Add getBlockProfileCount method to BlockFrequencyInfo

[eraman]

Summary

Deriving the count of a block from function's entry count and block's relative frequency is a useful utility. At present, ProfileCommon.h has a function that just does the arithmetic, and still needs to be passed the BFI of the block. Moving it to BFI makes it easier to use.

[davidxl]

I don't see any existing unittests covering BFI interfaces, it might be a good opportunity to add one.

[eraman]

Added a unit test for BlockFrequencyInfo

[tejohnson]

Looks like a good cleanup to me. You can clean up includes as noted below.

lib/Bitcode/Writer/BitcodeWriter.cpp

36–37

This include can presumably be removed with this change.

[davidxl]

lgtm (after addressing Teresa's comment)

[eraman]

Remove unused header

[eraman]

Dexon, does this patch look ok?

include/llvm/Analysis/BlockFrequencyInfo.h

 //===- BlockFrequencyInfo.h - 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.
 //
 //===----------------------------------------------------------------------===//
 //
 // Loops should be simplified before this analysis.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_ANALYSIS_BLOCKFREQUENCYINFO_H
 #define LLVM_ANALYSIS_BLOCKFREQUENCYINFO_H
 
+#include "llvm/ADT/Optional.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/BlockFrequency.h"
 #include <climits>
 
 namespace llvm {
 
 class BranchProbabilityInfo;
 class LoopInfo;
public:
 
   /// getblockFreq - Return block frequency. Return 0 if we don't have the
   /// information. Please note that initial frequency is equal to ENTRY_FREQ. It
   /// means that we should not rely on the value itself, but only on the
   /// comparison to the other block frequencies. We do this to avoid using of
   /// floating points.
   BlockFrequency getBlockFreq(const BasicBlock *BB) const;
 
+  /// \brief Returns the estimated profile count of \p BB.
+  /// This computes the relative block frequency of \p BB and multiplies it by
+  /// the enclosing function's count (if available) and returns the value.
+  Optional<uint64_t> getBlockProfileCount(const BasicBlock *BB) const;
+
   // Set the frequency of the given basic block.
   void setBlockFreq(const BasicBlock *BB, uint64_t Freq);
 
   /// calculate - compute block frequency info for the given function.
   void calculate(const Function &F, const BranchProbabilityInfo &BPI,
                  const LoopInfo &LI);
 
   // Print the block frequency Freq to OS using the current functions entry

include/llvm/ProfileData/ProfileCommon.h

 }
 
 SummaryEntryVector &ProfileSummary::getDetailedSummary() {
   if (!DetailedSummaryCutoffs.empty() && DetailedSummary.empty())
     computeDetailedSummary();
   return DetailedSummary;
 }
 
-/// Helper to compute the profile count for a block, based on the
-/// ratio of its frequency to the entry block frequency, multiplied
-/// by the entry block count.
-inline uint64_t getBlockProfileCount(uint64_t BlockFreq, uint64_t EntryFreq,
-                                     uint64_t EntryCount) {
-  APInt ScaledCount(128, EntryCount);
-  APInt BlockFreqAPInt(128, BlockFreq);
-  APInt EntryFreqAPInt(128, EntryFreq);
-  ScaledCount *= BlockFreqAPInt;
-  ScaledCount = ScaledCount.udiv(EntryFreqAPInt);
-  return ScaledCount.getLimitedValue();
-}
-
 } // end namespace llvm
 #endif

lib/Analysis/BlockFrequencyInfo.cpp

if (ViewBlockFreqPropagationDAG != GVDT_None)
     view();
 #endif
 }
 
 BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
   return BFI ? BFI->getBlockFreq(BB) : 0;
 }
 
+Optional<uint64_t>
+BlockFrequencyInfo::getBlockProfileCount(const BasicBlock *BB) const {
+  auto EntryCount = getFunction()->getEntryCount();
+  if (!EntryCount)
+    return None;
+  // Use 128 bit APInt to do the arithmetic to avoid overflow.
+  APInt BlockCount(128, EntryCount.getValue());
+  APInt BlockFreq(128, getBlockFreq(BB).getFrequency());
+  APInt EntryFreq(128, getEntryFreq());
+  BlockCount *= BlockFreq;
+  BlockCount = BlockCount.udiv(EntryFreq);
+  return BlockCount.getLimitedValue();
+}
+
 void BlockFrequencyInfo::setBlockFreq(const BasicBlock *BB,
                                       uint64_t Freq) {
   assert(BFI && "Expected analysis to be available");
   BFI->setBlockFreq(BB, Freq);
 }
 
 /// Pop up a ghostview window with the current block frequency propagation
 /// rendered using dot.

