Upgrade Emscripten to 5.0.6 & LLVM to 23 by akoeplinger · Pull Request #129299 · dotnet/runtime

akoeplinger · 2026-06-11T16:44:45Z

Summary

This change upgrades the Emscripten SDK used by the WebAssembly (browser/wasi)
build from 3.1.56 to 5.0.6, which also brings the bundled LLVM from
version 19 (API 1900) to version 23 (API 2300). It updates the native build
flags, the Mono LLVM backend to compile and behave correctly against the new
LLVM, reworks the browser JS loader to drop the separate worker module
(dotnet.native.worker.mjs), and adjusts/annotates tests affected by the new
toolchain. Arcade SDK and dotnet-install related packaging is also refreshed.

Motivation

Staying on a current Emscripten/LLVM toolchain keeps the WASM target aligned with
upstream fixes and modern WebAssembly features. The newer Emscripten reuses the
main module as the pthread worker (removing the need for a dedicated worker JS
file), provides better futimens/timestamp support in the browser file system,
and ships LLVM 23, which required a number of Mono backend adaptations.

Changes by area

Toolchain / version bumps

src/mono/browser/emscripten-version.txt, eng/native/tryrun.browser.cmake:
Emscripten 3.1.56 → 5.0.6.
eng/Versions.props: EmsdkVersion 3.1.56 → 5.0.6.
src/mono/mono.proj: python package path updated to the
Microsoft.NET.Runtime.Emscripten.5.0.6.Python.win-x64 package.
eng/Version.Details.xml, eng/Version.Details.props: refreshed Emscripten /
Node transport package versions to match the new SDK.
global.json: Arcade / Helix / SharedFramework / Microsoft.NET.Sdk.IL SDKs
bumped to 11.0.0-beta.26314.102 / 11.0.0-preview.6.26314.102.
NuGet.config, src/mono/wasm/Wasm.Build.Tests/data/nuget.config: added the
general-testing package source.

Native build flags

eng/native/configureplatform.cmake (CoreCLR browser): add
-sWASM_LEGACY_EXCEPTIONS=1 to compile and link options, drop -lbulkmemory
(bulk memory is now enabled via -mbulk-memory compile option).
src/mono/browser/browser.proj, src/mono/browser/build/BrowserWasmApp.targets,
src/mono/mono/mini/CMakeLists.txt: pass -sWASM_LEGACY_EXCEPTIONS=1 alongside
-fwasm-exceptions, and select the EH static lib variant via a new
CONFIGURATION_EH_LIB (eh-wasm vs eh-js) instead of hard-coding eh-js.
src/mono/browser/runtime/CMakeLists.txt,
src/mono/wasm/build/WasmApp.Common.targets: add --enable-multivalue to the
wasm-opt invocation and link the selected libmono-wasm-${CONFIGURATION_EH_LIB}.a.

Mono LLVM backend (LLVM 23 compatibility) — `src/mono/mono/mini`

mini-llvm-cpp.cpp / mini-llvm-cpp.h: thread an explicit LLVMContextRef
through mono_llvm_create_constant_data_array and mono_llvm_get_ptr_type,
and derive the context from the relevant value/module/function instead of
LLVMGetGlobalContext(). Use Intrinsic::getOrInsertDeclaration for
LLVM_API_VERSION >= 2100.
mini-llvm.c:
- Suppress -Wdeprecated-declarations / MSVC 4996 for the pervasive global
  LLVM-C type accessors.
- Mask constants in const_int8/const_int32 (and the 32-bit OP_STORE_*_IMM
  immediate path) so a negative int is not retained as upper bits — LLVM 23
  no longer truncates when SignExtend == FALSE, which previously corrupted
  subsequent ZExt constant folding.
- Add NaN-preserving FP narrowing: new emit_fpnarrow / quiet_nan_for_fptype
  that detect a NaN input and select a canonical quiet NaN, used by
  OP_FCONV_TO_R4 and by convert_full for float/double → half (scalar and
  vector). This guards against LLVM 23 lowering the software Half conversion to
  a hardware fptrunc that drops the NaN mantissa (turning NaN into ±Inf).
- Replace LLVMConstInt(..., -1, FALSE) with LLVMConstAllOnes(...) where an
  all-ones value is intended, and pass SignExtend = TRUE for the signed
  OP_ICOMPARE_IMM immediate.

