My previous attempt (#111904) hacked creation of Regions from metadata
into the bottom-up vectorizer. I got some feedback that it should be its
own pass. So now we have two SandboxIR function passes (`BottomUpVec`
and `RegionsFromMetadata`) that are interchangeable, and we could have
other SandboxIR function passes doing other kinds of transforms, so this
commit revamps pipeline creation and parsing.
First, `sandboxir::PassManager::setPassPipeline` now accepts pass
arguments in angle brackets. Pass arguments are arbitrary strings that
must be parsed by each pass, the only requirement is that nested angle
bracket pairs must be balanced, to allow for nested pipelines with more
arguments. For example:
```
bottom-up-vec<region-pass-1,region-pass-2<arg>,region-pass-3>
```
This has complicated the parser a little bit (the loop over pipeline
characters now contains a small state machine), and we now have some new
test cases to exercise the new features.
The main SandboxVectorizerPass now contains a customizable pipeline of
SandboxIR function passes, defined by the `sbvec-passes` flag. Region
passes for the bottom-up vectorizer pass are now in pass arguments (like
in the example above).
Because we have now several classes that can build sub-pass pipelines,
I've moved the logic that interacts with PassRegistry.def into its own
files (PassBuilder.{h,cpp} so it can be easily reused.
Finally, I've added a `RegionsFromMetadata` function pass, which will
allow us to run region passes in isolation from lit tests without
relying on the bottom-up vectorizer, and a new lit test that does
exactly this.
Note that the new pipeline parser now allows empty pipelines. This is
useful for testing. For example, if we use
```
-sbvec-passes="bottom-up-vec<>"
```
SandboxVectorizer converts LLVM IR to SandboxIR and runs the bottom-up
vectorizer, but no region passes afterwards.
```
-sbvec-passes=""
```
SandboxVectorizer converts LLVM IR to SandboxIR and runs no passes on
it. This is useful to exercise SandboxIR conversion on its own.
https://github.com/llvm/llvm-project/pull/111223 was reverted because of
a build failure with `-DBUILD_SHARED_LIBS=on`.
The Passes component depends on Vectorizer (because PassBuilder needs to
be able to instantiate SandboxVectorizerPass). This resulted in CMake
doing this
1. when it builds lib/libLLVMVectorize.so.20.0git it adds
lib/libLLVMSandboxIR.so.20.0git to the command line, because it's listed
as a dependency (as expected)
2. when it's trying to build lib/libLLVMPasses.so.20.0git it adds
lib/libLLVMVectorize.so.20.0git to the command line, because it's listed
as a dependency (also as expected). But not libLLVMSandboxIR.so.
When SandboxVectorizerPass has its ctors/dtors defined inline, this
caused "undefined reference to vtable" linker errors. This change works
around that by moving ctors/dtors out of line.
Also fix a bazel build problem by adding the new
`llvm/lib/Transforms/Vectorize/SandboxVectorizer/Passes/PassRegistry.def`
as a textual header in the Vectorizer target.
The main change is that the main SandboxVectorizer pass no longer has a
pipeline of function passes. Now it is a wrapper that creates sandbox IR
from functions before calling BottomUpVec.
BottomUpVec now builds its own RegionPassManager from the `sbvec-passes`
flag, using a PassRegistry.def file. For now, these region passes are
not run (BottomUpVec doesn't create Regions yet), and only a null pass
for testing exists.
This commit also changes the ownership model for sandboxir::PassManager:
instead of having a PassRegistry that owns passes, and PassManagers that
contain non-owning pointers to the passes, now PassManager owns (via
unique pointers) the passes it contains.
PassRegistry is now deleted, and the logic to parse and create a pass
pipeline is now in PassManager::setPassPipeline.
This patch adds the basic API for the Legality component of the
vectorizer. It also adds some very basic code in the bottom-up
vectorizer that uses the API.
This patch implements a new empty pass for the Bottom-up vectorizer and
creates a pass pipeline that includes it.
The SandboxVectorizer LLVM pass runs the Sandbox IR pass pipeline.
