LocalStackSlotAllocation improvements

First, taking advantage of the fact that the virtual base registers are allocated in order of the local frame offsets, remove the quadratic register-searching behavior. Because of the ordering, we only need to check the last virtual base register created.

Second, store the frame index in the FrameRef structure, and get the frame index and the local offset from this structure at the top of the loop iteration. This allows us to de-nest the loops in insertFrameReferenceRegisters (and I think makes the code cleaner). I also moved the needsFrameBaseReg check into the first loop over instructions so that we don't bother pushing FrameRefs for instructions that don't want a virtual base register anyway.

Lastly, and this is the only functionality change, avoid the creation of single-use virtual base registers. These are currently not useful because, in general, they end up replacing what would be one r+r instruction with an add and a r+i instruction. Committing this removes the XFAIL in CodeGen/PowerPC/2007-09-07-LoadStoreIdxForms.ll

Jim has okayed this off-list.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180799 91177308-0d34-0410-b5e6-96231b3b80d8
[mips] Clear isCommutable bit of instructions which are not commutable.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180801 91177308-0d34-0410-b5e6-96231b3b80d8
InstCombine: Fold more shuffles of shuffles.

Always fold a shuffle-of-shuffle into a single shuffle when there's only one
input vector in the first place. Continue to be more conservative when there's
multiple inputs.

rdar://13402653
PR15866

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180802 91177308-0d34-0410-b5e6-96231b3b80d8
[mips] Test for r179873.

Patch by Zoran Jovanovic.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180804 91177308-0d34-0410-b5e6-96231b3b80d8