JIT: Don't allocate string literals inside potential BBJ_THROW candidates

[EgorBo]

Together with #48589, this PR addresses #48573 (comment)

Example:

usingSystem;classProg{staticvoidMain(string[]args){ThrowIfNull(args,nameof(args));}privatestaticvoidThrowIfNull(objectarg,stringargName){if(argisnull)ThrowAE(argName);}privatestaticvoidThrowAE(stringarg)=>thrownewArgumentNullException(arg);}

Codegen diff for Main: https://www.diffchecker.com/tZAYRdBY

As you can see, nameof(args) literal is not allocated on heap during JIT compilation, a lazy-allocate helper is emitted instead.

jit-diff (jit-utils -f --pmi):

PMI CodeSize Diffs for System.Private.CoreLib.dll, framework assemblies for default jit
Summary of Code Size diffs:
(Lower is better)
Total bytes of base: 52999910
Total bytes of diff: 53048663
Total bytes of delta: 48753 (0.09% of base)
diff is a regression.
Top file regressions (bytes):
39746 : System.Collections.Immutable.dasm (3.08% of base)
3724 : System.Collections.Concurrent.dasm (0.96% of base)
3448 : FSharp.Core.dasm (0.09% of base)
468 : System.Private.DataContractSerialization.dasm (0.06% of base)
359 : System.Private.Xml.dasm (0.01% of base)
345 : System.Net.Sockets.dasm (0.20% of base)
244 : System.Net.Http.WinHttpHandler.dasm (0.26% of base)
118 : Microsoft.Diagnostics.Tracing.TraceEvent.dasm (0.00% of base)
74 : System.Data.Odbc.dasm (0.04% of base)
59 : System.Drawing.Primitives.dasm (0.15% of base)
50 : System.Private.CoreLib.dasm (0.00% of base)
40 : System.Net.Http.dasm (0.01% of base)
40 : Microsoft.Extensions.Logging.Console.dasm (0.09% of base)
20 : System.Net.WebSockets.dasm (0.05% of base)
18 : System.Text.RegularExpressions.dasm (0.01% of base)
15 total files with Code Size differences (0 improved, 15 regressed), 256 unchanged.
Top method regressions (bytes):
2025 (16.17% of base) : FSharp.Core.dasm - Array2DModule:CopyTo(ref,int,int,ref,int,int,int,int) (8 methods)
710 ( 5.09% of base) : System.Collections.Immutable.dasm - ImmutableHashSet`1:SymmetricExcept(IEnumerable`1,MutationInput):MutationResult (8 methods)
640 (14.24% of base) : System.Collections.Immutable.dasm - ImmutableList`1:ConvertAll(Func`2):ImmutableList`1:this (64 methods)
640 (14.24% of base) : System.Collections.Immutable.dasm - Builder:ConvertAll(Func`2):ImmutableList`1:this (64 methods)
580 ( 7.97% of base) : System.Collections.Immutable.dasm - Node:NodeTreeFromList(IOrderedCollection`1,int,int):Node (24 methods)
504 ( 7.04% of base) : System.Collections.Immutable.dasm - ImmutableHashSet`1:Intersect(IEnumerable`1,MutationInput):MutationResult (8 methods)
390 ( 4.44% of base) : System.Collections.Immutable.dasm - Builder:AddRange(IEnumerable`1):this (32 methods)
384 (25.08% of base) : System.Collections.Immutable.dasm - ImmutableSortedDictionary`2:.ctor(Node,int,IComparer`1,IEqualityComparer`1):this (8 methods)
352 (25.79% of base) : System.Collections.Immutable.dasm - MutationInput:.ctor(SortedInt32KeyNode`1,IEqualityComparer`1,IEqualityComparer`1,int):this (8 methods)
320 (15.62% of base) : System.Collections.Immutable.dasm - Builder:Sort(int,int,IComparer`1):this (16 methods)
320 ( 4.75% of base) : System.Collections.Immutable.dasm - Node:CopyTo(ref,int):this (16 methods)
320 ( 8.36% of base) : System.Collections.Immutable.dasm - Node:CopyTo(int,ref,int,int):this (8 methods)
320 ( 3.54% of base) : System.Collections.Immutable.dasm - Node:CopyTo(Array,int):this (16 methods)
310 ( 4.07% of base) : System.Collections.Immutable.dasm - ImmutableHashSet`1:Except(IEnumerable`1,IEqualityComparer`1,IEqualityComparer`1,SortedInt32KeyNode`1):MutationResult (8 methods)
308 (17.94% of base) : System.Collections.Immutable.dasm - Builder:get_Origin():MutationInput:this (16 methods)
300 ( 7.18% of base) : System.Collections.Immutable.dasm - Builder:set_KeyComparer(IEqualityComparer`1):this (16 methods)
272 ( 8.80% of base) : System.Collections.Immutable.dasm - ImmutableSortedDictionary`2:WithComparers(IComparer`1,IEqualityComparer`1):ImmutableSortedDictionary`2:this (8 methods)
256 (12.22% of base) : System.Collections.Immutable.dasm - ImmutableArray:Create(ref,int,int):ImmutableArray`1 (8 methods)
256 (10.68% of base) : System.Collections.Immutable.dasm - ImmutableArray:CreateRange(ImmutableArray`1,int,int,Func`2):ImmutableArray`1 (8 methods)
244 ( 3.75% of base) : System.Collections.Immutable.dasm - ImmutableSortedSet`1:SymmetricExcept(IEnumerable`1):ImmutableSortedSet`1:this (8 methods)
Top method regressions (percentages):
18 (100.00% of base) : System.Collections.Concurrent.dasm - ThrowHelper:ThrowKeyNullException()
23 (35.94% of base) : System.Private.DataContractSerialization.dasm - XmlReaderDelegator:ReadContentAsBoolean():bool:this
23 (35.94% of base) : System.Private.DataContractSerialization.dasm - XmlReaderDelegator:ReadContentAsSingle():float:this
23 (35.94% of base) : System.Private.DataContractSerialization.dasm - XmlReaderDelegator:ReadContentAsDouble():double:this
23 (35.94% of base) : System.Private.DataContractSerialization.dasm - XmlReaderDelegator:ReadContentAsDecimal():Decimal:this
23 (35.94% of base) : System.Private.DataContractSerialization.dasm - XmlReaderDelegator:ReadContentAsDateTime():DateTime:this
23 (35.94% of base) : System.Private.DataContractSerialization.dasm - XmlReaderDelegator:ReadContentAsInt():int:this
23 (35.94% of base) : System.Private.DataContractSerialization.dasm - XmlReaderDelegator:ReadContentAsLong():long:this
80 (26.76% of base) : System.Collections.Immutable.dasm - ImmutableList:ToImmutableList(Builder):ImmutableList`1 (8 methods)
80 (26.76% of base) : System.Collections.Immutable.dasm - ImmutableSortedDictionary:ToImmutableSortedDictionary(Builder):ImmutableSortedDictionary`2 (8 methods)
80 (26.76% of base) : System.Collections.Immutable.dasm - ImmutableSortedSet:ToImmutableSortedSet(Builder):ImmutableSortedSet`1 (8 methods)
352 (25.79% of base) : System.Collections.Immutable.dasm - MutationInput:.ctor(SortedInt32KeyNode`1,IEqualityComparer`1,IEqualityComparer`1,int):this (8 methods)
49 (25.65% of base) : System.Drawing.Primitives.dasm - Color:FromArgb(int,int,int,int):Color
80 (25.56% of base) : System.Collections.Immutable.dasm - ImmutableArray:ToImmutableArray(Builder):ImmutableArray`1 (8 methods)
80 (25.40% of base) : System.Collections.Immutable.dasm - NodeEnumerable:.ctor(SortedInt32KeyNode`1):this (8 methods)
384 (25.08% of base) : System.Collections.Immutable.dasm - ImmutableSortedDictionary`2:.ctor(Node,int,IComparer`1,IEqualityComparer`1):this (8 methods)
80 (23.81% of base) : System.Collections.Immutable.dasm - ImmutableHashSet`1:Union(IEnumerable`1):ImmutableHashSet`1:this (8 methods)
80 (23.81% of base) : System.Collections.Immutable.dasm - ImmutableDictionary`2:AddRange(IEnumerable`1):ImmutableDictionary`2:this (8 methods)
80 (23.26% of base) : System.Collections.Immutable.dasm - ImmutableArrayExtensions:Any(Builder):bool (8 methods)
80 (23.26% of base) : System.Collections.Concurrent.dasm - IDictionaryDebugView`2:.ctor(IDictionary`2):this (8 methods)
1191 total methods with Code Size differences (0 improved, 1191 regressed), 267367 unchanged.

