On Thu, 30 Jun 2011, Martin Jambor wrote:
> Hi,
>
> On Thu, Jun 30, 2011 at 03:39:55PM +0200, Martin Jambor wrote:
> > Hi,
> >
> > I had to add a test that the analyzed expression is not an SSA name.
> > This has been approved by Rchi on IRC yesterday. Thus, I have
> > committed the following as revision 175703 after successful run of c
> > and c++ testsuite on sparc64 (and a bootstrap and test with another
> > patch on x86_64-linux).
>
> I also tested fortran on sparc64 but missed a regression there
> (gfortran.dg/pr25923.f90). The problem is that *arg_1(D) is also
> scrutinized, get_object_alignment returns 8 for it and that is
> obviously not enough for SImode required alignment.
>
> I assume such loads have to be aligned for the mode on strict aligned
> targets and therefore they are OK. The question is, is that true for
> all MEM_REFs or only for those with zero offset? Since the original
> problem was that the expander expanded
>
> MEM[(struct ip *)ip_3 + 7B].s_addr;
>
> as if it was aligned, I suppose that MEM_REFs are generally fine and
> we can avoid this issue by skipping them just like the SSA_NAMEs. Is
> my reasoning correct?
Not really. This just highlights the issue that alignment on
strict-align targets is broken for any non-component-ref style
access. As we happily fold component-refs into the MEM_REFs offset
the issue is now more appearant.
For MEM_REFs the alignment is supposed to be at least that of
TYPE_ALIGN (TREE_TYPE (mem-ref)), even though the expanders
would ignore that.
Richard.
> Thanks,
>
> Martin
>
>
> >
> > Thanks,
> >
> > Martin
> >
> >
> > 2011-06-30 Martin Jambor <mjam...@suse.cz>
> >
> > PR tree-optimization/49094
> > * tree-sra.c (tree_non_mode_aligned_mem_p): New function.
> > (build_accesses_from_assign): Use it.
> >
> > * testsuite/gcc.dg/tree-ssa/pr49094.c: New test.
> >
> >
> > Index: src/gcc/tree-sra.c
> > ===================================================================
> > --- src.orig/gcc/tree-sra.c
> > +++ src/gcc/tree-sra.c
> > @@ -1050,6 +1050,26 @@ disqualify_ops_if_throwing_stmt (gimple
> > return false;
> > }
> >
> > +/* Return true iff type of EXP is not sufficiently aligned. */
> > +
> > +static bool
> > +tree_non_mode_aligned_mem_p (tree exp)
> > +{
> > + enum machine_mode mode = TYPE_MODE (TREE_TYPE (exp));
> > + unsigned int align;
> > +
> > + if (TREE_CODE (exp) == SSA_NAME
> > + || mode == BLKmode
> > + || !STRICT_ALIGNMENT)
> > + return false;
> > +
> > + align = get_object_alignment (exp, BIGGEST_ALIGNMENT);
> > + if (GET_MODE_ALIGNMENT (mode) > align)
> > + return true;
> > +
> > + return false;
> > +}
> > +
> > /* Scan expressions occuring in STMT, create access structures for all
> > accesses
> > to candidates for scalarization and remove those candidates which occur
> > in
> > statements or expressions that prevent them from being split apart.
> > Return
> > @@ -1074,7 +1094,10 @@ build_accesses_from_assign (gimple stmt)
> > lacc = build_access_from_expr_1 (lhs, stmt, true);
> >
> > if (lacc)
> > - lacc->grp_assignment_write = 1;
> > + {
> > + lacc->grp_assignment_write = 1;
> > + lacc->grp_unscalarizable_region |= tree_non_mode_aligned_mem_p (rhs);
> > + }
> >
> > if (racc)
> > {
> > @@ -1082,6 +1105,7 @@ build_accesses_from_assign (gimple stmt)
> > if (should_scalarize_away_bitmap && !gimple_has_volatile_ops (stmt)
> > && !is_gimple_reg_type (racc->type))
> > bitmap_set_bit (should_scalarize_away_bitmap, DECL_UID (racc->base));
> > + racc->grp_unscalarizable_region |= tree_non_mode_aligned_mem_p (lhs);
> > }
> >
> > if (lacc && racc
> > Index: src/gcc/testsuite/gcc.dg/tree-ssa/pr49094.c
> > ===================================================================
> > --- /dev/null
> > +++ src/gcc/testsuite/gcc.dg/tree-ssa/pr49094.c
> > @@ -0,0 +1,38 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-O" } */
> > +
> > +struct in_addr {
> > + unsigned int s_addr;
> > +};
> > +
> > +struct ip {
> > + unsigned char ip_p;
> > + unsigned short ip_sum;
> > + struct in_addr ip_src,ip_dst;
> > +} __attribute__ ((aligned(1), packed));
> > +
> > +struct ip ip_fw_fwd_addr;
> > +
> > +int test_alignment( char *m )
> > +{
> > + struct ip *ip = (struct ip *) m;
> > + struct in_addr pkt_dst;
> > + pkt_dst = ip->ip_dst ;
> > + if( pkt_dst.s_addr == 0 )
> > + return 1;
> > + else
> > + return 0;
> > +}
> > +
> > +int __attribute__ ((noinline, noclone))
> > +intermediary (char *p)
> > +{
> > + return test_alignment (p);
> > +}
> > +
> > +int
> > +main (int argc, char *argv[])
> > +{
> > + ip_fw_fwd_addr.ip_dst.s_addr = 1;
> > + return intermediary ((void *) &ip_fw_fwd_addr);
> > +}
>
>
--
Richard Guenther <rguent...@suse.de>
Novell / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer
