Optimize LiveIntervals::intervalIsInOneMBB().

No looping and binary searches necessary.

Return a pointer to the containing block instead of just a bool.

llvm-svn: 150218

1 files changed, 22 insertions, 17 deletions

diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index 1d5e3b1be75..7655cf5e930 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1086,23 +1086,28 @@ LiveIntervals::isReMaterializable(const LiveInterval &li,
   return true;
 }
 
-bool LiveIntervals::intervalIsInOneMBB(const LiveInterval &li) const {
-  LiveInterval::Ranges::const_iterator itr = li.ranges.begin();
-
-  MachineBasicBlock *mbb =  indexes_->getMBBCoveringRange(itr->start, itr->end);
-
-  if (mbb == 0)
-    return false;
-
-  for (++itr; itr != li.ranges.end(); ++itr) {
-    MachineBasicBlock *mbb2 =
-      indexes_->getMBBCoveringRange(itr->start, itr->end);
-
-    if (mbb2 != mbb)
-      return false;
-  }
-
-  return true;
+MachineBasicBlock*
+LiveIntervals::intervalIsInOneMBB(const LiveInterval &LI) const {
+  // A local live range must be fully contained inside the block, meaning it is
+  // defined and killed at instructions, not at block boundaries. It is not
+  // live in or or out of any block.
+  //
+  // It is technically possible to have a PHI-defined live range identical to a
+  // single block, but we are going to return false in that case.
+
+  SlotIndex Start = LI.beginIndex();
+  if (Start.isBlock())
+    return NULL;
+
+  SlotIndex Stop = LI.endIndex();
+  if (Stop.isBlock())
+    return NULL;
+
+  // getMBBFromIndex doesn't need to search the MBB table when both indexes
+  // belong to proper instructions.
+  MachineBasicBlock *MBB1 = indexes_->getMBBFromIndex(Start);
+  MachineBasicBlock *MBB2 = indexes_->getMBBFromIndex(Stop);
+  return MBB1 == MBB2 ? MBB1 : NULL;
 }
 
 float