1 files changed, 80 insertions, 0 deletions
diff --git a/llvm/lib/LTO/SummaryBasedOptimizations.cpp b/llvm/lib/LTO/SummaryBasedOptimizations.cpp
new file mode 100644
index 00000000000..8b1abb78462
--- /dev/null
+++ b/llvm/lib/LTO/SummaryBasedOptimizations.cpp
@@ -0,0 +1,80 @@
+//==-SummaryBasedOptimizations.cpp - Optimizations based on ThinLTO summary-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements optimizations that are based on the module summaries.
+// These optimizations are performed during the thinlink phase of the
+// compilation.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/SummaryBasedOptimizations.h"
+#include "llvm/Analysis/SyntheticCountsUtils.h"
+#include "llvm/IR/ModuleSummaryIndex.h"
+
+using namespace llvm;
+
+cl::opt<bool> ThinLTOSynthesizeEntryCounts(
+    "thinlto-synthesize-entry-counts", cl::init(false), cl::Hidden,
+    cl::desc("Synthesize entry counts based on the summary"));
+
+extern cl::opt<int> InitialSyntheticCount;
+
+static void initializeCounts(ModuleSummaryIndex &Index) {
+  auto Root = Index.calculateCallGraphRoot();
+  // Root is a fake node. All its successors are the actual roots of the
+  // callgraph.
+  // FIXME: This initializes the entry counts of only the root nodes. This makes
+  // sense when compiling a binary with ThinLTO, but for libraries any of the
+  // non-root nodes could be called from outside.
+  for (auto &C : Root.calls()) {
+    auto &V = C.first;
+    for (auto &GVS : V.getSummaryList()) {
+      auto S = GVS.get()->getBaseObject();
+      auto *F = cast<FunctionSummary>(S);
+      F->setEntryCount(InitialSyntheticCount);
+    }
+  }
+}
+
+void llvm::computeSyntheticCounts(ModuleSummaryIndex &Index) {
+  if (!ThinLTOSynthesizeEntryCounts)
+    return;
+
+  using Scaled64 = ScaledNumber<uint64_t>;
+  initializeCounts(Index);
+  auto GetCallSiteRelFreq = [](FunctionSummary::EdgeTy &Edge) {
+    return Scaled64(Edge.second.RelBlockFreq, -CalleeInfo::ScaleShift);
+  };
+  auto GetEntryCount = [](ValueInfo V) {
+    if (V.getSummaryList().size()) {
+      auto S = V.getSummaryList().front().get()->getBaseObject();
+      auto *F = cast<FunctionSummary>(S);
+      return F->entryCount();
+    } else {
+      return UINT64_C(0);
+    }
+  };
+  auto AddToEntryCount = [](ValueInfo V, uint64_t New) {
+    if (!V.getSummaryList().size())
+      return;
+    for (auto &GVS : V.getSummaryList()) {
+      auto S = GVS.get()->getBaseObject();
+      auto *F = cast<FunctionSummary>(S);
+      F->setEntryCount(SaturatingAdd(F->entryCount(), New));
+    }
+  };
+
+  // After initializing the counts in initializeCounts above, the counts have to
+  // be propagated across the combined callgraph.
+  // SyntheticCountsUtils::propagate takes care of this propagation on any
+  // callgraph that specialized GraphTraits.
+  SyntheticCountsUtils<ModuleSummaryIndex *>::propagate(
+      &Index, GetCallSiteRelFreq, GetEntryCount, AddToEntryCount);
+  Index.setHasSyntheticEntryCounts();
+}