Account for undef values from predecessors in extendSegmentsToUses

It is legal for a PHI node not to have a live value in a predecessor
as long as the end of the predecessor is jointly dominated by an undef
value.

llvm-svn: 335607

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/LiveRangeCalc.h b/llvm/lib/CodeGen/LiveRangeCalc.h
index c4914f23f56..b8502ac880e 100644
--- a/llvm/lib/CodeGen/LiveRangeCalc.h
+++ b/llvm/lib/CodeGen/LiveRangeCalc.h
@@ -282,6 +282,15 @@ public:
   /// Every predecessor of a live-in block must have been given a value with
   /// setLiveOutValue, the value may be null for live-trough blocks.
   void calculateValues();
+
+  /// A diagnostic function to check if the end of the block @p MBB is
+  /// jointly dominated by the blocks corresponding to the slot indices
+  /// in @p Defs. This function is mainly for use in self-verification
+  /// checks.
+  LLVM_ATTRIBUTE_UNUSED
+  static bool isJointlyDominated(const MachineBasicBlock *MBB,
+                                 ArrayRef<SlotIndex> Defs,
+                                 const SlotIndexes &Indexes);
 };
 
 } // end namespace llvm