Re: Gcc extra alignment..

[Graham Stott <grahams at redhat dot com>]

Graham Stott wrote:
> 
> Richard Henderson wrote:
> >
> > On Wed, Nov 01, 2000 at 09:55:31AM +0100, Christian Iseli wrote:
> > > I'm afraid things are not quite that simple.  I'm pretty sure people used
> > > the break statement to get out early of those phony loops.
> >
> > Sigh, yes indeed.  This one actually survived a bootstrap.
> >
> OK we now handle break statements but what about continue statements. I don't think
> this code will work for a do { ....} while (0) with a continue statement.
> 
> Graham

Here's a patch bootstrapped on x86 and also successfully compiled the following
simple test case.

------------------------------------------------------------------------------
extern int break_cond(void);
extern int cont_cond(void);

void dummy()
{
  do
  {
     if (cont_cond())
       continue;
     if (break_cond())
       break;
  } while (0);
}
------------------------------------------------------------------------------

ChangeLog
	* stmt.c (expand_start_null_loop): Generate and emit a label for
	use by possible continue statement.

-----------------------------------------------------------------------------------
Index: stmt.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/stmt.c,v
retrieving revision 1.172
diff -c -p -r1.172 stmt.c
*** stmt.c      2000/11/01 10:28:32     1.172
--- stmt.c      2000/11/01 12:40:09
*************** expand_start_null_loop ()
*** 2307,2320 ****
    thisloop->next = loop_stack;
    thisloop->all = nesting_stack;
    thisloop->depth = ++nesting_depth;
!   thisloop->data.loop.start_label = emit_note (NULL, NOTE_INSN_DELETED);
    thisloop->data.loop.end_label = gen_label_rtx ();
    thisloop->data.loop.alt_end_label = NULL_RTX;
!   thisloop->data.loop.continue_label = NULL_RTX;
    thisloop->exit_label = thisloop->data.loop.end_label;
    loop_stack = thisloop;
    nesting_stack = thisloop;

    return thisloop;
  }

--- 2307,2323 ----
    thisloop->next = loop_stack;
    thisloop->all = nesting_stack;
    thisloop->depth = ++nesting_depth;
!   thisloop->data.loop.start_label = gen_label_rtx ();
    thisloop->data.loop.end_label = gen_label_rtx ();
    thisloop->data.loop.alt_end_label = NULL_RTX;
!   thisloop->data.loop.continue_label = thisloop->data.loop.start_label;
    thisloop->exit_label = thisloop->data.loop.end_label;
    loop_stack = thisloop;
    nesting_stack = thisloop;

+   do_pending_stack_adjust();
+   emit_queue ();
+   emit_label(thisloop->data.loop.continue_label);
    return thisloop;
  }

------------------------------------------------------------------------------------

Graham