https://gcc.gnu.org/g:5a59807bef7e70e8216ce41c212b8ddb2d8caf22
commit 5a59807bef7e70e8216ce41c212b8ddb2d8caf22
Author: Ondřej Machota <ondrejmach...@gmail.com>
Date: Sat May 10 15:38:28 2025 +0200
rtl-ssa-dce: debugize_insns
Diff:
---
gcc/dce.cc | 82 ++++++++++++++++++++++++++++++++++++++++++++++++--
gcc/rtl-ssa/changes.cc | 7 +++--
2 files changed, 84 insertions(+), 5 deletions(-)
diff --git a/gcc/dce.cc b/gcc/dce.cc
index fdf5a35d6765..f12269f5dc97 100644
--- a/gcc/dce.cc
+++ b/gcc/dce.cc
@@ -1876,6 +1876,26 @@ rtl_ssa_dce::debuggize_insn (insn_info *insn)
}
+struct register_replacement {
+ unsigned int regno;
+ rtx expr;
+};
+
+static rtx
+replace_dead_reg(rtx x, const_rtx old_rtx ATTRIBUTE_UNUSED, void *data)
+{
+ auto replacement = static_cast<register_replacement *>(data);
+
+ if (REG_P (x) && REGNO (x) >= FIRST_VIRTUAL_REGISTER && replacement->regno ==
REGNO (x))
+ {
+ if (GET_MODE (x) == GET_MODE (replacement->expr))
+ return replacement->expr;
+ return lowpart_subreg (GET_MODE (x), replacement->expr, GET_MODE
(replacement->expr));
+ }
+
+ return NULL_RTX;
+}
+
void
rtl_ssa_dce::debugize_insns (const std::unordered_set<insn_info *>
&depends_on_dead_phi)
{
@@ -1895,8 +1915,61 @@ rtl_ssa_dce::debugize_insns (const
std::unordered_set<insn_info *> &depends_on_d
rtx_insn *rtl = insn->rtl ();
def_array defs = insn->defs ();
- // def_info* s = nullptr;
- // s->kind() == access_kind::SET
+ rtx rtx_set;
+
+ // If insn has debug uses and will be deleted, signalize it
+ if (!MAY_HAVE_DEBUG_BIND_INSNS ||
+ (rtx_set = single_set (rtl)) == NULL_RTX ||
+ side_effects_p (SET_SRC (rtx_set)) ||
+ asm_noperands (PATTERN (rtl)) >= 0)
+ continue;
+
+ // some of the checks might be duplicate:
+ if (insn->num_defs () != 1)
+ continue;
+
+ def_info *def = *defs.begin ();
+ if (def->kind () != access_kind::SET)
+ continue;
+
+ set_info *set = static_cast<set_info *> (def);
+ if (!set->has_nondebug_insn_uses ())
+ continue;
+
+ rtx dval = make_debug_expr_from_rtl (SET_DEST (rtx_set));
+
+ /* Emit a debug bind insn before the insn in which
+ reg dies. */
+ rtx bind_var_loc =
+ gen_rtx_VAR_LOCATION (GET_MODE (SET_DEST (rtx_set)),
+ DEBUG_EXPR_TREE_DECL (dval),
+ SET_SRC (rtx_set),
+ VAR_INIT_STATUS_INITIALIZED);
+
+ obstack_watermark watermark = crtl->ssa->new_change_attempt();
+ insn_info *debug_insn = crtl->ssa->create_insn(watermark, DEBUG_INSN,
bind_var_loc);
+ insn_change change(debug_insn);
+ change.new_uses = insn->uses();
+ change.move_range = insn_range_info(insn);
+
+ rtx_insn *bind = emit_debug_insn_before (bind_var_loc, rtl);
+
+ register_replacement replacement;
+ for (use_info *u : set->all_uses ()) {
+ // TODO: transform dependent insns
+ replacement.regno = u->regno();
+ replacement.expr = dval;
+
+ simplify_replace_fn_rtx(INSN_VAR_LOCATION_LOC(rtl), NULL_RTX,
replace_dead_reg, &replacement);
+ }
+
+ // note:
+ // 1. Walk over all insns from last to first. If an insntruction can be
+ // debugized, update a bitmap. If the instruction is dead, walk over
+ // its dependencies with worklist and reset the bitmap for visited
+ // instructions.
+ // 2. Do the actual debugizing.
+
rtx set;
// debugize_insns should be called only if MAY_HAVE_DEBUG_BIND_INSNS
if (MAY_HAVE_DEBUG_BIND_INSNS
@@ -1933,7 +2006,7 @@ rtl_ssa_dce::debugize_insns (const
std::unordered_set<insn_info *> &depends_on_d
insn_info *debug_insn = crtl->ssa->create_insn(watermark, DEBUG_INSN,
rtx bind_var_loc);
insn_change change(debug_insn);
change.move_range = insn_range_info(insn)
- // TODO: chains
+ // TODO: chains and defs
def_info *d = *defs.begin ();
if (d->kind() == access_kind::SET) {
@@ -1950,6 +2023,9 @@ rtl_ssa_dce::debugize_insns (const
std::unordered_set<insn_info *> &depends_on_d
// replacements[REGNO (SET_DEST (set))] = dval;
}
}
+
+ // TODO: check that all of the debug insn uses are live,
+ // othervise reset the instruction
}
static void
diff --git a/gcc/rtl-ssa/changes.cc b/gcc/rtl-ssa/changes.cc
index b9861d24d380..4657aec47cd8 100644
--- a/gcc/rtl-ssa/changes.cc
+++ b/gcc/rtl-ssa/changes.cc
@@ -256,7 +256,7 @@ rtl_ssa::changes_are_worthwhile (array_slice<insn_change
*const> changes,
// SET has been deleted. Clean up all remaining uses. Such uses are
// either dead phis or now-redundant live-out uses.
void
-function_info::process_uses_of_deleted_def (set_info *set)
+function_info::process_uses_of_deleted_def (set_info *set, auto_sbitmap&
visited_phis)
{
if (!set->has_any_uses ())
return;
@@ -860,7 +860,10 @@ function_info::change_insns (array_slice<insn_change *>
changes)
{
auto *set = dyn_cast<set_info *> (def);
if (set && set->has_any_uses ())
- process_uses_of_deleted_def (set);
+ {
+ auto_sbitmap phis(m_next_phi_uid);
+ process_uses_of_deleted_def (set);
+ }
remove_def (def);
}
