On Thu, 1 Dec 2011, Jakub Jelinek wrote:
> Hi!
>
> As discussed in the PR, in 4.7 we regressed some GDB testcases, because
> previously unused addressable vars were first previously optimized into
> non-addressable and only afterwards removed (which results in correct debug
> stmts covering those assignments), but after some recent changes it is
> CDDCE that removes them before they are update_address_taken optimized.
>
> In the PR I've offered a patch to schedule another update_address_taken
> pass before first cddce, but Michael is right that perhaps some other
> DCE pass could have similar issue.
>
> So this patch instead, if the DCEd var stores have addressable lhs, but
> with is_gimple_reg_type types, we add debug stmts even for them.
> Such variables aren't target_for_debug_bind though, which breaks
> var-tracking. So, the patch if all occurrences of the var are optimized
> away, just clears TREE_ADDRESSABLE bit like update_address_taken would,
> and, if that didn't happen until expansion, just ignores those debug
> stmts so that var-tracking isn't upset by seing non-tracked vars in debug
> insns.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2011-12-01 Jakub Jelinek <ja...@redhat.com>
>
> PR debug/50317
> * tree-ssa-dce.c (remove_dead_stmt): Add a debug stmt when removing
> as unnecessary a store to a variable with gimple reg type.
> * tree-ssa-live.c (remove_unused_locals): Clear TREE_ADDRESSABLE bit
> on local unreferenced variables.
This change seems wrong. We are turning valid gimple
# DEBUG D#2 => transfer.0 [with addres taken]
into invalid one
# DEBUG D#2 => transfer.0 [without address taken]
once you update that stmt with update_stmt you'll get an SSA operand
for transfer.0 which is not in SSA form because you fail to rewrite it
into.
Why do this in remove_unused_locals and not in update_address_taken?
Or, why do it at all?
I have a SSA operand checking patch that catches this now ...
Thanks,
Richard.
> * cfgexpand.c (expand_gimple_basic_block): Don't emit DEBUG_INSNs
> for !target_for_debug_bind variables.
>
> --- gcc/tree-ssa-live.c.jj 2011-11-28 15:41:46.376749700 +0100
> +++ gcc/tree-ssa-live.c 2011-12-01 12:04:12.920595572 +0100
> @@ -1,5 +1,5 @@
> /* Liveness for SSA trees.
> - Copyright (C) 2003, 2004, 2005, 2007, 2008, 2009, 2010
> + Copyright (C) 2003, 2004, 2005, 2007, 2008, 2009, 2010, 2011
> Free Software Foundation, Inc.
> Contributed by Andrew MacLeod <amacl...@redhat.com>
>
> @@ -814,7 +814,15 @@ remove_unused_locals (void)
> bitmap_set_bit (global_unused_vars, DECL_UID (var));
> }
> else
> - continue;
> + {
> + /* For unreferenced local vars drop TREE_ADDRESSABLE
> + bit in case it is referenced from debug stmts. */
> + if (DECL_CONTEXT (var) == current_function_decl
> + && TREE_ADDRESSABLE (var)
> + && is_gimple_reg_type (TREE_TYPE (var)))
> + TREE_ADDRESSABLE (var) = 0;
> + continue;
> + }
> }
> else if (TREE_CODE (var) == VAR_DECL
> && DECL_HARD_REGISTER (var)
> --- gcc/tree-ssa-dce.c.jj 2011-11-28 15:41:46.376749700 +0100
> +++ gcc/tree-ssa-dce.c 2011-12-01 12:04:12.920595572 +0100
> @@ -1215,6 +1215,26 @@ remove_dead_stmt (gimple_stmt_iterator *
> ei_next (&ei);
> }
>
> + /* If this is a store into a variable that is being optimized away,
> + add a debug bind stmt if possible. */
> + if (MAY_HAVE_DEBUG_STMTS
> + && gimple_assign_single_p (stmt)
> + && is_gimple_val (gimple_assign_rhs1 (stmt)))
> + {
> + tree lhs = gimple_assign_lhs (stmt);
> + if ((TREE_CODE (lhs) == VAR_DECL || TREE_CODE (lhs) == PARM_DECL)
> + && !DECL_IGNORED_P (lhs)
> + && is_gimple_reg_type (TREE_TYPE (lhs))
> + && !is_global_var (lhs)
> + && !DECL_HAS_VALUE_EXPR_P (lhs))
> + {
> + tree rhs = gimple_assign_rhs1 (stmt);
> + gimple note
> + = gimple_build_debug_bind (lhs, unshare_expr (rhs), stmt);
> + gsi_insert_after (i, note, GSI_SAME_STMT);
> + }
> + }
> +
> unlink_stmt_vdef (stmt);
> gsi_remove (i, true);
> release_defs (stmt);
> --- gcc/cfgexpand.c.jj 2011-12-01 11:44:56.156345109 +0100
> +++ gcc/cfgexpand.c 2011-12-01 12:37:57.764791257 +0100
> @@ -3903,6 +3903,11 @@ expand_gimple_basic_block (basic_block b
> rtx val;
> enum machine_mode mode;
>
> + if (TREE_CODE (var) != DEBUG_EXPR_DECL
> + && TREE_CODE (var) != LABEL_DECL
> + && !target_for_debug_bind (var))
> + goto delink_debug_stmt;
> +
> if (gimple_debug_bind_has_value_p (stmt))
> value = gimple_debug_bind_get_value (stmt);
> else
> @@ -3932,6 +3937,7 @@ expand_gimple_basic_block (basic_block b
> PAT_VAR_LOCATION_LOC (val) = (rtx)value;
> }
>
> + delink_debug_stmt:
> /* In order not to generate too many debug temporaries,
> we delink all uses of debug statements we already expanded.
> Therefore debug statements between definition and real
>
> Jakub
>
>
--
Richard Guenther <rguent...@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer
