Add a dominanance check interface that uses caching for instructions within same...

Summary:
This problem stems from the fact that instructions are allocated using new
in LLVM, i.e. there is no relationship that can be derived by just looking
at the pointer value.

This interface dispatches to appropriate dominance check given 2 instructions,
i.e. in case the instructions are in the same basic block, ordered basicblock
(with instruction numbering and caching) are used. Otherwise, dominator tree
is used.

This is a preparation patch for https://reviews.llvm.org/D32720

Reviewers: dberlin, hfinkel, davide

Subscribers: davide, mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D33380

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304764 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Transforms/Utils/OrderedInstructions.h b/include/llvm/Transforms/Utils/OrderedInstructions.h
new file mode 100644 (file)
index 0000000..e043ff3
--- /dev/null
+++ b/include/llvm/Transforms/Utils/OrderedInstructions.h
@@ -0,0 +1,51 @@
+//===- llvm/Transforms/Utils/OrderedInstructions.h -------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines an efficient way to check for dominance relation between 2
+// instructions.
+//
+// This interface dispatches to appropriate dominance check given 2
+// instructions, i.e. in case the instructions are in the same basic block,
+// OrderedBasicBlock (with instruction numbering and caching) are used.
+// Otherwise, dominator tree is used.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_UTILS_ORDEREDINSTRUCTIONS_H
+#define LLVM_TRANSFORMS_UTILS_ORDEREDINSTRUCTIONS_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/Analysis/OrderedBasicBlock.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Operator.h"
+
+namespace llvm {
+
+class OrderedInstructions {
+  /// Used to check dominance for instructions in same basic block.
+  mutable DenseMap<const BasicBlock *, std::unique_ptr<OrderedBasicBlock>>
+      OBBMap;
+
+  /// The dominator tree of the parent function.
+  DominatorTree *DT;
+
+public:
+  /// Constructor.
+  OrderedInstructions(DominatorTree *DT) : DT(DT) {}
+
+  /// Return true if first instruction dominates the second.
+  bool dominates(const Instruction *, const Instruction *) const;
+
+  /// Invalidate the OrderedBasicBlock cache when its basic block changes.
+  void invalidateBlock(BasicBlock *BB) { OBBMap.erase(BB); }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_UTILS_ORDEREDINSTRUCTIONS_H

diff --git a/lib/Transforms/Utils/CMakeLists.txt b/lib/Transforms/Utils/CMakeLists.txt
index 7a21c03da221ab57d6c6234354379ea3f6e5bdb3..83bc05d0311caebbc841dfe8ac11c4b29152a6b5 100644 (file)
--- a/lib/Transforms/Utils/CMakeLists.txt
+++ b/lib/Transforms/Utils/CMakeLists.txt
@@ -37,6 +37,7 @@ add_llvm_library(LLVMTransformUtils
   MetaRenamer.cpp
   ModuleUtils.cpp
   NameAnonGlobals.cpp
+  OrderedInstructions.cpp
   PredicateInfo.cpp
   PromoteMemoryToRegister.cpp
   StripGCRelocates.cpp

diff --git a/lib/Transforms/Utils/OrderedInstructions.cpp b/lib/Transforms/Utils/OrderedInstructions.cpp
new file mode 100644 (file)
index 0000000..2e67e0d
--- /dev/null
+++ b/lib/Transforms/Utils/OrderedInstructions.cpp
@@ -0,0 +1,33 @@
+//===-- OrderedInstructions.cpp - Instruction dominance function ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines utility to check dominance relation of 2 instructions.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/OrderedInstructions.h"
+using namespace llvm;
+
+/// Given 2 instructions, use OrderedBasicBlock to check for dominance relation
+/// if the instructions are in the same basic block, Otherwise, use dominator
+/// tree.
+bool OrderedInstructions::dominates(const Instruction *InstA,
+                                    const Instruction *InstB) const {
+  const BasicBlock *IBB = InstA->getParent();
+  // Use ordered basic block to do dominance check in case the 2 instructions
+  // are in the same basic block.
+  if (IBB == InstB->getParent()) {
+    auto OBB = OBBMap.find(IBB);
+    if (OBB == OBBMap.end())
+      OBB = OBBMap.insert({IBB, make_unique<OrderedBasicBlock>(IBB)}).first;
+    return OBB->second->dominates(InstA, InstB);
+  } else {
+    return DT->dominates(InstA->getParent(), InstB->getParent());
+  }
+}

diff --git a/unittests/Transforms/Utils/CMakeLists.txt b/unittests/Transforms/Utils/CMakeLists.txt
index 0fc19ef09fb01ffa5d97a1f443a12e2e9a3abc20..475c365dddc47565fbbc93eb2bfe2af1f4970cd1 100644 (file)
--- a/unittests/Transforms/Utils/CMakeLists.txt
+++ b/unittests/Transforms/Utils/CMakeLists.txt
@@ -11,5 +11,6 @@ add_llvm_unittest(UtilsTests
   FunctionComparator.cpp
   IntegerDivision.cpp
   Local.cpp
+  OrderedInstructions.cpp
   ValueMapperTest.cpp
   )

diff --git a/unittests/Transforms/Utils/OrderedInstructions.cpp b/unittests/Transforms/Utils/OrderedInstructions.cpp
new file mode 100644 (file)
index 0000000..1d6df17
--- /dev/null
+++ b/unittests/Transforms/Utils/OrderedInstructions.cpp
@@ -0,0 +1,65 @@
+//===- OrderedInstructions.cpp - Unit tests for OrderedInstructions  ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/OrderedInstructions.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+/// Check intra-basicblock and inter-basicblock dominance using
+/// OrderedInstruction.
+TEST(OrderedInstructionsTest, DominanceTest) {
+  LLVMContext Ctx;
+  Module M("test", Ctx);
+  IRBuilder<> B(Ctx);
+  FunctionType *FTy =
+      FunctionType::get(Type::getVoidTy(Ctx), {B.getInt8PtrTy()}, false);
+  Function *F = cast<Function>(M.getOrInsertFunction("f", FTy));
+
+  // Create the function as follow and check for dominance relation.
+  //
+  // test():
+  //  bbx:
+  //    loadx;
+  //    loady;
+  //  bby:
+  //    loadz;
+  //    return;
+  //
+  // More specifically, check for loadx -> (dominates) loady,
+  // loady -> loadx and loady -> loadz.
+  //
+  // Create BBX with 2 loads.
+  BasicBlock *BBX = BasicBlock::Create(Ctx, "bbx", F);
+  B.SetInsertPoint(BBX);
+  Argument *PointerArg = &*F->arg_begin();
+  LoadInst *LoadInstX = B.CreateLoad(PointerArg);
+  LoadInst *LoadInstY = B.CreateLoad(PointerArg);
+
+  // Create BBY with 1 load.
+  BasicBlock *BBY = BasicBlock::Create(Ctx, "bby", F);
+  B.SetInsertPoint(BBY);
+  LoadInst *LoadInstZ = B.CreateLoad(PointerArg);
+  B.CreateRet(LoadInstZ);
+  std::unique_ptr<DominatorTree> DT(new DominatorTree(*F));
+  OrderedInstructions OI(&*DT);
+
+  // Intra-BB dominance test.
+  EXPECT_TRUE(OI.dominates(LoadInstX, LoadInstY));
+  EXPECT_FALSE(OI.dominates(LoadInstY, LoadInstX));
+
+  // Inter-BB dominance test.
+  EXPECT_TRUE(OI.dominates(LoadInstY, LoadInstZ));
+}