Hi,
This is a v2, original patch is here:
https://gcc.gnu.org/pipermail/gcc-patches/2023-November/637606.html
This addresses review feedback and:
- Fixes a bug in the previous version in
function_info::finalize_new_accesses; we should now correctly handle
the case where properties.refs () has two writes to a resource and we're
adding a new (temporary) set for that resource.
- Drops some handling for new uses which isn't needed now that RTL-SSA can
infer uses of mem (since g:505f1202e3a1a1aecd0df10d0f1620df6fea4ab5).
Bootstrapped/regtested as a series on aarch64-linux-gnu, OK for trunk?
Thanks,
Alex
-- >8 --
The upcoming aarch64 load pair pass needs to form store pairs, and can
re-order stores over loads when alias analysis determines this is safe.
In the case that both mem defs have uses in the RTL-SSA IR, and both
stores require re-ordering over their uses, we represent that as
(tentative) deletion of the original store insns and creation of a new
insn, to prevent requiring repeated re-parenting of uses during the
pass. We then update all mem uses that require re-parenting in one go
at the end of the pass.
To support this, RTL-SSA needs to handle inserting new insns (rather
than just changing existing ones), so this patch adds support for that.
New insns (and new accesses) are temporaries, allocated above a temporary
obstack_watermark, such that the user can easily back out of a change without
awkward bookkeeping.
gcc/ChangeLog:
* rtl-ssa/accesses.cc (function_info::create_set): New.
* rtl-ssa/accesses.h (access_info::is_temporary): New.
* rtl-ssa/changes.cc (move_insn): Handle new (temporary) insns.
(function_info::finalize_new_accesses): Handle new/temporary
user-created accesses.
(function_info::apply_changes_to_insn): Ensure m_is_temp flag
on new insns gets cleared.
(function_info::change_insns): Handle new/temporary insns.
(function_info::create_insn): New.
* rtl-ssa/changes.h (class insn_change): Make function_info a
friend class.
* rtl-ssa/functions.h (function_info): Declare new entry points:
create_set, create_insn. Declare new change_alloc helper.
* rtl-ssa/insns.cc (insn_info::print_full): Identify temporary insns in
dump.
* rtl-ssa/insns.h (insn_info): Add new m_is_temp flag and accompanying
is_temporary accessor.
* rtl-ssa/internals.inl (insn_info::insn_info): Initialize m_is_temp to
false.
* rtl-ssa/member-fns.inl (function_info::change_alloc): New.
* rtl-ssa/movement.h (restrict_movement_for_defs_ignoring): Add
handling for temporary defs.
diff --git a/gcc/rtl-ssa/accesses.cc b/gcc/rtl-ssa/accesses.cc
index 510545a8bad..76d70fd8bd3 100644
--- a/gcc/rtl-ssa/accesses.cc
+++ b/gcc/rtl-ssa/accesses.cc
@@ -1456,6 +1456,16 @@ function_info::make_uses_available (obstack_watermark
&watermark,
return use_array (new_uses, num_uses);
}
+set_info *
+function_info::create_set (obstack_watermark &watermark,
+ insn_info *insn,
+ resource_info resource)
+{
+ auto set = change_alloc<set_info> (watermark, insn, resource);
+ set->m_is_temp = true;
+ return set;
+}
+
// Return true if ACCESS1 can represent ACCESS2 and if ACCESS2 can
// represent ACCESS1.
static bool
diff --git a/gcc/rtl-ssa/accesses.h b/gcc/rtl-ssa/accesses.h
index fce31d46717..7e7a90ece97 100644
--- a/gcc/rtl-ssa/accesses.h
+++ b/gcc/rtl-ssa/accesses.h
@@ -204,6 +204,10 @@ public:
// in the main instruction pattern.
bool only_occurs_in_notes () const { return m_only_occurs_in_notes; }
+ // Return true if this is a temporary access, e.g. one created for
+ // an insn that is about to be inserted.
+ bool is_temporary () const { return m_is_temp; }
+
protected:
access_info (resource_info, access_kind);
diff --git a/gcc/rtl-ssa/changes.cc b/gcc/rtl-ssa/changes.cc
index aab532b9f26..2f2d12d5f30 100644
--- a/gcc/rtl-ssa/changes.cc
+++ b/gcc/rtl-ssa/changes.cc
@@ -394,14 +394,20 @@ move_insn (insn_change &change, insn_info *after)
// At the moment we don't support moving instructions between EBBs,
// but this would be worth adding if it's useful.
insn_info *insn = change.insn ();
- gcc_assert (after->ebb () == insn->ebb ());
+
bb_info *bb = after->bb ();
basic_block cfg_bb = bb->cfg_bb ();
- if (insn->bb () != bb)
- // Force DF to mark the old block as dirty.
- df_insn_delete (rtl);
- ::remove_insn (rtl);
+ if (!insn->is_temporary ())
+ {
+ gcc_assert (after->ebb () == insn->ebb ());
+
+ if (insn->bb () != bb)
+ // Force DF to mark the old block as dirty.
