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

[Carl Ritson via llvm-commits]

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@@ -400,24 +400,48 @@ void PHIElimination::LowerPHINode(MachineBasicBlock &MBB,
     }
 
     LiveInterval &DestLI = LIS->getInterval(DestReg);
-    assert(!DestLI.empty() && "PHIs should have nonempty LiveIntervals.");
-    if (DestLI.endIndex().isDead()) {
-      // A dead PHI's live range begins and ends at the start of the MBB, but
-      // the lowered copy, which will still be dead, needs to begin and end at
-      // the copy instruction.
-      VNInfo *OrigDestVNI = DestLI.getVNInfoAt(MBBStartIndex);
-      assert(OrigDestVNI && "PHI destination should be live at block entry.");
-      DestLI.removeSegment(MBBStartIndex, MBBStartIndex.getDeadSlot());
-      DestLI.createDeadDef(DestCopyIndex.getRegSlot(),
-                           LIS->getVNInfoAllocator());
-      DestLI.removeValNo(OrigDestVNI);
-    } else {
-      // Otherwise, remove the region from the beginning of MBB to the copy
-      // instruction from DestReg's live interval.
-      DestLI.removeSegment(MBBStartIndex, DestCopyIndex.getRegSlot());
-      VNInfo *DestVNI = DestLI.getVNInfoAt(DestCopyIndex.getRegSlot());
+    assert(!DestLI.empty() && "PHIs should have non-empty LiveIntervals.");
+
+    SlotIndex NewStart = DestCopyIndex.getRegSlot();
+
+    SmallVector<LiveRange *> ToUpdate;
+    ToUpdate.push_back(&DestLI);
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perlfu wrote:

Done

https://github.com/llvm/llvm-project/pull/69429