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[wasm] Publish __stack_pointer before SuppressGCTransition native calls #130924

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[wasm] Publish __stack_pointer before SuppressGCTransition native calls #130924

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1d83d2d
[wasm] Publish __stack_pointer before SuppressGCTransition native calls
lewing Jul 16, 2026
7c75d25
Drop redundant stack-pointer REG_NA guard
lewing Jul 16, 2026
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14 changes: 14 additions & 0 deletions src/coreclr/jit/codegenwasm.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2906,6 +2906,20 @@ void CodeGen::genCallInstruction(GenTreeCall* call)

params.wasmSignature = m_compiler->info.compCompHnd->getWasmTypeSymbol(typeStack.Data(), typeStack.Height());

// R2R keeps its shadow SP in a local and leaves the __stack_pointer global stale; the PInvoke
// prolog (JIT_PInvokeBegin) normally publishes the current SP to __stack_pointer before native
// code runs, but that prolog/epilog is skipped for SuppressGCTransition calls (see Lowering).
// Without a publish, the native SuppressGCTransition callee allocates its shadow frame from the
// stale global (our caller's SP, above our frame) and overlaps/clobbers our address-taken locals.
// Publish our shadow SP here so the callee allocates below our frame. This is a net-zero operation
// on the Wasm operand stack, so it is safe to emit with the call arguments already pushed.
if (call->IsUnmanaged() && call->IsSuppressGCTransition())
{
GetEmitter()->emitIns_I(INS_local_get, EA_PTRSIZE, GetStackPointerRegIndex());
GetEmitter()->emitIns_I(INS_global_set, EA_HANDLE_CNS_RELOC,
(cnsval_ssize_t)(size_t)m_compiler->eeGetWasmWellKnownGlobals()->stackPointer);
}

// A non-null target expression always indicates an indirect call on Wasm,
// as currently the only possible result of the target expression would be a
// table index which must be used via call_indirect
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