+ df_insn_delete (rtl);
+ ::remove_insn (rtl);
+ }
+
::add_insn_after (rtl, after_rtl, cfg_bb);
}
@@ -437,12 +443,33 @@ function_info::finalize_new_accesses (insn_change
&change, insn_info *pos)
{
def_info *def = find_access (change.new_defs, ref.regno);
gcc_assert (def);
+
+ if (def->m_is_temp && is_a<set_info *> (def) && def->last_def ())
+ {
+ // For temporary sets being added with this change, we keep track of
+ // the corresponding permanent def using the last_def link.
+ //
+ // So if we have one of these, follow it to get the permanent def.
+ def = def->last_def ();
+ gcc_assert (!def->m_is_temp && !def->m_has_been_superceded);
+ }
+
if (def->m_is_temp)
{
- // At present, the only temporary instruction definitions we
- // create are clobbers, such as those added during recog.
- gcc_assert (is_a<clobber_info *> (def));
- def = allocate<clobber_info> (change.insn (), ref.regno);
+ if (is_a<clobber_info *> (def))
+ def = allocate<clobber_info> (change.insn (), ref.regno);
+ else if (is_a<set_info *> (def))
+ {
+ // Install the permanent set in the last_def link of the
+ // temporary def. This allows us to find the permanent def
+ // later in case we see a second write to the same resource.
+ def_info *perm_def = allocate<set_info> (change.insn (),
+ def->resource ());
+ def->set_last_def (perm_def);
+ def = perm_def;
+ }
+ else
+ gcc_unreachable ();
}
else if (!def->m_has_been_superceded)
{
@@ -645,6 +672,8 @@ function_info::apply_changes_to_insn (insn_change &change)
insn->set_accesses (builder.finish ().begin (), num_defs, num_uses);
}
+
+ insn->m_is_temp = false;
}
// Add a temporary placeholder instruction after AFTER.
@@ -677,7 +706,8 @@ function_info::change_insns (array_slice<insn_change *>
changes)
if (!change->is_deletion ())
{
// Remove any notes that are no longer relevant.
- update_notes (change->rtl ());
+ if (!change->insn ()->m_is_temp)
+ update_notes (change->rtl ());
// Make sure that the placement of this instruction would still
// leave room for previous instructions.
@@ -686,6 +716,17 @@ function_info::change_insns (array_slice<insn_change *>
changes)
// verify_insn_changes is supposed to make sure that this holds.
gcc_unreachable ();
min_insn = later_insn (min_insn, change->move_range.first);
+
+ if (change->insn ()->m_is_temp)
+ {
+ change->m_insn = allocate<insn_info> (change->insn ()->bb (),
+ change->rtl (),
+ change->insn_uid ());
+
+ // Set the flag again so subsequent logic is aware.
+ // It will be cleared later on.
+ change->m_insn->m_is_temp = true;
+ }
}
}
@@ -784,7 +825,8 @@ function_info::change_insns (array_slice<insn_change *>
changes)
// Remove the placeholder first so that we have a wider range of
// program points when inserting INSN.
insn_info *after = placeholder->prev_any_insn ();
- remove_insn (insn);
+ if (!insn->is_temporary ())
+ remove_insn (insn);
remove_insn (placeholder);
insn->set_bb (after->bb ());
add_insn_after (insn, after);
@@ -1105,6 +1147,28 @@ function_info::perform_pending_updates ()
return changed_cfg;
}
+insn_info *
+function_info::create_insn (obstack_watermark &watermark,
+ rtx_code insn_code,
+ rtx pat)
+{
+ rtx_insn *rti = nullptr;
+
+ // TODO: extend, move in to emit-rtl.cc.
+ switch (insn_code)
+ {
+ case INSN:
+ rti = make_insn_raw (pat);
+ break;
+ default:
+ gcc_unreachable ();
+ }
+
+ auto insn = change_alloc<insn_info> (watermark, nullptr, rti, INSN_UID
(rti));
+ insn->m_is_temp = true;
+ return insn;
+}
+
// Print a description of CHANGE to PP.
void
rtl_ssa::pp_insn_change (pretty_printer *pp, const insn_change &change)
diff --git a/gcc/rtl-ssa/changes.h b/gcc/rtl-ssa/changes.h
index d56e3a646e2..d91cf432afe 100644
--- a/gcc/rtl-ssa/changes.h
+++ b/gcc/rtl-ssa/changes.h
@@ -32,6 +32,8 @@ namespace rtl_ssa {
// something that we might do.
class insn_change
{
+ friend class function_info;
+
public:
enum delete_action { DELETE };
diff --git a/gcc/rtl-ssa/functions.h b/gcc/rtl-ssa/functions.h
index ecb40fdaf57..4ffd3fa44e2 100644
--- a/gcc/rtl-ssa/functions.h
+++ b/gcc/rtl-ssa/functions.h
@@ -68,6 +68,16 @@ public:
// Return the SSA information for CFG_BB.
bb_info *bb (basic_block cfg_bb) const { return m_bbs[cfg_bb->index]; }
+ // Create a temporary def.
