[DebugInfo] Insert DEBUG_VALUEs after each register redefinition

Summary:
When reinserting debug values after register allocation, make sure to
insert debug values after each redefinition of debug value register in
the slot index range. The reason for this is that DwarfDebug will end
the range of a debug variable when the physical reg is defined. For
instructions with e.g. tied operands this result in prematurely ended
debug range.

This resolves pr34545

Patch by Karl-Johan Karlsson and Bjorn Pettersson

Reviewers: rnk, aprantl

Reviewed By: rnk

Subscribers: bjope, llvm-commits

Differential Revision: https://reviews.llvm.org/D38229

llvm-svn: 314974