[Thumb1] Any imm8 should have cost of 1
A simple MOVS rd, imm8 can materialize [-128, 127] in signed i8 type or
[0, 255] in unsigned i8 type on Thumb1.
Differential Revision: https://reviews.llvm.org/D52257
Zhaoshi Zheng <firstname.lastname@example.org> on Sep 24 2018, 9:15 AM.Authored by