+ set_info *create_set (obstack_watermark &watermark,
+ insn_info *insn,
+ resource_info resource);
+
+ // Create a temporary insn with code INSN_CODE and pattern PAT.
+ insn_info *create_insn (obstack_watermark &watermark,
+ rtx_code insn_code,
+ rtx pat);
+
// Return a list of all the instructions in the function, in reverse
// postorder. The list includes both real and artificial instructions.
//
@@ -195,6 +205,10 @@ public:
// Print the contents of the function to PP.
void print (pretty_printer *pp) const;
+ // Allocate an object of type T above the obstack watermark WM.
+ template<typename T, typename... Ts>
+ T *change_alloc (obstack_watermark &wm, Ts... args);
+
private:
class bb_phi_info;
class build_info;
diff --git a/gcc/rtl-ssa/insns.cc b/gcc/rtl-ssa/insns.cc
index 5fde3f2bb4b..2fa48e0dacd 100644
--- a/gcc/rtl-ssa/insns.cc
+++ b/gcc/rtl-ssa/insns.cc
@@ -192,6 +192,11 @@ insn_info::print_full (pretty_printer *pp) const
pp_newline_and_indent (pp, 0);
pp_string (pp, "has volatile refs");
}
+ if (m_is_temp)
+ {
+ pp_newline_and_indent (pp, 0);
+ pp_string (pp, "temporary");
+ }
}
pp_indentation (pp) -= 2;
}
diff --git a/gcc/rtl-ssa/insns.h b/gcc/rtl-ssa/insns.h
index a604fe295cd..6d0506706ad 100644
--- a/gcc/rtl-ssa/insns.h
+++ b/gcc/rtl-ssa/insns.h
@@ -306,6 +306,8 @@ public:
// Print a full description of the instruction.
void print_full (pretty_printer *) const;
+ bool is_temporary () const { return m_is_temp; }
+
private:
// The first-order way of representing the order between instructions
// is to assign "program points", with higher point numbers coming
@@ -414,8 +416,11 @@ private:
unsigned int m_has_pre_post_modify : 1;
unsigned int m_has_volatile_refs : 1;
+ // Indicates the insn is a temporary / new user-allocated insn.
+ unsigned int m_is_temp : 1;
+
// For future expansion.
- unsigned int m_spare : 27;
+ unsigned int m_spare : 26;
// The program point at which the instruction occurs.
//
diff --git a/gcc/rtl-ssa/internals.inl b/gcc/rtl-ssa/internals.inl
index e49297c12b3..907c4504352 100644
--- a/gcc/rtl-ssa/internals.inl
+++ b/gcc/rtl-ssa/internals.inl
@@ -415,6 +415,7 @@ inline insn_info::insn_info (bb_info *bb, rtx_insn *rtl,
int cost_or_uid)
m_is_asm (false),
m_has_pre_post_modify (false),
m_has_volatile_refs (false),
+ m_is_temp (false),
m_spare (0),
m_point (0),
m_cost_or_uid (cost_or_uid),
diff --git a/gcc/rtl-ssa/member-fns.inl b/gcc/rtl-ssa/member-fns.inl
index ce2db045b78..b8940ca5566 100644
--- a/gcc/rtl-ssa/member-fns.inl
+++ b/gcc/rtl-ssa/member-fns.inl
@@ -962,4 +962,16 @@ function_info::add_regno_clobber (obstack_watermark
&watermark,
return true;
}
+template<typename T, typename... Ts>
+inline T *
+function_info::change_alloc (obstack_watermark &wm, Ts... args)
+{
+ static_assert (std::is_trivially_destructible<T>::value,
+ "destructor won't be called");
+ static_assert (alignof (T) <= obstack_alignment,
+ "too much alignment required");
+ void *addr = XOBNEW (wm, T);
+ return new (addr) T (std::forward<Ts> (args)...);
+}
+
}
diff --git a/gcc/rtl-ssa/movement.h b/gcc/rtl-ssa/movement.h
index ec076db406f..41226dd3666 100644
--- a/gcc/rtl-ssa/movement.h
+++ b/gcc/rtl-ssa/movement.h
@@ -182,6 +182,11 @@ restrict_movement_for_defs_ignoring (insn_range_info
&move_range,
{
for (def_info *def : defs)
{
+ // Skip fresh defs that are being inserted, as these shouldn't
+ // constrain movement.
+ if (def->is_temporary ())
+ continue;
+
// If the definition is a clobber, we can move it with respect
// to other clobbers.
//
@@ -247,7 +252,8 @@ restrict_movement_for_defs_ignoring (insn_range_info
&move_range,
// Make sure that we don't move stores between basic blocks, since we
// don't have enough information to tell whether it's safe.
- if (def_info *def = memory_access (defs))
+ def_info *def = memory_access (defs);
+ if (def && !def->is_temporary ())
{
move_range = move_later_than (move_range, def->bb ()->head_insn ());
move_range = move_earlier_than (move_range, def->bb ()->end_insn ());
