Reg struct copy.

[sandreenko]

This PR changes the way we handle struct copies.
cc8c366: First, it deletes rationalize transformation that was converting ASG(LCL_VAR struct, smth) into STORE_BLK or STORE_OBJ.
3bc8f8e: Then it skips fgMorphOneAsgBlockOp transformation for ASG(LCL_VAR struct, smth), where struct can be replaced with a primitive type.

The overall diffs are positive, but small because of most of these structs are still marked as doNotEnreg in impNormStructVal, it will be fixed next.

Positive diffs come from:

1. using movups (for STORE_LCL_VAR instead of movdqu that is currently used for STORE_BLK), there was a PR https://github.com/dotnet/runtime/pull/1367/files that would use movups for all, but for now, it is useful for me to have different codegen for them, allows me to find diffs easily.
2. VN and CSE can propagate ASG(struct, 0) and similar constructions now, so we can coalesce chains of struct assignments now for zero-init, I will add non-zero cases later. It gives us diffs like -29 (-53.70% of base) : System.Private.CoreLib.dasm - SyncSuccessSentinelStateMachineBox[VoidTaskResult][System.Threading.Tasks.VoidTaskResult]:.ctor():this, that will be an issue in the next PR, see the discussion here First Class Structs: stop lying about underlying type. #1231 (comment);

The negative diffs come from:

1. STORE_BLK contained logic is less efficient, it often doesn't mark Data as contained when it is generating only one instruction;
2. fgMorphOneAsgBlockOp could retype structs with one gcField into primitive type copy without barriers and reporting, now we are generating costly STORE_OBJ, a primitive fix for it fails on a few library tests, I am checking them now.

