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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270291 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 5 insertions, 4 deletions

diff --git a/include/llvm/CodeGen/LiveInterval.h b/include/llvm/CodeGen/LiveInterval.h
index 1be6ed673f2..7e699f386ed 100644
--- a/include/llvm/CodeGen/LiveInterval.h
+++ b/include/llvm/CodeGen/LiveInterval.h
@@ -712,10 +712,6 @@ namespace llvm {
     /// are not considered valid and should only exist temporarily).
     void removeEmptySubRanges();
 
-    /// Construct main live range by merging the SubRanges of @p LI.
-    void constructMainRangeFromSubranges(const SlotIndexes &Indexes,
-                                         VNInfo::Allocator &VNIAllocator);
-
     /// getSize - Returns the sum of sizes of all the LiveRange's.
     ///
     unsigned getSize() const;
diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index 0dac2939059..e1bdd09708b 100644
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -410,6 +410,11 @@ extern cl::opt<bool> UseSegmentSetForPhysRegs;
     /// on each virtual register.
     void renameDisconnectedComponents();
 
+    /// For live interval \p LI with correct SubRanges construct matching
+    /// information for the main live range. Expects the main live range to not
+    /// have any segments or value numbers.
+    void constructMainRangeFromSubranges(LiveInterval &LI);
+
   private:
     /// Compute live intervals for all virtual registers.
     void computeVirtRegs();