[PHIElimination] Handle subranges in LiveInterval updates (#69429)

Add subrange tracking and handling for LiveIntervals during PHI
elimination.
This requires extending MachineBasicBlock::SplitCriticalEdge to also
update subrange intervals.

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index ef8e1bd..d9e2268 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -1283,6 +1283,8 @@ MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(
           assert(VNI &&
                  "PHI sources should be live out of their predecessors.");
           LI.addSegment(LiveInterval::Segment(StartIndex, EndIndex, VNI));
+          for (auto &SR : LI.subranges())
+            SR.addSegment(LiveInterval::Segment(StartIndex, EndIndex, VNI));
         }
       }
     }
@@ -1302,8 +1304,16 @@ MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(
         VNInfo *VNI = LI.getVNInfoAt(PrevIndex);
         assert(VNI && "LiveInterval should have VNInfo where it is live.");
         LI.addSegment(LiveInterval::Segment(StartIndex, EndIndex, VNI));
+        // Update subranges with live values
+        for (auto &SR : LI.subranges()) {
+          VNInfo *VNI = SR.getVNInfoAt(PrevIndex);
+          if (VNI)
+            SR.addSegment(LiveInterval::Segment(StartIndex, EndIndex, VNI));
+        }
       } else if (!isLiveOut && !isLastMBB) {
         LI.removeSegment(StartIndex, EndIndex);
+        for (auto &SR : LI.subranges())
+          SR.removeSegment(StartIndex, EndIndex);
       }
     }