On Mon, 29 Apr 2019, Richard Biener wrote:
>
> The following fixes PR90273 where the testcase exhibits an excessive
> number of debug stmts after the recent fixes to CFG cleanup to not
> throw away debug stmts it cannot move but instead move and reset them.
> This excessiveness causes compile-time and memory-usage to go through the
> roof.
>
> The fix is to deploy a simple debug-stmt DCE eliminating all but the
> last debug-bind (of non-DEBUG_EXPR_DECL vars) in a series of
> debug-bind-only stmts. This simple DCE is hooked into the DCE
> pass and implemented BB-local.
>
> Bootstrapped / tested a slightly older version, re-bootstrap/regtest
> in progress on x86_64-unknown-linux-gnu.
Testing went OK.
> OK for trunk and branch?
>
> Thanks,
> Richard.
>
> 2019-04-29 Richard Biener <rguent...@suse.de>
>
> PR tree-optimization/90273
> * tree-ssa-dce.c (eliminate_unnecessary_stmts): Eliminate
> useless debug stmts.
>
> Index: gcc/tree-ssa-dce.c
> ===================================================================
> --- gcc/tree-ssa-dce.c (revision 270640)
> +++ gcc/tree-ssa-dce.c (working copy)
> @@ -1237,6 +1237,7 @@ eliminate_unnecessary_stmts (void)
> bb = h.pop ();
>
> /* Remove dead statements. */
> + auto_bitmap debug_seen;
> for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi = psi)
> {
> stmt = gsi_stmt (gsi);
> @@ -1282,11 +1283,15 @@ eliminate_unnecessary_stmts (void)
> }
> }
> if (!dead)
> - continue;
> + {
> + bitmap_clear (debug_seen);
> + continue;
> + }
> }
> if (!is_gimple_debug (stmt))
> something_changed = true;
> remove_dead_stmt (&gsi, bb, to_remove_edges);
> + continue;
> }
> else if (is_gimple_call (stmt))
> {
> @@ -1352,6 +1357,18 @@ eliminate_unnecessary_stmts (void)
> break;
> }
> }
> + else if (gimple_debug_bind_p (stmt))
> + {
> + /* We are only keeping the last debug-bind of a
> + non-DEBUG_EXPR_DECL variable in a series of
> + debug-bind stmts. */
> + tree var = gimple_debug_bind_get_var (stmt);
> + if (TREE_CODE (var) != DEBUG_EXPR_DECL
> + && !bitmap_set_bit (debug_seen, DECL_UID (var)))
> + remove_dead_stmt (&gsi, bb, to_remove_edges);
> + continue;
> + }
> + bitmap_clear (debug_seen);
> }
>
> /* Remove dead PHI nodes. */
>
--
Richard Biener <rguent...@suse.de>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)
