If we duplicate an instruction then we must also clear kill flags on any uses we rewrite.
Otherwise we might be killing a register which was used in other BBs.
For example, here the entry BB ended up with these instructions, the ADD having been tail duplicated.
%vreg24<def> = t2ADDri %vreg10<kill>, 1, pred:14, pred:%noreg, opt:%noreg; GPRnopc:%vreg24 rGPR:%vreg10
%vreg22<def> = COPY %vreg10; GPR:%vreg22 rGPR:%vreg10
The copy here is inserted after the add and so needs vreg10 to be live.
llvm-svn: 236782
