On Tue, 24 Jun 2003, Randy.Dunlap wrote:
>
> + if (reg_01.version >= 0x20)
> + *(int *)®_03 = io_apic_read(apic, 3);
There's a lot of these
*(int *)®_03
kinds of things there, and the fact is, gcc's alias analysis doesn't like
them, _and_ they are ugly.
The alias analysis I could care less about, since a good alias analysis
would take static address information into account, and gcc at least last
time I looked wasn't. So we don't even bother using it for now.
We may want to reconsider that eventually, though, since more recent
versions of gcc at least try to make their alias analysis useful with
things like "attribute((may_alias))" or whatever the syntax was.
But the ugliness part I care about, and I wonder if it wouldn't be better
in this case to just make the register definition a "union", and have
something like
union reg_03 {
u32 value;
struct {
u32 boot_DT:1,
reserved:31;
} bits;
};
and then you can avoid the ugly dereference/cast/address-of thing, and
just say
reg_03.value
or
reg_03.bits.boot_DT
which looks a lot cleaner.
This is what unions are _designed_ for.
Linus
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This archive was generated by hypermail 2b29 : Mon Jun 30 2003 - 22:00:18 EST