lib/Bitcode/Writer/BitcodeWriter.cpp

 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/UseListOrder.h"
 #include "llvm/IR/ValueSymbolTable.h"
-#include "llvm/ProfileData/ProfileCommon.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cctype>
 #include <map>
 using namespace llvm;
 
for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
       if (!I->getType()->isVoidTy())
         ++InstID;
 
       if (EmitSummaryIndex) {
         if (auto CS = ImmutableCallSite(&*I)) {
           auto *CalledFunction = CS.getCalledFunction();
           if (CalledFunction && CalledFunction->hasName() &&
               !CalledFunction->isIntrinsic()) {
-            uint64_t ScaledCount = 0;
-            if (HasProfileData)
-              ScaledCount = getBlockProfileCount(
-                  BFI->getBlockFreq(&(*BB)).getFrequency(), BFI->getEntryFreq(),
-                  F.getEntryCount().getValue());
+            auto ScaledCount = BFI ? BFI->getBlockProfileCount(&*BB) : None;
             unsigned CalleeId = VE.getValueID(
                 M->getValueSymbolTable().lookup(CalledFunction->getName()));
-            CallGraphEdges[CalleeId] += ScaledCount;
+            CallGraphEdges[CalleeId] +=
+                (ScaledCount ? ScaledCount.getValue() : 0);
           }
         }
         findRefEdges(&*I, VE, RefEdges, Visited);
       }
 
       // If the instruction has metadata, write a metadata attachment later.
       NeedsMetadataAttachment |= I->hasMetadataOtherThanDebugLoc();
 

unittests/Analysis/BlockFrequencyInfoTest.cpp

+//===- BlockFrequencyInfoTest.cpp - BlockFrequencyInfo unit tests ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/BlockFrequencyInfo.h"
+#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/raw_ostream.h"
+#include "gtest/gtest.h"
+
+namespace llvm {
+namespace {
+
+class BlockFrequencyInfoTest : public testing::Test {
+protected:
+  std::unique_ptr<BranchProbabilityInfo> BPI;
+  std::unique_ptr<DominatorTree> DT;
+  std::unique_ptr<LoopInfo> LI;
+
+  BlockFrequencyInfo buildBFI(Function &F) {
+    DT.reset(new DominatorTree(F));
+    LI.reset(new LoopInfo(*DT));
+    BPI.reset(new BranchProbabilityInfo(F, *LI));
+    return BlockFrequencyInfo(F, *BPI, *LI);
+  }
+  std::unique_ptr<Module> makeLLVMModule() {
+    const char *ModuleStrig = "define i32 @f(i32 %x) {\n"
+                              "bb0:\n"
+                              "  %y1 = icmp eq i32 %x, 0 \n"
+                              "  br i1 %y1, label %bb1, label %bb2 \n"
+                              "bb1:\n"
+                              "  br label %bb3\n"
+                              "bb2:\n"
+                              "  br label %bb3\n"
+                              "bb3:\n"
+                              "  %y2 = phi i32 [0, %bb1], [1, %bb2] \n"
+                              "  ret i32 %y2\n"
+                              "}\n";
+    LLVMContext &C = getGlobalContext();
+    SMDiagnostic Err;
+    return parseAssemblyString(ModuleStrig, Err, C);
+  }
+};
+
+TEST_F(BlockFrequencyInfoTest, Basic) {
+  auto M = makeLLVMModule();
+  Function *F = M->getFunction("f");
+  F->setEntryCount(100);
+
+  BlockFrequencyInfo BFI = buildBFI(*F);
+  BasicBlock &BB0 = F->getEntryBlock();
+  BasicBlock *BB1 = BB0.getTerminator()->getSuccessor(0);
+  BasicBlock *BB2 = BB0.getTerminator()->getSuccessor(1);
+  BasicBlock *BB3 = BB1->getSingleSuccessor();
+
+  uint64_t BB0Freq = BFI.getBlockFreq(&BB0).getFrequency();
+  uint64_t BB1Freq = BFI.getBlockFreq(BB1).getFrequency();
+  uint64_t BB2Freq = BFI.getBlockFreq(BB2).getFrequency();
+  uint64_t BB3Freq = BFI.getBlockFreq(BB3).getFrequency();
+
+  EXPECT_EQ(BB0Freq, BB3Freq);
+  EXPECT_EQ(BB0Freq, BB1Freq + BB2Freq);
+  EXPECT_EQ(BB0Freq, BB3Freq);
+
+  EXPECT_EQ(BFI.getBlockProfileCount(&BB0).getValue(), 100);
+  EXPECT_EQ(BFI.getBlockProfileCount(BB3).getValue(), 100);
+  EXPECT_EQ(BFI.getBlockProfileCount(BB1).getValue(), 100 * BB1Freq / BB0Freq);
+  EXPECT_EQ(BFI.getBlockProfileCount(BB2).getValue(), 100 * BB2Freq / BB0Freq);
+}
+
+} // end anonymous namespace
+} // end namespace llvm

unittests/Analysis/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Analysis
   AsmParser
   Core
   Support
   )
 
 add_llvm_unittest(AnalysisTests
   AliasAnalysisTest.cpp
+  BlockFrequencyInfoTest.cpp
   CallGraphTest.cpp
   CFGTest.cpp
   CGSCCPassManagerTest.cpp
   LazyCallGraphTest.cpp
   LoopPassManagerTest.cpp
   ScalarEvolutionTest.cpp
   MixedTBAATest.cpp
   ValueTrackingTest.cpp
   UnrollAnalyzer.cpp
   )