Browser JS loader — drop the separate pthread worker module

Newer Emscripten reuses the main script as the worker, so the dedicated
dotnet.native.worker.mjs / js-module-threads asset is removed end to end:

src/mono/browser/runtime/loader/run.ts: workers now bootstrap via the main
module; createEmscriptenWorker sets up handlers and dispatches the load
message, and is invoked when running in a worker.
allocate workers from loaderHelpers.scriptUrl instead of resolving the js-module-threads asset.
remove the jsModuleWorker resource and js-module-threads behavior.
Build/packaging: no longer copy/track dotnet.native.worker.mjs.
WebAssembly SDK tasks: BootJsonData.cs, BootJsonBuilderHelper.cs drop the
jsModuleWorker boot-resource group.

File system timestamps (browser nanosecond support)

src/libraries/System.Private.CoreLib/src/System/IO/FileStatus.Unix.cs: remove
the TARGET_BROWSER/TARGET_WASI special case that wrote both access and write
times together; the new Emscripten honors per-field futimens/utimensat.
System.IO.FileSystem.Tests: refactor the temporal-resolution model in
BaseGetSetTimes to SecondTemporalResolution /
MilliSecondTemporalResolution / NanoSecondTemporalResolution (and the
Not* variants), and remove now-obsolete Browser carve-outs/ActiveIssues in
File/Copy.cs, File/GetSetTimes.cs, and FileInfo/GetSetTimes.cs.

Test annotations for the new toolchain

System.Runtime.Tests HalfTests.cs / HalfTests.GenericMath.cs: add
ActiveIssue (MonoAOT: LLVM 23 regressions in Half NaN handling #129507) for iOS on the Half NaN/conversion math tests.
Wasm.Build.Tests: EventPipeDiagnosticsTests annotated with ActiveIssue
([wasm] Wasm.Build.Tests EventPipeDiagnosticsTests CPU-sampling tests fail after emsdk 5.0.6 / LLVM 23 legacy-EH change #129584); BuildEnvironment/ProjectProviderBase/WasmSdkBasedProjectProvider
updated to stop expecting dotnet.native.worker.mjs.
Interop and JIT/Loader tests: add ActiveIssue (MonoInterp/Minijit win-x64: COM interop (SafeArray/Variant/struct reverse-pinvoke) test failures #129581 / MonoAOT: LLVM 23 regressions in FullAOT JIT test outcomes #129508) for Mono on
COM/VARIANT/struct-marshalling and several nullable/localloc/GVM tests
(including IL .custom ActiveIssueAttribute entries).

Active issues caused by this upgrade

Followup #129396

Copilot

Pull request overview

This PR updates the Mono WASM/Browser toolchain to Emscripten (emsdk) 5.0.6, and refreshes several repo toolset dependency versions (Arcade/Helix/SDK pins) plus related engineering scripts/templates.

Changes:

Bump Emscripten version from 3.1.56 → 5.0.6 and update the Windows Python package path used for Browser/WASI builds.
Refresh dependency/version pins in global.json, eng/Versions.props, and eng/Version.Details.*.
Update engineering infrastructure (NuGet feed setup scripts, ADO templates, OpenBSD rootfs behavior, Helix monitor timeout), and add an opt-in native compiler detection target.

