Re: spec2000 regression

[Jan Hubicka <jh@suse.cz>]

> >>>>> "Jan" == Jan Hubicka <jh@suse.cz> writes:
> 
> > So remaining patch I can't analyze completely is yours to alias.c
> > I've failed to find the corresponding email at gcc-patches mailing list
> > (even when I believe I've went across it in the pass)
> 
> The subject line is "PATCH to get_alias_set".  There were two messages.
> 
> > so please can you double-check the patch and try to explain me what
> > exactly it is shooting for?
> 
> It's trying to avoid recalculating the alias set for a variable.  I suppose
> it could cause a performance regression if the initial alias set were
> wrong, but I would expect that to cause other problems as well.
Hi,
the problem is that actually code first sets the DECL_RTL and then calls
set_mem_attributes, that calls get_alias_set, but it thinks that the alias set
is already computed, but it isn't.

I am now testing following patch. OK to install if it succeeds?

It fixes my testcase:

long *a;
short *b;
main()
{
  *a = 1;
  *b = 2;
  return *a;
}

Now gets again:

	pushl	%ebp
	movl	%esp, %ebp
	pushl	%eax
	pushl	%eax
	movl	a, %eax
	andl	$-16, %esp
	movl	$1, (%eax)
	movl	b, %eax
	movw	$2, (%eax)
	movl	%ebp, %esp
	movl	$1, %eax
	popl	%ebp
	ret

Honza

Wed Aug 15 14:38:26 CEST 2001  Jan Hubicka  <jh@suse.cz>
	* alias.c (get_alias_set): Check that the alias set is already
	computed.

Index: alias.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/alias.c,v
retrieving revision 1.137
diff -c -3 -p -r1.137 alias.c
*** alias.c	2001/08/08 16:56:50	1.137
--- alias.c	2001/08/15 12:38:13
*************** get_alias_set (t)
*** 530,536 ****
  	 return it.  This is necessary for C++ anonymous unions, whose
  	 component variables don't look like union members (boo!).  */
        if (TREE_CODE (t) == VAR_DECL
! 	  && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM)
  	return MEM_ALIAS_SET (DECL_RTL (t));
  
        /* Give the language another chance to do something special.  */
--- 530,537 ----
  	 return it.  This is necessary for C++ anonymous unions, whose
  	 component variables don't look like union members (boo!).  */
        if (TREE_CODE (t) == VAR_DECL
! 	  && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM
! 	  && MEM_ALIAS_SET (DECL_RTL (t)))
  	return MEM_ALIAS_SET (DECL_RTL (t));
  
        /* Give the language another chance to do something special.  */