Port runtime PR dotnet/runtime#133111 R2R changes to SDK Crossgen tasks - #56395

## Why

CoreCLR WASI composite ReadyToRun currently names the composite owner
image `composite-r2r.wasm`. `PrepareForReadyToRunCompilation` in
Crossgen2Tasks forces that name whenever `Crossgen2Tool` TargetOS is
`wasi`. The browser composite work in #134618 uses the task's default
name instead: `<entry>.r2r.wasm`, the main assembly name with
`.r2r.wasm`.

This PR drops the TargetOS special case so WASI gets the same owner name
as browser. It lands ahead of the dotnet/sdk#56395 port, so that PR
doesn't carry the WASI rule into the SDK.

The two delivery models stay different on purpose. Browser instantiates
the composite at runtime through the JS loader. WASI composes it offline
into the host with `wasm-merge`/`wasm-opt`. Only the naming contract
changes.

## Design

The composite's own file name, as written by crossgen2, is the single
authority. It is also the owner name every component stub records.

- **`PrepareForReadyToRunCompilation`:** the `wasi` branch is removed. A
wasm composite owner is now `<entry>.r2r.wasm` on both targets.
- **`WasiApp.CoreCLR.targets`:** the composite path now comes from the
planned composite compilation, `@(_ReadyToRunCompileList)` with
`CreateCompositeImage=true`, via `%(OutputR2RImage)`. The build errors
unless there is exactly one composite compilation. Because the path
isn't hardcoded, WASI keeps working with either SDK naming.
- **`wasi_r2r_probe.hpp`:** the host reserves a 256-byte composite name
buffer, zero-initialized, and exports its address and capacity
(`wasi_r2r_composite_name_base`, `wasi_r2r_composite_name_cap`). The
probe serves the composite only when the requested name matches the
recorded name, and only if that name is non-empty. An uncomposed host
therefore serves no composite. There is no wildcard matching and no name
compiled into C++.
- **`ComposeWasiReadyToRun`:** the composer reads the two new exports
and checks that the name is non-empty, contains no NUL, and fits the
buffer. Its shim now imports `webcil.memory` and includes an active data
segment that writes `Path.GetFileName(CompositePath)`, NUL-terminated,
into the host buffer. This is the same mechanism that already installs
the payload. A prebuilt host, such as the runtime-test corerun, can
therefore be composed with a composite of any name.
- **Docs:** updated the WASI host composition section of
`docs/design/mono/webcil.md` and
`docs/workflow/building/coreclr/wasi-r2r.md`.

## Validation

- `./build.sh clr+libs+host+packs -os wasi -arch wasm -c Release`
finished with 0 warnings and 0 errors.
- `./dotnet.sh publish
src/mono/sample/wasi/console/Wasi.Console.Sample.csproj -c Release
-p:TargetOS=wasi -p:TargetArchitecture=wasm -p:RuntimeFlavor=CoreCLR
-p:PublishReadyToRun=true` succeeded. The composer logged
`composite='Wasi.Console.Sample.r2r.wasm'`.
- The published app ran under wasmtime with `DOTNET_ReadyToRunLogFile`
set. It exited 0, and the log shows `Ready to Run initialized
successfully` for System.Private.CoreLib, Wasi.Console.Sample,
System.Runtime, System.Console, System.Threading and
System.Runtime.InteropServices.
- **Negative check:** I composed the same host with a copy of the
composite renamed to `Wrong.r2r.wasm`. Startup then traps in `EEStartup`
because CoreLib's owner composite isn't served. A name mismatch fails
loudly rather than silently interpreting.
- **Non-R2R publish** of the same sample: the app runs on the
interpreter, and the log shows `Ready to Run header not found`.
- **Not run:** browser `ReadyToRunTests`. The removed code only executed
when TargetOS was `wasi`, and the browser naming path is unchanged.

## Interaction with #134813

This PR merges cleanly with #134813's head (checked with `git
merge-tree`); it doesn't depend on #134813. The runtime-test harness in
#134813 passes the same `composite-r2r.wasm` path to both crossgen2 and
`WasiR2RComposer.proj`. The composer records that name in the shared
corerun, so the harness needs no changes. I did not build or run the
runtime tests with both PRs merged.

## Follow-up in dotnet/sdk#56395

- Remove the `wasi` TargetOS block from `CreateReadyToRunFileToPublish`.
- Change `It_uses_the_fixed_wasm_path_for_a_wasi_composite_owner` to
expect `<entry>.r2r.wasm`, the same as browser.

