Index: lib/Target/ARM/ARMConstantIslandPass.cpp
===================================================================
--- lib/Target/ARM/ARMConstantIslandPass.cpp
+++ lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -2130,6 +2130,13 @@
       //   %idx = tLSLri %idx, 2
       //   %base = tLEApcrelJT
       //   %t = tLDRr %idx, %base
+      //
+      //   1) %base and %idx cannot be the same reg as during expansion, they
+      //      need to be in different registers.
+      //   2) %base cannot be redefined after %t. Otherwise, it becomes
+      //      %base =
+      //      %base =
+      //      tBB %base, %idx
       unsigned BaseReg = User.MI->getOperand(0).getReg();
 
       if (User.MI->getIterator() == User.MI->getParent()->begin())
@@ -2141,6 +2148,8 @@
         continue;
       IdxReg = Shift->getOperand(2).getReg();
       unsigned ShiftedIdxReg = Shift->getOperand(0).getReg();
+      if (BaseReg == IdxReg)
+        continue;
 
       // It's important that IdxReg is live until the actual TBB/TBH. Most of
       // the range is checked later, but the LEA might still clobber it and not
@@ -2158,6 +2167,12 @@
 
       // If we're in PIC mode, there should be another ADD following.
       auto *TRI = STI->getRegisterInfo();
+
+      // %base cannot be redefined after the load as it will appear before
+      // TBB/TBH.
+      if (registerDefinedBetween(BaseReg, Load->getNextNode(), MBB->end(), TRI))
+        continue;
+
       if (isPositionIndependentOrROPI) {
         MachineInstr *Add = Load->getNextNode();
         if (Add->getOpcode() != ARM::tADDrr ||