Reviewed changes

Copilot reviewed 8 out of 17 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/mono/mono.proj	Updates Browser/WASI Windows Python path property to match the new Emscripten package ID/version.
src/mono/browser/emscripten-version.txt	Updates tracked Emscripten version to 5.0.6.
global.json	Updates Arcade/Helix/SharedFramework SDK pins and IL SDK version.
eng/Versions.props	Updates `EmsdkVersion` to 5.0.6.
eng/Version.Details.xml	Updates dependency versions/SHAs to the newer dotnet/dotnet toolset flow.
eng/Version.Details.props	Updates derived toolset version properties to match `Version.Details.xml`.
eng/native/tryrun.browser.cmake	Updates the version marker for the browser-wasm try_run cache to 5.0.6.
eng/common/templates/vmr-build-pr.yml	Switches VMR GitHub endpoint to `public`.
eng/common/templates/job/job.yml	Removes public-only CG skip step (logic moved elsewhere).
eng/common/SetupNugetSources.sh	Avoids triggering repo toolset setup as a side effect of feed configuration.
eng/common/SetupNugetSources.ps1	Same as above for PowerShell.
eng/common/native/LocateNativeCompiler.targets	Adds an opt-in target to infer linker flags via `init-compiler.sh` output.
eng/common/cross/build-rootfs.sh	Adjusts OpenBSD rootfs package extraction, symlink logic, and cleanup.
eng/common/core-templates/steps/enable-internal-sources.yml	Adds non-Windows feed setup path (Bash) alongside Windows (PowerShell).
eng/common/core-templates/job/job.yml	Sets public-project variables to skip CG detection / CodeQL auto-injection.
eng/common/core-templates/job/helix-job-monitor.yml	Gives Helix monitor tool more buffer time vs. ADO job timeout.

akoeplinger · 2026-06-11T17:21:07Z

/azp run runtime-wasm

azure-pipelines · 2026-06-11T17:21:19Z

Azure Pipelines successfully started running 1 pipeline(s).

(cherry picked from commit ea0ec7c)

Copilot

Pull request overview

Copilot reviewed 12 out of 21 changed files in this pull request and generated no new comments.

Copilot

Pull request overview

Copilot reviewed 13 out of 22 changed files in this pull request and generated 2 comments.

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 58 out of 61 changed files in this pull request and generated 3 comments.

Copilot

Pull request overview

Copilot reviewed 58 out of 61 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

src/mono/browser/runtime/assets.ts:30

instantiate_asset no longer recognizes the legacy "js-module-threads" behavior and will now throw in the default case if a custom/older boot config still includes it. Even though the dedicated worker module is being removed, it’s safer to keep accepting this behavior as a no-op for backward compatibility (same as dotnetwasm/symbols).

    switch (asset.behavior) {
        case "dotnetwasm":
        case "js-module-diagnostics":
        case "symbols":
            // do nothing
            break;

pavelsavara · 2026-06-21T13:18:38Z

/azp run runtime-wasm

azure-pipelines · 2026-06-21T13:18:48Z

Azure Pipelines successfully started running 1 pipeline(s).

pavelsavara · 2026-06-21T13:18:56Z

/azp run runtime-extra-platforms

azure-pipelines · 2026-06-21T13:19:08Z

Azure Pipelines successfully started running 1 pipeline(s).

Copilot

Pull request overview

Copilot reviewed 40 out of 43 changed files in this pull request and generated 5 comments.

    prepareAssetsWorker();
    const promises = importModules();
    const es6Modules = await Promise.all(promises);
+    (globalThis as any).name = "em-pthread";
    await initializeModules(es6Modules as any);


 			values [ins->dreg] = LLVMBuildSIToFP (builder, lhs, LLVMFloatType (), "");
 			break;
 		case OP_FCONV_TO_R4:
-			values [ins->dreg] = emit_fpnarrow (ctx, lhs, LLVMFloatType ());
+			values [ins->dreg] = LLVMBuildFPTrunc (builder, lhs, LLVMFloatType (), "");
 			break;