> [!NOTE]
> This pull request description was generated with assistance from
GitHub Copilot.

Co-authored-by: Copilot App <[email protected]>

## Summary

- Enable `PublishReadyToRunComposite` for CoreCLR browser-wasm when
WebCIL is enabled. Composite is opt-in; the default per-assembly R2R
mode is unchanged.
- Publish the composite owner (`<entry>.r2r.wasm`, the name crossgen2
records in each component stub) as a static web asset with a
`readyToRunComposite` trait, defined through `DefineStaticWebAssets`.
- `GenerateWasmBootJson` routes the owner to `resources.coreAssembly`
and flags it `isCompositeImage: true`. The loader keeps its `.wasm`
virtual path and leaves it out of the TPA, and component stubs stay in
the TPA. Owner identity comes from the flag, not the file name, so an
ordinary library named `*.r2r` still loads as a managed assembly.
- Route composite component stubs through `ConvertDllsToWebcil`, keep
the linked R2R closure across repeated trimmed publishes, and prune
stale per-app images and stubs.
- Invalidate per-app R2R images when the composite mode or crossgen2
arguments change. Component stubs share the per-assembly `<name>.wasm`
names, so without this, switching composite to per-assembly shipped
stale stubs that failed at startup.
- Composite needs ReadyToRun tasks that name the owner
`<entry>.r2r.wasm`. The base SDK doesn't yet (dotnet/sdk#56395), so a
composite publish with stock SDK tasks fails fast with an actionable
error. Wasm.Build.Tests use the in-repo Crossgen2Tasks, which now also
ship in the `BuildWasmApps` Helix payload.

## Validation

On `main` as of 2026-09-29, including WebCIL wrapper v2 (#134312), WASI
composite in the shared Crossgen2Tasks (#133265), and the browser R2R
strip defaults (#134690):

- Rebuilt the CoreCLR browser Release runtime pack (`clr+libs+host`) and
the WebAssembly SDK pack.
- `Wasm.Build.Tests.ReadyToRunTests`: 10/10 passed. This covers:
  - composite trimmed, untrimmed and native-relinked, run in Chrome
  - a repeated trimmed publish
  - a composite → per-assembly → composite switch
  - per-assembly publish, native relink and dev-loop build
  - composite without WebCIL (negative)
- Negative checks:
- With the composite mode removed from the invalidation stamp, the
mode-switch assertion fails.
- With stock SDK ReadyToRun tasks, composite publish hits the new error.
- CI: `PublishRunAllPagesComposite` passed on Helix on Linux and
Windows. The remaining failures matched known issues (#133953, #133373).

Benchmark (`IndexOfMax<double>(3079)`, browser, earlier revision of this
PR): composite R2R ran the SIMD path with a median of **4,040 ns/op**,
vs. **1,013,940 ns/op** interpreted and **10,652,060 ns/op** with
per-assembly R2R.

Part of testing #134559. That issue's default per-assembly
scenario is not changed by this PR.

> [!NOTE]
> This pull request description was generated with GitHub Copilot
assistance.

---------

Co-authored-by: Copilot App <[email protected]>

Composite CoreCLR WASM R2R needs ReadyToRun SDK tasks that name the
owner image <entry>.r2r.wasm (dotnet/sdk#56395), which the SDK shipped
in the BrowserWasmCoreCLR perf artifact does not have yet.
dotnet/runtime#135204 stages runtime's wasm-aware Crossgen2Tasks shim
into that artifact as staging/Crossgen2Tasks.

Copy the shim into the Helix payload when present, export its location
as PERFLAB_WASM_CROSSGEN2_TASKS_DIR for the r2r_composite lane only, and
in composite mode pass it to the WebAssembly SDK through
Crossgen2SdkOverridePropsPath/Crossgen2SdkOverrideTargetsPath. These must
be environment properties because the SDK reads them during props
evaluation. Per-assembly R2R keeps the SDK's own ReadyToRun tasks.

TODO: remove once the SDK carries dotnet/sdk#56395
(dotnet/runtime#135023).

Co-authored-by: Copilot App <[email protected]>

…ifact (#135204)

The new composite R2R microbenchmark lane in dotnet/performance#5324
(`coreclr_r2r_composite_v8`) publishes CoreCLR browser-wasm with
`PublishReadyToRunComposite`. #134618's
`_WasmCoreClrValidateCompositeTasks` rejects that publish unless the SDK
ReadyToRun tasks name the owner `<entry>.r2r.wasm`. The SDK tasks only
learn to do that in dotnet/sdk#56395, which hasn't reached runtime's
global.json SDK yet (11.0.100-rc.1.26420.103).

