https://gcc.gnu.org/g:668fb8231327b7385492464ab879fe06f9859ca1
commit 668fb8231327b7385492464ab879fe06f9859ca1
Author: Ondřej Machota <ondrejmach...@gmail.com>
Date: Tue Apr 8 23:27:00 2025 +0200
rtl-ssa-dce: delete dead debug insns
Diff:
---
gcc/dce.cc | 138 ++++++++++++++++---------------------------------------------
1 file changed, 35 insertions(+), 103 deletions(-)
diff --git a/gcc/dce.cc b/gcc/dce.cc
index c0ca89980254..40b4cd991151 100644
--- a/gcc/dce.cc
+++ b/gcc/dce.cc
@@ -1421,42 +1421,24 @@ bool is_prelive(insn_info *insn)
gcc_assert (insn->is_real());
auto rtl = insn->rtl();
- /* I guess that a lot of conditions bellow are captured by artificial uses
- of bb head and end insns. */
for (def_info * def : insn->defs()) {
/* The purpose of this pass is not to eliminate stores to memory... */
if (def->is_mem())
- // TODO : clobbered memory?
return true;
gcc_assert(def->is_reg());
- /* this ignores clobbers, which is probably fine */
/* gcc.c-torture/execute/20000503-1.c - flags register is unused. Not all
hard registers should be marked... */
+
+ /* this ignores clobbers, which is probably fine */
if (def->kind() != access_kind::SET)
continue;
- /* This might be messed up a bit */
- // if (def->regno() == FRAME_POINTER_REGNUM
- // || def->regno() == STACK_POINTER_REGNUM)
- // return true;
-
/* needed by gcc.c-torture/execute/pr51447.c */
if (HARD_REGISTER_NUM_P (def->regno())
&& global_regs[def->regno()])
- // { std::cout << "marked global reg: " << def->regno() << " in " <<
insn->uid() << '\n';
- return true;
- // }
-
- // if (!HARD_FRAME_POINTER_IS_FRAME_POINTER
- // && def->regno() == HARD_FRAME_POINTER_REGNUM)
- // return true;
-
- // if (FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
- // && fixed_regs[ARG_POINTER_REGNUM]
- // && def->regno() == ARG_POINTER_REGNUM)
- // return true;
+ return true;
unsigned int picreg = PIC_OFFSET_TABLE_REGNUM;
if (picreg != INVALID_REGNUM
@@ -1469,20 +1451,24 @@ bool is_prelive(insn_info *insn)
}
static void
-rtl_ssa_dce_mark_prelive_insn(insn_info *info, vec<insn_info *> &worklist,
+rtl_ssa_dce_mark_prelive_insn(insn_info *insn, auto_vec<set_info *> &worklist,
std::unordered_set<insn_info *> &marked)
{
if (dump_file)
- fprintf(dump_file, "Insn %d is prelive\n", info->uid());
+ fprintf(dump_file, "Insn %d marked as prelive\n", insn->uid());
- marked.emplace(info);
- worklist.safe_push(info);
+ marked.emplace(insn);
+ for (use_info *use : insn->uses()) {
+ set_info* set = use->def();
+ if (set)
+ worklist.safe_push(set);
+ }
}
-static auto_vec<insn_info *>
+static auto_vec<set_info *>
rtl_ssa_dce_mark_prelive(std::unordered_set<insn_info *> &marked)
{
- auto_vec<insn_info *> worklist;
+ auto_vec<set_info *> worklist;
for (insn_info * insn : crtl->ssa->all_insns()) {
if (is_prelive(insn))
rtl_ssa_dce_mark_prelive_insn(insn, worklist, marked);
@@ -1497,16 +1483,7 @@ rtl_ssa_dce_mark()
std::unordered_set<insn_info *> marked{};
/* Phi insn might have more that one phi node:
gcc/gcc/testsuite/gcc.c-torture/execute/20000224-1.c */
std::unordered_set<phi_info *> marked_phi_nodes{};
- auto prelive_insns = rtl_ssa_dce_mark_prelive(marked);
- /* Extract uses from prelive insns to worklist */
- auto_vec<set_info *> worklist{};
- for (insn_info * insn : prelive_insns) {
- for (auto&& use : insn->uses()) {
- set_info* set = use->def();
- if (set)
- worklist.safe_push(set);
- }
- }
+ auto worklist = rtl_ssa_dce_mark_prelive(marked);
