Refactor indirect call promotion profitability analysis (NFC)

Summary:
Refactored the profitability analysis out of the IC promotion pass and
into lib/Analysis so that it can be accessed by the summary index
builder in a follow-on patch to enable IC promotion in ThinLTO (D21932).

Reviewers: davidxl, xur

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D22182

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275216 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 110 insertions, 0 deletions

diff --git a/include/llvm/Analysis/IndirectCallPromotionAnalysis.h b/include/llvm/Analysis/IndirectCallPromotionAnalysis.h
new file mode 100644
index 00000000000..007e4d8602f
--- /dev/null
+++ b/include/llvm/Analysis/IndirectCallPromotionAnalysis.h
@@ -0,0 +1,67 @@
+//===- IndirectCallPromotionAnalysis.h - Indirect call analysis -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// Interface to identify indirect call promotion candidates.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_INDIRECTCALLPROMOTIONANALYSIS_H
+#define LLVM_ANALYSIS_INDIRECTCALLPROMOTIONANALYSIS_H
+
+#include "llvm/ProfileData/InstrProf.h"
+
+namespace llvm {
+
+class Instruction;
+
+// Class for identifying profitable indirect call promotion candidates when
+// the indirect-call value profile metadata is available.
+class ICallPromotionAnalysis {
+private:
+  // Allocate space to read the profile annotation.
+  std::unique_ptr<InstrProfValueData[]> ValueDataArray;
+
+  // Count is the call count for the direct-call target and
+  // TotalCount is the call count for the indirect-call callsite.
+  // Return true we should promote this indirect-call target.
+  bool isPromotionProfitable(uint64_t Count, uint64_t TotalCount);
+
+  // Returns the number of profitable candidates to promote for the
+  // current ValueDataArray and the given \p Inst.
+  uint32_t getProfitablePromotionCandidates(const Instruction *Inst,
+                                            uint32_t NumVals,
+                                            uint64_t TotalCount);
+
+  // Noncopyable
+  ICallPromotionAnalysis(const ICallPromotionAnalysis &other) = delete;
+  ICallPromotionAnalysis &
+  operator=(const ICallPromotionAnalysis &other) = delete;
+
+public:
+  ICallPromotionAnalysis();
+
+  /// \brief Returns reference to array of InstrProfValueData for the given
+  /// instruction \p I.
+  ///
+  /// The \p NumVals, \p TotalCount and \p NumCandidates
+  /// are set to the number of values in the array, the total profile count
+  /// of the indirect call \p I, and the number of profitable candidates
+  /// in the given array (which is sorted in reverse order of profitability).
+  ///
+  /// The returned array space is owned by this class, and overwritten on
+  /// subsequent calls.
+  ArrayRef<InstrProfValueData>
+  getPromotionCandidatesForInstruction(const Instruction *I, uint32_t &NumVals,
+                                       uint64_t &TotalCount,
+                                       uint32_t &NumCandidates);
+};
+
+} // end namespace llvm
+
+#endif
diff --git a/include/llvm/Analysis/IndirectCallSiteVisitor.h b/include/llvm/Analysis/IndirectCallSiteVisitor.h
new file mode 100644
index 00000000000..71a8cb88632
--- /dev/null
+++ b/include/llvm/Analysis/IndirectCallSiteVisitor.h
@@ -0,0 +1,43 @@
+//===-- IndirectCallSiteVisitor.h - indirect call-sites visitor -----------===//
+//
+//                      The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements defines a visitor class and a helper function that find
+// all indirect call-sites in a function.
+
+#include "llvm/IR/InstVisitor.h"
+#include <vector>
+
+namespace llvm {
+// Visitor class that finds all indirect call sites.
+struct PGOIndirectCallSiteVisitor
+    : public InstVisitor<PGOIndirectCallSiteVisitor> {
+  std::vector<Instruction *> IndirectCallInsts;
+  PGOIndirectCallSiteVisitor() {}
+
+  void visitCallSite(CallSite CS) {
+    if (CS.getCalledFunction() || !CS.getCalledValue())
+      return;
+    Instruction *I = CS.getInstruction();
+    if (CallInst *CI = dyn_cast<CallInst>(I)) {
+      if (CI->isInlineAsm())
+        return;
+    }
+    if (isa<Constant>(CS.getCalledValue()))
+      return;
+    IndirectCallInsts.push_back(I);
+  }
+};
+
+// Helper function that finds all indirect call sites.
+static inline std::vector<Instruction *> findIndirectCallSites(Function &F) {
+  PGOIndirectCallSiteVisitor ICV;
+  ICV.visit(F);
+  return ICV.IndirectCallInsts;
+}
+}