LLVM Bug Fix 13709: Remove needless lsr(Rp, #32) instruction access the

LLVM Bug Fix 13709: Remove needless lsr(Rp, #32) instruction access the
subreg_hireg of register pair Rp.

	* lib/Target/Hexagon/HexagonPeephole.cpp(PeepholeDoubleRegsMap): New
	 DenseMap similar to PeepholeMap that additionally records subreg info
	 too.
        (runOnMachineFunction): Record information in PeepholeDoubleRegsMap
        and copy propagate the high sub-reg of Rp0 in Rp1 = lsr(Rp0, #32) to
	the instruction Rx = COPY Rp1:logreg_subreg.
	* test/CodeGen/Hexagon/remove_lsr.ll: New test.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163214 91177308-0d34-0410-b5e6-96231b3b80d8