This PR switches the default backend on x86, for both the
`cranelift-codegen` crate and for Wasmtime, to the new
(`MachInst`-style, `VCode`-based) backend that has been under
development and testing for some time now.
The old backend is still available by default in builds with the
`old-x86-backend` feature, or by requesting `BackendVariant::Legacy`
from the appropriate APIs.
As part of that switch, it adds some more runtime-configurable plumbing
to the testing infrastructure so that tests can be run using the
appropriate backend. `clif-util test` is now capable of parsing a
backend selector option from filetests and instantiating the correct
backend.
CI has been updated so that the old x86 backend continues to run its
tests, just as we used to run the new x64 backend separately.
At some point, we will remove the old x86 backend entirely, once we are
satisfied that the new backend has not caused any unforeseen issues and
we do not need to revert.
I had missed that the CI config didn't actually run the tests, because
(I think) `matrix.target` is not set by default (?). All of our hosts
are native x86-64, so we can just gate on OS (Ubuntu) instead.
I also discovered that while I had been testing with the gdb tests
locally, when *all* `debug::*` tests are run, there are two that do not
pass on the new backend because of specific differences in compiled
code. One is a value-lifetime issue (the value is "optimized out" at the
point the breakpoint is set) and the other has to do with basic-block
order (it is trying to match against hardcoded machine-code offsets
which have changed).
* Move most wasmtime tests into one test suite
This commit moves most wasmtime tests into a single test suite which
gets compiled into one executable instead of having lots of test
executables. The goal here is to reduce disk space on CI, and this
should be achieved by having fewer executables which means fewer copies
of `libwasmtime.rlib` linked across binaries on the system. More
importantly though this means that DWARF debug information should only
be in one executable rather than duplicated across many.
* Share more build caches
Globally set `RUSTFLAGS` to `-Dwarnings` instead of individually so all
build steps share the same value.
* Allow some dead code in cranelift-codegen
Prevents having to fix all warnings for all possible feature
combinations, only the main ones which come up.
* Update some debug file paths
