AArch64: Remove Cortex-A57 FMA steering pass

  As a minor cleanup remove Cortex-A57 FMA steering pass.  Since Cortex-A57 is
pretty old, there isn't any benefit of keeping this.

Passes regress & bootstrap, OK for commit?

gcc:
	* config.gcc (extra_objs): Remove cortex-a57-fma-steering.o.
	* config/aarch64/aarch64-passes.def: Remove pass_fma_steering.	
	* config/aarch64/aarch64-protos.h: Remove make_pass_fma_steering.
	* config/aarch64/aarch64-tuning-flags.def (RENAME_FMA_REGS): Remove.	
	* config/aarch64/cortex-a57-fma-steering.cc: Delete file.
	* config/aarch64/t-aarch64: Remove cortex-a57-fma-steering.o rules.	
	* config/aarch64/tuning_models/cortexa57.h (cortexa57_tunings):
        Remove RENAME_FMA_REGS tuning.

---
  

Wilco Dijkstra <Wilco.Dijkstra@arm.com> writes:
> As a minor cleanup remove Cortex-A57 FMA steering pass.  Since Cortex-A57 is
> pretty old, there isn't any benefit of keeping this.
>
> Passes regress & bootstrap, OK for commit?
>
> gcc:
> 	* config.gcc (extra_objs): Remove cortex-a57-fma-steering.o.
> 	* config/aarch64/aarch64-passes.def: Remove pass_fma_steering.	
> 	* config/aarch64/aarch64-protos.h: Remove make_pass_fma_steering.
> 	* config/aarch64/aarch64-tuning-flags.def (RENAME_FMA_REGS): Remove.	
> 	* config/aarch64/cortex-a57-fma-steering.cc: Delete file.
> 	* config/aarch64/t-aarch64: Remove cortex-a57-fma-steering.o rules.	
> 	* config/aarch64/tuning_models/cortexa57.h (cortexa57_tunings):
>         Remove RENAME_FMA_REGS tuning.

This would probably be a reasonable compromise if the pass ever became a
maintenance burden.  But I'm not sure the pass is a burden at the moment.
TBH, I don't remember having had to think about it for years :)

So IMO we should keep the pass, but reconsider removing it if in future
it requires non-trivial effort to keep working.

That said, the fact the patch requires no testsuite changes suggests
that the pass could easily become ineffective without anyone noticing.
So I won't object if other maintainers are in favour.

