Recommit r231168: unique_ptrify LiveRange::segmentSet

GCC 4.7's libstdc++ doesn't have std::map::emplace, but it does have
std::unordered_map::emplace, and the use case here doesn't appear to
need ordering. The container has been changed in a separate/precursor
patch, and now this patch should hopefully build cleanly even with
GCC 4.7.

& then I realized the order of the container did matter, so extra
handling of ordering was added in r231189.

Original commit message:
This makes LiveRange non-copyable, and LiveInterval is already
non-movable (due to the explicit dtor), so now it's non-copyable and
non-movable.

Fix the one case where we were relying on the (deprecated in C++11)
implicit copy ctor of LiveInterval (which happened to work because the
ctor created an object with a null segmentSet, so double-deleting the
null pointer was fine).

llvm-svn: 231192

include/llvm/CodeGen/LiveInterval.h

@@ -199,7 +199,7 @@ namespace llvm {
     // of live ranges of physical registers in computeRegUnitRange.
     // After that the set is flushed to the segment vector and deleted.
     typedef std::set<Segment> SegmentSet;
-    SegmentSet *segmentSet;
+    std::unique_ptr<SegmentSet> segmentSet;
 
     typedef Segments::iterator iterator;
     iterator begin() { return segments.begin(); }
@@ -218,15 +218,13 @@ namespace llvm {
     const_vni_iterator vni_end() const   { return valnos.end(); }
 
     /// Constructs a new LiveRange object.
-    LiveRange(bool UseSegmentSet = false) : segmentSet(nullptr) {
-      if (UseSegmentSet)
-        segmentSet = new SegmentSet();
-    }
+    LiveRange(bool UseSegmentSet = false)
+        : segmentSet(UseSegmentSet ? llvm::make_unique<SegmentSet>()
+                                   : nullptr) {}
 
     /// Constructs a new LiveRange object by copying segments and valnos from
     /// another LiveRange.
-    LiveRange(const LiveRange &Other, BumpPtrAllocator &Allocator)
-        : segmentSet(nullptr) {
+    LiveRange(const LiveRange &Other, BumpPtrAllocator &Allocator) {
       assert(Other.segmentSet == nullptr &&
              "Copying of LiveRanges with active SegmentSets is not supported");
 
@@ -240,8 +238,6 @@ namespace llvm {
       }
     }
 
-    ~LiveRange() { delete segmentSet; }
-
     /// advanceTo - Advance the specified iterator to point to the Segment
     /// containing the specified position, or end() if the position is past the
     /// end of the range.  If no Segment contains this position, but the
@@ -745,8 +741,6 @@ namespace llvm {
 #endif
 
   private:
-    LiveInterval& operator=(const LiveInterval& rhs) = delete;
-
     /// Appends @p Range to SubRanges list.
     void appendSubRange(SubRange *Range) {
       Range->Next = SubRanges;

lib/CodeGen/LiveInterval.cpp

@@ -743,7 +743,6 @@ void LiveRange::flushSegmentSet() {
       segments.empty() &&
       "segment set can be used only initially before switching to the array");
   segments.append(segmentSet->begin(), segmentSet->end());
-  delete segmentSet;
   segmentSet = nullptr;
   verify();
 }

lib/CodeGen/LiveStackAnalysis.cpp

@@ -61,8 +61,10 @@ LiveStacks::getOrCreateInterval(int Slot, const TargetRegisterClass *RC) {
   assert(Slot >= 0 && "Spill slot indice must be >= 0");
   SS2IntervalMap::iterator I = S2IMap.find(Slot);
   if (I == S2IMap.end()) {
-    I = S2IMap.insert(I, std::make_pair(Slot,
-            LiveInterval(TargetRegisterInfo::index2StackSlot(Slot), 0.0F)));
+    I = S2IMap.emplace(std::piecewise_construct, std::forward_as_tuple(Slot),
+                       std::forward_as_tuple(
+                           TargetRegisterInfo::index2StackSlot(Slot), 0.0F))
+            .first;
     S2RCMap.insert(std::make_pair(Slot, RC));
   } else {
     // Use the largest common subclass register class.