LiveIntervalAnalysis: Rework constructMainRangeFromSubranges()

We now use LiveRangeCalc::extendToUses() instead of a specially designed
algorithm in constructMainRangeFromSubranges():
- The original motivation for constructMainRangeFromSubranges() were
  differences between the main liverange and subranges because of hidden
  dead definitions. This case however cannot happen anymore with the
  DetectDeadLaneMasks pass in place.
- It simplifies the code.
- This fixes a longstanding bug where we did not properly create new SSA
  values on merging control flow (the MachineVerifier missed most of
  these cases).
- Move constructMainRangeFromSubranges() to LiveIntervalAnalysis and
  LiveRangeCalc to better match the implementation/available helper
  functions.

This re-applies r269016. The fixes from r270290 and r270259 should avoid
the machine verifier problems this time.

llvm-svn: 270291

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index 2a7989d..a0e6e20 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1585,3 +1585,9 @@ void LiveIntervals::renameDisconnectedComponents() {
     SubRegClasses.renameComponents(*LI);
   }
 }
+
+void LiveIntervals::constructMainRangeFromSubranges(LiveInterval &LI) {
+  assert(LRCalc && "LRCalc not initialized.");
+  LRCalc->reset(MF, getSlotIndexes(), DomTree, &getVNInfoAllocator());
+  LRCalc->constructMainRangeFromSubranges(LI);
+}