Check proper live range in extendPHIRanges

The function extendPHIRanges checks the main range of the original live
interval, even when dealing with a subrange. This could also lead to an
assert when the subrange is not live at the extension point, but the
main range is. To avoid this, check the corresponding subrange of the
original live range, instead of always checking the main range.

Review (as a part of a bigger set of changes):
https://reviews.llvm.org/D26359

llvm-svn: 287571

2 files changed, 17 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/SplitKit.cpp b/llvm/lib/CodeGen/SplitKit.cpp
index 2d5a9d6a92c..b881c6d650e 100644
--- a/llvm/lib/CodeGen/SplitKit.cpp
+++ b/llvm/lib/CodeGen/SplitKit.cpp
@@ -1092,13 +1092,19 @@ static bool removeDeadSegment(SlotIndex Def, LiveRange &LR) {
 }
 
 void SplitEditor::extendPHIRange(MachineBasicBlock &B, LiveRangeCalc &LRC,
-                                 LiveRange &LR, ArrayRef<SlotIndex> Undefs) {
+                                 LiveRange &LR, LaneBitmask LM,
+                                 ArrayRef<SlotIndex> Undefs) {
   for (MachineBasicBlock *P : B.predecessors()) {
     SlotIndex End = LIS.getMBBEndIdx(P);
     SlotIndex LastUse = End.getPrevSlot();
     // The predecessor may not have a live-out value. That is OK, like an
     // undef PHI operand.
-    if (Edit->getParent().liveAt(LastUse))
+    LiveInterval &PLI = Edit->getParent();
+    // Need the cast because the inputs to ?: would otherwise be deemed
+    // "incompatible": SubRange vs LiveInterval.
+    LiveRange &PSR = (LM != ~0u) ? getSubRangeForMask(LM, PLI)
+                                 : static_cast<LiveRange&>(PLI);
+    if (PSR.liveAt(LastUse))
       LRC.extend(LR, End, /*PhysReg=*/0, Undefs);
   }
 }
@@ -1120,7 +1126,7 @@ void SplitEditor::extendPHIKillRanges() {
     LiveRangeCalc &LRC = getLRCalc(RegIdx);
     MachineBasicBlock &B = *LIS.getMBBFromIndex(V->def);
     if (!removeDeadSegment(V->def, LI))
-      extendPHIRange(B, LRC, LI, /*Undefs=*/{});
+      extendPHIRange(B, LRC, LI, ~0u, /*Undefs=*/{});
   }
 
   SmallVector<SlotIndex, 4> Undefs;
@@ -1141,7 +1147,7 @@ void SplitEditor::extendPHIKillRanges() {
                    &LIS.getVNInfoAllocator());
       Undefs.clear();
       LI.computeSubRangeUndefs(Undefs, PS.LaneMask, MRI, *LIS.getSlotIndexes());
-      extendPHIRange(B, SubLRC, S, Undefs);
+      extendPHIRange(B, SubLRC, S, PS.LaneMask, Undefs);
     }
   }
 }
diff --git a/llvm/lib/CodeGen/SplitKit.h b/llvm/lib/CodeGen/SplitKit.h
index 94a1a28b9ff..a75738aaf44 100644
--- a/llvm/lib/CodeGen/SplitKit.h
+++ b/llvm/lib/CodeGen/SplitKit.h
@@ -386,10 +386,14 @@ private:
   /// Return true if any ranges were skipped.
   bool transferValues();
 
-  /// Live range @p LR has a live PHI def at the beginning of block @p B.
-  /// Extend the range @p LR of all predecessor values that reach this def.
+  /// Live range @p LR corresponding to the lane Mask @p LM has a live
+  /// PHI def at the beginning of block @p B. Extend the range @p LR of
+  /// all predecessor values that reach this def. If @p LR is a subrange,
+  /// the array @p Undefs is the set of all locations where it is undefined
+  /// via <def,read-undef> in other subranges for the same register.
   void extendPHIRange(MachineBasicBlock &B, LiveRangeCalc &LRC,
-                      LiveRange &LR, ArrayRef<SlotIndex>);
+                      LiveRange &LR, LaneBitmask LM,
+                      ArrayRef<SlotIndex> Undefs);
 
   /// extendPHIKillRanges - Extend the ranges of all values killed by original
   /// parent PHIDefs.