Quite a size regression (for obvious reasons) but each regression is basically a saved GC allocation.
~ +10 bytes of machine code per each literal (in the cold sections)

PS: 67% of the regression is in System.Collections.Immutable.dasm

[EgorBo]

@dotnet/jit-contrib PTAL

[AndyAyersMS]

67% of the regression is in System.Collections.Immutable

Is there a pattern to the methods in this assembly that we might want to reconsider?

[EgorBo]

@BruceForstall you're right, I've changed the logic to just scan a top-level node of the current statement in fgMorphConst and got almost the same jit-diff with basically zero overhead for JIT.

@AndyAyersMS from my understanding, System.Collections.Immutable has a lot of generic types with multiple generic arguments so all diffs are multiplied by some big value (PMI mode)

[BruceForstall]

@AndyAyersMS from my understanding, System.Collections.Immutable has a lot of generic types with multiple generic arguments so all diffs are multiplied by some big value (PMI mode)

I believe you're correct. However, have you tried crossgen/crossgen2 libraries SuperPMI asm diffs, or using "jit-diff" without "--pmi", to see if that's the case?

[EgorBo]

@AndyAyersMS from my understanding, System.Collections.Immutable has a lot of generic types with multiple generic arguments so all diffs are multiplied by some big value (PMI mode)

I believe you're correct. However, have you tried crossgen/crossgen2 libraries SuperPMI asm diffs, or using "jit-diff" without "--pmi", to see if that's the case?

yeah with crossgen it's 20x smaller:

Total bytes of delta: 2241 (0.01% of base)
diff is a regression.
Top file regressions (bytes):
1676 : System.Collections.Immutable.dasm (0.74% of base)
201 : FSharp.Core.dasm (0.02% of base)
121 : System.Net.Sockets.dasm (0.08% of base)
102 : System.Collections.Concurrent.dasm (0.22% of base)
72 : System.Net.Http.WinHttpHandler.dasm (0.11% of base)
20 : System.Drawing.Primitives.dasm (0.06% of base)
15 : System.Private.CoreLib.dasm (0.00% of base)
14 : System.Net.WebSockets.dasm (0.03% of base)
8 : System.Private.DataContractSerialization.dasm (0.00% of base)
6 : System.Net.Http.dasm (0.00% of base)
6 : System.Private.Xml.dasm (0.00% of base)