Re: [PATCH] bitint, v2: Avoid rewriting large/huge _BitInt vars into SSA after bitint lowering [PR114278]

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Mar 11, 2024 at 11:31:51AM +0100, Richard Biener wrote:
> On Mon, 11 Mar 2024, Jakub Jelinek wrote:
> 
> > On Sat, Mar 09, 2024 at 12:25:42PM +0100, Richard Biener wrote:
> > > Ideally we?d clear TREE_ADDRESSABLE but set DECL_NOT_GIMPLE_REG,
> > > I think the analysis where we check the base would be a more
> > > appropriate place to enforce that.
> > 
> > So like this?
> 
> Hm, I was thinking of non_rewritable_lvalue_p/non_rewritable_mem_ref_base
> though that requires duplicating, so I guess handling in maybe_optimize_var 
> would work.

I was considering it, but it looked like a waste to me, using bitmap bits
for something that is always the case, we don't want to rewrite any
large/huge _BitInt to SSA form after the lowering, not just some of them.

> I do now wonder whether setting DECL_NOT_GIMPLE_REG_P in bitfield
> lowering would prevail?

Guess I can certainly try to set DECL_NOT_GIMPLE_REG_P on the large/huge
_BitInt PARM_DECLs/RESULT_DECLs during bitint lowering even when they are
TREE_ADDRESSABLE at that point; the VAR_DECLs have array types of limbs and
so shouldn't be a problem.

> (sorry for approving the earlier patch now, I was too quick and didn't
> remember the discussion)

Sorry, already committed, I can revert or incrementally adjust.

	Jakub