbsolutePath(String):bool
-11 (-27.500% of base) : Microsoft.VisualBasic.Core.dasm - FileSystem:ChDrive(String)
-11 (-25.000% of base) : System.Drawing.Common.dasm - Font:IsVerticalName(String):bool
-26 (-24.762% of base) : System.Private.Xml.dasm - XmlAutoDetectWriter:IsHtmlTag(String):bool
-11 (-24.444% of base) : System.Private.DataContractSerialization.dasm - XmlUTF8NodeWriter:WritePrefix(String):this
-21 (-24.419% of base) : System.Private.Xml.dasm - ValidateNames:StartsWithXml(String):bool
672 total methods with Code Size differences (670 improved, 2 regressed), 190515 unchanged.

[sandreenko]

Hi @nathan-moore, thanks for the change.

@sandreenko Are JIT improvements still being accepted or should I shelve this for the time being?

The master branch is currently blocked for feature changes but it won't be long (~few weeks) until we open in for post-5.0 PRs, so you could keep it as an open PR, I have marked it as 6.0 so we don't mix it with 5.0 fixes.

[nathan-moore]

@sandreenko PTAL

[sandreenko]

PTAL @dotnet/jit-contrib

[sandreenko]

The change makes sense, thanks @nathan-moore , but I do not have enough expertise in this area to approve, @briansull could you please take a look?

I have left a few requests for comments for unclear parts, also expect outerloop/stress/jitstress testing for this change before the merge.

[briansull]

Taking a look at this

[briansull]

I would like to see some small updates then I will approve.

[briansull]

Comment should read:

// Is the current assertion a valid constant int32 assertion?

[nathan-moore]

This is the pre-existing style for this else if chain. I can change them over, but I personally like having the form there.

[briansull]

Looks Good

[am11]

fixes #11623

@briansull, @nathan-moore fyi: his keyword has closed the issue when PR was merged but the original repro in the issue persists (bound check elides with length > 4 but not with length >= 5): #11623 (comment). Should we reopen the issue?

[danmoseley]

@briansull I happened to notice the question above wasn't answered.

[briansull]

We closed the issue #11623 when PR was merged
but the original repro in the issue persists (bound check elides with length > 4 but not with length >= 5):

I will reopen it.