On Tue, 12 May 2020, Richard Biener wrote:
>
> This removes debug-bind resets aka
>
> # DEBUG b = NULL
>
> when the reset variable is otherwise unused. I've gathered statistics
> for a single TU, fold-const.ii which at -O2 -g shows
>
> 28 ssa "dead debug bind reset" 1
> 34 einline "dead debug bind reset" 340
> 54 release_ssa "dead debug bind reset" 176
> 54 release_ssa "live debug bind reset of dead var" 4
> 86 inline "dead debug bind reset" 5131
> 86 inline "live debug bind reset of dead var" 61
> 241 optimized "dead debug bind reset" 970
> 241 optimized "live debug bind reset of dead var" 287
>
> where "live debug bind reset of dead var" means the variable is unused
> but there were debug binds with a value for them and
> "dead debug bind reset" means the variable is unused and there were
> only debug bind resets (each reset of the same variable is counted
> for both counters). This shows A considerable amount of dead stmts
> removed esp. after IPA inlining.
>
> Bootstrap and regtest running on x86_64-unknown-linux-gnu.
This is what I have applied after consulting with Jakub.
Richard.
>From 6657b248e2c1978862ae81bf589c555b0465ae82 Mon Sep 17 00:00:00 2001
From: Richard Biener <rguent...@suse.de>
Date: Tue, 14 Jan 2020 15:31:18 +0100
Subject: [PATCH] remove dead debug-bind resets
This removes debug-bind resets aka
# DEBUG b = NULL
when the reset variable is otherwise unused. I've gathered statistics
for a single TU, fold-const.ii which at -O2 -g shows
28 ssa "dead debug bind reset" 1
34 einline "dead debug bind reset" 340
54 release_ssa "dead debug bind reset" 176
54 release_ssa "live debug bind reset of dead var" 4
86 inline "dead debug bind reset" 5131
86 inline "live debug bind reset of dead var" 61
241 optimized "dead debug bind reset" 970
241 optimized "live debug bind reset of dead var" 287
where "live debug bind reset of dead var" means the variable is unused
but there were debug binds with a value for them and
"dead debug bind reset" means the variable is unused and there were
only debug bind resets (each reset of the same variable is counted
for both counters). This shows A considerable amount of dead stmts
removed esp. after IPA inlining.
2020-05-12 Richard Biener <rguent...@suse.de>
* tree-ssa-live.c (remove_unused_locals): Remove dead debug
bind resets.
---
gcc/tree-ssa-live.c | 31 ++++++++++++++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/gcc/tree-ssa-live.c b/gcc/tree-ssa-live.c
index f3975320e8c..21a9ee43e6b 100644
--- a/gcc/tree-ssa-live.c
+++ b/gcc/tree-ssa-live.c
@@ -743,6 +743,7 @@ remove_unused_locals (void)
mark_scope_block_unused (DECL_INITIAL (current_function_decl));
usedvars = BITMAP_ALLOC (NULL);
+ auto_bitmap useddebug;
/* Walk the CFG marking all referenced symbols. */
FOR_EACH_BB_FN (bb, cfun)
@@ -763,7 +764,21 @@ remove_unused_locals (void)
do it. If the block is not otherwise used, the stmt will
be cleaned up in clean_unused_block_pointer. */
if (is_gimple_debug (stmt))
- continue;
+ {
+ if (gimple_debug_bind_p (stmt))
+ {
+ tree var = gimple_debug_bind_get_var (stmt);
+ if (VAR_P (var))
+ {
+ if (!gimple_debug_bind_get_value (stmt))
+ /* Run the 2nd phase. */
+ have_local_clobbers = true;
+ else
+ bitmap_set_bit (useddebug, DECL_UID (var));
+ }
+ }
+ continue;
+ }
if (gimple_clobber_p (stmt))
{
@@ -846,6 +861,20 @@ remove_unused_locals (void)
if (b)
TREE_USED (b) = true;
}
+ else if (gimple_debug_bind_p (stmt))
+ {
+ tree var = gimple_debug_bind_get_var (stmt);
+ if (VAR_P (var)
+ && !bitmap_bit_p (useddebug, DECL_UID (var))
+ && !is_used_p (var))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Dead debug bind reset to %u\n",
+ DECL_UID (var));
+ gsi_remove (&gsi, true);
+ continue;
+ }
+ }
gsi_next (&gsi);
}
}
--
2.25.1
