if (SwitchMBB + 1 != FuncInfo.MF->end())
NextBlock = SwitchMBB + 1;
+
+ // Create a vector of Cases, sorted so that we can efficiently create a binary
+ // search tree from them.
+ CaseVector Cases;
+ Clusterify(Cases, SI);
+
+ // Get the default destination MBB.
MachineBasicBlock *Default = FuncInfo.MBBMap[SI.getDefaultDest()];
- // If there is only the default destination, branch to it if it is not the
- // next basic block. Otherwise, just fall through.
- if (!SI.getNumCases()) {
+ if (isa<UnreachableInst>(SI.getDefaultDest()->getFirstNonPHIOrDbg()) &&
+ !Cases.empty()) {
+ // Replace an unreachable default destination with the most popular case
+ // destination.
+ DenseMap<const BasicBlock *, uint64_t> Popularity;
+ uint64_t MaxPop = 0;
+ const BasicBlock *MaxBB = nullptr;
+ for (auto I : SI.cases()) {
+ const BasicBlock *BB = I.getCaseSuccessor();
+ if (++Popularity[BB] > MaxPop) {
+ MaxPop = Popularity[BB];
+ MaxBB = BB;
+ }
+ }
+
+ // Set new default.
+ assert(MaxPop > 0);
+ assert(MaxBB);
+ Default = FuncInfo.MBBMap[MaxBB];
+
+ // Remove cases that were pointing to the destination that is now the default.
+ Cases.erase(std::remove_if(Cases.begin(), Cases.end(),
+ [&](const Case &C) { return C.BB == Default; }),
+ Cases.end());
+ }
+
+ // If there is only the default destination, go there directly.
+ if (Cases.empty()) {
// Update machine-CFG edges.
SwitchMBB->addSuccessor(Default);
// If this is not a fall-through branch, emit the branch.
- if (Default != NextBlock)
- DAG.setRoot(DAG.getNode(ISD::BR, getCurSDLoc(),
- MVT::Other, getControlRoot(),
- DAG.getBasicBlock(Default)));
-
+ if (Default != NextBlock) {
+ DAG.setRoot(DAG.getNode(ISD::BR, getCurSDLoc(), MVT::Other,
+ getControlRoot(), DAG.getBasicBlock(Default)));
+ }
return;
}
- // If there are any non-default case statements, create a vector of Cases
- // representing each one, and sort the vector so that we can efficiently
- // create a binary search tree from them.
- CaseVector Cases;
- Clusterify(Cases, SI);
-
- // Get the Value to be switched on and default basic blocks, which will be
- // inserted into CaseBlock records, representing basic blocks in the binary
- // search tree.
+ // Get the Value to be switched on.
const Value *SV = SI.getCondition();
// Push the initial CaseRec onto the worklist