On Fri, Jul 1, 2011 at 11:21 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> Hi!
>
> For debug stmt uses, we don't want any PHI nodes to be created
> just because of them, so the debug uses need to be ignored
> during decisions which PHI nodes to add.
> Unfortunately that means get_current_def can't be always trusted.
> The following patch trusts it in a few cases where I'm reasonably
> sure it is trustable. Perhaps some more cases could be added in
> the future if anyone has ideas...
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok.
Thanks,
Richard.
> 2011-07-01 Jakub Jelinek <ja...@redhat.com>
>
> PR debug/49602
> * tree-into-ssa.c (rewrite_debug_stmt_uses): Disregard
> get_current_def return value if it can't be trusted to be
> the current value of the variable in the current bb.
>
> * gcc.dg/pr49602.c: New test.
>
> --- gcc/tree-into-ssa.c.jj 2011-06-23 10:13:58.000000000 +0200
> +++ gcc/tree-into-ssa.c 2011-07-01 20:39:40.000000000 +0200
> @@ -1343,7 +1343,41 @@ rewrite_debug_stmt_uses (gimple stmt)
> }
> }
> else
> - def = get_current_def (var);
> + {
> + def = get_current_def (var);
> + /* Check if get_current_def can be trusted. */
> + if (def)
> + {
> + basic_block bb = gimple_bb (stmt);
> + basic_block def_bb
> + = SSA_NAME_IS_DEFAULT_DEF (def)
> + ? NULL : gimple_bb (SSA_NAME_DEF_STMT (def));
> +
> + /* If definition is in current bb, it is fine. */
> + if (bb == def_bb)
> + ;
> + /* If definition bb doesn't dominate the current bb,
> + it can't be used. */
> + else if (def_bb && !dominated_by_p (CDI_DOMINATORS, bb, def_bb))
> + def = NULL;
> + /* If there is just one definition and dominates the current
> + bb, it is fine. */
> + else if (get_phi_state (var) == NEED_PHI_STATE_NO)
> + ;
> + else
> + {
> + struct def_blocks_d *db_p = get_def_blocks_for (var);
> +
> + /* If there are some non-debug uses in the current bb,
> + it is fine. */
> + if (bitmap_bit_p (db_p->livein_blocks, bb->index))
> + ;
> + /* Otherwise give up for now. */
> + else
> + def = NULL;
> + }
> + }
> + }
> if (def == NULL)
> {
> gimple_debug_bind_reset_value (stmt);
> --- gcc/testsuite/gcc.dg/pr49602.c.jj 2011-07-01 20:42:44.000000000 +0200
> +++ gcc/testsuite/gcc.dg/pr49602.c 2011-07-01 18:49:04.000000000 +0200
> @@ -0,0 +1,17 @@
> +/* PR debug/49602 */
> +/* { dg-do compile } */
> +/* { dg-options "-g -O2" } */
> +
> +static void
> +foo (int *x)
> +{
> +}
> +
> +void
> +bar (int *x)
> +{
> + int i;
> + for (i = 0; i == 1; ++i)
> + x = 0;
> + foo (x);
> +}
>
> Jakub
>
