Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool>

This is to be consistent with StringSet and ultimately with the standard
library's associative container insert function.

This lead to updating SmallSet::insert to return pair<iterator, bool>,
and then to update SmallPtrSet::insert to return pair<iterator, bool>,
and then to update all the existing users of those functions...

llvm-svn: 222334

llvm/lib/CodeGen/MachineBasicBlock.cpp

@@ -1066,7 +1066,7 @@ bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
   MachineBasicBlock::succ_iterator SI = succ_begin();
   while (SI != succ_end()) {
     const MachineBasicBlock *MBB = *SI;
-    if (!SeenMBBs.insert(MBB) ||
+    if (!SeenMBBs.insert(MBB).second ||
         (MBB != DestA && MBB != DestB && !MBB->isLandingPad())) {
       // This is a superfluous edge, remove it.
       SI = removeSuccessor(SI);