JIT: update non-null assertion prop to destructure VNs

[AndyAyersMS]

In addition to checking for assertions based on the VN of an address, try and
destructure the VN to find the "base" address, and check its VNs as well.

This lets us get rid of some extra null checks, typically ones that are at
an offset from an existing non-null pointer.

Closes #49180.

[AndyAyersMS]

cc @dotnet/jit-contrib

About 900 methods (some dups, so total number of impacted methods is less) with diffs across the SPMI bundle. Mostly small improvements.

Bench            : 105 total methods with Code Size differences (102 improved, 3 regressed), 1 unchanged.
Libs -crossgen   : 174 total methods with Code Size differences (171 improved, 3 regressed), 3 unchanged.
Libs -crossgen2  : 138 total methods with Code Size differences (135 improved, 3 regressed), 1 unchanged.
Libs -pmi        : 528 total methods with Code Size differences (523 improved, 5 regressed), 2 unchanged.
Tests            :  33 total methods with Code Size differences ( 33 improved, 0 regressed), 0 unchanged.

For instance, in benchmarks:

Top method regressions (bytes):
           6 ( 2.14% of base) : 6766.dasm - System.Text.Json.Utf8JsonReader:EndArray():this
           6 ( 2.14% of base) : 6857.dasm - System.Text.Json.Utf8JsonReader:EndObject():this
           6 ( 4.38% of base) : 6896.dasm - System.Text.Json.Utf8JsonWriter:ValidateEnd(ubyte):this

Top method improvements (bytes):
         -70 (-1.50% of base) : 19790.dasm - System.Reflection.PortableExecutable.PEBuilder:WritePEHeader(System.Reflection.Metadata.BlobBuilder,System.Reflection.PortableExecutable.PEDirectoriesBuilder,System.Collections.Immutable.ImmutableArray`1[SerializedSection]):this
         -56 (-1.52% of base) : 17261.dasm - Microsoft.CodeAnalysis.CommonReferenceManager`2[__Canon,__Canon][System.__Canon,System.__Canon]:ResolveMetadataReferences(System.__Canon,System.Collections.Generic.Dictionary`2[__Canon,__Canon],byref,byref,byref,byref,byref,Microsoft.CodeAnalysis.DiagnosticBag):System.Collections.Immutable.ImmutableArray`1[ResolvedReference]:this
         -38 (-3.05% of base) : 2515.dasm - Utf8Json.Resolvers.Internal.DynamicObjectTypeBuilder:IsSideEffectFreeConstructorType(System.Reflection.ConstructorInfo):bool
         -32 (-1.19% of base) : 9052.dasm - System.Uri:GetCanonicalPath(byref,int):this
         -21 (-1.39% of base) : 5136.dasm - System.Memory.ReadOnlySequence:GlobalSetup():this
         -19 (-2.59% of base) : 2443.dasm - System.Reflection.Emit.ILGenerator:Emit(System.Reflection.Emit.OpCode,System.Reflection.ConstructorInfo):this
         -18 (-1.75% of base) : 2146.dasm - System.Reflection.Emit.DynamicILGenerator:Emit(System.Reflection.Emit.OpCode,System.Reflection.MethodInfo):this
         -18 (-3.01% of base) : 2461.dasm - System.Reflection.Emit.ILGenerator:Emit(System.Reflection.Emit.OpCode,System.Reflection.MethodInfo):this
         -18 (-1.27% of base) : 5991.dasm - <WriteAsyncInternal>d__183`1[AsyncReadWriteAdapter][System.Net.Security.AsyncReadWriteAdapter]:MoveNext():this
         -17 (-7.36% of base) : 6733.dasm - Newtonsoft.Json.JsonReader:Pop():int:this
         -16 (-2.30% of base) : 10520.dasm - System.Buffers.ReadOnlySequence`1[Byte][System.Byte]:Slice(long,long):System.Buffers.ReadOnlySequence`1[Byte]:this
         -16 (-8.70% of base) : 9544.dasm - Sigil.Impl.ExtensionMethods:IsPrefix(System.Reflection.Emit.OpCode):bool
         -16 (-3.89% of base) : 18816.dasm - Microsoft.CodeAnalysis.CSharp.CodeGen.CodeGenerator:EmitConversionExpression(Microsoft.CodeAnalysis.CSharp.BoundConversion,bool):this
         -15 (-0.89% of base) : 9989.dasm - Microsoft.Extensions.Caching.Memory.MemoryCache:SetEntry(Microsoft.Extensions.Caching.Memory.CacheEntry):this
         -15 (-0.52% of base) : 17036.dasm - Microsoft.CodeAnalysis.CSharp.Syntax.InternalSyntax.LanguageParser:ParseNamespaceBody(byref,byref,byref,ushort):this
         -15 (-9.04% of base) : 12390.dasm - System.Text.Json.Utf8JsonReader:GetBoolean():bool:this
         -14 (-1.23% of base) : 1193.dasm - System.Reflection.Emit.ILGenerator:Emit(System.Reflection.Emit.OpCode,int):this
         -14 (-0.32% of base) : 9539.dasm - Sigil.Emit`1[__Canon][System.__Canon]:ValidateTryCatchFinallyBranches():this
         -12 (-2.74% of base) : 19610.dasm - Microsoft.Cci.FullMetadataWriter:PopulatePropertyMapTableRows():this
         -12 (-1.72% of base) : 2462.dasm - System.Reflection.Emit.ILGenerator:EmitCall(System.Reflection.Emit.OpCode,System.Reflection.MethodInfo,System.Type[]):this

Sample diff. In this method there were several sets of these.

