|
In an expression like this, if the inner mask (M') 'covers' all the
bits of the effective mask (M) corresponding to OP(_, K), IOW if
(M' & M) == M, then the inner mask (M') is unneeded and can be
optimized away, giving: OP((x | y), K).
For example, with this simplification, code like:
int foo(int x, int y)
{
return (((x & 0x0fffffff) | y) & 0xfff);
}
is now optimized into the minimal:
foo:
or.32 %r4 <- %arg1, %arg2
and.32 %r5 <- %r4, $0xfff
ret.32 %r5
while previously, the inner mask was not optimized away:
foo:
and.32 %r2 <- %arg1, $0xfffffff
or.32 %r4 <- %r2, %arg2
and.32 %r5 <- %r4, $0xfff
ret.32 %r5
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
|
