see https://github.com/bytecodealliance/wasmtime/pull/1816
DEPRECATION NOTICE: the Cranelift developer team intends to stop maintaining
the `cranelift-faerie` crate and remove it from the `wasmtime` git repository
on or after August 3, 2020. We recommend users use its successor, the
`cranelift-object` crate.
These libcalls are useful for 32-bit platforms.
On x86_32 in particular, commit 4ec16fa0 added support for legalizing
64-bit shifts through SIMD operations. However, that legalization
requires SIMD to be enabled and SSE 4.1 to be supported, which is not
acceptable as a hard requirement.
Experience with the `define_function` API has shown that returning
borrowed slices of `TrapSite` is not ideal: the returned slice
represents a borrow on the entire `Module`, which makes calling back
into methods taking `&mut self` a bit tricky.
To eliminate the problem, let's require the callers of `define_function`
to provide `TrapSink` instances. This style of API enables them to
control when and how traps are collected, and makes the `object` and
`faerie` backends simpler/more efficient by not having to worry about
trap collection.
The current interface of `cranelift-module` requires consumers who want
to be informed about traps to discover that information through
`Module::Product`, which is backend-specific. Since it's advantageous
to manipulate this information in a backend-agnostic way, this patch
changes `Module::define_function{,_bytes}` to return information about
the traps contained in the function being defined.
* move trap site definitions into cranelift-module
`cranelift-faerie` and `cranelift-object` already have identical
definitions of structures to represent trap sites. We might as well
merge them ahead of work to define functions via a raw slice of bytes
with associated traps, which will need some kind of common structure for
representing traps anyway.
* cranelift-module: add `define_function_bytes` interface
This interface is useful when the client needs to precisely specify the
ordering of bytes in a particular function.
* add comment about saving files for `perf`
This removes the need to call `finalize_definitions` for cranelift-object.
`finalize_definitions` is only intended for backends that produce
finalized functions and data objects, which cranelift-object does not.
