8 files changed, 205 insertions, 0 deletions
diff --git a/llvm/include/llvm/Analysis/BlockFrequencyInfo.h b/llvm/include/llvm/Analysis/BlockFrequencyInfo.h
index ed473abf3b3..7d48dfc9121 100644
--- a/llvm/include/llvm/Analysis/BlockFrequencyInfo.h
+++ b/llvm/include/llvm/Analysis/BlockFrequencyInfo.h
@@ -43,6 +43,8 @@ public:
 
   BlockFrequencyInfo &operator=(BlockFrequencyInfo &&RHS);
 
+  ~BlockFrequencyInfo();
+
   const Function *getFunction() const;
   const BranchProbabilityInfo *getBPI() const;
   void view() const;
diff --git a/llvm/include/llvm/Analysis/LazyBlockFrequencyInfo.h b/llvm/include/llvm/Analysis/LazyBlockFrequencyInfo.h
new file mode 100644
index 00000000000..a2d24bb9eb8
--- /dev/null
+++ b/llvm/include/llvm/Analysis/LazyBlockFrequencyInfo.h
@@ -0,0 +1,125 @@
+//===- LazyBlockFrequencyInfo.h - Lazy Block Frequency Analysis -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This is an alternative analysis pass to BlockFrequencyInfoWrapperPass.  The
+// difference is that with this pass the block frequencies are not computed when
+// the analysis pass is executed but rather when the BFI results is explicitly
+// requested by the analysis client.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_LAZYBLOCKFREQUENCYINFO_H
+#define LLVM_ANALYSIS_LAZYBLOCKFREQUENCYINFO_H
+
+#include "llvm/Analysis/BlockFrequencyInfo.h"
+#include "llvm/Pass.h"
+
+namespace llvm {
+class AnalysisUsage;
+class BranchProbabilityInfo;
+class Function;
+class LoopInfo;
+
+/// \brief This is an alternative analysis pass to
+/// BlockFrequencyInfoWrapperPass.  The difference is that with this pass the
+/// block frequencies are not computed when the analysis pass is executed but
+/// rather when the BFI results is explicitly requested by the analysis client.
+///
+/// There are some additional requirements for any client pass that wants to use
+/// the analysis:
+///
+/// 1. The pass needs to initialize dependent passes with:
+///
+///   INITIALIZE_PASS_DEPENDENCY(LazyBFIPass)
+///
+/// 2. Similarly, getAnalysisUsage should call:
+///
+///   LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AU)
+///
+/// 3. The computed BFI should be requested with
+///    getAnalysis<LazyBlockFrequencyInfoPass>().getBFI() before either LoopInfo
+///    or BPI could be invalidated for example by changing the CFG.
+///
+/// Note that it is expected that we wouldn't need this functionality for the
+/// new PM since with the new PM, analyses are executed on demand.
+class LazyBlockFrequencyInfoPass : public FunctionPass {
+
+  /// Wraps a BFI to allow lazy computation of the block frequencies.
+  ///
+  /// A pass that only conditionally uses BFI can uncondtionally require the
+  /// analysis without paying for the overhead if BFI doesn't end up being used.
+  class LazyBlockFrequencyInfo {
+  public:
+    LazyBlockFrequencyInfo()
+        : Calculated(false), F(nullptr), BPI(nullptr), LI(nullptr) {}
+
+    /// Set up the per-function input.
+    void setAnalysis(const Function *F, const BranchProbabilityInfo *BPI,
+                     const LoopInfo *LI) {
+      this->F = F;
+      this->BPI = BPI;
+      this->LI = LI;
+    }
+
+    /// Retrieve the BFI with the block frequencies computed.
