If a val# is defined by an implicit_def and it is being removed, all of the copies...

If a val# is defined by an implicit_def and it is being removed, all of the copies off the val# were removed. This causes problem later since the scavenger will see uses of registers without defs. The proper solution is to change the copies into implicit_def's instead.

TurnCopyIntoImpDef turns a copy into implicit_def and remove the val# defined by it. This causes an scavenger assertion later if the def reaches other blocks. Disable the transformation if the value live interval extends beyond its def block.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73478 91177308-0d34-0410-b5e6-96231b3b80d8