Thanks,
Richard

>
> ---
>
> diff --git a/gcc/config.gcc b/gcc/config.gcc
> index 55e37146ee0356b67b8a1a09d263eccdf69cd91a..97ef3ae77fb97b347ba43e55f7a05f5438a96a43 100644
> --- a/gcc/config.gcc
> +++ b/gcc/config.gcc
> @@ -350,7 +350,7 @@ aarch64*-*-*)
>  	c_target_objs="aarch64-c.o"
>  	cxx_target_objs="aarch64-c.o"
>  	d_target_objs="aarch64-d.o"
> -	extra_objs="aarch64-builtins.o aarch-common.o aarch64-sve-builtins.o aarch64-sve-builtins-shapes.o aarch64-sve-builtins-base.o aarch64-sve-builtins-sve2.o aarch64-sve-builtins-sme.o cortex-a57-fma-steering.o aarch64-speculation.o aarch-bti-insert.o aarch64-cc-fusion.o aarch64-early-ra.o aarch64-ldp-fusion.o"
> +	extra_objs="aarch64-builtins.o aarch-common.o aarch64-sve-builtins.o aarch64-sve-builtins-shapes.o aarch64-sve-builtins-base.o aarch64-sve-builtins-sve2.o aarch64-sve-builtins-sme.o aarch64-speculation.o aarch-bti-insert.o aarch64-cc-fusion.o aarch64-early-ra.o aarch64-ldp-fusion.o"
>  	target_gtfiles="\$(srcdir)/config/aarch64/aarch64-protos.h \$(srcdir)/config/aarch64/aarch64-builtins.h \$(srcdir)/config/aarch64/aarch64-builtins.cc \$(srcdir)/config/aarch64/aarch64-sve-builtins.h \$(srcdir)/config/aarch64/aarch64-sve-builtins.cc"
>  	target_has_targetm_common=yes
>  	;;
> diff --git a/gcc/config/aarch64/aarch64-passes.def b/gcc/config/aarch64/aarch64-passes.def
> index 9cf9d3e13b2cb0d0bf9c34439785e8ca704230fe..d80b9c6f39c3b56aa6251a81590172f70b31e01e 100644
> --- a/gcc/config/aarch64/aarch64-passes.def
> +++ b/gcc/config/aarch64/aarch64-passes.def
> @@ -19,7 +19,6 @@
>     <http://www.gnu.org/licenses/>.  */
>  
>  INSERT_PASS_BEFORE (pass_sched, 1, pass_aarch64_early_ra);
> -INSERT_PASS_AFTER (pass_regrename, 1, pass_fma_steering);
>  INSERT_PASS_BEFORE (pass_reorder_blocks, 1, pass_track_speculation);
>  INSERT_PASS_BEFORE (pass_late_thread_prologue_and_epilogue, 1, pass_switch_pstate_sm);
>  INSERT_PASS_BEFORE (pass_late_thread_prologue_and_epilogue, 1, pass_late_track_speculation);
> diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
> index fa7bc8029be04f6530d2aee2ead4d754ba3b2550..afdf7d01adb3bdafd15d0422c3b2dfd680383bef 100644
> --- a/gcc/config/aarch64/aarch64-protos.h
> +++ b/gcc/config/aarch64/aarch64-protos.h
> @@ -1199,7 +1199,6 @@ std::string aarch64_get_extension_string_for_isa_flags (aarch64_feature_flags,
>  							aarch64_feature_flags);
>  
>  rtl_opt_pass *make_pass_aarch64_early_ra (gcc::context *);
> -rtl_opt_pass *make_pass_fma_steering (gcc::context *);
>  rtl_opt_pass *make_pass_track_speculation (gcc::context *);
>  rtl_opt_pass *make_pass_late_track_speculation (gcc::context *);
>  rtl_opt_pass *make_pass_insert_bti (gcc::context *ctxt);
> diff --git a/gcc/config/aarch64/aarch64-tuning-flags.def b/gcc/config/aarch64/aarch64-tuning-flags.def
> index 1feff3beb348f45c254c5a7c346a1a9674dee362..b1ab068f4073f459e829503f59c9de236cffb63a 100644
> --- a/gcc/config/aarch64/aarch64-tuning-flags.def
> +++ b/gcc/config/aarch64/aarch64-tuning-flags.def
> @@ -28,8 +28,6 @@
>       INTERNAL_NAME gives the internal name suitable for appending to
>       AARCH64_TUNE_ to give an enum name. */
>  
> -AARCH64_EXTRA_TUNING_OPTION ("rename_fma_regs", RENAME_FMA_REGS)
> -
>  /* Some of the optional shift to some arthematic instructions are
>     considered cheap.  Logical shift left <=4 with or without a
>     zero extend are considered cheap.  Sign extend; non logical shift left
> diff --git a/gcc/config/aarch64/cortex-a57-fma-steering.cc b/gcc/config/aarch64/cortex-a57-fma-steering.cc
> deleted file mode 100644
> index fd6da66d855e36cd023b5343c392cd2f7f062d1b..0000000000000000000000000000000000000000
> --- a/gcc/config/aarch64/cortex-a57-fma-steering.cc
> +++ /dev/null
> @@ -1,1096 +0,0 @@
> -/* FMA steering optimization pass for Cortex-A57.
> -   Copyright (C) 2015-2025 Free Software Foundation, Inc.
> -   Contributed by ARM Ltd.
> -
> -   This file is part of GCC.
> -
> -   GCC is free software; you can redistribute it and/or modify it
> -   under the terms of the GNU General Public License as published by
> -   the Free Software Foundation; either version 3, or (at your option)
> -   any later version.
> -
> -   GCC is distributed in the hope that it will be useful, but
> -   WITHOUT ANY WARRANTY; without even the implied warranty of
> -   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> -   General Public License for more details.
> -
> -   You should have received a copy of the GNU General Public License
> -   along with GCC; see the file COPYING3.  If not see
> -   <http://www.gnu.org/licenses/>.  */
> -
> -#define IN_TARGET_CODE 1
> -
> -#include "config.h"
> -#define INCLUDE_LIST
> -#include "system.h"
