+ // Prepare cases vector.
+ CaseVector Cases;
+ unsigned numCmps = Clusterify(Cases, SI);
+ DEBUG(dbgs() << "Clusterify finished. Total clusters: " << Cases.size()
+ << ". Total compares: " << numCmps << "\n");
+ DEBUG(dbgs() << "Cases: " << Cases << "\n");
+ (void)numCmps;
+
+ ConstantInt *LowerBound = nullptr;
+ ConstantInt *UpperBound = nullptr;
+ std::vector<IntRange> UnreachableRanges;
+
+ if (isa<UnreachableInst>(Default->getFirstNonPHIOrDbg())) {
+ // Make the bounds tightly fitted around the case value range, becase we
+ // know that the value passed to the switch must be exactly one of the case
+ // values.
+ assert(!Cases.empty());
+ LowerBound = cast<ConstantInt>(Cases.front().Low);
+ UpperBound = cast<ConstantInt>(Cases.back().High);
+
+ DenseMap<BasicBlock *, unsigned> Popularity;
+ unsigned MaxPop = 0;
+ BasicBlock *PopSucc = nullptr;
+
+ IntRange R = { INT64_MIN, INT64_MAX };
+ UnreachableRanges.push_back(R);
+ for (const auto &I : Cases) {
+ int64_t Low = cast<ConstantInt>(I.Low)->getSExtValue();
+ int64_t High = cast<ConstantInt>(I.High)->getSExtValue();
+
+ IntRange &LastRange = UnreachableRanges.back();
+ if (LastRange.Low == Low) {
+ // There is nothing left of the previous range.
+ UnreachableRanges.pop_back();
+ } else {
+ // Terminate the previous range.
+ assert(Low > LastRange.Low);
+ LastRange.High = Low - 1;
+ }
+ if (High != INT64_MAX) {
+ IntRange R = { High + 1, INT64_MAX };
+ UnreachableRanges.push_back(R);
+ }
+
+ // Count popularity.
+ int64_t N = High - Low + 1;
+ unsigned &Pop = Popularity[I.BB];
+ if ((Pop += N) > MaxPop) {
+ MaxPop = Pop;
+ PopSucc = I.BB;
+ }
+ }
+#ifndef NDEBUG
+ /* UnreachableRanges should be sorted and the ranges non-adjacent. */
+ for (auto I = UnreachableRanges.begin(), E = UnreachableRanges.end();
+ I != E; ++I) {
+ assert(I->Low <= I->High);
+ auto Next = I + 1;
+ if (Next != E) {
+ assert(Next->Low > I->High);
+ }
+ }
+#endif
+
+ // Use the most popular block as the new default, reducing the number of
+ // cases.
+ assert(MaxPop > 0 && PopSucc);
+ Default = PopSucc;
+ for (CaseItr I = Cases.begin(); I != Cases.end();) {
+ if (I->BB == PopSucc)
+ I = Cases.erase(I);
+ else
+ ++I;
+ }
+
+ // If there are no cases left, just branch.
+ if (Cases.empty()) {
+ BranchInst::Create(Default, CurBlock);
+ SI->eraseFromParent();
+ return;
+ }
+ }
+