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Currently, in simplify_mask_or_and(), only the cases where
(M' & M) == 0 or (M' & M) == M are simplified. However, if the
combined mask (M' & M) is different than the original inner mask
(M'), this inner mask can be replaced by the smaller combined one,
giving: OP(((x & (M' & M)) | y), K).
For example, code like:
int foo(int x, int y)
{
return (((x & 0xfffffff0) | y) & 0xfff);
}
is now simplified into:
foo:
and.32 %r2 <- %arg1, $0xff0
or.32 %r4 <- %r2, %arg2
and.32 %r5 <- %r4, $0xfff
ret.32 %r5
while previously, the mask was not reduced:
foo:
and.32 %r2 <- %arg1, $0xfffffff0
...
Note: this is not a very effective simplification like directly
removing an instruction, nevertheless the smaller mask can
trigger other simplifications and may also be advantageous
for a subsequent code generation phase.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
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