Profile: set branch weight metadata with data generated from profiling.
This patch implements ProfileDataLoader which loads profile data generated by
-insert-edge-profiling and updates branch weight metadata accordingly.
Patch by Alastair Murray.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162799 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ProfileDataLoaderPass.cpp b/lib/Analysis/ProfileDataLoaderPass.cpp
new file mode 100644
index 0000000..2a61a0b
--- /dev/null
+++ b/lib/Analysis/ProfileDataLoaderPass.cpp
@@ -0,0 +1,188 @@
+//===- ProfileDataLoaderPass.cpp - Set branch weight metadata from prof ---===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass loads profiling data from a dump file and sets branch weight
+// metadata.
+//
+// TODO: Replace all "profile-metadata-loader" strings with "profile-loader"
+// once ProfileInfo etc. has been removed.
+//
+//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "profile-metadata-loader"
+#include "llvm/BasicBlock.h"
+#include "llvm/InstrTypes.h"
+#include "llvm/Module.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/MDBuilder.h"
+#include "llvm/Metadata.h"
+#include "llvm/Pass.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/ProfileDataLoader.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/Format.h"
+#include "llvm/ADT/Statistic.h"
+#include <vector>
+using namespace llvm;
+
+STATISTIC(NumEdgesRead, "The # of edges read.");
+STATISTIC(NumTermsAnnotated, "The # of terminator instructions annotated.");
+
+static cl::opt<std::string>
+ProfileMetadataFilename("profile-file", cl::init("llvmprof.out"),
+ cl::value_desc("filename"),
+ cl::desc("Profile file loaded by -profile-metadata-loader"));
+
+namespace {
+ /// This pass loads profiling data from a dump file and sets branch weight
+ /// metadata.
+ class ProfileMetadataLoaderPass : public ModulePass {
+ std::string Filename;
+ public:
+ static char ID; // Class identification, replacement for typeinfo
+ explicit ProfileMetadataLoaderPass(const std::string &filename = "")
+ : ModulePass(ID), Filename(filename) {
+ initializeProfileMetadataLoaderPassPass(*PassRegistry::getPassRegistry());
+ if (filename.empty()) Filename = ProfileMetadataFilename;
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesAll();
+ }
+
+ virtual const char *getPassName() const {
+ return "Profile loader";
+ }
+
+ virtual void readEdge(unsigned, ProfileData&, ProfileData::Edge,
+ std::vector<unsigned>&);
+ virtual unsigned matchEdges(Module&, ProfileData&, std::vector<unsigned>&);
+ virtual void setBranchWeightMetadata(Module&, ProfileData&);
+
+ virtual bool runOnModule(Module &M);
+ };
+} // End of anonymous namespace
+
+char ProfileMetadataLoaderPass::ID = 0;
+INITIALIZE_PASS_BEGIN(ProfileMetadataLoaderPass, "profile-metadata-loader",
+ "Load profile information from llvmprof.out", false, true)
+INITIALIZE_PASS_END(ProfileMetadataLoaderPass, "profile-metadata-loader",
+ "Load profile information from llvmprof.out", false, true)
+
+char &llvm::ProfileMetadataLoaderPassID = ProfileMetadataLoaderPass::ID;
+
+/// createProfileMetadataLoaderPass - This function returns a Pass that loads
+/// the profiling information for the module from the specified filename,
+/// making it available to the optimizers.
+ModulePass *llvm::createProfileMetadataLoaderPass() {
+ return new ProfileMetadataLoaderPass();
+}
+ModulePass *llvm::createProfileMetadataLoaderPass(const std::string &Filename) {
+ return new ProfileMetadataLoaderPass(Filename);
+}
+
+/// readEdge - Take the value from a profile counter and assign it to an edge.
