-funswitch-loops not effective?

[Richard Henderson]

On Tue, Jan 18, 2005 at 08:54:14PM +0100, Richard Guenther wrote:
> If so, why don't we model this
> invariant and exploit it in the optimizers?

Because with function inlining, it is exceedingly hard to do this.

What you wind up with is "this field cannot be modified except
within this region".  Which, unless you come up with some way to
model this that's better than what we've thought up before, will
degenerate into the equivalent of RTX_UNCHANGING_P.  Which I think
everyone will agree was a nightmare.


r~