[BPI] Add new LazyBPI analysis

Summary:
The motivation is the same as in D22141: In order to add the hotness
attribute to optimization remarks we need BFI to be available in all
passes that emit optimization remarks.  BFI depends on BPI so unless we
make this lazy as well we would still compute BPI unconditionally.

The solution is to use the new LazyBPI pass in LazyBFI and only compute
BPI when computation of BFI is requested by the client.

I extended the laziness test using a LoopDistribute test to also cover
BPI.

Reviewers: hfinkel, davidxl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D22835

llvm-svn: 277083

include/llvm/Analysis/LazyBlockFrequencyInfo.h

@@ -18,6 +18,7 @@
 #define LLVM_ANALYSIS_LAZYBLOCKFREQUENCYINFO_H
 
 #include "llvm/Analysis/BlockFrequencyInfo.h"
+#include "llvm/Analysis/LazyBranchProbabilityInfo.h"
 #include "llvm/Pass.h"
 
 namespace llvm {
@@ -57,21 +58,21 @@ class LazyBlockFrequencyInfoPass : public FunctionPass {
   class LazyBlockFrequencyInfo {
   public:
     LazyBlockFrequencyInfo()
-        : Calculated(false), F(nullptr), BPI(nullptr), LI(nullptr) {}
+        : Calculated(false), F(nullptr), BPIPass(nullptr), LI(nullptr) {}
 
     /// Set up the per-function input.
-    void setAnalysis(const Function *F, const BranchProbabilityInfo *BPI,
+    void setAnalysis(const Function *F, LazyBranchProbabilityInfoPass *BPIPass,
                      const LoopInfo *LI) {
       this->F = F;
-      this->BPI = BPI;
+      this->BPIPass = BPIPass;
       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);
+        assert(F && BPIPass && LI && "call setAnalysis");
+        BFI.calculate(*F, BPIPass->getBPI(), *LI);
         Calculated = true;
       }
       return BFI;
@@ -91,7 +92,7 @@ class LazyBlockFrequencyInfoPass : public FunctionPass {
     BlockFrequencyInfo BFI;
     bool Calculated;
     const Function *F;
-    const BranchProbabilityInfo *BPI;
+    LazyBranchProbabilityInfoPass *BPIPass;
     const LoopInfo *LI;
   };
 

include/llvm/Analysis/LazyBranchProbabilityInfo.h

@@ -0,0 +1,109 @@
+//===- LazyBranchProbabilityInfo.h - Lazy Branch Probability ----*- 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 BranchProbabilityInfoWrapperPass.
+// The difference is that with this pass the branch probabilities are not
+// computed when the analysis pass is executed but rather when the BPI results
+// is explicitly requested by the analysis client.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_LAZYBRANCHPROBABILITYINFO_H
+#define LLVM_ANALYSIS_LAZYBRANCHPROBABILITYINFO_H
+
+#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/Pass.h"
+
+namespace llvm {
+class AnalysisUsage;
+class Function;
+class LoopInfo;
+
+/// \brief This is an alternative analysis pass to
+/// BranchProbabilityInfoWrapperPass.  The difference is that with this pass the
+/// branch probabilities are not computed when the analysis pass is executed but
+/// rather when the BPI 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(LazyBPIPass)
+///
+/// 2. Similarly, getAnalysisUsage should call:
+///
+///   LazyBranchProbabilityInfoPass::getLazyBPIAnalysisUsage(AU)
+///
+/// 3. The computed BPI should be requested with
+///    getAnalysis<LazyBranchProbabilityInfoPass>().getBPI() before LoopInfo
+///    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 LazyBranchProbabilityInfoPass : public FunctionPass {
+
+  /// Wraps a BPI to allow lazy computation of the branch probabilities.
+  ///
+  /// A pass that only conditionally uses BPI can uncondtionally require the
+  /// analysis without paying for the overhead if BPI doesn't end up being used.
+  class LazyBranchProbabilityInfo {
+  public:
+    LazyBranchProbabilityInfo(const Function *F, const LoopInfo *LI)
+        : Calculated(false), F(F), LI(LI) {}
+
+    /// Retrieve the BPI with the branch probabilities computed.
+    BranchProbabilityInfo &getCalculated() {
+      if (!Calculated) {
+        assert(F && LI && "call setAnalysis");
+        BPI.calculate(*F, *LI);
+        Calculated = true;
+      }
+      return BPI;
+    }
+
+    const BranchProbabilityInfo &getCalculated() const {
+      return const_cast<LazyBranchProbabilityInfo *>(this)->getCalculated();
+    }
+
+  private:
+    BranchProbabilityInfo BPI;
+    bool Calculated;
+    const Function *F;
+    const LoopInfo *LI;
+  };
+
+  std::unique_ptr<LazyBranchProbabilityInfo> LBPI;
+
+public:
+  static char ID;
+
+  LazyBranchProbabilityInfoPass();
+
+  /// \brief Compute and return the branch probabilities.
+  BranchProbabilityInfo &getBPI() { return LBPI->getCalculated(); }
+
+  /// \brief Compute and return the branch probabilities.
+  const BranchProbabilityInfo &getBPI() const { return LBPI->getCalculated(); }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+  /// Helper for client passes to set up the analysis usage on behalf of this
+  /// pass.
+  static void getLazyBPIAnalysisUsage(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 LBPI.
+void initializeLazyBPIPassPass(PassRegistry &Registry);
+}
+#endif

