This reverts commit 23a5073600.
Although this patch achieved better codegen in most cases, it is really
important to accurately describe the cost of instructions. So I revert it.
A LUI instruction with flag RISCVII::MO_HI is usually used in conjunction
with ADDI, and jointly complete address computation. To bind the cost
evaluation of address computation, the LUI should not be regarded as a cheap
move separately, which is consistent with ADDI.
In this test case, it improves the unroll-loop code that the rematerialization
of array's base address miss MachineCSE with Heuristics #1 at isProfitableToCSE.
Reviewed By: asb, frasercrmck
Differential Revision: https://reviews.llvm.org/D118216
Ben Shi