[PATCH 0/4] rtl-ssa: Some small, obvious fixes

[PATCH 0/4] rtl-ssa: Some small, obvious fixes

[Richard Sandiford]

This series contains some small fixes to RTL-SSA.  Tested on
aarch64-linux-gnu & x86_64-linux-gnu, pushed as obvious.

Richard Sandiford (4):
  rtl-ssa: Fix null deref in first_any_insn_use
  rtl-ssa: Fix handling of deleted insns
  rtl-ssa: Don't insert after insns that can throw
  rtl-ssa: Avoid creating duplicated phis

 gcc/rtl-ssa.h              | 1 +
 gcc/rtl-ssa/blocks.cc      | 5 +++++
 gcc/rtl-ssa/changes.cc     | 5 ++++-
 gcc/rtl-ssa/member-fns.inl | 2 +-
 gcc/rtl-ssa/movement.h     | 3 ++-
 5 files changed, 13 insertions(+), 3 deletions(-)

-- 
2.25.1

[PATCH 1/4] rtl-ssa: Fix null deref in first_any_insn_use

[Richard Sandiford]

first_any_insn_use implicitly (but contrary to its documentation)
assumed that there was at least one use.

gcc/
	* rtl-ssa/member-fns.inl (first_any_insn_use): Handle null
	m_first_use.
---
 gcc/rtl-ssa/member-fns.inl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/rtl-ssa/member-fns.inl b/gcc/rtl-ssa/member-fns.inl
index c127fab8b98..3fdca14e0ef 100644
--- a/gcc/rtl-ssa/member-fns.inl
+++ b/gcc/rtl-ssa/member-fns.inl
@@ -215,7 +215,7 @@ set_info::last_nondebug_insn_use () const
 inline use_info *
 set_info::first_any_insn_use () const
 {
-  if (m_first_use->is_in_any_insn ())
+  if (m_first_use && m_first_use->is_in_any_insn ())
     return m_first_use;
   return nullptr;
 }
-- 
2.25.1

[PATCH 2/4] rtl-ssa: Fix handling of deleted insns

[Richard Sandiford]

RTL-SSA queues up some invasive changes for later.  But sometimes
the insns involved in those changes can be deleted by later
optimisations, making the queued change unnecessary.  This patch
checks for that case.

gcc/
	* rtl-ssa/changes.cc (function_info::perform_pending_updates): Check
	whether an insn has been replaced by a note.
---
 gcc/rtl-ssa/changes.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/gcc/rtl-ssa/changes.cc b/gcc/rtl-ssa/changes.cc
index 73ab3ccfd24..de6222ae736 100644
--- a/gcc/rtl-ssa/changes.cc
+++ b/gcc/rtl-ssa/changes.cc
@@ -983,7 +983,10 @@ function_info::perform_pending_updates ()
   for (insn_info *insn : m_queued_insn_updates)
     {
       rtx_insn *rtl = insn->rtl ();
-      if (JUMP_P (rtl))
+      if (NOTE_P (rtl))
+	// The insn was later optimized away, typically to a NOTE_INSN_DELETED.
+	;
+      else if (JUMP_P (rtl))
 	{
 	  if (INSN_CODE (rtl) == NOOP_MOVE_INSN_CODE)
 	    {
-- 
2.25.1

[PATCH 3/4] rtl-ssa: Don't insert after insns that can throw

[Richard Sandiford]

rtl_ssa::can_insert_after didn't handle insns that can throw.
Fixing that avoids a regression with a later patch.

gcc/
	* rtl-ssa.h: Include cfgbuild.h.
	* rtl-ssa/movement.h (can_insert_after): Replace is_jump with the
	more comprehensive control_flow_insn_p.
---
 gcc/rtl-ssa.h          | 1 +
 gcc/rtl-ssa/movement.h | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/gcc/rtl-ssa.h b/gcc/rtl-ssa.h
index 7355c6c4463..3a3c8b50ee2 100644
--- a/gcc/rtl-ssa.h
+++ b/gcc/rtl-ssa.h
@@ -49,6 +49,7 @@
 #include "obstack-utils.h"
 #include "mux-utils.h"
 #include "rtlanal.h"
+#include "cfgbuild.h"
 
 // Provides the global crtl->ssa.
 #include "memmodel.h"
diff --git a/gcc/rtl-ssa/movement.h b/gcc/rtl-ssa/movement.h
index d9945f49172..67370947dbd 100644
--- a/gcc/rtl-ssa/movement.h
+++ b/gcc/rtl-ssa/movement.h
@@ -61,7 +61,8 @@ move_earlier_than (insn_range_info range, insn_info *insn)
 inline bool
 can_insert_after (insn_info *insn)
 {
-  return insn->is_bb_head () || (insn->is_real () && !insn->is_jump ());
+  return (insn->is_bb_head ()
+	  || (insn->is_real () && !control_flow_insn_p (insn->rtl ())));
 }
 
 // Try to restrict move range MOVE_RANGE so that it is possible to
-- 
2.25.1

[PATCH 4/4] rtl-ssa: Avoid creating duplicated phis

[Richard Sandiford]

If make_uses_available was called twice for the same use,
we could end up trying to create duplicate definitions for
the same extended live range.

gcc/
	* rtl-ssa/blocks.cc (function_info::create_degenerate_phi): Check
	whether the requested phi already exists.
---
 gcc/rtl-ssa/blocks.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gcc/rtl-ssa/blocks.cc b/gcc/rtl-ssa/blocks.cc
index d46cbf1e388..ecce7a68c59 100644
--- a/gcc/rtl-ssa/blocks.cc
+++ b/gcc/rtl-ssa/blocks.cc
@@ -525,6 +525,11 @@ function_info::create_phi (ebb_info *ebb, resource_info resource,
 phi_info *
 function_info::create_degenerate_phi (ebb_info *ebb, set_info *def)
 {
+  // Allow the function to be called twice in succession for the same def.
+  def_lookup dl = find_def (def->resource (), ebb->phi_insn ());
+  if (set_info *set = dl.matching_set ())
+    return as_a<phi_info *> (set);
+
   access_info *input = def;
   phi_info *phi = create_phi (ebb, def->resource (), &input, 1);
   if (def->is_reg ())
-- 
2.25.1