[SandboxVec] Add barebones Region class. (llvm#108899)

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.

llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/Region.h

@@ -0,0 +1,106 @@
+//===- Region.h -------------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_VECTORIZE_SANDBOXVECTORIZER_REGION_H
+#define LLVM_TRANSFORMS_VECTORIZE_SANDBOXVECTORIZER_REGION_H
+
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/iterator_range.h"
+#include "llvm/SandboxIR/SandboxIR.h"
+#include "llvm/Support/InstructionCost.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm::sandboxir {
+
+/// The main job of the Region is to point to new instructions generated by
+/// vectorization passes. It is the unit that RegionPasses operate on with their
+/// runOnRegion() function.
+///
+/// The region allows us to stack transformations horizontally, meaning that
+/// each transformation operates on a single region and the resulting region is
+/// the input to the next transformation, as opposed to vertically, which is the
+/// common way of applying a transformation across the whole BB. This enables us
+/// to check for profitability and decide whether we accept or rollback at a
+/// region granularity, which is much better than doing this at the BB level.
+///
+// Traditional approach: transformations applied vertically for the whole BB
+// BB
+// +----+
+// | |
+// | |
+// | | -> Transform1 -> ... -> TransformN -> Check Cost
+// | |
+// | |
+// +----+
+//
+// Region-based approach: transformations applied horizontally, for each Region
+// BB
+// +----+
+// |Rgn1| -> Transform1 -> ... -> TransformN -> Check Cost
+// | |
+// |Rgn2| -> Transform1 -> ... -> TransformN -> Check Cost
+// | |
+// |Rgn3| -> Transform1 -> ... -> TransformN -> Check Cost
+// +----+
+
+class Region {
+ /// All the instructions in the Region. Only new instructions generated during
+ /// vectorization are part of the Region.
+ SetVector<Instruction *> Insts;
+
+ /// A unique ID, used for debugging.
+ unsigned RegionID = 0;
+
+ Context &Ctx;
+
+ /// The basic block containing this region.
+ BasicBlock &BB;
+
+ // TODO: Add cost modeling.
+ // TODO: Add a way to encode/decode region info to/from metadata.
+
+public:
+ Region(Context &Ctx, BasicBlock &BB);
+ ~Region();
+
+ BasicBlock *getParent() const { return &BB; }
+ Context &getContext() const { return Ctx; }
+ /// Returns the region's unique ID.
+ unsigned getID() const { return RegionID; }
+
+ /// Adds I to the set.
+ void add(Instruction *I);
+ /// Removes I from the set.
+ void remove(Instruction *I);
+ /// Returns true if I is in the Region.
+ bool contains(Instruction *I) const { return Insts.contains(I); }
+ /// Returns true if the Region has no instructions.
+ bool empty() const { return Insts.empty(); }
+
+ using iterator = decltype(Insts.begin());
+ iterator begin() { return Insts.begin(); }
+ iterator end() { return Insts.end(); }
+ iterator_range<iterator> insts() { return make_range(begin(), end()); }
+
+#ifndef NDEBUG
+ /// This is an expensive check, meant for testing.
+ bool operator==(const Region &Other) const;
+ bool operator!=(const Region &other) const { return !(*this == other); }
+
+ void dump(raw_ostream &OS) const;
+ void dump() const;
+ friend raw_ostream &operator<<(raw_ostream &OS, const Region &Rgn) {
+ Rgn.dump(OS);
+ return OS;
+ }
+#endif
+};
+
+} // namespace llvm::sandboxir
+
+#endif // LLVM_TRANSFORMS_VECTORIZE_SANDBOXVECTORIZER_REGION_H

llvm/lib/Transforms/Vectorize/CMakeLists.txt

@@ -5,6 +5,7 @@ add_llvm_component_library(LLVMVectorize
  LoopVectorize.cpp
  SandboxVectorizer/DependencyGraph.cpp
  SandboxVectorizer/Passes/BottomUpVec.cpp
+ SandboxVectorizer/Region.cpp
  SandboxVectorizer/SandboxVectorizer.cpp
  SLPVectorizer.cpp
  Vectorize.cpp