+    <!-- TEMPORARY: pinned to the staged emsdk 5.0.6 SDK build on the ci.dot.net/dev feed (only 11.0.100-preview.6.26314.102 is staged there).
+         WorkloadTesting.Core.targets installs the SDK at this version from ci.dot.net/dev; do NOT follow
+         $(MicrosoftNETWorkloadEmscriptenCurrentManifest110100TransportVersion): merges from main bump it past the staged build,
+         and that SDK exists on neither ci.dot.net/dev nor production (dotnet-install fails, MSB3073).
+         Repin to the production .NET 11 emsdk 5.0.6 manifest transport (and drop the ci.dot.net/dev wiring) before merge. See dotnet/runtime#113786. -->
+    <_DotnetSdkVersion>11.0.100-preview.6.26314.102</_DotnetSdkVersion>
    <SdkVersionForWorkloadTesting Condition="$([System.String]::Compare('$(_GlobalJsonSdkVersion)', '$(_DotnetSdkVersion)')) &lt;= 0">$(_DotnetSdkVersion)</SdkVersionForWorkloadTesting>


+    <!-- Replace ci.dot.net/public with ci.dot.net/dev in the script using the platform's native tools.
+         This avoids MSBuild's string/item-list parsing pitfalls (e.g. ';' splitting in WriteLinesToFile,
+         line-ending and escaping issues) when round-tripping an entire shell/PowerShell script through
+         MSBuild properties. We're already invoking these shells right after, so leverage them directly. -->
+    <Message Text="** Replacing ci.dot.net/public with ci.dot.net/dev in $(_DotNetInstallScriptPath)" Importance="High" />
+
+    <Exec Condition="!$([MSBuild]::IsOSPlatform('windows'))"
+          IgnoreStandardErrorWarningFormat="true"
+          Command="sed -i.bak 's|ci\.dot\.net/public|ci.dot.net/dev|g' &quot;$(_DotNetInstallScriptPath)&quot; &amp;&amp; rm -f &quot;$(_DotNetInstallScriptPath).bak&quot;" />
+    <Exec Condition="$([MSBuild]::IsOSPlatform('windows'))"
+          IgnoreStandardErrorWarningFormat="true"
+          Command='powershell -ExecutionPolicy ByPass -NoProfile -Command "(Get-Content -Raw -LiteralPath &apos;$(_DotNetInstallScriptPath)&apos;).Replace(&apos;ci.dot.net/public&apos;, &apos;ci.dot.net/dev&apos;) | Set-Content -NoNewline -LiteralPath &apos;$(_DotNetInstallScriptPath)&apos;"' />


    <add key="dotnet11" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet11/nuget/v3/index.json" />
    <add key="dotnet11-transport" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet11-transport/nuget/v3/index.json" />
    <add key="dotnet-diagnostics-tests" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-diagnostics-tests/nuget/v3/index.json" />
+    <add key="general-testing" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/general-testing/nuget/v3/index.json" />
  </packageSources>


