1 files changed, 106 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/IndirectCallPromotionAnalysis.cpp b/llvm/lib/Analysis/IndirectCallPromotionAnalysis.cpp
new file mode 100644
index 000000000000..68153de8219f
--- /dev/null
+++ b/llvm/lib/Analysis/IndirectCallPromotionAnalysis.cpp
@@ -0,0 +1,106 @@
+//===-- IndirectCallPromotionAnalysis.cpp - Find promotion candidates ===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Helper methods for identifying profitable indirect call promotion
+// candidates for an instruction when the indirect-call value profile metadata
+// is available.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/IndirectCallPromotionAnalysis.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Analysis/IndirectCallVisitor.h"
+#include "llvm/IR/CallSite.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/InstVisitor.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/ProfileData/InstrProf.h"
+#include "llvm/Support/Debug.h"
+#include <string>
+#include <utility>
+#include <vector>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "pgo-icall-prom-analysis"
+
+// The percent threshold for the direct-call target (this call site vs the
+// remaining call count) for it to be considered as the promotion target.
+static cl::opt<unsigned> ICPRemainingPercentThreshold(
+    "icp-remaining-percent-threshold", cl::init(30), cl::Hidden, cl::ZeroOrMore,
+    cl::desc("The percentage threshold against remaining unpromoted indirect "
+             "call count for the promotion"));
+
+// The percent threshold for the direct-call target (this call site vs the
+// total call count) for it to be considered as the promotion target.
+static cl::opt<unsigned>
+    ICPTotalPercentThreshold("icp-total-percent-threshold", cl::init(5),
+                             cl::Hidden, cl::ZeroOrMore,
+                             cl::desc("The percentage threshold against total "
+                                      "count for the promotion"));
+
+// Set the maximum number of targets to promote for a single indirect-call
+// callsite.
+static cl::opt<unsigned>
+    MaxNumPromotions("icp-max-prom", cl::init(3), cl::Hidden, cl::ZeroOrMore,
+                     cl::desc("Max number of promotions for a single indirect "
+                              "call callsite"));
+
+ICallPromotionAnalysis::ICallPromotionAnalysis() {
+  ValueDataArray = std::make_unique<InstrProfValueData[]>(MaxNumPromotions);
+}
+
+bool ICallPromotionAnalysis::isPromotionProfitable(uint64_t Count,
+                                                   uint64_t TotalCount,
+                                                   uint64_t RemainingCount) {
+  return Count * 100 >= ICPRemainingPercentThreshold * RemainingCount &&
+         Count * 100 >= ICPTotalPercentThreshold * TotalCount;
+}
+
+// Indirect-call promotion heuristic. The direct targets are sorted based on
+// the count. Stop at the first target that is not promoted. Returns the
+// number of candidates deemed profitable.
+uint32_t ICallPromotionAnalysis::getProfitablePromotionCandidates(
+    const Instruction *Inst, uint32_t NumVals, uint64_t TotalCount) {
+  ArrayRef<InstrProfValueData> ValueDataRef(ValueDataArray.get(), NumVals);
+
+  LLVM_DEBUG(dbgs() << " \nWork on callsite " << *Inst
+                    << " Num_targets: " << NumVals << "\n");
+
+  uint32_t I = 0;
+  uint64_t RemainingCount = TotalCount;
+  for (; I < MaxNumPromotions && I < NumVals; I++) {
+    uint64_t Count = ValueDataRef[I].Count;
+    assert(Count <= RemainingCount);
+    LLVM_DEBUG(dbgs() << " Candidate " << I << " Count=" << Count
+                      << "  Target_func: " << ValueDataRef[I].Value << "\n");
+
+    if (!isPromotionProfitable(Count, TotalCount, RemainingCount)) {
+      LLVM_DEBUG(dbgs() << " Not promote: Cold target.\n");
+      return I;
+    }
+    RemainingCount -= Count;
+  }
+  return I;
+}
+
+ArrayRef<InstrProfValueData>
+ICallPromotionAnalysis::getPromotionCandidatesForInstruction(
+    const Instruction *I, uint32_t &NumVals, uint64_t &TotalCount,
+    uint32_t &NumCandidates) {
+  bool Res =
+      getValueProfDataFromInst(*I, IPVK_IndirectCallTarget, MaxNumPromotions,
+                               ValueDataArray.get(), NumVals, TotalCount);
+  if (!Res) {
+    NumCandidates = 0;
+    return ArrayRef<InstrProfValueData>();
+  }
+  NumCandidates = getProfitablePromotionCandidates(I, NumVals, TotalCount);
+  return ArrayRef<InstrProfValueData>(ValueDataArray.get(), NumVals);
+}