See https://github.com/llvm/llvm-project/pull/86857/files#r1548822138

If we know the lowest bit of gpr5 is 0( slwi 5, 6, 1), PPC should be able to fold

li 3, 1 rlwimi 3, 5, 0, 0, 30 

to

addi 3, 5, 1 

Or

ori 3, 5, 1