+void ProfileMetadataLoaderPass::readEdge(unsigned ReadCount,
+ ProfileData &PB, ProfileData::Edge e,
+ std::vector<unsigned> &Counters) {
+ if (ReadCount < Counters.size()) {
+ unsigned weight = Counters[ReadCount];
+ assert(weight != ProfileDataLoader::Uncounted);
+ PB.addEdgeWeight(e, weight);
+
+ DEBUG(dbgs() << "-- Read Edge Counter for " << e
+ << " (# "<< (ReadCount) << "): "
+ << PB.getEdgeWeight(e) << "\n");
+ }
+}
+
+/// matchEdges - Link every profile counter with an edge.
+unsigned ProfileMetadataLoaderPass::matchEdges(Module &M, ProfileData &PB,
+ std::vector<unsigned> &Counters) {
+ if (Counters.size() == 0) return 0;
+
+ unsigned ReadCount = 0;
+
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+ if (F->isDeclaration()) continue;
+ DEBUG(dbgs() << "Loading edges in '" << F->getName() << "'\n");
+ readEdge(ReadCount++, PB, PB.getEdge(0, &F->getEntryBlock()), Counters);
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
+ TerminatorInst *TI = BB->getTerminator();
+ for (unsigned s = 0, e = TI->getNumSuccessors(); s != e; ++s) {
+ readEdge(ReadCount++, PB, PB.getEdge(BB,TI->getSuccessor(s)),
+ Counters);
+ }
+ }
+ }
+
+ return ReadCount;
+}
+
+/// setBranchWeightMetadata - Translate the counter values associated with each
+/// edge into branch weights for each conditional branch (a branch with 2 or
+/// more desinations).
+void ProfileMetadataLoaderPass::setBranchWeightMetadata(Module &M,
+ ProfileData &PB) {
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+ if (F->isDeclaration()) continue;
+ DEBUG(dbgs() << "Setting branch metadata in '" << F->getName() << "'\n");
+
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
+ TerminatorInst *TI = BB->getTerminator();
+ unsigned NumSuccessors = TI->getNumSuccessors();
+
+ // If there is only one successor then we can not set a branch
+ // probability as the target is certain.
+ if (NumSuccessors < 2) continue;
+
+ // Load the weights of all edges leading from this terminator.
+ DEBUG(dbgs() << "-- Terminator with " << NumSuccessors
+ << " successors:\n");
+ std::vector<uint32_t> Weights(NumSuccessors);
+ for (unsigned s = 0 ; s < NumSuccessors ; ++s) {
+ ProfileData::Edge edge = PB.getEdge(BB, TI->getSuccessor(s));
+ Weights[s] = (uint32_t)PB.getEdgeWeight(edge);
+ DEBUG(dbgs() << "---- Edge '" << edge << "' has weight "
+ << Weights[s] << "\n");
+ }
+
+ // Set branch weight metadata. This will set branch probabilities of
+ // 100%/0% if that is true of the dynamic execution.
+ // BranchProbabilityInfo can account for this when it loads this metadata
+ // (it gives the unexectuted branch a weight of 1 for the purposes of
+ // probability calculations).
+ MDBuilder MDB(TI->getContext());
+ MDNode *Node = MDB.createBranchWeights(Weights);
+ TI->setMetadata(LLVMContext::MD_prof, Node);
+ NumTermsAnnotated++;
+ }
+ }
+}
+
+bool ProfileMetadataLoaderPass::runOnModule(Module &M) {
+ ProfileDataLoader PDL("profile-data-loader", Filename);
+ ProfileData PB;
+
+ std::vector<unsigned> Counters = PDL.getRawEdgeCounts();
+
+ unsigned ReadCount = matchEdges(M, PB, Counters);
+
+ if (ReadCount != Counters.size()) {
+ errs() << "WARNING: profile information is inconsistent with "
+ << "the current program!\n";
+ }
+ NumEdgesRead = ReadCount;
+
+ setBranchWeightMetadata(M, PB);
+
+ return ReadCount > 0;
+}