[Instrumentation] Add Call Graph Profile pass

This patch adds support for generating a call graph profile from Branch Frequency Info.

The CGProfile module pass simply gets the block profile count for each BB and scans for call instructions. For each call instruction it adds an edge from the current function to the called function with the current BB block profile count as the weight.

After scanning all the functions, it generates an appending module flag containing the data. The format looks like:

!llvm.module.flags = !{!0}

!0 = !{i32 5, !"CG Profile", !1}
!1 = !{!2, !3, !4} ; List of edges
!2 = !{void ()* @a, void ()* @b, i64 32} ; Edge from a to b with a weight of 32
!3 = !{void (i1)* @freq, void ()* @a, i64 11}
!4 = !{void (i1)* @freq, void ()* @b, i64 20}

Differential Revision: https://reviews.llvm.org/D48105

llvm-svn: 335306

4 files changed, 114 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index a2559bc70b1..defb54e19bf 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -694,6 +694,8 @@ void PassManagerBuilder::populateModulePassManager(
     MPM.add(createConstantMergePass());     // Merge dup global constants
   }
 
+  MPM.add(createCGProfilePass());
+
   if (MergeFunctions)
     MPM.add(createMergeFunctionsPass());
 
diff --git a/llvm/lib/Transforms/Instrumentation/CGProfile.cpp b/llvm/lib/Transforms/Instrumentation/CGProfile.cpp
new file mode 100644
index 00000000000..cb1fcb21425
--- /dev/null
+++ b/llvm/lib/Transforms/Instrumentation/CGProfile.cpp
@@ -0,0 +1,110 @@
+//===-- CGProfile.cpp -----------------------------------------------------===//
+//
+//                      The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/MapVector.h"
+#include "llvm/Analysis/BlockFrequencyInfo.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/Transforms/Instrumentation.h"
+
+#include <array>
+
+using namespace llvm;
+
+class CGProfilePass : public ModulePass {
+public:
+  static char ID;
+
+  CGProfilePass() : ModulePass(ID) {
+    initializeCGProfilePassPass(*PassRegistry::getPassRegistry());
+  }
+
+  StringRef getPassName() const override { return "CGProfilePass"; }
+
+private:
+  bool runOnModule(Module &M) override;
+  bool addModuleFlags(
+      Module &M,
+      MapVector<std::pair<Function *, Function *>, uint64_t> &Counts) const;
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addRequired<BlockFrequencyInfoWrapperPass>();
+    AU.addRequired<BranchProbabilityInfoWrapperPass>();
+  }
+};
+
+bool CGProfilePass::runOnModule(Module &M) {
+  if (skipModule(M))
+    return false;
+
+  MapVector<std::pair<Function *, Function *>, uint64_t> Counts;
+
+  for (auto &F : M) {
+    if (F.isDeclaration())
+      continue;
+    getAnalysis<BranchProbabilityInfoWrapperPass>(F).getBPI();
+    auto &BFI = getAnalysis<BlockFrequencyInfoWrapperPass>(F).getBFI();
+    for (const auto &BB : F) {
+      Optional<uint64_t> BBCount = BFI.getBlockProfileCount(&BB);
+      if (!BBCount)
+        continue;
+      for (const auto &I : BB) {
+        auto *CI = dyn_cast<CallInst>(&I);
+        if (!CI)
+          continue;
+        Function *CalledF = CI->getCalledFunction();
+        if (!CalledF || CalledF->isIntrinsic())
+          continue;
+
+        uint64_t &Count = Counts[std::make_pair(&F, CalledF)];
+        Count = SaturatingAdd(Count, *BBCount);
+      }
+    }
+  }
+
+  return addModuleFlags(M, Counts);
+}
+
+bool CGProfilePass::addModuleFlags(
+    Module &M,
+    MapVector<std::pair<Function *, Function *>, uint64_t> &Counts) const {
+  if (Counts.empty())
+    return false;
+
+  LLVMContext &Context = M.getContext();
+  MDBuilder MDB(Context);
+  std::vector<Metadata *> Nodes;
+
+  for (auto E : Counts) {
+    SmallVector<Metadata *, 3> Vals;
+    Vals.push_back(ValueAsMetadata::get(E.first.first));
+    Vals.push_back(ValueAsMetadata::get(E.first.second));
+    Vals.push_back(MDB.createConstant(
+        ConstantInt::get(Type::getInt64Ty(Context), E.second)));
+    Nodes.push_back(MDNode::get(Context, Vals));
+  }
+
+  M.addModuleFlag(Module::Append, "CG Profile", MDNode::get(Context, Nodes));
+  return true;
+}
+
+char CGProfilePass::ID = 0;
+INITIALIZE_PASS_BEGIN(CGProfilePass, "cg-profile",
+                      "Generate profile information from the call graph.",
+                      false, false)
+INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
+INITIALIZE_PASS_END(CGProfilePass, "cg-profile",
+                    "Generate profile information from the call graph.", false,
+                    false)
+
+ModulePass *llvm::createCGProfilePass() { return new CGProfilePass(); }
diff --git a/llvm/lib/Transforms/Instrumentation/CMakeLists.txt b/llvm/lib/Transforms/Instrumentation/CMakeLists.txt
index 66fdcb3ccc4..5d008482319 100644
--- a/llvm/lib/Transforms/Instrumentation/CMakeLists.txt
+++ b/llvm/lib/Transforms/Instrumentation/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_llvm_library(LLVMInstrumentation
   AddressSanitizer.cpp
   BoundsChecking.cpp
+  CGProfile.cpp
   DataFlowSanitizer.cpp
   GCOVProfiling.cpp
   MemorySanitizer.cpp
diff --git a/llvm/lib/Transforms/Instrumentation/Instrumentation.cpp b/llvm/lib/Transforms/Instrumentation/Instrumentation.cpp
index 8e9eea96ced..fbd651f3f20 100644
--- a/llvm/lib/Transforms/Instrumentation/Instrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/Instrumentation.cpp
@@ -60,6 +60,7 @@ void llvm::initializeInstrumentation(PassRegistry &Registry) {
   initializeAddressSanitizerModulePass(Registry);
   initializeBoundsCheckingLegacyPassPass(Registry);
   initializeGCOVProfilerLegacyPassPass(Registry);
+  initializeCGProfilePassPass(Registry);
   initializePGOInstrumentationGenLegacyPassPass(Registry);
   initializePGOInstrumentationUseLegacyPassPass(Registry);
   initializePGOIndirectCallPromotionLegacyPassPass(Registry);