[spec] Preserve host function arguments on divergence - #2231
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Summary
Previously, the reduction rule for host function divergence dropped the call arguments
val^nfrom the resulting configuration.According to the WebAssembly specificaiton, the post-conditions for executing host functions must match those in the execution rule for invoking host functions. However, a host function that takes one or more arguments, one reduction step by
Step/call_ref-hostfunc-divremovesval^nand leaves only(REF.FUNC_ADDR a) (CALL_REF yy). Neither host-function execution rule can then apply because the required operands are missing.Fix
The updated rule preserves the complete configuration, making the divergence case as exact self-loop as intended.