This fixes PR51528 by hiding the issue that SRA generates
copy in/out with a type not suitable for preserving the data
(any non-mode-precision thing). It fixes it by instead of
emitting
x$i_8 = x.i;
D.1720 = x;
D.1720.i = x$i_8;
for an assign to an unscalarized D.1720 from a partly scalarized x
(so the aggregate assignment prevails) emit
x.i = x$i_8;
D.1720 = x;
instead. This allows the unfortunate copy in/out to be optimized
away (and thus its undefined behavior).
Basically whenever the aggregate copy will prevail prefer to
restore the RHS and reload the LHS components - just like we
do for aggregate uses/destinations of call statements.
I think we can still clean up the aggregate copy path a lot,
but that's for 4.8 (unless new bugs pop up).
Bootstrap and regtest pending on x86_64-unknown-linux-gnu.
Richard.
2012-01-27 Richard Guenther <rguent...@suse.de>
PR tree-optimization/51528
* tree-sra.c (sra_modify_assign): Handle the default fallback
for aggregate assigns better.
* gcc.dg/torture/pr51528.c: New testcase.
Index: gcc/tree-sra.c
===================================================================
*** gcc/tree-sra.c (revision 183616)
--- gcc/tree-sra.c (working copy)
*************** sra_modify_assign (gimple *stmt, gimple_
*** 3060,3104 ****
}
else
{
! if (racc)
{
! if (!racc->grp_to_be_replaced && !racc->grp_unscalarized_data)
{
! if (dump_file)
! {
! fprintf (dump_file, "Removing load: ");
! print_gimple_stmt (dump_file, *stmt, 0, 0);
! }
!
! if (TREE_CODE (lhs) == SSA_NAME)
! {
! rhs = get_repl_default_def_ssa_name (racc);
! if (!useless_type_conversion_p (TREE_TYPE (lhs),
! TREE_TYPE (rhs)))
! rhs = fold_build1_loc (loc, VIEW_CONVERT_EXPR,
! TREE_TYPE (lhs), rhs);
! }
! else
! {
! if (racc->first_child)
! generate_subtree_copies (racc->first_child, lhs,
! racc->offset, 0, 0, gsi,
! false, false, loc);
!
! gcc_assert (*stmt == gsi_stmt (*gsi));
! unlink_stmt_vdef (*stmt);
! gsi_remove (gsi, true);
! sra_stats.deleted++;
! return SRA_AM_REMOVED;
! }
}
- else if (racc->first_child)
- generate_subtree_copies (racc->first_child, lhs, racc->offset,
- 0, 0, gsi, false, true, loc);
}
if (access_has_children_p (lacc))
! generate_subtree_copies (lacc->first_child, rhs, lacc->offset,
! 0, 0, gsi, true, true, loc);
}
}
--- 3061,3124 ----
}
else
{
! if (racc
! && !racc->grp_to_be_replaced && !racc->grp_unscalarized_data)
{
! if (dump_file)
! {
! fprintf (dump_file, "Removing load: ");
! print_gimple_stmt (dump_file, *stmt, 0, 0);
! }
!
! if (TREE_CODE (lhs) == SSA_NAME)
! {
! rhs = get_repl_default_def_ssa_name (racc);
! if (!useless_type_conversion_p (TREE_TYPE (lhs),
! TREE_TYPE (rhs)))
! rhs = fold_build1_loc (loc, VIEW_CONVERT_EXPR,
! TREE_TYPE (lhs), rhs);
! }
! else
{
! if (racc->first_child)
! generate_subtree_copies (racc->first_child, lhs,
! racc->offset, 0, 0, gsi,
! false, false, loc);
!
! gcc_assert (*stmt == gsi_stmt (*gsi));
! unlink_stmt_vdef (*stmt);
! gsi_remove (gsi, true);
! sra_stats.deleted++;
! return SRA_AM_REMOVED;
}
}
+
+ /* If there is no unscalarized data on the RHS replace
+ the aggregate copy by piecewise storing into the LHS. */
+ if (access_has_children_p (racc) && racc->grp_covered)
+ {
+ generate_subtree_copies (racc->first_child, lhs, racc->offset,
+ 0, 0, gsi, false, false, loc);
+ gcc_assert (!access_has_children_p (lacc));
+ gcc_assert (*stmt == gsi_stmt (*gsi));
+ unlink_stmt_vdef (*stmt);
+ gsi_remove (gsi, true);
+ sra_stats.deleted++;
+ return SRA_AM_REMOVED;
+ }
+
+ /* If there is unscalarized data on the RHS the aggregate
+ copy will prevail, so simply update the RHS from its
+ scalarized components. */
+ if (access_has_children_p (racc))
+ generate_subtree_copies (racc->first_child, racc->base,
+ 0, 0, 0, gsi, false, false, loc);
+
+ /* The aggregate copy has prevailed. Re-load the LHS components
+ from the LHS. */
if (access_has_children_p (lacc))
! generate_subtree_copies (lacc->first_child, lhs,
! 0, 0, 0, gsi, true, true, loc);
}
}
Index: gcc/testsuite/gcc.dg/torture/pr51528.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr51528.c (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr51528.c (revision 0)
***************
*** 0 ****
--- 1,46 ----
+ /* { dg-do run } */
+ /* { dg-options "-fno-early-inlining" } */
+
+ extern void abort (void);
+
+ union U
+ {
+ int i;
+ _Bool b;
+ };
+
+ _Bool gb;
+
+ void __attribute__ ((noinline))
+ use_bool (union U u)
+ {
+ gb = u.b;
+ }
+
+ union U
+ bar (void)
+ {
+ union U u;
+ u.i = 0xFFFE;
+ return u;
+ }
+
+ union U __attribute__ ((noinline))
+ foo (void)
+ {
+ union U u,v;
+
+ u.b = 1;
+ use_bool (u);
+ u = bar ();
+
+ return u;
+ }
+
+ int main (int argc, char **argv)
+ {
+ union U u = foo ();
+ if (u.i != 0xFFFE)
+ abort ();
+ return 0;
+ }
