- Adds support for inserting vzerouppers before tail-calls.
This is enabled implicitly by having MachineInstr::copyImplicitOps preserve
regmask operands, which allows VZeroUpperInserter to see where tail-calls use
vector registers.
- Fixes a bug that caused the previous version of this optimization to miss some
vzeroupper insertion points in loops. (Loops-with-vector-code that followed
loops-without-vector-code were mistakenly overlooked by the previous version).
- New algorithm never revisits instructions.
Fixes <rdar://problem/16228798>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204021 91177308-0d34-0410-b5e6-96231b3b80d8