include/llvm/InitializePasses.h

@@ -165,6 +165,7 @@ void initializeIntervalPartitionPass(PassRegistry&);
 void initializeJumpThreadingPass(PassRegistry&);
 void initializeLCSSAWrapperPassPass(PassRegistry &);
 void initializeLegacyLICMPassPass(PassRegistry&);
+void initializeLazyBranchProbabilityInfoPassPass(PassRegistry&);
 void initializeLazyBlockFrequencyInfoPassPass(PassRegistry&);
 void initializeLazyValueInfoWrapperPassPass(PassRegistry&);
 void initializeLintPass(PassRegistry&);

lib/Analysis/Analysis.cpp

@@ -54,6 +54,7 @@ void llvm::initializeAnalysis(PassRegistry &Registry) {
   initializeIVUsersWrapperPassPass(Registry);
   initializeInstCountPass(Registry);
   initializeIntervalPartitionPass(Registry);
+  initializeLazyBranchProbabilityInfoPassPass(Registry);
   initializeLazyBlockFrequencyInfoPassPass(Registry);
   initializeLazyValueInfoWrapperPassPass(Registry);
   initializeLintPass(Registry);

lib/Analysis/CMakeLists.txt

@@ -37,6 +37,7 @@ add_llvm_library(LLVMAnalysis
   Interval.cpp
   IntervalPartition.cpp
   IteratedDominanceFrontier.cpp
+  LazyBranchProbabilityInfo.cpp
   LazyBlockFrequencyInfo.cpp
   LazyCallGraph.cpp
   LazyValueInfo.cpp

lib/Analysis/LazyBlockFrequencyInfo.cpp

@@ -15,7 +15,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/LazyBlockFrequencyInfo.h"
-#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/Analysis/LazyBranchProbabilityInfo.h"
 #include "llvm/Analysis/LoopInfo.h"
 
 using namespace llvm;
@@ -24,7 +24,7 @@ using namespace llvm;
 
 INITIALIZE_PASS_BEGIN(LazyBlockFrequencyInfoPass, DEBUG_TYPE,
                       "Lazy Block Frequency Analysis", true, true)
-INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(LazyBPIPass)
 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
 INITIALIZE_PASS_END(LazyBlockFrequencyInfoPass, DEBUG_TYPE,
                     "Lazy Block Frequency Analysis", true, true)
@@ -40,7 +40,7 @@ void LazyBlockFrequencyInfoPass::print(raw_ostream &OS, const Module *) const {
 }
 
 void LazyBlockFrequencyInfoPass::getAnalysisUsage(AnalysisUsage &AU) const {
-  AU.addRequired<BranchProbabilityInfoWrapperPass>();
+  LazyBranchProbabilityInfoPass::getLazyBPIAnalysisUsage(AU);
   AU.addRequired<LoopInfoWrapperPass>();
   AU.setPreservesAll();
 }
@@ -48,21 +48,20 @@ void LazyBlockFrequencyInfoPass::getAnalysisUsage(AnalysisUsage &AU) const {
 void LazyBlockFrequencyInfoPass::releaseMemory() { LBFI.releaseMemory(); }
 
 bool LazyBlockFrequencyInfoPass::runOnFunction(Function &F) {
-  BranchProbabilityInfo &BPI =
-      getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
+  auto &BPIPass = getAnalysis<LazyBranchProbabilityInfoPass>();
   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
-  LBFI.setAnalysis(&F, &BPI, &LI);
+  LBFI.setAnalysis(&F, &BPIPass, &LI);
   return false;
 }
 
 void LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AnalysisUsage &AU) {
-  AU.addRequired<BranchProbabilityInfoWrapperPass>();
+  LazyBranchProbabilityInfoPass::getLazyBPIAnalysisUsage(AU);
   AU.addRequired<LazyBlockFrequencyInfoPass>();
   AU.addRequired<LoopInfoWrapperPass>();
 }
 
 void llvm::initializeLazyBFIPassPass(PassRegistry &Registry) {
-  INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass);
+  initializeLazyBPIPassPass(Registry);
   INITIALIZE_PASS_DEPENDENCY(LazyBlockFrequencyInfoPass);
   INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass);
 }

