rtl-ssa: Provide easier access to debug uses [PR113089]

This patch adds some accessors to set_info and use_info to make it
easier to get at and iterate through uses in debug insns.

It is used by the aarch64 load/store pair fusion pass in a subsequent
patch to fix PR113089, i.e. to update debug uses in the pass.

gcc/ChangeLog:

	PR target/113089
	* rtl-ssa/accesses.h (use_info::next_debug_insn_use): New.
	(debug_insn_use_iterator): New.
	(set_info::first_debug_insn_use): New.
	(set_info::debug_insn_uses): New.
	* rtl-ssa/member-fns.inl (use_info::next_debug_insn_use): New.
	(set_info::first_debug_insn_use): New.
	(set_info::debug_insn_uses): New.

2 files changed, 42 insertions, 0 deletions

diff --git a/gcc/rtl-ssa/accesses.h b/gcc/rtl-ssa/accesses.h
index 6a3ecd3..c57b8a8 100644
--- a/gcc/rtl-ssa/accesses.h
+++ b/gcc/rtl-ssa/accesses.h
@@ -357,6 +357,10 @@ public:
   //    next_use () && next_use ()->is_in_any_insn () ? next_use () : nullptr
   use_info *next_any_insn_use () const;
 
+  // Return the next use by a debug instruction, or null if none.
+  // This is only valid if if is_in_debug_insn ().
+  use_info *next_debug_insn_use () const;
+
   // Return the previous use by a phi node in the list, or null if none.
   //
   // This is only valid if is_in_phi ().  It is equivalent to:
@@ -458,6 +462,8 @@ using reverse_use_iterator = list_iterator<use_info, &use_info::prev_use>;
 // of use in the same definition.
 using nondebug_insn_use_iterator
   = list_iterator<use_info, &use_info::next_nondebug_insn_use>;
+using debug_insn_use_iterator
+  = list_iterator<use_info, &use_info::next_debug_insn_use>;
 using any_insn_use_iterator
   = list_iterator<use_info, &use_info::next_any_insn_use>;
 using phi_use_iterator = list_iterator<use_info, &use_info::prev_phi_use>;
@@ -680,6 +686,10 @@ public:
   use_info *first_nondebug_insn_use () const;
   use_info *last_nondebug_insn_use () const;
 
+  // Return the first use of the set by debug instructions, or null if
+  // there is no such use.
+  use_info *first_debug_insn_use () const;
+
   // Return the first use of the set by any kind of instruction, or null
   // if there are no such uses.  The uses are in the order described above.
   use_info *first_any_insn_use () const;
@@ -731,6 +741,9 @@ public:
   // List the uses of the set by nondebug instructions, in reverse postorder.
   iterator_range<nondebug_insn_use_iterator> nondebug_insn_uses () const;
 
+  // List the uses of the set by debug instructions, in reverse postorder.
+  iterator_range<debug_insn_use_iterator> debug_insn_uses () const;
+
   // Return nondebug_insn_uses () in reverse order.
   iterator_range<reverse_use_iterator> reverse_nondebug_insn_uses () const;
 
diff --git a/gcc/rtl-ssa/member-fns.inl b/gcc/rtl-ssa/member-fns.inl
index 8e1c17c..e4825ad 100644
--- a/gcc/rtl-ssa/member-fns.inl
+++ b/gcc/rtl-ssa/member-fns.inl
@@ -120,6 +120,15 @@ use_info::next_any_insn_use () const
 }
 
 inline use_info *
+use_info::next_debug_insn_use () const
+{
+  if (auto use = next_use ())
+    if (use->is_in_debug_insn ())
+      return use;
+  return nullptr;
+}
+
+inline use_info *
 use_info::prev_phi_use () const
 {
   // This is used less often than next_nondebug_insn_use, so it doesn't
@@ -213,6 +222,20 @@ set_info::last_nondebug_insn_use () const
 }
 
 inline use_info *
+set_info::first_debug_insn_use () const
+{
+  use_info *use;
+  if (has_nondebug_insn_uses ())
+    use = last_nondebug_insn_use ()->next_use ();
+  else
+    use = first_use ();
+
+  if (use && use->is_in_debug_insn ())
+    return use;
+  return nullptr;
+}
+
+inline use_info *
 set_info::first_any_insn_use () const
 {
   if (m_first_use && m_first_use->is_in_any_insn ())
@@ -310,6 +333,12 @@ set_info::nondebug_insn_uses () const
   return { first_nondebug_insn_use (), nullptr };
 }
 
+inline iterator_range<debug_insn_use_iterator>
+set_info::debug_insn_uses () const
+{
+  return { first_debug_insn_use (), nullptr };
+}
+
 inline iterator_range<reverse_use_iterator>
 set_info::reverse_nondebug_insn_uses () const
 {