[LiveIntervals] Fix early-clobber handling in handleMoveUp

Without this fix, handleMoveUp can create an invalid live range like
this:

[98904e,98908r:0)[98908e,227504r:1)

where the two segments overlap, but only because we have lost the "e"
(early-clobber) on the end point of the first segment.

Differential Revision: https://reviews.llvm.org/D82110

llvm/lib/CodeGen/LiveIntervals.cpp

@@ -1342,7 +1342,7 @@ class LiveIntervals::HMEditor {
           OldIdxOut->start = NewIdxDef;
           OldIdxVNI->def = NewIdxDef;
           if (OldIdxIn != E && SlotIndex::isEarlierInstr(NewIdx, OldIdxIn->end))
-            OldIdxIn->end = NewIdx.getRegSlot();
+            OldIdxIn->end = NewIdxDef;
         }
       } else if (OldIdxIn != E
           && SlotIndex::isEarlierInstr(NewIdxOut->start, NewIdx)

llvm/unittests/MI/LiveIntervalTest.cpp

@@ -443,6 +443,21 @@ TEST(LiveIntervalTest, DeadSubRegMoveUp) {
   });
 }
 
+TEST(LiveIntervalTest, EarlyClobberSubRegMoveUp) {
+  // handleMoveUp had a bug where moving an early-clobber subreg def into the
+  // middle of an earlier segment resulted in an invalid live range.
+  liveIntervalTest(R"MIR(
+    %4:sreg_32 = IMPLICIT_DEF
+    %6:sreg_32 = IMPLICIT_DEF
+    undef early-clobber %9.sub0:sreg_64 = WWM %4:sreg_32, implicit $exec
+    %5:sreg_32 = S_FLBIT_I32_B32 %9.sub0:sreg_64
+    early-clobber %9.sub1:sreg_64 = WWM %6:sreg_32, implicit $exec
+    %7:sreg_32 = S_FLBIT_I32_B32 %9.sub1:sreg_64
+)MIR", [](MachineFunction &MF, LiveIntervals &LIS) {
+    testHandleMove(MF, LIS, 4, 3);
+  });
+}
+
 TEST(LiveIntervalTest, TestMoveSubRegDefAcrossUseDef) {
   liveIntervalTest(R"MIR(
     %1:vreg_64 = IMPLICIT_DEF