[gcc r14-8360] rtl-ssa: Ensure new defs get inserted [PR113070]

[gcc r14-8360] rtl-ssa: Ensure new defs get inserted [PR113070]

[Alex Coplan]

https://gcc.gnu.org/g:6dd613df59060fb54c4e3f66f39cf59bc44d118a

commit r14-8360-g6dd613df59060fb54c4e3f66f39cf59bc44d118a
Author: Alex Coplan <alex.coplan@arm.com>
Date:   Fri Jan 12 09:09:10 2024 +0000

    rtl-ssa: Ensure new defs get inserted [PR113070]
    
    In r14-5820-ga49befbd2c783e751dc2110b544fe540eb7e33eb I added support to
    RTL-SSA for inserting new insns, which included support for users
    creating new defs.
    
    However, I missed that apply_changes_to_insn needed updating to ensure
    that the new defs actually got inserted into the main def chain.  This
    meant that when the aarch64 ldp/stp pass inserted a new stp insn, the
    stp would just get skipped over during subsequent alias analysis, as its
    def never got inserted into the memory def chain.  This (unsurprisingly)
    led to wrong code.
    
    This patch fixes the issue by ensuring new user-created defs get
    inserted.  I would have preferred to have used a flag internal to the
    defs instead of a separate data structure to keep track of them, but since
    machine_mode increased to 16 bits we're already at 64 bits in access_info,
    and we can't really reuse m_is_temp as the logic in finalize_new_accesses
    requires it to get cleared.
    
    gcc/ChangeLog:
    
            PR target/113070
            * rtl-ssa.h: Include hash-set.h.
            * rtl-ssa/changes.cc (function_info::finalize_new_accesses): Add
            new_sets parameter and use it to keep track of new user-created sets.
            (function_info::apply_changes_to_insn): Also call add_def on new sets.
            (function_info::change_insns): Add hash_set to keep track of new
            user-created defs.  Plumb it through.
            * rtl-ssa/functions.h: Add hash_set parameter to finalize_new_accesses and
            apply_changes_to_insn.

Diff:
---
 gcc/rtl-ssa.h           |  1 +
 gcc/rtl-ssa/changes.cc  | 35 ++++++++++++++++++++++++++---------
 gcc/rtl-ssa/functions.h |  6 ++++--
 3 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/gcc/rtl-ssa.h b/gcc/rtl-ssa.h
index f0cf656f5ac..17337639ae8 100644
--- a/gcc/rtl-ssa.h
+++ b/gcc/rtl-ssa.h
@@ -50,6 +50,7 @@
 #include "mux-utils.h"
 #include "rtlanal.h"
 #include "cfgbuild.h"
+#include "hash-set.h"
 
 // Provides the global crtl->ssa.
 #include "memmodel.h"
diff --git a/gcc/rtl-ssa/changes.cc b/gcc/rtl-ssa/changes.cc
index 8181e5248c5..11639e81bb7 100644
--- a/gcc/rtl-ssa/changes.cc
+++ b/gcc/rtl-ssa/changes.cc
@@ -427,9 +427,11 @@ update_insn_in_place (insn_change &change)
 // pending clobbers into actual definitions.
 //
 // POS gives the final position of INSN, which hasn't yet been moved into
-// place.
+// place.  Keep track of any newly-created set_infos being added with this
+// change by adding them to NEW_SETS.
 void
-function_info::finalize_new_accesses (insn_change &change, insn_info *pos)
+function_info::finalize_new_accesses (insn_change &change, insn_info *pos,
+				      hash_set<def_info *> &new_sets)
 {
   insn_info *insn = change.insn ();
 
@@ -465,6 +467,12 @@ function_info::finalize_new_accesses (insn_change &change, insn_info *pos)
 		// later in case we see a second write to the same resource.
 		def_info *perm_def = allocate<set_info> (change.insn (),
 							 def->resource ());
+
+		// Keep track of the new set so we remember to add it to the
+		// def chain later.
+		if (new_sets.add (perm_def))
+		  gcc_unreachable (); // We shouldn't see duplicates here.
+
 		def->set_last_def (perm_def);
 		def = perm_def;
 	      }
@@ -643,9 +651,12 @@ function_info::finalize_new_accesses (insn_change &change, insn_info *pos)
 }
 
 // Copy information from CHANGE to its underlying insn_info, given that
-// the insn_info has already been placed appropriately.
+// the insn_info has already been placed appropriately.  NEW_SETS contains the
+// new set_infos that are being added as part of this change (as opposed to
+// being moved or repurposed from existing instructions).
 void
-function_info::apply_changes_to_insn (insn_change &change)
+function_info::apply_changes_to_insn (insn_change &change,
+				      hash_set<def_info *> &new_sets)
 {
   insn_info *insn = change.insn ();
   if (change.is_deletion ())
@@ -657,10 +668,11 @@ function_info::apply_changes_to_insn (insn_change &change)
   // Copy the cost.
   insn->set_cost (change.new_cost);
 
-  // Add all clobbers.  Sets and call clobbers never move relative to
-  // other definitions, so are OK as-is.
+  // Add all clobbers and newly-created sets.  Existing sets and call
+  // clobbers never move relative to other definitions, so are OK as-is.
   for (def_info *def : change.new_defs)
-    if (is_a<clobber_info *> (def) && !def->is_call_clobber ())
+    if ((is_a<clobber_info *> (def) && !def->is_call_clobber ())
+	|| (is_a<set_info *> (def) && new_sets.contains (def)))
       add_def (def);
 
   // Add all uses, now that their position is final.
@@ -791,6 +803,10 @@ function_info::change_insns (array_slice<insn_change *> changes)
       placeholders[i] = placeholder;
     }
 
+  // We need to keep track of newly-added sets as these need adding to
+  // the def chain later.
+  hash_set<def_info *> new_sets;
+
   // Finalize the new list of accesses for each change.  Don't install them yet,
   // so that we still have access to the old lists below.
   //
@@ -804,7 +820,8 @@ function_info::change_insns (array_slice<insn_change *> changes)
       insn_info *placeholder = placeholders[i];
       if (!change.is_deletion ())
 	finalize_new_accesses (change,
-			       placeholder ? placeholder : change.insn ());
+			       placeholder ? placeholder : change.insn (),
+			       new_sets);
     }
 
   // Remove all definitions that are no longer needed.  After the above,
@@ -859,7 +876,7 @@ function_info::change_insns (array_slice<insn_change *> changes)
 
   // Apply the changes to the underlying insn_infos.
   for (insn_change *change : changes)
-    apply_changes_to_insn (*change);
+    apply_changes_to_insn (*change, new_sets);
 
   // Now that the insns and accesses are up to date, add any REG_UNUSED notes.
   for (insn_change *change : changes)
diff --git a/gcc/rtl-ssa/functions.h b/gcc/rtl-ssa/functions.h
index e00a398069a..f5aca643beb 100644
--- a/gcc/rtl-ssa/functions.h
+++ b/gcc/rtl-ssa/functions.h
@@ -301,8 +301,10 @@ private:
   void process_uses_of_deleted_def (set_info *);
   insn_info *add_placeholder_after (insn_info *);
   void possibly_queue_changes (insn_change &);
-  void finalize_new_accesses (insn_change &, insn_info *);
-  void apply_changes_to_insn (insn_change &);
+  void finalize_new_accesses (insn_change &, insn_info *,
+			      hash_set<def_info *> &);
+  void apply_changes_to_insn (insn_change &,
+			      hash_set<def_info *> &);
 
   void init_function_data ();
   void calculate_potential_phi_regs (build_info &);