lib/Analysis/LazyBranchProbabilityInfo.cpp

@@ -0,0 +1,63 @@
+//===- LazyBranchProbabilityInfo.cpp - Lazy Branch Probability 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 BranchProbabilityInfoWrapperPass.
+// The difference is that with this pass the branch probabilities are not
+// computed when the analysis pass is executed but rather when the BPI results
+// is explicitly requested by the analysis client.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/LazyBranchProbabilityInfo.h"
+#include "llvm/Analysis/LoopInfo.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "lazy-branch-prob"
+
+INITIALIZE_PASS_BEGIN(LazyBranchProbabilityInfoPass, DEBUG_TYPE,
+                      "Lazy Branch Probability Analysis", true, true)
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
+INITIALIZE_PASS_END(LazyBranchProbabilityInfoPass, DEBUG_TYPE,
+                    "Lazy Branch Probability Analysis", true, true)
+
+char LazyBranchProbabilityInfoPass::ID = 0;
+
+LazyBranchProbabilityInfoPass::LazyBranchProbabilityInfoPass()
+    : FunctionPass(ID) {
+  initializeLazyBranchProbabilityInfoPassPass(*PassRegistry::getPassRegistry());
+}
+
+void LazyBranchProbabilityInfoPass::print(raw_ostream &OS,
+                                          const Module *) const {
+  LBPI->getCalculated().print(OS);
+}
+
+void LazyBranchProbabilityInfoPass::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.addRequired<LoopInfoWrapperPass>();
+  AU.setPreservesAll();
+}
+
+void LazyBranchProbabilityInfoPass::releaseMemory() { LBPI.reset(); }
+
+bool LazyBranchProbabilityInfoPass::runOnFunction(Function &F) {
+  LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+  LBPI = llvm::make_unique<LazyBranchProbabilityInfo>(&F, &LI);
+  return false;
+}
+
+void LazyBranchProbabilityInfoPass::getLazyBPIAnalysisUsage(AnalysisUsage &AU) {
+  AU.addRequired<LazyBranchProbabilityInfoPass>();
+  AU.addRequired<LoopInfoWrapperPass>();
+}
+
+void llvm::initializeLazyBPIPassPass(PassRegistry &Registry) {
+  INITIALIZE_PASS_DEPENDENCY(LazyBranchProbabilityInfoPass);
+  INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass);
+}

test/Analysis/BranchProbabilityInfo/basic.ll

@@ -1,4 +1,5 @@
 ; RUN: opt < %s -analyze -branch-prob | FileCheck %s
+; RUN: opt < %s -analyze -lazy-branch-prob | FileCheck %s
 ; RUN: opt < %s -passes='print<branch-prob>' -disable-output 2>&1 | FileCheck %s
 
 define i32 @test1(i32 %i, i32* %a) {

test/Transforms/LoopDistribute/diagnostics-with-hotness-lazy-BFI.ll

@@ -1,18 +1,24 @@
 ; Check that BFI is not computed when -pass-remarks-with-hotness is off
 
 ; RUN: opt -loop-distribute -S -pass-remarks-missed=loop-distribute \
-; RUN:     -debug-only=block-freq -pass-remarks-with-hotness < %s 2>&1 | FileCheck %s --check-prefix=HOTNESS
+; RUN:     -debug-only=block-freq,branch-prob -pass-remarks-with-hotness \
+; RUN:     < %s 2>&1 | FileCheck %s --check-prefix=HOTNESS
 ; RUN: opt -loop-distribute -S -pass-remarks-missed=loop-distribute \
-; RUN:     -debug-only=block-freq                            < %s 2>&1 | FileCheck %s --check-prefix=NO_HOTNESS
+; RUN:     -debug-only=block-freq,branch-prob \
+; RUN:     < %s 2>&1 | FileCheck %s --check-prefix=NO_HOTNESS
 
 ; RUN: opt -passes='require<aa>,loop-distribute' -S -pass-remarks-missed=loop-distribute \
-; RUN:     -debug-only=block-freq -pass-remarks-with-hotness < %s 2>&1 | FileCheck %s --check-prefix=HOTNESS
+; RUN:     -debug-only=block-freq,branch-prob -pass-remarks-with-hotness \
+; RUN:     < %s 2>&1 | FileCheck %s --check-prefix=HOTNESS
 ; RUN: opt -passes='require<aa>,loop-distribute' -S -pass-remarks-missed=loop-distribute \
-; RUN:     -debug-only=block-freq                            < %s 2>&1 | FileCheck %s --check-prefix=NO_HOTNESS
+; RUN:     -debug-only=block-freq,branch-prob \
+; RUN:     < %s 2>&1 | FileCheck %s --check-prefix=NO_HOTNESS
 
 ; REQUIRES: asserts
 
+; HOTNESS: Branch Probability Info : forced
 ; HOTNESS: block-frequency: forced
+; NO_HOTNESS-NOT: Branch Probability Info : forced
 ; NO_HOTNESS-NOT: block-frequency: forced
 
 ; This is the input program: