Re: Patch: Add a stop bit in alignment for alloc.

["H. J. Lu" <hjl at lucon dot org>]

On Tue, Mar 02, 2004 at 06:24:44PM -0800, Jim Wilson wrote:
> On Tue, 2004-03-02 at 12:36, H. J. Lu wrote:
> > 	* config/tc-ia64.c (align_frag): New.
> > 	(md_assemble): Set the tc_frag_data field in align_frag for
> > 	IA64_OPCODE_FIRST instructions.
> > 	(ia64_md_do_align): Set align_frag.
> > 	(ia64_handle_align): Add a stop bit if needed.
> 
> This looks good to me.
> 
> However, I don't think it is fool proof.  When we create an
> rs_align_code frag, we call frag_align_code, which calls frag_var, which
> calls frag_grow with the requested alignment - 1.  If there is no room
> left in this obstack, then frag_grow will create a new frag.  So in some
> cases, the alignment frag will be the one after align_frag.
> 
> There is also a loop in frag_grow which implies that the alignment frag
> could be arbitrarily later, however, it isn't clear to me why the loop
> is there.  So it looks like in rare cases the alignment frag could be
> two after align_frag, and maybe in even rarer cases it could be farther.
> 
> In order to handle this, I think we need a loop to search forward from
> align_frag to find the real alignment frag.  The first frag starting
> from align_frag that has rs_align_code is the alignment frag.

Here is the new patch.


H.J.

Attachment: gas-ia64-alloc-3.patch
Description: Text document