Global Instruction Selector could not select the code:
%0:gprb(s32) = G_CONSTANT i32 -1
In DAG selector the similar code is selected to the instruction MVNi
using custom operand `mod_imm_not`. Changing its definition from
`PatLeaf` to `ImmLeaf` and providing counterpart for `imm_not_XFORM`
make the relevant rule available for GlobalISel too.
b0785cd1cb