JIT: always home register params on wasm

[AndyAyersMS]

Always home the live params on Wasm (we do not produce or rely on the calleeRegArgMaskLiveIn). Initialize this anyways to avoid random behavior in case somebody does look at it.

Addresses the caller-side this-drop blocker in #129850.

SuperPMI (corelib crossgen2, browser): +28 bytes / 4 contexts / 0.00%.

Note

This change was authored with the assistance of GitHub Copilot.

[Copilot]

Pull request overview

This PR fixes a wasm-specific prolog correctness issue where register-parameter homing could be skipped due to calleeRegArgMaskLiveIn not being populated on wasm (since wasm uses WasmRegAlloc rather than LSRA). The change makes wasm always invoke genHomeRegisterParams during prolog generation and updates wasm’s homing filter to use ref-counts instead of entry liveness.

Changes:

• In genFnProlog, always call genHomeRegisterParams under TARGET_WASM instead of gating on calleeRegArgMaskLiveIn.
• In wasm genHomeRegisterParams, switch the “spill / don’t spill” decision from fgFirstBB->bbLiveIn to lvRefCnt().

Reviewed changes

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

File	Description
src/coreclr/jit/codegenwasm.cpp	Changes wasm parameter-homing eligibility check to use ref-counts rather than entry liveness.
src/coreclr/jit/codegencommon.cpp	Makes wasm prolog always home register params, bypassing the calleeRegArgMaskLiveIn gate used for LSRA-based targets.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

[AndyAyersMS]

@adamperlin PTAL
@dotnet/wasm-contrib FYI

This gets us bit farther through SPC bring up.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

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

[Copilot]

Pull request overview

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

[AndyAyersMS]

Looks like we still have some older versions of node out there?

Console log: 'Directed_2' from job baee6d6c-7469-4026-9784-a026a91fe247 (azurelinux.3.amd64.open.rt) using docker image mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-26.04-helix-webassembly-amd64@sha256:3ef1314b50ac039078f6406d649d5ac72715deccd07bcbfe3dd43fa438be3fbd on a00LCE7
...
Running: node --stack-size=8192 /root/helix/work/correlation/corerun.js -c /root/helix/work/correlation /root/helix/work/workitem/e/JIT/Directed/Directed_2/Directed_2.dll
failed to asynchronously prepare wasm: CompileError: WebAssembly.instantiate(): invalid value type 'exn', enable with --experimental-wasm-exnref @+58
warning: Loading from a file URI (file:///root/helix/work/correlation/corerun.wasm) is not supported in most browsers. See https://emscripten.org/docs/getting_started/FAQ.html#how-do-i-run-a-local-webserver-for-testing-why-does-my-program-stall-in-downloading-or-preparing
Aborted(CompileError: WebAssembly.instantiate(): invalid value type 'exn', enable with --experimental-wasm-exnref @+58)
file:///root/helix/work/correlation/corerun.js:461
  /** @suppress {checkTypes} */ var e = new WebAssembly.RuntimeError(what);
                                        ^

RuntimeError: Aborted(CompileError: WebAssembly.instantiate(): invalid value type 'exn', enable with --experimental-wasm-exnref @+58)
    at abort (file:///root/helix/work/correlation/corerun.js:461:41)
    at instantiateArrayBuffer (file:///root/helix/work/correlation/corerun.js:530:5)
    at async createWasm (file:///root/helix/work/correlation/corerun.js:608:16)
    at async createDotnetRuntime (file:///root/helix/work/correlation/corerun.js:7517:15)

Node.js v23.11.1

[Copilot]

Pull request overview

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

[pavelsavara]

invalid value type 'exn', enable with --experimental-wasm-exnref @+58)
Node.js v23.11.1

Node version seems ok, we just need to pass --experimental-wasm-exnref in more scripts
#130550

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

[pavelsavara]

Node version seems ok, we just need to pass --experimental-wasm-exnref in more scripts #130550

Fixed now @AndyAyersMS

Log

node version: v23.11.1
Timeout in ms: 900000
Running: node --experimental-wasm-exnref --stack-size=8192 /root/helix/work/correlation/corerun.js -c /root/helix/work/correlation /root/helix/work/workitem/e/JIT/Directed/Directed_2/Directed_2.dll
19:04:04.786 Running test: JIT/Directed/perffix/primitivevt/callconv3_d/callconv3_d.dll
PASSED

...

PASSED
19:04:05.416 Passed test: JIT/Directed/shift/uint16_ro/uint16_ro.dll
Kill watchdog with PID 46
Expected: 100
Actual: 100
END EXECUTION - PASSED