* Cranelift: disable egraphs in fuzzing for now.
As per [this comment], with a few recent discussions it's become clear
that we want to refactor egraphs in a way that will subsume, or make
irrelevant, some of the recent fuzzbugs that have arisen (and likely
lead to others, which we'll want to fix!). Rather than chase these down
then refactor later, it probably makes sense not to spend the human time
or fuzzing time doing so. This PR turns off egraphs support in fuzzing
configurations for now, to be re-enabled later.
[this comment]: https://github.com/bytecodealliance/wasmtime/issues/5126#issuecomment-1291222515
* Disable in cranelift-fuzzgen as well.
* fuzzgen: Test compiler flags
* cranelift: Generate `all()` function for all enum flags
This allows a user to iterate all flags that exist.
* fuzzgen: Minimize regalloc_checker compiles
* fuzzgen: Limit the amount of test case inputs
* fuzzgen: Add egraphs flag
It's finally here! 🥳
* cranelift: Add fuzzing comment to settings
* fuzzgen: Add riscv64
* fuzzgen: Unconditionally enable some flags
Remove the boolean types from cranelift, and the associated instructions breduce, bextend, bconst, and bint. Standardize on using 1/0 for the return value from instructions that produce scalar boolean results, and -1/0 for boolean vector elements.
Fixes#3205
Co-authored-by: Afonso Bordado <afonso360@users.noreply.github.com>
Co-authored-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Co-authored-by: Chris Fallin <chris@cfallin.org>
* fuzzgen: Disable verifier after NaN Canonicalization
We are currently running the verifier twice, once after the nan canonicalization pass, and again when JIT compiling the code.
The verifier first runs in the NaN Canonicalization pass. If it fails it prevents us from getting a nice `cargo fuzz fmt` test case.
So disable the verifier there, but ensure its enabled when JIT compiling.
* fuzzgen: Force enable verifier in cranelift-icache
This is already the default, but since we no longer run the verifier in `fuzzgen` its important to ensure that it runs in the fuzz targets.
This is the implementation of https://github.com/bytecodealliance/wasmtime/issues/4155, using the "inverted API" approach suggested by @cfallin (thanks!) in Cranelift, and trait object to provide a backend for an all-included experience in Wasmtime.
After the suggestion of Chris, `Function` has been split into mostly two parts:
- on the one hand, `FunctionStencil` contains all the fields required during compilation, and that act as a compilation cache key: if two function stencils are the same, then the result of their compilation (`CompiledCodeBase<Stencil>`) will be the same. This makes caching trivial, as the only thing to cache is the `FunctionStencil`.
- on the other hand, `FunctionParameters` contain the... function parameters that are required to finalize the result of compilation into a `CompiledCode` (aka `CompiledCodeBase<Final>`) with proper final relocations etc., by applying fixups and so on.
Most changes are here to accomodate those requirements, in particular that `FunctionStencil` should be `Hash`able to be used as a key in the cache:
- most source locations are now relative to a base source location in the function, and as such they're encoded as `RelSourceLoc` in the `FunctionStencil`. This required changes so that there's no need to explicitly mark a `SourceLoc` as the base source location, it's automatically detected instead the first time a non-default `SourceLoc` is set.
- user-defined external names in the `FunctionStencil` (aka before this patch `ExternalName::User { namespace, index }`) are now references into an external table of `UserExternalNameRef -> UserExternalName`, present in the `FunctionParameters`, and must be explicitly declared using `Function::declare_imported_user_function`.
- some refactorings have been made for function names:
- `ExternalName` was used as the type for a `Function`'s name; while it thus allowed `ExternalName::Libcall` in this place, this would have been quite confusing to use it there. Instead, a new enum `UserFuncName` is introduced for this name, that's either a user-defined function name (the above `UserExternalName`) or a test case name.
- The future of `ExternalName` is likely to become a full reference into the `FunctionParameters`'s mapping, instead of being "either a handle for user-defined external names, or the thing itself for other variants". I'm running out of time to do this, and this is not trivial as it implies touching ISLE which I'm less familiar with.
The cache computes a sha256 hash of the `FunctionStencil`, and uses this as the cache key. No equality check (using `PartialEq`) is performed in addition to the hash being the same, as we hope that this is sufficient data to avoid collisions.
A basic fuzz target has been introduced that tries to do the bare minimum:
- check that a function successfully compiled and cached will be also successfully reloaded from the cache, and returns the exact same function.
- check that a trivial modification in the external mapping of `UserExternalNameRef -> UserExternalName` hits the cache, and that other modifications don't hit the cache.
- This last check is less efficient and less likely to happen, so probably should be rethought a bit.
Thanks to both @alexcrichton and @cfallin for your very useful feedback on Zulip.
Some numbers show that for a large wasm module we're using internally, this is a 20% compile-time speedup, because so many `FunctionStencil`s are the same, even within a single module. For a group of modules that have a lot of code in common, we get hit rates up to 70% when they're used together. When a single function changes in a wasm module, every other function is reloaded; that's still slower than I expect (between 10% and 50% of the overall compile time), so there's likely room for improvement.
Fixes#4155.
* fuzzgen: Add float support
Add support for generating floats and some float instructions.
* fuzzgen: Enable NaN Canonicalization
Both IEEE754 and the Wasm spec are somewhat loose about what is allowed
to be returned from NaN producing operations. And in practice this changes
from X86 to Aarch64 and others. Even in the same host machine, the
interpreter may produce a code sequence different from cranelift that
generates different NaN's but produces legal results according to the spec.
These differences cause spurious failures in the fuzzer. To fix this
we enable the NaN Canonicalization pass that replaces any NaN's produced
with a single fixed canonical NaN value.
* fuzzgen: Use `MultiAry` when inserting opcodes
This deduplicates a few inserters!
* cranelift: Initial fuzzer implementation
* cranelift: Generate multiple test cases in fuzzer
* cranelift: Separate function generator in fuzzer
* cranelift: Insert random instructions in fuzzer
* cranelift: Rename gen_testcase
* cranelift: Implement div for unsigned values in interpreter
* cranelift: Run all test cases in fuzzer
* cranelift: Comment options in function_runner
* cranelift: Improve fuzzgen README.md
* cranelift: Fuzzgen remove unused variable
* cranelift: Fuzzer code style fixes
Thanks! @bjorn3
* cranelift: Fix nits in CLIF fuzzer
Thanks @cfallin!
* cranelift: Implement Arbitrary for TestCase
* cranelift: Remove gen_testcase
* cranelift: Move fuzzers to wasmtime fuzz directory
* cranelift: CLIF-Fuzzer ignore tests that produce traps
* cranelift: CLIF-Fuzzer create new fuzz target to validate generated testcases
* cranelift: Store clif-fuzzer config in a separate struct
* cranelift: Generate variables upfront per function
* cranelift: Prevent publishing of fuzzgen crate