This PR copies the in-tree wasm-aware task shim, the same one
Wasm.Build.Tests use via
`Crossgen2SdkOverridePropsPath`/`Crossgen2SdkOverrideTargetsPath`, into
the `BrowserWasmCoreCLR` perf artifact. The shim comes from
`artifacts/bin/Crossgen2Tasks/<config>/`, which `Build.proj` already
produces.

Staged layout (flat, no config subfolder; this is the path
dotnet/performance consumes):

```
staging/Crossgen2Tasks/Crossgen2Tasks.dll
staging/Crossgen2Tasks/Microsoft.NET.CrossGen.props
staging/Crossgen2Tasks/Microsoft.NET.CrossGen.targets
```

The step fails if the source directory or any of these three files is
missing. Only the CoreCLR leg (`includeCoreClrToolchainPacks: true`)
changes; the Mono artifact is untouched.

This is temporary: remove it once dotnet/sdk#56395 reaches global.json.
Tracked by #135023.

Validation: YAML parses (`python3 yaml.safe_load`) and `git diff
--check` is clean. The pipeline itself hasn't run yet.

> [!NOTE]
> This PR was generated with the help of GitHub Copilot.

Co-authored-by: Copilot App <[email protected]>
Copilot-Session: a287cfc0-a881-4272-9024-bdaf9d9db4ef

* Add CoreCLR WASM composite R2R microbenchmark lane

Add a coreclr_r2r_composite_v8 job (r2rRunType r2r_composite) alongside
the per-assembly coreclr_r2r_v8 lane. The mode flows through
run_performance_job.py (R2RType=r2r_composite, a separate PerfLab
history) to a new --wasm-ready-to-run-composite micro_benchmarks option,
which sets PERFLAB_WASM_READY_TO_RUN_COMPOSITE for MSBuild.

MicroBenchmarks.Wasm.targets now sets PublishReadyToRunComposite from
the selected mode, validates it, and in composite mode verifies that
exactly one <entry>.r2r.wasm composite image was produced with
component inputs and that it was defined as the readyToRunComposite
publish asset that GenerateWasmBootJson routes to coreAssembly.

Depends on dotnet/runtime#134618.

Co-authored-by: Copilot App <[email protected]>

* Use runtime's Crossgen2Tasks shim for CoreCLR WASM composite R2R

Composite CoreCLR WASM R2R needs ReadyToRun SDK tasks that name the
owner image <entry>.r2r.wasm (dotnet/sdk#56395), which the SDK shipped
in the BrowserWasmCoreCLR perf artifact does not have yet.
dotnet/runtime#135204 stages runtime's wasm-aware Crossgen2Tasks shim
into that artifact as staging/Crossgen2Tasks.

Copy the shim into the Helix payload when present, export its location
as PERFLAB_WASM_CROSSGEN2_TASKS_DIR for the r2r_composite lane only, and
in composite mode pass it to the WebAssembly SDK through
Crossgen2SdkOverridePropsPath/Crossgen2SdkOverrideTargetsPath. These must
be environment properties because the SDK reads them during props
evaluation. Per-assembly R2R keeps the SDK's own ReadyToRun tasks.

TODO: remove once the SDK carries dotnet/sdk#56395
(dotnet/runtime#135023).

Co-authored-by: Copilot App <[email protected]>

* Clear inherited Crossgen2 SDK override paths for WASM R2R

configure_wasm_crossgen2_sdk_override now removes inherited
Crossgen2SdkOverridePropsPath/Crossgen2SdkOverrideTargetsPath before
deciding whether to apply the shim, so per-assembly R2R always keeps
the SDK's ReadyToRun tasks and a composite run without a staged shim
cannot pick up a stale path. PERFLAB_WASM_CROSSGEN2_TASKS_DIR remains
the only way to select a shim.

Co-authored-by: Copilot App <[email protected]>

* Fail fast on a present but incomplete Crossgen2Tasks shim

A BrowserWasmCoreCLR directory artifact with a staging/Crossgen2Tasks
folder that lacks the required files was treated like an artifact
without the shim, silently falling back to the SDK ReadyToRun tasks.
Only a missing folder (directory artifacts) or no extracted entries
(archives) now means "no shim"; anything else must contain
Crossgen2Tasks.dll and Microsoft.NET.CrossGen.props/.targets or
build_wasm_coreclr_payload raises ValueError. Add archive coverage.

Co-authored-by: Copilot App <[email protected]>

---------

Co-authored-by: Copilot App <[email protected]>