…umber as intrinsics Mono's LLVM backend has end-to-end plumbing for OP_FMA, OP_FCOPYSIGN, OP_SQRTF, etc., but a handful of obvious BCL entry points fall through to the C# implementations: * `MathF.Abs(float)` and `MathF.Log(float)` are not recognized in the MathF block of intrinsics.c, even though MathF.Sqrt/Sin/Cos/Exp/Log2/ Log10/Floor/Ceiling/Truncate all are. (Math.Abs(float) is recognized via the Math (float) fallback, but Math.Log(float) doesn't exist — only MathF.Log does.) Adding INTRINS_LOGF + OP_LOGF closes the gap; MathF.Abs reuses the existing OP_ABSF / INTRINS_ABSF. * `Single.MinNumber/MaxNumber` and `Double.MinNumber/MaxNumber` (forwarders for INumber<TSelf>.{Min,Max}Number) are IEEE 754-2008 numNum semantics: when exactly one argument is NaN, return the non-NaN; when both are NaN, return NaN. These map exactly to llvm.minnum / llvm.maxnum, which on AArch64 lower to a single fminnm/fmaxnm instruction. Without recognition the C# bodies inline to a fcmp+select chain — semantically correct, but several instructions on every target. Mono had no recognition for the Single/Double primitive classes previously; this adds a focused block that only handles MinNumber and MaxNumber. (Min/Max forward to Math/MathF and are caught by the existing recognition there.) Adds: * OP_LOGF / OP_FMINNUM / OP_FMAXNUM / OP_RMINNUM / OP_RMAXNUM in mini-ops.h. * INTRINS_LOGF / INTRINS_MINNUM / INTRINS_MINNUMF / INTRINS_MAXNUM / INTRINS_MAXNUMF in llvm-intrinsics.h. * Case handlers in mini-llvm.c (OP_LOGF reuses the existing scalar-1-arg pattern; the four num/numF ops share a single block that selects the correct intrinsic by opcode). * Recognition in intrinsics.c — MathF.Abs/MathF.Log added to the existing MathF (float) block; MinNumber/MaxNumber added in a new Single/Double block placed after the Math block. Validation: on the PR dotnet#129299 branch (emsdk 5.0.6 / LLVM 23) stacked with the Min/Max NaN fix from PR dotnet#129593, full AOT + LLVM run of System.Runtime.Tests on iossimulator-arm64: HalfTests 1442/1442 pass HalfTests_GenericMath 356/356 pass SingleTests 1334/1334 pass DoubleTests 1559/1559 pass (no regression vs the dotnet#129593-only baseline; covers MinNumber/ MaxNumber on Single/Double) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Re-link the disabled Mono full-AOT tests from the #129508 tracking issue to the individual PRs that fix them (nullabletypes -> #129702, call05_large/small -> #129708, WPF_3226 -> #129710, b143840 -> #129713, UnitTest_GVM_TypeLoadException -> #129715). The tests stay disabled; Runtime_105619 keeps the #129508 link.

Upgrade emsdk to 5.0.6

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Add general-testing feed

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pavelsavara and others added 3 commits June 11, 2026 19:36

rebase

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(cherry picked from commit ea0ec7c)

Remove lbulkmemory

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Update to llvm 23.x

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Fix llvm version check in src/mono/CMakeLists.txt

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akoeplinger force-pushed the emsdk-upgrade branch from 41540c2 to ea8bd08 Compare June 11, 2026 19:07

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Fix llvm warnings/errors

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This was referenced Jun 12, 2026

[browser][coreCLR] Wasm.Console.Node.Sample - undefined symbol: SystemInteropJS_GetManagedStackTrace #129229

Closed

[browser] Could not resolve type with token 01000001 from typeref #126997

Open

build-analysis Bot mentioned this pull request Jun 20, 2026

LibraryImportGenerator.Unit.Tests crashing on linux-x64 mono interpreter #100800

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Potential fix for pull request finding

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Copilot AI review requested due to automatic review settings June 21, 2026 09:14

Merge branch 'main' into emsdk-upgrade

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Comment thread src/mono/browser/runtime/loader/run.ts

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pavelsavara added 2 commits June 21, 2026 12:27

pin more

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fix pin

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Merge branch 'main' into emsdk-upgrade

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cleanup 129507 & emit_fpnarrow

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fix 129508 maybe

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browser-wasm linux Release LibraryTests queues timing out #117974

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Rare flaky timeout in CreateFileChangeToken_RootDeletedAndRecreated_TokenFiresWhenFileCreated #129691

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Intermittent build failure in AfterSourceBuild: "Could not write state file" #76488

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Summary

Motivation

Changes by area

Toolchain / version bumps

Native build flags

Mono LLVM backend (LLVM 23 compatibility) — src/mono/mono/mini

Browser JS loader — drop the separate pthread worker module

File system timestamps (browser nanosecond support)

Test annotations for the new toolchain

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pavelsavara commented Jun 21, 2026

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akoeplinger commented Jun 11, 2026 •

edited by pavelsavara

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Mono LLVM backend (LLVM 23 compatibility) — `src/mono/mono/mini`