Fix renameDisconnectedComponents() creating vreg uses that can be
reached from function begin withouthaving a definition (or explicit
live-in). Fix this by inserting IMPLICIT_DEF instruction before
control-flow joins as necessary.
Removes an assert from MachineScheduler because we may now get
additional IMPLICIT_DEF when preparing the scheduling policy.
This fixes the underlying problem of http://llvm.org/PR27705
llvm-svn: 270259
Matthias Braun