4 files changed, 89 insertions, 8 deletions
diff --git a/llvm/lib/CodeGen/CMakeLists.txt b/llvm/lib/CodeGen/CMakeLists.txt
index a9a3d85f3c2..817d4e89cf1 100644
--- a/llvm/lib/CodeGen/CMakeLists.txt
+++ b/llvm/lib/CodeGen/CMakeLists.txt
@@ -37,6 +37,7 @@ add_llvm_library(LLVMCodeGen
   InterleavedAccessPass.cpp
   IntrinsicLowering.cpp
   LatencyPriorityQueue.cpp
+  LazyMachineBlockFrequencyInfo.cpp
   LexicalScopes.cpp
   LiveDebugValues.cpp
   LiveDebugVariables.cpp
diff --git a/llvm/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp b/llvm/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp
new file mode 100644
index 00000000000..34611f8064d
--- /dev/null
+++ b/llvm/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp
@@ -0,0 +1,74 @@
+///===- LazyMachineBlockFrequencyInfo.cpp - Lazy Machine Block Frequency --===//
+///
+///                     The LLVM Compiler Infrastructure
+///
+/// This file is distributed under the University of Illinois Open Source
+/// License. See LICENSE.TXT for details.
+///
+///===---------------------------------------------------------------------===//
+/// \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 {
+  LMBFI.getCalculated().print(OS, M);
+}
+
+void LazyMachineBlockFrequencyInfoPass::getAnalysisUsage(
+    AnalysisUsage &AU) const {
+  AU.addRequired<MachineBranchProbabilityInfo>();
+  AU.addRequired<MachineLoopInfo>();
+  AU.setPreservesAll();
+  MachineFunctionPass::getAnalysisUsage(AU);
+}
+
+void LazyMachineBlockFrequencyInfoPass::releaseMemory() {
+  LMBFI.releaseMemory();
+}
+
+bool LazyMachineBlockFrequencyInfoPass::runOnMachineFunction(
+    MachineFunction &MF) {
+  auto &BPIPass = getAnalysis<MachineBranchProbabilityInfo>();
+  auto &LI = getAnalysis<MachineLoopInfo>();
+  LMBFI.setAnalysis(&MF, &BPIPass, &LI);
+  return false;
+}
+
+void LazyMachineBlockFrequencyInfoPass::getLazyMachineBFIAnalysisUsage(
+    AnalysisUsage &AU) {
+  AU.addRequired<LazyMachineBlockFrequencyInfoPass>();
+  AU.addRequired<MachineBranchProbabilityInfo>();
+  AU.addRequired<MachineLoopInfo>();
+}
+
+void llvm::initializeLazyMachineBFIPassPass(PassRegistry &Registry) {
+  INITIALIZE_PASS_DEPENDENCY(LazyMachineBlockFrequencyInfoPass);
+  INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo);
+  INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo);
+}
diff --git a/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp b/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
index c496e3226e5..557b5f8824d 100644
--- a/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
+++ b/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
@@ -172,10 +172,9 @@ void MachineBlockFrequencyInfo::getAnalysisUsage(AnalysisUsage &AU) const {
   MachineFunctionPass::getAnalysisUsage(AU);
 }
 
-bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
-  MachineBranchProbabilityInfo &MBPI =
-      getAnalysis<MachineBranchProbabilityInfo>();
-  MachineLoopInfo &MLI = getAnalysis<MachineLoopInfo>();
+void MachineBlockFrequencyInfo::calculate(
+    const MachineFunction &F, const MachineBranchProbabilityInfo &MBPI,
+    const MachineLoopInfo &MLI) {
   if (!MBFI)
     MBFI.reset(new ImplType);
   MBFI->calculate(F, MBPI, MLI);
@@ -184,6 +183,13 @@ bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
        F.getName().equals(ViewBlockFreqFuncName))) {
     view();
   }
+}
+
+bool MachineBlockFrequencyInfo::runOnMachineFunction(MachineFunction &F) {
+  MachineBranchProbabilityInfo &MBPI =
+      getAnalysis<MachineBranchProbabilityInfo>();
+  MachineLoopInfo &MLI = getAnalysis<MachineLoopInfo>();
+  calculate(F, MBPI, MLI);
   return false;
 }
 
diff --git a/llvm/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp b/llvm/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
index 0fc286969eb..b76e75a4bd4 100644
--- a/llvm/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
+++ b/llvm/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
@@ -14,7 +14,7 @@
 ///===---------------------------------------------------------------------===//
 
 #include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
-#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
+#include "llvm/CodeGen/LazyMachineBlockFrequencyInfo.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/LLVMContext.h"
@@ -64,7 +64,7 @@ bool MachineOptimizationRemarkEmitterPass::runOnMachineFunction(
   MachineBlockFrequencyInfo *MBFI;
 
   if (MF.getFunction()->getContext().getDiagnosticHotnessRequested())
-    MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
+    MBFI = &getAnalysis<LazyMachineBlockFrequencyInfoPass>().getBFI();
   else
     MBFI = nullptr;
 
@@ -74,7 +74,7 @@ bool MachineOptimizationRemarkEmitterPass::runOnMachineFunction(
 
 void MachineOptimizationRemarkEmitterPass::getAnalysisUsage(
     AnalysisUsage &AU) const {
-  AU.addRequired<MachineBlockFrequencyInfo>();
+  LazyMachineBlockFrequencyInfoPass::getLazyMachineBFIAnalysisUsage(AU);
   AU.setPreservesAll();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
@@ -85,6 +85,6 @@ static const char ore_name[] = "Machine Optimization Remark Emitter";
 
 INITIALIZE_PASS_BEGIN(MachineOptimizationRemarkEmitterPass, ORE_NAME, ore_name,
                       false, true)
-INITIALIZE_PASS_DEPENDENCY(MachineBlockFrequencyInfo)
+INITIALIZE_PASS_DEPENDENCY(LazyMachineBFIPass)
 INITIALIZE_PASS_END(MachineOptimizationRemarkEmitterPass, ORE_NAME, ore_name,
                     false, true)