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.
This resolves the work started in https://github.com/bytecodealliance/cranelift/pull/1231 and https://github.com/bytecodealliance/wasmtime/pull/1436. Cranelift filetests currently have the ability to run CLIF functions with a signature like `() -> b*` and check that the result is true under the `test run` directive. This PR adds the ability to call functions with arbitrary arguments and non-boolean returns and either print the result or check against a list of expected results:
- `run` commands look like `; run: %add(2, 2) == 4` or `; run: %add(2, 2) != 5` and verify that the executed CLIF function returns the expected value
- `print` commands look like `; print: %add(2, 2)` and print the result of the function to stdout
To make this work, this PR compiles a single Cranelift `Function` into a `CompiledFunction` using a `SingleFunctionCompiler`. Because we will not know the signature of the function until runtime, we use a `Trampoline` to place the values in the appropriate location for the calling convention; this should look a lot like what @alexcrichton is doing with `VMTrampoline` in wasmtime (see 3b7cb6ee64/crates/api/src/func.rs (L510-L526), 3b7cb6ee64/crates/jit/src/compiler.rs (L260)). To avoid re-compiling `Trampoline`s for the same function signatures, `Trampoline`s are cached in the `SingleFunctionCompiler`.
* Add AArch64 tests to CI
This commit enhances our CI with an AArch64 builder. Currently we have
no physical hardware to run on so for now we run all tests in an
emulator. The AArch64 build is cross-compiled from x86_64 from Linux.
Tests all happen in release mode with a recent version of QEMU (recent
version because it's so much faster, and in release mode because debug
mode tests take quite a long time in an emulator).
The goal here was not to get all tests passing on CI, but rather to get
AArch64 running on CI and get it green at the same time. To achieve that
goal many tests are now ignored on aarch64 platforms. Many tests fail
due to unimplemented functionality in the aarch64 backend (#1521), and
all wasmtime tests involving compilation are also disabled due to
panicking attempting to generate generate instruction offset information
for trap symbolication (#1523).
Despite this, though, all Cranelift tests and other wasmtime tests
should be runnin on AArch64 through QEMU with this PR. Additionally
we'll have an AArch64 binary release of Wasmtime for Linux, although it
won't be too useful just yet since it will panic on almost all wasm
modules.
* Review comments
This is necessary to avoid build errors from dead code (and I didn't want to litter all of the structs with `#[allow(dead_code)]` just to remove in a subsequent PR).
* Add ability to run CLIF IR using `clif-util run [-v] {file}` and add `test run` to cranelift-filetests to allow executing CLIF
This re-factors the compile/execute parts to a FunctionRunner that is shared between cranelift-filetests and clif-util. CLIF can be now be run using `clif-util run` as well as during `clif-util test` for files with a `test run` header. As before, only functions suffixed with a `run` comment are executed. The `run: fn(...) == ...` expression syntax is left for a subsequent change.
