Re: [PATCH] Some middle-end improvements for bitfield handling

[Paolo Bonzini <bonzini at gnu dot org>]

>     We may want to lower bitfields in some cases, for example if
>     the vectorizer determines that accesses in a loop can be vectorized.
>
> I don't follow.  How could it do that for fields that were not arrays?
> We don't currently support arrays of bitfields.

For array of structs, as in

	struct x {
	  unsigned a : 3;
	  unsigned b : 1;
	  unsigned c : 5;
	} a[128];

	struct x *p;
	for (p = a; p < a + 128; p++)
	  p->b = 1;

which may get optimized to

	int *p;

	for (p = (int *) a; p < (int *) (a + 128); p++)
	  p->b |= 0x88888888;

Nice savings.