[SystemZ] Improve handling of PC-relative addresses

The backend previously folded offsets into PC-relative addresses
whereever possible.  That's the right thing to do when the address
can be used directly in a PC-relative memory reference (using things
like LRL).  But if we have a register-based memory reference and need
to load the PC-relative address separately, it's better to use an anchor
point that could be shared with other accesses to the same area of the
variable.

Fixes a FIXME.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191524 91177308-0d34-0410-b5e6-96231b3b80d8
[SystemZ] Rein back the use of block operations

The backend tries to use block operations like MVC, NC, OC and XC for
simple scalar operations.  For correctness reasons, it rejects any case
in which the regions might partially overlap.  However, for performance
reasons, it should also reject cases where the regions might be equal,
since the instruction might then not use the fast path.

This fixes a performance regression seen in bzip2.  We may want to limit
the optimisation even more in future, or even remove it entirely, but I'll
try with this for now.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191525 91177308-0d34-0410-b5e6-96231b3b80d8
Transforms: Use getFirstNonPHI to set the insertion point for PHIs

We were previously using getFirstInsertionPt to insert PHI
instructions when vectorizing, but getFirstInsertionPt also skips past
landingpads, causing this to generate invalid IR.

We can avoid this issue by using getFirstNonPHI instead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191526 91177308-0d34-0410-b5e6-96231b3b80d8