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
diff --git a/llvm/lib/CodeGen/OptimizePHIs.cpp b/llvm/lib/CodeGen/OptimizePHIs.cpp
index d28292d..a1042e7 100644
--- a/llvm/lib/CodeGen/OptimizePHIs.cpp
+++ b/llvm/lib/CodeGen/OptimizePHIs.cpp
@@ -92,7 +92,7 @@
   unsigned DstReg = MI->getOperand(0).getReg();
 
   // See if we already saw this register.
-  if (!PHIsInCycle.insert(MI))
+  if (!PHIsInCycle.insert(MI).second)
     return true;
 
   // Don't scan crazily complex things.
@@ -137,7 +137,7 @@
          "PHI destination is not a virtual register");
 
   // See if we already saw this register.
-  if (!PHIsInCycle.insert(MI))
+  if (!PHIsInCycle.insert(MI).second)
     return true;
 
   // Don't scan crazily complex things.