This patch implements a ready-list-based scheduler that operates on
DependencyGraph.
It is used by the sandbox vectorizer to test the legality of vectorizing
a group of instrs.
SchedBundle is a helper container, containing all DGNodes that
correspond to the instructions that we are attempting to schedule with
trySchedule(Instrs).
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.
This patch implements the UnscheduledSuccs counter in DGNode. It counts
the number of unscheduled successors and is used by the scheduler to
determine when a node is ready.
When NewInterval is below DAGInterval we used to revisit instructions
already visited. This patch fixes this by separating the scan in two:
1. The full scan of the NewInterval, and
2. The cross-interval scan for DAGInterval.
This is further explained in the new description.
This patch implements `Interval::comesBefore(const Interval &Other)`
which returns true if this interval is strictly before Other in program
order. The function asserts that the intervals are disjoint.
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.
[Retry 110696 with a proper rebase.]
Seed collection will assemble instructions to be vectorized into
SeedBundles. This data structure is not intended to be used directly,
but will be the basis for load bundles, store bundles, and so on.
This patch implements the MemDGNode class for DAG nodes that are
candidates
for memory dependencies. These nodes form a chain that is accessible by
`getPrevNode()` and `getNextNode()`.
It also implements a builder class that creates MemDGNode intervals from
Instructions.
This patch converts InstrInterval class to a class template and renames
InstrInterval to Itnerval.
This change will allow us to reuse the Interval for dependency graph
nodes.
I'm planning to add RegionPass and RegionPassManager next to the
equivalent FunctionPass and FunctionPassManager in SandboxIR, which
means that SandboxIR has to know about Regions.
There's nothing vectorizer-specific about the Region class, and the only
thing using Regions at this moment is the unit test, so this is a
straightforward file move.
For each region, we create a metadata node. Then when an instruction is
added to the Region, it gets tagged with the metadata node for that
region. In the following example, we have a Region that contains only
the `%t0` instruction.
```
define i8 @foo(i8 %v0, i8 %v1) {
%t0 = add i8 %v0, 1, !sbvec !0
%t1 = add i8 %t0, %v1
ret i8 %t1
}
!0 = distinct !{!"region"}
```
This commit also adds a function to create regions from metadata already
present in a Function.
This metadata can be used for debugging: if we dump IR before a Region
pass, the IR will contain enough info to re-create the Region and run
the pass by itself in a later invocation.
---------
Co-authored-by: Alina Sbirlea <alina.g.simion@gmail.com>
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.
A region identifies a set of vector instructions generated by
vectorization passes. The vectorizer can then run a series of
RegionPasses on the region, evaluate the cost, and commit/reject the
transforms on a region-by-region basis, instead of an entire basic
block.
This is heavily based ov @vporpo's prototype. In particular, the doc
comment for the Region class is all his. The rest of this commit is
mostly boilerplate around a SetVector: getters, iterators, and some
debug helpers.
This patch adds support for a user-defined pass-pipeline that overrides
the default pipeline of the vectorizer.
This will commonly be used by lit tests.