+    BlockFrequencyInfo &getCalculated() {
+      if (!Calculated) {
+        assert(F && BPI && LI && "call setAnalysis");
+        BFI.calculate(*F, *BPI, *LI);
+        Calculated = true;
+      }
+      return BFI;
+    }
+
+    const BlockFrequencyInfo &getCalculated() const {
+      return const_cast<LazyBlockFrequencyInfo *>(this)->getCalculated();
+    }
+
+    void releaseMemory() {
+      BFI.releaseMemory();
+      Calculated = false;
+      setAnalysis(nullptr, nullptr, nullptr);
+    }
+
+  private:
+    BlockFrequencyInfo BFI;
+    bool Calculated;
+    const Function *F;
+    const BranchProbabilityInfo *BPI;
+    const LoopInfo *LI;
+  };
+
+  LazyBlockFrequencyInfo LBFI;
+
+public:
+  static char ID;
+
+  LazyBlockFrequencyInfoPass();
+
+  /// \brief Compute and return the block frequencies.
+  BlockFrequencyInfo &getBFI() { return LBFI.getCalculated(); }
+
+  /// \brief Compute and return the block frequencies.
+  const BlockFrequencyInfo &getBFI() const { return LBFI.getCalculated(); }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+  /// Helper for client passes to set up the analysis usage on behalf of this
+  /// pass.
+  static void getLazyBFIAnalysisUsage(AnalysisUsage &AU);
+
+  bool runOnFunction(Function &F) override;
+  void releaseMemory() override;
+  void print(raw_ostream &OS, const Module *M) const override;
+};
+
+/// \brief Helper for client passes to initialize dependent passes for LBFI.
+void initializeLazyBFIPassPass(PassRegistry &Registry);
+}
+#endif
diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
index 12de6310c5f..59ee09432ee 100644
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/include/llvm/InitializePasses.h
@@ -160,6 +160,7 @@ void initializeIntervalPartitionPass(PassRegistry&);
 void initializeJumpThreadingPass(PassRegistry&);
 void initializeLCSSAWrapperPassPass(PassRegistry &);
 void initializeLegacyLICMPassPass(PassRegistry&);
+void initializeLazyBlockFrequencyInfoPassPass(PassRegistry&);
 void initializeLazyValueInfoWrapperPassPass(PassRegistry&);
 void initializeLintPass(PassRegistry&);
 void initializeLiveDebugValuesPass(PassRegistry&);
diff --git a/llvm/lib/Analysis/Analysis.cpp b/llvm/lib/Analysis/Analysis.cpp
index 099ac15245c..2bcfe402e68 100644
--- a/llvm/lib/Analysis/Analysis.cpp
+++ b/llvm/lib/Analysis/Analysis.cpp
@@ -54,6 +54,7 @@ void llvm::initializeAnalysis(PassRegistry &Registry) {
   initializeIVUsersPass(Registry);
   initializeInstCountPass(Registry);
   initializeIntervalPartitionPass(Registry);
+  initializeLazyBlockFrequencyInfoPassPass(Registry);
   initializeLazyValueInfoWrapperPassPass(Registry);
   initializeLintPass(Registry);
   initializeLoopInfoWrapperPassPass(Registry);
diff --git a/llvm/lib/Analysis/BlockFrequencyInfo.cpp b/llvm/lib/Analysis/BlockFrequencyInfo.cpp
index de1c8553c93..1dd8f4fdfcf 100644
--- a/llvm/lib/Analysis/BlockFrequencyInfo.cpp
+++ b/llvm/lib/Analysis/BlockFrequencyInfo.cpp
@@ -129,6 +129,12 @@ BlockFrequencyInfo &BlockFrequencyInfo::operator=(BlockFrequencyInfo &&RHS) {
   return *this;
 }
 
+// Explicitly define the default constructor otherwise it would be implicitly
+// defined at the first ODR-use which is the BFI member in the
+// LazyBlockFrequencyInfo header.  The dtor needs the BlockFrequencyInfoImpl
+// template instantiated which is not available in the header.
