https://gcc.gnu.org/g:d1b901b1b3a2335abacdf4a3b69df3c5d8b9fdbc
commit d1b901b1b3a2335abacdf4a3b69df3c5d8b9fdbc
Author: Ondřej Machota <ondrejmach...@gmail.com>
Date: Fri Jun 27 13:24:06 2025 +0200
rtl-ssa-dce: improve code, do not mark uses inside notes
Diff:
---
gcc/dce.cc | 108 +++++++++++++++++++++++++++++++++----------------
gcc/rtl-ssa/changes.cc | 4 +-
2 files changed, 76 insertions(+), 36 deletions(-)
diff --git a/gcc/dce.cc b/gcc/dce.cc
index 1aa5c6539664..3654a5101106 100644
--- a/gcc/dce.cc
+++ b/gcc/dce.cc
@@ -1374,6 +1374,8 @@ private:
bool can_delete_call (const_rtx);
bool is_rtx_prelive (const_rtx);
bool is_prelive (insn_info *);
+ bool mark_if_not_visited (const set_info *);
+ void append_not_visited_sets (auto_vec<set_info *> &, use_array &);
void mark_prelive_insn (insn_info *, auto_vec<set_info *> &);
auto_vec<set_info *> mark_prelive ();
void mark ();
@@ -1507,25 +1509,84 @@ rtl_ssa_dce::is_prelive (insn_info *insn)
return is_rtx_prelive (insn->rtl ());
}
-// Marks INSN and adds its uses to worklist if INSN is not a debug instruction
+
+// Mark SET as visited and return true if SET->insn() is not nullptr and SET
+// has not been visited. Otherwise return false.
+bool
+rtl_ssa_dce::mark_if_not_visited (const set_info *set)
+{
+ insn_info *insn = set->insn ();
+ if (!insn)
+ return false;
+
+ if (insn->is_phi ())
+ {
+ const phi_info *phi = static_cast<const phi_info *> (set);
+ auto uid = phi->uid ();
+
+ if (bitmap_bit_p (m_marked_phis, uid))
+ return false;
+
+ bitmap_set_bit (m_marked_phis, uid);
+ if (dump_file)
+ fprintf (dump_file, "Phi node %d:%d marked as live\n", set->regno ()
,insn->uid ());
+ } else
+ {
+ auto uid = insn->uid ();
+ if (m_marked.get_bit (uid))
+ return false;
+
+ m_marked.set_bit (uid);
+ if (dump_file)
+ fprintf (dump_file, "Insn %d marked as live\n", insn->uid ());
+ }
+
+ return true;
+}
+
+// For each use in USES, if use->def () is non-null and has not been visited,
+// mark it as visited and append it to WORKLIST.
+void
+rtl_ssa_dce::append_not_visited_sets (auto_vec<set_info *>& worklist,
use_array& uses) {
+ for (use_info *use : uses)
+ {
+ // This seems to be a good idea, however there is a problem is
process_uses_of_deleted_def
+ if (use->only_occurs_in_notes())
+ continue;
+
+ set_info *parent_set = use->def ();
+ if (!parent_set)
+ continue;
+
+ if (!mark_if_not_visited (parent_set))
+ continue;
+
+ // mark_if_not_visited will return false if insn is nullptr
+ // insn_info *insn = parent_set->insn ();
+ // gcc_checking_assert (insn);
+
+ // if (dump_file)
+ // fprintf (dump_file, "Adding insn %d to worklist\n", insn->uid
());
+ worklist.safe_push (parent_set);
+ }
+}
+
+// Mark INSN and add its uses to WORKLIST if INSN is not a debug instruction
void
rtl_ssa_dce::mark_prelive_insn (insn_info *insn, auto_vec<set_info *>
&worklist)
{
if (dump_file)
fprintf (dump_file, "Insn %d marked as prelive\n", insn->uid ());
+ // A phi node will never be prelive.
m_marked.set_bit(insn->uid ());
// Debug instruction are not added to worklist. They would wake up possibly
dead
// instructions
if (insn->is_debug_insn ())
return;
- for (use_info *use : insn->uses ())
- {
- set_info *set = use->def ();
- if (set)
- worklist.safe_push (set);
- }
+ use_array uses = insn->uses ();
+ append_not_visited_sets (worklist, uses);
}
// Scans all instructions and marks all which are prelive
@@ -1556,41 +1617,18 @@ rtl_ssa_dce::mark ()
{
set_info *set = worklist.pop ();
insn_info *insn = set->insn ();
- if (!insn)
- continue;
-
- // Skip already visited visited instructions.
- auto uid = insn->uid ();
- if (m_marked.get_bit(uid) && !insn->is_phi ())
- continue;
-
- m_marked.set_bit (uid);
+ // a set without an insn will not be added to the worklist
+ gcc_checking_assert (insn);
use_array uses = insn->uses ();
if (insn->is_phi ())
{
phi_info *phi = static_cast<phi_info *> (set);
- auto phi_uid = phi->uid ();
- // Skip already visited phi node.
- if (bitmap_bit_p(m_marked_phis, phi_uid))
- continue;
-
- bitmap_set_bit (m_marked_phis, phi_uid);
uses = phi->inputs ();
}
- if (dump_file)
- fprintf (dump_file, "Adding insn %d to worklist\n", insn->uid ());
-
- for (use_info *use : uses)
- {
- set_info *parent_set = use->def ();
- if (!parent_set)
- continue;
-
- worklist.safe_push (parent_set);
- }
+ append_not_visited_sets(worklist, uses);
}
}
@@ -1630,9 +1668,9 @@ rtl_ssa_dce::reset_dead_debug ()
bool is_parent_marked = false;
if (parent_insn->is_phi ()) {
auto phi = static_cast<phi_info *> (def);
- is_parent_marked = bitmap_bit_p(m_marked_phis, phi->uid ());
+ is_parent_marked = bitmap_bit_p (m_marked_phis, phi->uid ());
} else {
- is_parent_marked = m_marked.get_bit(parent_insn->uid ());
+ is_parent_marked = m_marked.get_bit (parent_insn->uid ());
}
if (!is_parent_marked) {
diff --git a/gcc/rtl-ssa/changes.cc b/gcc/rtl-ssa/changes.cc
index 3c0fb51cc866..6598ebc1df13 100644
--- a/gcc/rtl-ssa/changes.cc
+++ b/gcc/rtl-ssa/changes.cc
@@ -285,7 +285,9 @@ function_info::process_uses_of_deleted_def (set_info *set)
}
else
{
- gcc_assert (use->is_live_out_use ());
+ // following assert causes crash when running rtl_ssa_dce with
+ // deleting eq_notes on testsuite
+ // gcc_assert (use->is_live_out_use ());
remove_use (use);
}
// The phi handling above might have removed multiple uses of this_set.