;; SourceLocalSymbol:GetDeclaratorSyntax():Microsoft.CodeAnalysis.SyntaxNode:this

 G_M46873_IG04:        ; gcrefRegs=00000040 {rsi}, byrefRegs=00000000 {}, byref
        ; gcrRegs -[rax] +[rsi]
        ; byrRegs -[rsi]
        lea      rax, bword ptr [rsi+40]
        ; byrRegs +[rax]
-       mov      rcx, gword ptr [rax]
-       ; gcrRegs +[rcx]
-       mov      edx, dword ptr [rax+8]
-       mov      edx, dword ptr [rax+16]
-       mov      edx, dword ptr [rax+20]
-       mov      rax, rcx
+       mov      rax, gword ptr [rax]
        ; gcrRegs +[rax]
        ; byrRegs -[rax]
        jmp      G_M46873_IG24

A handful of regressions where the extra morphing this engenders causes a computation to be narrowed so that it can no longer share the value from a wider computation done earlier.

;; BEFORE

G_M14663_IG08:        ; gcrefRegs=00000000 {}, byrefRegs=00000042 {rcx rsi}, byref, isz
       ; byrRegs -[rax rdx]
       shr      qword ptr [rcx+8], 1
       test     byte  ptr [rcx+8], 1

;; AFTER
G_M14663_IG08:        ; gcrefRegs=00000000 {}, byrefRegs=00000042 {rcx rsi}, byref, isz
       shr      qword ptr [rcx+8], 1
       mov      rcx, qword ptr [rcx+8]
       ; byrRegs -[rcx]
       test     cl, 1

[AndyAyersMS]

Ideally perhaps this while loop would be unnecessary, and VN creation would fold chains of constant adds into a single add.

Also note there is a similar loop on the gen side in optCreateAssertion which given a dereference through a byref, tries to walk the VN back to the inspiring gc ref.

[AndyAyersMS]

Also we should be able to get rid of the IR destructuring (see first part of optAssertionProp_Ind for example) for global prop as the VN destructuring should be equivalent, but when I did that I lost some of the diffs, and it creates more divergence between local prop and global prop.

[GrabYourPitchforks]

I pulled in this private against my local branch and confirmed that the codegen appears optimized now. Thanks! :)

[AndyAyersMS]

Thanks!

Sure, glad this was one we could fix without too much trouble. Diff from your example was over in the issue, I'll copy it here...

;  V01 arg1         [V01,T01] (  4,  3.50)     int  ->  rdx
 ;# V02 OutArgs      [V02    ] (  1,  1   )  lclBlk ( 0) [rsp+0x00]   "OutgoingArgSpace"
 ;  V03 tmp1         [V03,T03] (  3,  2   )   ubyte  ->  rcx         "Inline return value spill temp"
-;  V04 tmp2         [V04,T02] (  3,  4   )   byref  ->  rcx         "Inlining Arg"
+;  V04 tmp2         [V04,T02] (  2,  3   )   byref  ->  rcx         "Inlining Arg"
 ;
 ; Lcl frame size = 0

@@ -22,11 +22,10 @@ G_M44576_IG02:
        jae      SHORT G_M44576_IG04
                                                ;; bbWeight=1    PerfScore 3.50
 G_M44576_IG03:
-       cmp      dword ptr [rcx], ecx
        mov      eax, edx
        movzx    rcx, byte  ptr [rcx+rax]
        jmp      SHORT G_M44576_IG05
-                                               ;; bbWeight=0.50 PerfScore 3.12
+                                               ;; bbWeight=0.50 PerfScore 2.12
 G_M44576_IG04:
        xor      ecx, ecx
                                                ;; bbWeight=0.50 PerfScore 0.12
@@ -34,7 +33,7 @@ G_M44576_IG05:
        jmp      Console:WriteLine(int)
                                                ;; bbWeight=1    PerfScore 2.00

-; Total bytes of code 29, prolog size 0, PerfScore 11.65, instruction count 10, allocated bytes for code 29 (MethodHash=7cd251df) for method C:M(int):this
+; Total bytes of code 27, prolog size 0, PerfScore 10.45, instruction count 9, allocated bytes for code 27 (MethodHash=7cd251df) for method C:M(int):this

[briansull]

Looks Good

[AndyAyersMS]

Improvement: DrewScoggins/performance-2#4223