use approach with copysign for handling negative zero
format
refactor for better branch prediction
move copysign back to internal branch
format
fix
use abs instead branches
better comments
switch arms for better branch prediction
instead of always being relative to CARGO_MANIFEST_DIR, each use site is
responsible for either putting that variable or another one (set by a
build.rs) at the start of witx paths.
The fundamental problem is that the target distance of jump-like operations may change in the DWARF expression translation process. Intervening DW_OP_deref will expand to about 10 bytes, for example.
So the jumps must be relocated. We approach this task by inserting artificial LandingPad markers (new CompiledExpressionParts constructors) into the parsed vector at actual Jump targets.
LandingPads are identified by JumpTargetMarker tokens which are generated on the fly.
Additionally we now parse the Jump instructions. These also get their corresponding JumpTargetMarker token.
We bail in two situations:
frame_base is too complicated (i.e. itself contains Jump)
some jump distance in the original expression is fishy.
No point in resorting to LEB128 encoding for such constants,
using the native `u32` is faster and more compact.
Adds `write_u32` method to facilitate this.
This commit extracts the two implementations of `Compiler` into two
separate crates, `wasmtime-cranelfit` and `wasmtime-lightbeam`. The
`wasmtime-jit` crate then depends on these two and instantiates them
appropriately. The goal here is to start reducing the weight of the
`wasmtime-environ` crate, which currently serves as a common set of
types between all `wasmtime-*` crates. Long-term I'd like to remove the
dependency on Cranelift from `wasmtime-environ`, but that's going to
take a lot more work.
In the meantime I figure it's a good way to get started by separating
out the lightbeam/cranelift function compilers from the
`wasmtime-environ` crate. We can continue to iterate on moving things
out in the future, too.
* a certain subset of io::Errors are expected - these we have
a (platform-specific, because windows) method to translate into
one of the wasi errno variants in the Error enum.
* some io::Errors are unexpected - wasi-common doesnt expect them from
the underlying OS. rather than preserve any fidelity in reporting
those to the user (only the unix impl attempts this), lets collect
those as an `Error::UnexpectedIo(#[source] std::io::Error)`.
Rather than trace at the conversion site, we rely on the wiggle error
conversion hooks to trace the `Error`'s `Debug` impl, and then
we convert all of these unexpected into `Errno::Io` for returning
to the guest.
This is a different behavior from before, and I don't have any firm
guarantees that nobody was depending on the old behavior, but it
appears to me that none of those unexpected errnos were reasonable
to expect from any of the filesystem syscalls wasi-common is making.
this is a bug - the TODO was never resolved, even when the code to
implement it was added right below :)
tracing is already in the transitive deps via wiggle, so no extra
trouble there. tracing::debug is more appropriate than eprintln