while (!worklist.is_empty()) {
set_info* set = worklist.pop();
@@ -1581,78 +1558,31 @@ rtl_ssa_dce_sweep(std::unordered_set<insn_info *>
marked)
crtl->ssa->change_insns(changes);
}
-// WIP
-static void
-rtl_ssa_dce_transform_insns_to_debug() {
- std::unordered_set<int> is_debug;
- // Should we use ssa when modifing insns? if yes, we want in-place replace
-
- /* chceme prochazet v post orderu, abychom nejdrive zpracovali zavislosti
- a pak az definici nelze jen menit instrukce, protoze musime informaci
- propagovat pres phi node */
- /* We check, whether all insns that use a definition from the current insn
- are only debug insns */
- for (insn_info * insn : crtl->ssa->reverse_all_insns()) {
- if (insn->is_debug_insn()) { // phi is never debug
- // TODO : store info about this insn
- is_debug.emplace(insn->uid());
- continue;
- }
+static void reset_debug_insn_uses(insn_info * insn) {
+ gcc_assert(insn->is_debug_insn());
- if (insn->is_phi()) {
- // for each phi_info
- for (def_info *def : insn->defs()) {
- phi_info *pi = as_a<phi_info *> (def);
-
- }
- }
+ if (dump_file)
+ fprintf(dump_file, "Resetting debug insn: %d\n", insn->uid());
- rtx_insn * rtl = insn->rtl();
- rtx set;
- if (!(MAY_HAVE_DEBUG_BIND_INSNS
- && (set = single_set (rtl)) != NULL_RTX
- && (!side_effects_p (SET_SRC (set))
- && asm_noperands (PATTERN (rtl)) < 0))) {
+ insn_change change (insn);
+ change.new_uses = {};
+ INSN_VAR_LOCATION_LOC (insn->rtl()) = gen_rtx_UNKNOWN_VAR_LOC ();
+ crtl->ssa->change_insn (change);
+}
+
+// WIP
+static void
+rtl_ssa_dce_reset_dead_debug(std::unordered_set<insn_info *> &marked) {
+ for (insn_info *insn : crtl->ssa->all_insns()) {
+ if (!insn->is_debug_insn())
continue;
- }
- bool should_be_debug = true;
- for (def_info *def : insn->defs()) {
- // TODO : how to cast this correctly? - clobber_info
- // access_kind for def_insn is only SET or CLOBBER
- if (def->kind() == access_kind::CLOBBER)
- continue;
- set_info* si = as_a<set_info*>(def);
- // TODO : use has_nondebug_uses or has_nondebug_insn_uses - what is the
difference? phi?
- // after that we will use rtl-ssa change API to make the insn debug (it
will hopefully
- // recalculate has_nondebug_uses of other instructions...)
- for (use_info * use : si->all_uses()) {
- auto iii = use->insn()->is_debug_insn();
+ for (use_info * use: insn->uses()) {
+ if (marked.count(use->def()->insn()) == 0) {
+ reset_debug_insn_uses(insn);
+ break;
}
}
-
- if (!should_be_debug) {
- continue;
- }
-
- // TODO : perform a change
- /* Create DEBUG_EXPR (and DEBUG_EXPR_DECL). */
- rtx dval = make_debug_expr_from_rtl (SET_DEST (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 (set)),
- DEBUG_EXPR_TREE_DECL (dval),
- SET_SRC (set),
- VAR_INIT_STATUS_INITIALIZED);
-
- rtx_insn * bind = emit_debug_insn_before (bind_var_loc, rtl);
- // auto debug_insn = insn_info(insn->bb(), bind, 0);
- auto attempt = crtl->ssa->new_change_attempt ();
- auto change = insn_change(insn);
- // TODO : delete rtx from cfg and replace insn in ssa to debug_insn
- // delete_insn_and_edges or delete_insn - do we need to delete edges?
}
}
@@ -1681,6 +1611,8 @@ rtl_ssa_dce()
rtl_ssa_dce_init();
// debug(crtl->ssa);
std::unordered_set<insn_info *> marked = rtl_ssa_dce_mark();
+ if (MAY_HAVE_DEBUG_BIND_INSNS)
+ rtl_ssa_dce_reset_dead_debug(marked);
rtl_ssa_dce_sweep(marked);
// std::cerr << "\033[31m" << "SSA debug start" << "\033[0m" << "\n";
// debug (crtl->ssa);
