1 files changed, 96 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp b/llvm/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp
new file mode 100644
index 000000000000..cef5085ae079
--- /dev/null
+++ b/llvm/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp
@@ -0,0 +1,96 @@
+///===- LazyMachineBlockFrequencyInfo.cpp - Lazy Machine Block Frequency --===//
+///
+/// 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 is an alternative analysis pass to MachineBlockFrequencyInfo.  The
+/// difference is that with this pass the block frequencies are not computed
+/// when the analysis pass is executed but rather when the BFI result is
+/// explicitly requested by the analysis client.
+///
+///===---------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/LazyMachineBlockFrequencyInfo.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "lazy-machine-block-freq"
+
+INITIALIZE_PASS_BEGIN(LazyMachineBlockFrequencyInfoPass, DEBUG_TYPE,
+                      "Lazy Machine Block Frequency Analysis", true, true)
+INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
+INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
+INITIALIZE_PASS_END(LazyMachineBlockFrequencyInfoPass, DEBUG_TYPE,
+                    "Lazy Machine Block Frequency Analysis", true, true)
+
+char LazyMachineBlockFrequencyInfoPass::ID = 0;
+
+LazyMachineBlockFrequencyInfoPass::LazyMachineBlockFrequencyInfoPass()
+    : MachineFunctionPass(ID) {
+  initializeLazyMachineBlockFrequencyInfoPassPass(
+      *PassRegistry::getPassRegistry());
+}
+
+void LazyMachineBlockFrequencyInfoPass::print(raw_ostream &OS,
+                                              const Module *M) const {
+  getBFI().print(OS, M);
+}
+
+void LazyMachineBlockFrequencyInfoPass::getAnalysisUsage(
+    AnalysisUsage &AU) const {
+  AU.addRequired<MachineBranchProbabilityInfo>();
+  AU.setPreservesAll();
+  MachineFunctionPass::getAnalysisUsage(AU);
+}
+
+void LazyMachineBlockFrequencyInfoPass::releaseMemory() {
+  OwnedMBFI.reset();
+  OwnedMLI.reset();
+  OwnedMDT.reset();
+}
+
+MachineBlockFrequencyInfo &
+LazyMachineBlockFrequencyInfoPass::calculateIfNotAvailable() const {
+  auto *MBFI = getAnalysisIfAvailable<MachineBlockFrequencyInfo>();
+  if (MBFI) {
+    LLVM_DEBUG(dbgs() << "MachineBlockFrequencyInfo is available\n");
+    return *MBFI;
+  }
+
+  auto &MBPI = getAnalysis<MachineBranchProbabilityInfo>();
+  auto *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
+  auto *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
+  LLVM_DEBUG(dbgs() << "Building MachineBlockFrequencyInfo on the fly\n");
+  LLVM_DEBUG(if (MLI) dbgs() << "LoopInfo is available\n");
+
+  if (!MLI) {
+    LLVM_DEBUG(dbgs() << "Building LoopInfo on the fly\n");
+    // First create a dominator tree.
+    LLVM_DEBUG(if (MDT) dbgs() << "DominatorTree is available\n");
+
+    if (!MDT) {
+      LLVM_DEBUG(dbgs() << "Building DominatorTree on the fly\n");
+      OwnedMDT = std::make_unique<MachineDominatorTree>();
+      OwnedMDT->getBase().recalculate(*MF);
+      MDT = OwnedMDT.get();
+    }
+
+    // Generate LoopInfo from it.
+    OwnedMLI = std::make_unique<MachineLoopInfo>();
+    OwnedMLI->getBase().analyze(MDT->getBase());
+    MLI = OwnedMLI.get();
+  }
+
+  OwnedMBFI = std::make_unique<MachineBlockFrequencyInfo>();
+  OwnedMBFI->calculate(*MF, MBPI, *MLI);
+  return *OwnedMBFI.get();
+}
+
+bool LazyMachineBlockFrequencyInfoPass::runOnMachineFunction(
+    MachineFunction &F) {
+  MF = &F;
+  return false;
+}