1 files changed, 84 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/TailDuplication.cpp b/llvm/lib/CodeGen/TailDuplication.cpp
new file mode 100644
index 000000000000..ba348b4a9d41
--- /dev/null
+++ b/llvm/lib/CodeGen/TailDuplication.cpp
@@ -0,0 +1,84 @@
+//===- TailDuplication.cpp - Duplicate blocks into predecessors' tails ----===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file This pass duplicates basic blocks ending in unconditional branches
+/// into the tails of their predecessors, using the TailDuplicator utility
+/// class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/TailDuplicator.h"
+#include "llvm/Pass.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "tailduplication"
+
+namespace {
+
+class TailDuplicateBase : public MachineFunctionPass {
+  TailDuplicator Duplicator;
+  bool PreRegAlloc;
+public:
+  TailDuplicateBase(char &PassID, bool PreRegAlloc)
+    : MachineFunctionPass(PassID), PreRegAlloc(PreRegAlloc) {}
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addRequired<MachineBranchProbabilityInfo>();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+};
+
+class TailDuplicate : public TailDuplicateBase {
+public:
+  static char ID;
+  TailDuplicate() : TailDuplicateBase(ID, false) {
+    initializeTailDuplicatePass(*PassRegistry::getPassRegistry());
+  }
+};
+
+class EarlyTailDuplicate : public TailDuplicateBase {
+public:
+  static char ID;
+  EarlyTailDuplicate() : TailDuplicateBase(ID, true) {
+    initializeEarlyTailDuplicatePass(*PassRegistry::getPassRegistry());
+  }
+};
+
+} // end anonymous namespace
+
+char TailDuplicate::ID;
+char EarlyTailDuplicate::ID;
+
+char &llvm::TailDuplicateID = TailDuplicate::ID;
+char &llvm::EarlyTailDuplicateID = EarlyTailDuplicate::ID;
+
+INITIALIZE_PASS(TailDuplicate, DEBUG_TYPE, "Tail Duplication", false, false)
+INITIALIZE_PASS(EarlyTailDuplicate, "early-tailduplication",
+                "Early Tail Duplication", false, false)
+
+bool TailDuplicateBase::runOnMachineFunction(MachineFunction &MF) {
+  if (skipFunction(MF.getFunction()))
+    return false;
+
+  auto MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
+  Duplicator.initMF(MF, PreRegAlloc, MBPI, /*LayoutMode=*/false);
+
+  bool MadeChange = false;
+  while (Duplicator.tailDuplicateBlocks())
+    MadeChange = true;
+
+  return MadeChange;
+}