llvm/lib/Transforms/Vectorize/SandboxVectorizer/Region.cpp

@@ -0,0 +1,46 @@
+//===- Region.cpp ---------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Vectorize/SandboxVectorizer/Region.h"
+
+namespace llvm::sandboxir {
+
+Region::Region(Context &Ctx, BasicBlock &BB) : Ctx(Ctx), BB(BB) {
+ static unsigned StaticRegionID;
+ RegionID = StaticRegionID++;
+}
+
+Region::~Region() {}
+
+void Region::add(Instruction *I) { Insts.insert(I); }
+
+void Region::remove(Instruction *I) { Insts.remove(I); }
+
+#ifndef NDEBUG
+bool Region::operator==(const Region &Other) const {
+ if (Insts.size() != Other.Insts.size())
+ return false;
+ if (!std::is_permutation(Insts.begin(), Insts.end(), Other.Insts.begin()))
+ return false;
+ return true;
+}
+
+void Region::dump(raw_ostream &OS) const {
+ OS << "RegionID: " << getID() << "\n";
+ for (auto *I : Insts)
+ OS << *I << "\n";
+}
+
+void Region::dump() const {
+ dump(dbgs());
+ dbgs() << "\n";
+}
+
+} // namespace llvm::sandboxir
+
+#endif // NDEBUG

llvm/unittests/Transforms/Vectorize/SandboxVectorizer/CMakeLists.txt

@@ -9,4 +9,5 @@ set(LLVM_LINK_COMPONENTS
 
 add_llvm_unittest(SandboxVectorizerTests
  DependencyGraphTest.cpp
+ RegionTest.cpp
  )

llvm/unittests/Transforms/Vectorize/SandboxVectorizer/RegionTest.cpp

@@ -0,0 +1,82 @@
+//===- RegionTest.cpp -----------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Vectorize/SandboxVectorizer/Region.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/SandboxIR/SandboxIR.h"
+#include "llvm/Support/SourceMgr.h"
+#include "gmock/gmock-matchers.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+struct RegionTest : public testing::Test {
+ LLVMContext C;
+ std::unique_ptr<Module> M;
+
+ void parseIR(LLVMContext &C, const char *IR) {
+ SMDiagnostic Err;
+ M = parseAssemblyString(IR, Err, C);
+ if (!M)
+ Err.print("RegionTest", errs());
+ }
+};
+
+TEST_F(RegionTest, Basic) {
+ parseIR(C, R"IR(
+define i8 @foo(i8 %v0, i8 %v1) {
+ %t0 = add i8 %v0, 1
+ %t1 = add i8 %t0, %v1
+ ret i8 %t1
+}
+)IR");
+ llvm::Function *LLVMF = &*M->getFunction("foo");
+ sandboxir::Context Ctx(C);
+ auto *F = Ctx.createFunction(LLVMF);
+ auto *BB = &*F->begin();
+ auto It = BB->begin();
+ auto *T0 = cast<sandboxir::Instruction>(&*It++);
+ auto *T1 = cast<sandboxir::Instruction>(&*It++);
+ auto *Ret = cast<sandboxir::Instruction>(&*It++);
+ sandboxir::Region Rgn(Ctx, *BB);
+
+ // Check getters
+ EXPECT_EQ(BB, Rgn.getParent());
+ EXPECT_EQ(&Ctx, &Rgn.getContext());
+ EXPECT_EQ(0U, Rgn.getID());
+
+ // Check add / remove / empty.
+ EXPECT_TRUE(Rgn.empty());
+ Rgn.add(T0);
+ EXPECT_FALSE(Rgn.empty());
+ Rgn.remove(T0);
+ EXPECT_TRUE(Rgn.empty());
+
+ // Check iteration.
+ Rgn.add(T0);
+ Rgn.add(T1);
+ Rgn.add(Ret);
+ // Use an ordered matcher because we're supposed to preserve the insertion
+ // order for determinism.
+ EXPECT_THAT(Rgn.insts(), testing::ElementsAre(T0, T1, Ret));
+
+ // Check contains
+ EXPECT_TRUE(Rgn.contains(T0));
+ Rgn.remove(T0);
+ EXPECT_FALSE(Rgn.contains(T0));
+
+#ifndef NDEBUG
+ // Check equality comparison. Insert in reverse order into `Other` to check
+ // that comparison is order-independent.
+ sandboxir::Region Other(Ctx, *BB);
+ Other.add(Ret);
+ EXPECT_NE(Rgn, Other);
+ Other.add(T1);
+ EXPECT_EQ(Rgn, Other);
+#endif
+}