+BlockFrequencyInfo::~BlockFrequencyInfo() {}
+
 void BlockFrequencyInfo::calculate(const Function &F,
                                    const BranchProbabilityInfo &BPI,
                                    const LoopInfo &LI) {
diff --git a/llvm/lib/Analysis/CMakeLists.txt b/llvm/lib/Analysis/CMakeLists.txt
index ee9edd8b01a..5c6011d77ce 100644
--- a/llvm/lib/Analysis/CMakeLists.txt
+++ b/llvm/lib/Analysis/CMakeLists.txt
@@ -37,6 +37,7 @@ add_llvm_library(LLVMAnalysis
   Interval.cpp
   IntervalPartition.cpp
   IteratedDominanceFrontier.cpp
+  LazyBlockFrequencyInfo.cpp
   LazyCallGraph.cpp
   LazyValueInfo.cpp
   Lint.cpp
diff --git a/llvm/lib/Analysis/LazyBlockFrequencyInfo.cpp b/llvm/lib/Analysis/LazyBlockFrequencyInfo.cpp
new file mode 100644
index 00000000000..7debfde87d2
--- /dev/null
+++ b/llvm/lib/Analysis/LazyBlockFrequencyInfo.cpp
@@ -0,0 +1,68 @@
+//===- LazyBlockFrequencyInfo.cpp - Lazy Block Frequency Analysis ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This is an alternative analysis pass to BlockFrequencyInfoWrapperPass.  The
+// difference is that with this pass the block frequencies are not computed when
+// the analysis pass is executed but rather when the BFI results is explicitly
+// requested by the analysis client.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/LazyBlockFrequencyInfo.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/Analysis/LoopInfo.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "lazy-block-freq"
+
+INITIALIZE_PASS_BEGIN(LazyBlockFrequencyInfoPass, DEBUG_TYPE,
+                      "Lazy Block Frequency Analysis", true, true)
+INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
+INITIALIZE_PASS_END(LazyBlockFrequencyInfoPass, DEBUG_TYPE,
+                    "Lazy Block Frequency Analysis", true, true)
+
+char LazyBlockFrequencyInfoPass::ID = 0;
+
+LazyBlockFrequencyInfoPass::LazyBlockFrequencyInfoPass() : FunctionPass(ID) {
+  initializeLazyBlockFrequencyInfoPassPass(*PassRegistry::getPassRegistry());
+}
+
+void LazyBlockFrequencyInfoPass::print(raw_ostream &OS, const Module *) const {
+  LBFI.getCalculated().print(OS);
+}
+
+void LazyBlockFrequencyInfoPass::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.addRequired<BranchProbabilityInfoWrapperPass>();
+  AU.addRequired<LoopInfoWrapperPass>();
+  AU.setPreservesAll();
+}
+
+void LazyBlockFrequencyInfoPass::releaseMemory() { LBFI.releaseMemory(); }
+
+bool LazyBlockFrequencyInfoPass::runOnFunction(Function &F) {
+  BranchProbabilityInfo &BPI =
+      getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
+  LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+  LBFI.setAnalysis(&F, &BPI, &LI);
+  return false;
+}
+
+void LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AnalysisUsage &AU) {
+  AU.addRequired<BranchProbabilityInfoWrapperPass>();
+  AU.addRequired<LazyBlockFrequencyInfoPass>();
+  AU.addRequired<LoopInfoWrapperPass>();
+}
+
+void llvm::initializeLazyBFIPassPass(PassRegistry &Registry) {
+  INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass);
+  INITIALIZE_PASS_DEPENDENCY(LazyBlockFrequencyInfoPass);
+  INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass);
+}
diff --git a/llvm/test/Analysis/BlockFrequencyInfo/basic.ll b/llvm/test/Analysis/BlockFrequencyInfo/basic.ll
index 44bfc36a711..a957adc6502 100644
--- a/llvm/test/Analysis/BlockFrequencyInfo/basic.ll
+++ b/llvm/test/Analysis/BlockFrequencyInfo/basic.ll
@@ -1,4 +1,5 @@
 ; RUN: opt < %s -analyze -block-freq | FileCheck %s
+; RUN: opt < %s -analyze -lazy-block-freq | FileCheck %s
 ; RUN: opt < %s -passes='print<block-freq>' -disable-output 2>&1 | FileCheck %s
 
 define i32 @test1(i32 %i, i32* %a) {