diffs for the Reg struct copies commit, x64, crossgen framework

Total bytes of diff: -4957 (-0.02% of base)
    diff is an improvement.
Top file improvements (bytes):
       -1274 : Microsoft.Diagnostics.Tracing.TraceEvent.dasm (-0.04% of base)
       -1075 : System.Private.Xml.dasm (-0.03% of base)
        -496 : System.Linq.Expressions.dasm (-0.02% of base)
        -324 : System.Data.Common.dasm (-0.03% of base)
        -322 : System.Private.CoreLib.dasm (-0.01% of base)
        -308 : System.Transactions.Local.dasm (-0.30% of base)
        -179 : Newtonsoft.Json.dasm (-0.03% of base)
        -140 : Microsoft.CodeAnalysis.CSharp.dasm (-0.01% of base)
        -140 : Microsoft.CodeAnalysis.VisualBasic.dasm (-0.01% of base)
        -114 : System.Linq.dasm (-0.08% of base)
         -98 : System.Linq.Parallel.dasm (-0.02% of base)
         -76 : System.Security.AccessControl.dasm (-0.12% of base)
         -62 : xunit.performance.metrics.dasm (-0.46% of base)
         -56 : System.Private.DataContractSerialization.dasm (-0.01% of base)
         -54 : Microsoft.CodeAnalysis.dasm (-0.01% of base)
         -36 : System.IO.FileSystem.dasm (-0.06% of base)
         -35 : xunit.execution.dotnet.dasm (-0.02% of base)
         -28 : Microsoft.CSharp.dasm (-0.01% of base)
         -24 : System.Reflection.Metadata.dasm (-0.01% of base)
         -20 : System.Security.Cryptography.X509Certificates.dasm (-0.01% of base)
37 total files with Code Size differences (37 improved, 0 regressed), 72 unchanged.
Top method improvements (bytes):
        -304 (-0.91% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - Microsoft.Diagnostics.Tracing.Parsers.ClrTraceEventParser:EnumerateTemplates(System.Func`3[[System.String, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.String, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[Microsoft.Diagnostics.Tracing.EventFilterResponse, Microsoft.Diagnostics.Tracing.TraceEvent, Version=2.0.49.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]],System.Action`1[[Microsoft.Diagnostics.Tracing.TraceEvent, Microsoft.Diagnostics.Tracing.TraceEvent, Version=2.0.49.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]]):this
        -296 (-0.82% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - Microsoft.Diagnostics.Tracing.Parsers.ClrPrivateTraceEventParser:EnumerateTemplates(System.Func`3[[System.String, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.String, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[Microsoft.Diagnostics.Tracing.EventFilterResponse, Microsoft.Diagnostics.Tracing.TraceEvent, Version=2.0.49.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]],System.Action`1[[Microsoft.Diagnostics.Tracing.TraceEvent, Microsoft.Diagnostics.Tracing.TraceEvent, Version=2.0.49.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]]):this
        -256 (-0.53% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - Microsoft.Diagnostics.Tracing.Parsers.KernelTraceEventParser:EnumerateTemplates(System.Func`3[[System.String, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.String, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[Microsoft.Diagnostics.Tracing.EventFilterResponse, Microsoft.Diagnostics.Tracing.TraceEvent, Version=2.0.49.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]],System.Action`1[[Microsoft.Diagnostics.Tracing.TraceEvent, Microsoft.Diagnostics.Tracing.TraceEvent, Version=2.0.49.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]]):this
         -74 (-0.07% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - Microsoft.Diagnostics.Tracing.Parsers.ApplicationServerTraceEventParser:EnumerateTemplates(System.Func`3[[System.String, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.String, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[Microsoft.Diagnostics.Tracing.EventFilterResponse, Microsoft.Diagnostics.Tracing.TraceEvent, Version=2.0.49.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]],System.Action`1[[Microsoft.Diagnostics.Tracing.TraceEvent, Microsoft.Diagnostics.Tracing.TraceEvent, Version=2.0.49.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]]):this
         -50 (-2.43% of base) : System.Private.Xml.dasm - System.Xml.Schema.Compiler:CalculateEffectiveTotalRange(System.Xml.Schema.XmlSchemaParticle,byref,byref):this
         -50 (-2.42% of base) : System.Private.Xml.dasm - System.Xml.Schema.SchemaCollectionCompiler:CalculateEffectiveTotalRange(System.Xml.Schema.XmlSchemaParticle,byref,byref):this
         -44 (-1.50% of base) : Microsoft.CodeAnalysis.CSharp.dasm - Microsoft.CodeAnalysis.CSharp.LocalRewriter:MakeDecimalLiteral(Microsoft.CodeAnalysis.CSharp.CSharpSyntaxNode,Microsoft.CodeAnalysis.ConstantValue):Microsoft.CodeAnalysis.CSharp.BoundExpression:this
         -44 (-2.42% of base) : System.Data.Common.dasm - System.Data.Common.TimeSpanStorage:Aggregate(System.Int32[],int):System.Object:this
         -40 (-0.87% of base) : Microsoft.CodeAnalysis.VisualBasic.dasm - Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax.ExpressionEvaluator:PerformCompileTimeBinaryOperation(ushort,byte,Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax.CConst,Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax.CConst,Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax.ExpressionSyntax):Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax.CConst
         -40 (-1.66% of base) : Newtonsoft.Json.dasm - Newtonsoft.Json.Utilities.ConvertUtils:DecimalTryParse(System.Char[],int,int,byref):int
         -32 (-3.02% of base) : System.Private.Xml.dasm - System.Xml.Schema.SchemaCollectionCompiler:CalculateSequenceRange(System.Xml.Schema.XmlSchemaSequence,byref,byref):this
         -30 (-2.48% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - Microsoft.Diagnostics.Tracing.StartStopActivityComputer:FixAndProcessWindowsASP(Microsoft.Diagnostics.Tracing.TraceEvent,System.Collections.Generic.KeyValuePair`2[System.Guid,System.Guid][]):this
         -30 (-3.35% of base) : System.Private.Xml.dasm - System.Xml.Schema.Compiler:IsSequenceFromChoice(System.Xml.Schema.XmlSchemaSequence,System.Xml.Schema.XmlSchemaChoice):bool:this
         -30 (-1.68% of base) : System.Private.Xml.dasm - System.Xml.Xsl.IlGen.XmlILOptimizerVisitor:FoldArithmetic(int,System.Xml.Xsl.Qil.QilLiteral,System.Xml.Xsl.Qil.QilLiteral):System.Xml.Xsl.Qil.QilNode:this
         -26 (-0.66% of base) : Microsoft.CodeAnalysis.CSharp.dasm - Microsoft.CodeAnalysis.CSharp.Binder:DoUncheckedConversion(byte,Microsoft.CodeAnalysis.ConstantValue):System.Object
         -26 (-0.57% of base) : Microsoft.CodeAnalysis.VisualBasic.dasm - Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax.Scanner:ScanNumericLiteral(Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax.SyntaxList`1[[Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax.VisualBasicSyntaxNode, Microsoft.CodeAnalysis.VisualBasic, Version=1.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]):Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax.SyntaxToken:this
         -26 (-2.50% of base) : System.Private.CoreLib.dasm - System.TimeZoneInfo:CreateAdjustmentRuleFromTimeZoneInformation(byref,System.DateTime,System.DateTime,int):AdjustmentRule
         -24 (-0.37% of base) : Microsoft.CodeAnalysis.CSharp.dasm - Microsoft.CodeAnalysis.CSharp.Binder:FoldNeverOverflowBinaryOperators(int,Microsoft.CodeAnalysis.ConstantValue,Microsoft.CodeAnalysis.ConstantValue):System.Object
         -24 (-2.11% of base) : Microsoft.CSharp.dasm - Microsoft.CSharp.RuntimeBinder.Semantics.ExpressionBinder:BindDecimalConstCast(Microsoft.CSharp.RuntimeBinder.Semantics.CType,Microsoft.CSharp.RuntimeBinder.Semantics.CType,Microsoft.CSharp.RuntimeBinder.Semantics.ExprConstant):Microsoft.CSharp.RuntimeBinder.Semantics.Expr
         -24 (-1.17% of base) : Microsoft.Diagnostics.Tracing.TraceEvent.dasm - <>c__DisplayClass0_0:<.ctor>b__1(Microsoft.Diagnostics.Tracing.TraceEvent):this

Total diffs for frameworks:
x64 Total bytes of diff: -5890 (-0.02% of base)
1338 total methods with Code Size differences (1262 improved, 76 regressed), 178158 unchanged.

arm64 Total bytes of diff: -23656 (-0.02% of base)
489 total methods with Code Size differences (311 improved, 178 regressed), 157900 unchanged.

arm Total bytes of diff: -1576 (-0.00% of base)
250 total methods with Code Size differences (169 improved, 81 regressed), 158053 unchanged.

x86 Total bytes of diff: -2962 (-0.01% of base)
580 total methods with Code Size differences (535 improved, 45 regressed), 178824 unchanged.

Based on #1231 (comment).

Side note: varTypeIsSmall and similar functions in vartype.h should assert on TYP_STRUCT because they don't have enough information to get a correct result, the callers should be responsible for handling that. It is a preexisting issue, but that change bumps its priority, I am working on a fix in another branch.

[sandreenko]

PTAL @CarolEidt @dotnet/jit-contrib

[sandreenko]

That is loweing, so nobody will read these flags, but I set them to have closer diffs.

[CarolEidt]

LGTM

[sandreenko]

Merged my changes with the new assert from #32750.

[sandreenko]

@kunalspathak thanks for your feedback, I added an example where var is not a struct, but ASG is.