At -O0, multiple uses of a virtual registers in the same BB are being marked

"kill". This looks like a bug upstream. Since that's going to take some time
to understand, loosen the assertion and disable the optimization when
multiple kills are seen.

llvm-svn: 144568

llvm/lib/CodeGen/TwoAddressInstructionPass.cpp

@@ -502,7 +502,8 @@ MachineInstr *findLocalKill(unsigned Reg, MachineBasicBlock *MBB,
       continue;
     if (!UI.getOperand().isKill())
       return 0;
-    assert(!KillMI && "More than one local kills?");
+    if (KillMI)
+      return 0;  // -O0 kill markers cannot be trusted?
     KillMI = UseMI;
   }