RegisterScavenger: Introduce backward() mode.
This adds two pieces:
- RegisterScavenger:::enterBasicBlockEnd() which behaves similar to
enterBasicBlock() but starts tracking at the end of the basic block.
- A RegisterScavenger::backward() method. It is subtly different
from the existing unprocess() method which only considers uses with
the kill flag set: If a value is dead at the end of a basic block with
a last use inside the basic block, unprocess() will fail to mark it as
live. However we cannot change/fix this behaviour because unprocess()
needs to perform the exact reverse operation of forward().
Differential Revision: http://reviews.llvm.org/D21873
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@276043 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed