[ARM][LowOverheadLoops] Add LR def safety check
Converting the *LoopStart pseudo instructions into DLS/WLS results in
LR being defined. These instructions were inserted on the assumption
that LR would already contain the loop counter because a mov is
introduced during ISel as the the consumers in the loop can only use
LR. That assumption proved wrong!
So perform a safety check, finding an appropriate place to insert the
DLS/WLS instructions or revert if this isn't possible.
Differential Revision: https://reviews.llvm.org/D67539
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@372111 91177308-0d34-0410-b5e6-96231b3b80d8
15 files changed: