Recommit r231175: Change LiveStackAnalysis::SS2IntervalMap from std::map to std::unordered_map

The order of this container was needed at one point - so, at that point
create a temporary array of pointers, sort those, then iterate them.
This keeps lookup efficient (& the lesser issue, of allowing the use of
emplace... ), object identity preserved, and ordered iteration in the
one place that requires it.

While this has no functional change, I realize it does mean allocating
an extra data structure and performing a sort - so if this looks suspect
to anyone regarding perf characteristics, I'm all ears.

llvm-svn: 231189

1 files changed, 10 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/StackSlotColoring.cpp b/llvm/lib/CodeGen/StackSlotColoring.cpp
index cc72e5e51f2..a5a175f2c8f 100644
--- a/llvm/lib/CodeGen/StackSlotColoring.cpp
+++ b/llvm/lib/CodeGen/StackSlotColoring.cpp
@@ -184,10 +184,18 @@ void StackSlotColoring::InitializeSlots() {
   UsedColors.resize(LastFI);
   Assignments.resize(LastFI);
 
+  typedef std::iterator_traits<LiveStacks::iterator>::value_type Pair;
+  SmallVector<Pair *, 16> Intervals;
+  Intervals.reserve(LS->getNumIntervals());
+  for (auto &I : *LS)
+    Intervals.push_back(&I);
+  std::sort(Intervals.begin(), Intervals.end(),
+            [](Pair *LHS, Pair *RHS) { return LHS->first < RHS->first; });
+
   // Gather all spill slots into a list.
   DEBUG(dbgs() << "Spill slot intervals:\n");
-  for (LiveStacks::iterator i = LS->begin(), e = LS->end(); i != e; ++i) {
-    LiveInterval &li = i->second;
+  for (auto *I : Intervals) {
+    LiveInterval &li = I->second;
     DEBUG(li.dump());
     int FI = TargetRegisterInfo::stackSlot2Index(li.reg);
     if (MFI->isDeadObjectIndex(FI))