Pushing on the `val_stack` vector is CL's biggest source of calls to
malloc/realloc/free, by some margin. It accounts for about 27.7% of all heap
blocks allocated when compiling wasm_lua_binarytrees. This change removes
pretty much all dynamic allocation by changing to a SmallVec<[Value; 8]>
instead. A fixed size of 4 gets all the gains to be had, in testing, so 8
gives some safety margin and is harmless from a stack-use perspective: 8
Values will occupy 32 bytes.
As a bonus, this change also reduces the compiler's dynamic instruction count
by about 0.5%.
This commit adds a hook to the `ModuleEnvironment` trait to learn when a
custom section in a wasm file is read. This hook can in theory be used
to parse and handle custom sections as they appear in the wasm file
without having to re-iterate over the wasm file after cranelift has
already parsed the wasm file.
The `translate_module` function is now less strict in that it doesn't
require sections to be in a particular order, but it's figured that the
wasm file is already validated elsewhere to verify the section order.
This removes the explicit dependency on target-lexicon for the embedder,
which can instead use the ISA's name directly. It can simplify
dependency management, in particular avoid the need for synchronizing
the target-lexicon dependencies versions.
It also tweak the error when an ISA isn't built as part of Cranelift to
be a SupportDisabled error; this was dead code before this.
