shift. 16-bit: imm6<5:3> = '001', 8 - <imm> is encded in imm6<2:0> 32-bit: imm6<5:4> = '01',16 - <imm> is encded in imm6<3:0> 64-bit: imm6<5> = '1', 32 - <imm> is encded in imm6<4:0> git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126723 91177308-0d34-0410-b5e6-96231b3b80d8