This commit fixes `Clone for wasm_val_t` to avoid attempting to chase a
null pointer. It also fixes the implementation for `FuncRef` values by
cloning their internal `wasm_ref_t` as well.
Currently `Func::new` will panic if one of the arguments of the function
is a reference type and the `Store` doesn't have reference types
enabled. This happens because cranelift isn't configure to enable stack
maps but the register allocators expects them to exist when reference
types are seen.
The fix here is to always enable reference types in cranelift for our
trampoline generation and `Func::new`. This should hopefully ensure that
trampolines are generated correctly and they'll just not be able to get
hooked up to an `Instance` because validation will prevent reference
types from being used elsewhere.
This is tricky: the control flow implicitly implied by the operand makes
it so that the output register may be undefined, if we mark it only as a
"def". Make it a "mod" instead, which matches our usage in the codebase,
and will make it crash if the output operand isn't unconditionally
defined before the instruction.
* wasmtime-c-api: Only drop non-null `*mut wasm_ref_t`s
* wasmtime-c-api: Handle null refs in `wasm_val_t` to `Val` conversion
* wasmtime-c-api: Don't unwrap and rewrap `Option`s
The `unwrap` can panic, and there isn't any point to this unwrap+rewrap.
* wasmtime-c-api: Add conversions between `funcref` and `wasm_func_t`
* wasmtime-c-api: More ownership documentation for `wasmtime.h`
Certain operations (e.g. widening) will have operands with types like `NxM` but will return results with types like `(N*2)x(M/2)` (double the lane width, halve the number of lanes; maintain the same number of vector bits). This is equivalent to applying two `DerivedFunction`s to the type: `DerivedFunction::DoubleWidth` then `DerivedFunction::HalfVector`. Since there is no easy way to apply multiple `DerivedFunction`s (e.g. most of the logic is one-level deep, 1d5a678124/cranelift/codegen/meta/src/gen_inst.rs (L618-L621)), I added `DerivedFunction::MergeLanes` to do the necessary type conversion.
