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[Wasm] Fix FP-based stack slot lookup #128958

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Merged
kg merged 1 commit into from
Jun 4, 2026
Merged

[Wasm] Fix FP-based stack slot lookup #128958

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15 changes: 15 additions & 0 deletions src/coreclr/vm/gcinfodecoder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2166,6 +2166,9 @@ template <> OBJECTREF* TGcInfoDecoder<InterpreterGcInfoEncoding>::GetStackSlot(
}
#endif

#ifdef TARGET_WASM
TADDR GetWasmFramePointerFromStackPointer(TADDR sp);
#endif
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template <typename GcInfoEncoding> OBJECTREF* TGcInfoDecoder<GcInfoEncoding>::GetStackSlot(
INT32 spOffset,
Expand All @@ -2188,6 +2191,17 @@ template <typename GcInfoEncoding> OBJECTREF* TGcInfoDecoder<GcInfoEncoding>::Ge
_ASSERTE( GC_FRAMEREG_REL == spBase );
_ASSERTE( NO_STACK_BASE_REGISTER != m_StackBaseRegister );

#ifdef TARGET_WASM
// Wasm is a bit strange and when we do SetStackBaseRegister(REG_FPBASE)
// what that actually does is set it to REG_NA, which currently has the value 2.
_ASSERTE( 2 == m_StackBaseRegister );
// We have the stack pointer, use it to recover the frame pointer.
TADDR pFrameReg = GetWasmFramePointerFromStackPointer((TADDR)pRD->SP);
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pObjRef = (OBJECTREF*)(pFrameReg + spOffset);

#else // TARGET_WASM

SIZE_T * pFrameReg = (SIZE_T*) GetRegisterSlot(m_StackBaseRegister, pRD);

#if defined(TARGET_UNIX) && !defined(FEATURE_NATIVEAOT)
Expand All @@ -2201,6 +2215,7 @@ template <typename GcInfoEncoding> OBJECTREF* TGcInfoDecoder<GcInfoEncoding>::Ge
#endif // TARGET_UNIX && !FEATURE_NATIVEAOT

pObjRef = (OBJECTREF*)(*pFrameReg + spOffset);
#endif // !TARGET_WASM
}

return pObjRef;
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