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[wasm] Insert GC Polls in Cycles - #136406
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adamperlin wants to merge 3 commits into
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…back-edges and mark cycle headers as BBF_NEEDS_GCPOLL
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🟡 Changes recommended
The regression tests do not deterministically verify poll emission or collection safety with live references and interior byrefs.
1 open issue
What changed in this PR
Adds GC poll placement for WebAssembly control-flow cycles, addressing the Wasm ReadyToRun polling gap described in #133431.
Changes:
- Marks cycle headers for polling, including implicit cycles through tail calls.
- Makes the frame-size node available outside target guards and adds debug display support.
- Adds browser/CoreCLR regression cases for loops, live references, interior byrefs, and tail calls.
| File | Description |
|---|---|
src/tests/JIT/Regression_3/WasmGCPolls/WasmGCPollsTailCalls.ilproj |
Builds the IL test helper library. |
src/tests/JIT/Regression_3/WasmGCPolls/WasmGCPollsTailCalls.il |
Adds tail-call and control-flow edge cases. |
src/tests/JIT/Regression_3/WasmGCPolls/WasmGCPolls.csproj |
Configures isolated browser/CoreCLR ReadyToRun tests. |
src/tests/JIT/Regression_3/WasmGCPolls/WasmGCPolls.cs |
Checks results across several cycle shapes. |
src/coreclr/jit/gtlist.h |
Moves the frame-size node into the unconditional node list. |
src/coreclr/jit/gentree.cpp |
Handles frame-size nodes in debug output. |
src/coreclr/jit/flowgraph.cpp |
Detects cycles and marks headers for GC polls. |
src/coreclr/jit/compiler.h |
Declares the cycle-marking helper. |
Review effort: Balanced
Comment on lines
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| Assert.Equal(expected, SimpleCycle(iterations)); | ||
| Assert.Equal(expected, ReferenceCycle(iterations)); | ||
| Assert.Equal(expected, InteriorByrefCycle(iterations)); |
This was referenced Oct 24, 2026
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Resolves #133431. We don't have fully interruptible GC mode in Wasm, so if we have a cycle there may not be an opportunity for a GC; insert GC polls at cycle headers to conservatively ensure we do have GC opporunities.