If the effective mask (M) corresponding to OP(_, K) is different than the combined mask (C & M), then the inner mask (C) can be replaced by the smaller (C & M), giving: OP((x | M'), K) with M' == (C & M). For example, code like: int foo(int x) { return (x | 0xfffffff0) & 0xfff; } is now simplified into: foo: or.32 %r2 <- %arg1, $0xff0 and.32 %r3 <- %r2, $0xfff ret.32 %r3 while previously, the constant was not reduced: foo: or.32 %r2 <- %arg1, $0xfffffff0 and.32 %r3 <- %r2, $0xfff ret.32 %r3 Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>