Add RuntimeHelpers.IsRuntimeAsync intrinsic

[jakobbotsch]

The interpreter and JIT fold this intrinsic to a constant based on whether the calling function is runtime async.

The motivation is cases like #130872 and #130689 where there is a worry about potentially regressing async1 callers, especially for .NET 11 where runtime async is opt-in in Roslyn.

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[Copilot]

Pull request overview

This PR introduces a new RuntimeHelpers.IsRuntimeAsync() intrinsic in System.Private.CoreLib, and wires it up so both the CoreCLR JIT and the CoreCLR interpreter fold it to a compile-time constant based on whether the current compilation is for an async-calling-convention method (runtime-async).

Changes:

• Add RuntimeHelpers.IsRuntimeAsync() as an [Intrinsic] internal API stub in CoreLib.
• Extend CoreCLR JIT named-intrinsic plumbing to recognize the method and expand it to true / false during import based on compIsAsync().
• Extend CoreCLR interpreter named-intrinsic plumbing to recognize and constant-fold the method based on sig.isAsyncCall().

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs	Adds the new internal [Intrinsic] method stub IsRuntimeAsync().
src/coreclr/jit/namedintrinsiclist.h	Adds a new NamedIntrinsic enum value for RuntimeHelpers.IsRuntimeAsync.
src/coreclr/jit/importercalls.cpp	Recognizes and expands the intrinsic during import to a constant using compIsAsync().
src/coreclr/jit/fgbasic.cpp	Marks the intrinsic as foldable during IL stack simulation for jump target discovery.
src/coreclr/interpreter/intrinsics.cpp	Maps RuntimeHelpers.IsRuntimeAsync to the new NamedIntrinsic.
src/coreclr/interpreter/compiler.cpp	Expands the intrinsic to an ldc.i4 constant based on isAsyncCall(), and treats it as “must expand” for interpretation.

[jakobbotsch]

@EgorBot -intel -amd -arm --envvars DOTNET_JitDisasm:ReadLineAsync

usingSystem;usingSystem.Collections.Generic;usingSystem.IO;usingSystem.Text;usingSystem.Threading.Tasks;usingBenchmarkDotNet.Attributes;publicclassStreamReaderReadLineTests{privatestring_text;privatebyte[]_bytes;[ParamsSource(nameof(GetLineLengthRanges))]publicRangeLineLengthRange{get;set;}publicstaticIEnumerable<Range>GetLineLengthRanges(){yieldreturnnewRange(){Min=0,Max=0};yieldreturnnewRange(){Min=1,Max=1};yieldreturnnewRange(){Min=1,Max=8};yieldreturnnewRange(){Min=9,Max=32};yieldreturnnewRange(){Min=33,Max=128};yieldreturnnewRange(){Min=129,Max=1024};yieldreturnnewRange(){Min=1025,Max=2048};yieldreturnnewRange(){Min=0,Max=1024};}publicclassRange{publicintMin{get;set;}publicintMax{get;set;}publicoverridestringToString()=>$"[{Min,4}, {Max,4}]";}[GlobalSetup]publicvoidGlobalSetup(){_text=GenerateLinesText(LineLengthRange,16*1024);_bytes=Encoding.UTF8.GetBytes(_text);}[Benchmark]publicasyncTaskReadLineAsync(){using(StreamReaderreader=newStreamReader(newMemoryStream(_bytes))){while(awaitreader.ReadLineAsync()!=null);}}privatestaticstringGenerateLinesText(RangelineLengthRange,inttextTargetLength){intmin=lineLengthRange.Min;intmax=lineLengthRange.Max;stringnewLine=Environment.NewLine;varsb=newStringBuilder(textTargetLength+max+newLine.Length);varrandom=newRandom(42);while(sb.Length<textTargetLength){intcharsCount=random.Next(min,max);for(intc=0;c<charsCount;c++)sb.Append((char)random.Next('0','z'));sb.Append(newLine);}returnsb.ToString();}}

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

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[jakobbotsch]

cc @dotnet/jit-contrib PTAL @EgorBo@BrzVlad

Reverted the StreamReader change, I will fold it into #130689 instead, I was just checking that the intrinsic worked.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

[tannergooding]

Is this something we're going to consider making public longer term, or is it one of the internal-only APIs? -- Mostly wondering if I need to be tracking something for api-review, not asking for it to be or not.

[jakobbotsch]

Is this something we're going to consider making public longer term, or is it one of the internal-only APIs? -- Mostly wondering if I need to be tracking something for api-review, not asking for it to be or not.

I'm not sure yet. I think if everything was runtime async by default we would not need it. I think time will tell how often we end up needing this.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.

[jakobbotsch]

/ba-g Timeouts