> -#include "coretypes.h"
> -#include "backend.h"
> -#include "target.h"
> -#include "rtl.h"
> -#include "df.h"
> -#include "insn-config.h"
> -#include "regs.h"
> -#include "memmodel.h"
> -#include "emit-rtl.h"
> -#include "recog.h"
> -#include "cfganal.h"
> -#include "insn-attr.h"
> -#include "context.h"
> -#include "tree-pass.h"
> -#include "function-abi.h"
> -#include "regrename.h"
> -#include "aarch64-protos.h"
> -
> -/* For better performance, the destination of FMADD/FMSUB instructions should
> -   have the same parity as their accumulator register if the accumulator
> -   contains the result of a previous FMUL or FMADD/FMSUB instruction if
> -   targetting Cortex-A57 processors.  Performance is also increased by
> -   otherwise keeping a good balance in the parity of the destination register
> -   of FMUL or FMADD/FMSUB.
> -
> -   This pass ensure that registers are renamed so that these conditions hold.
> -   We reuse the existing register renaming facility from regrename.cc to build
> -   dependency chains and expose candidate registers for renaming.
> -
> -
> -   The algorithm has three steps:
> -
> -   First, the functions of the register renaming pass are called.  These
> -   analyze the instructions and produce a list of def/use chains of
> -   instructions.
> -
> -   Next, this information is used to build trees of multiply and
> -   multiply-accumulate instructions.  The roots of these trees are any
> -   multiply, or any multiply-accumulate whose accumulator is not dependent on
> -   a multiply or multiply-accumulate instruction.  A child is added to the
> -   tree where a dependency chain exists between the result of the parent
> -   instruction and the accumulator operand of the child, as in the diagram
> -   below:
> -
> -		 fmul s2, s0, s1
> -		/		\
> -   fmadd s0, s1, s1, s2   fmadd s4, s1, s1 s2
> -	    |
> -   fmadd s3, s1, s1, s0
> -
> -   Trees made of a single instruction are permitted.
> -
> -   Finally, renaming is performed.  The parity of the destination register at
> -   the root of a tree is checked against the current balance of multiply and
> -   multiply-accumulate on each pipeline.  If necessary, the root of a tree is
> -   renamed, in which case the rest of the tree is then renamed to keep the same
> -   parity in the destination registers of all instructions in the tree.  */
> -
> -
> -
> -/* Forward declarations.  */
> -class fma_node;
> -class fma_root_node;
> -class func_fma_steering;
> -
> -/* Dependencies between FMUL or FMADD/FMSUB instructions and subsequent
> -   FMADD/FMSUB instructions form a graph.  This is because alternatives can
> -   make a register be set by several FMUL or FMADD/FMSUB instructions in
> -   different basic blocks and because of loops.  For ease of browsing, the
> -   connected components of this graph are broken up into forests of trees.
> -   Forests are represented by fma_forest objects, contained in the fma_forests
> -   list.  Using a separate object for the forests allows for a better use of
> -   memory as there is some information that is global to each forest, such as
> -   the number of FMSUB and FMADD/FMSUB instructions currently scheduled on each
> -   floating-point execution pipelines.  */
> -
> -class fma_forest
> -{
> -public:
> -  fma_forest (func_fma_steering *, fma_root_node *, int);
> -  ~fma_forest ();
> -
> -  int get_id ();
> -  std::list<fma_root_node *> *get_roots ();
> -  func_fma_steering *get_globals ();
> -  int get_target_parity ();
> -  void fma_node_created (fma_node *);
> -  void merge_forest (fma_forest *);
> -  void dump_info ();
> -  void dispatch ();
> -
> -private:
> -  /* Prohibit copy construction.  */
> -  fma_forest (const fma_forest &);
> -
> -  /* The list of roots that form this forest.  */
> -  std::list<fma_root_node *> *m_roots;
> -
> -  /* Target parity the destination register of all FMUL and FMADD/FMSUB
> -     instructions in this forest should have.  */
> -  int m_target_parity;
> -
> -  /* Link to the instance of func_fma_steering holding data related to the
> -     FMA steering of the current function (cfun).  */
> -  func_fma_steering *m_globals;
> -
> -  /* Identifier for the forest (used for dumps).  */
> -  int m_id;
> -
> -  /* Total number of nodes in the forest (for statistics).  */
> -  int m_nb_nodes;
> -};
> -
> -class fma_node
> -{
> -public:
> -  fma_node (fma_node *parent, du_chain *chain);
> -  ~fma_node ();
> -
> -  bool root_p ();
> -  fma_forest *get_forest ();
> -  std::list<fma_node *> *get_children ();
> -  rtx_insn *get_insn ();
> -  void add_child (fma_node *);
> -  int get_parity ();
> -  void set_head (du_head *);
> -  void rename (fma_forest *);
> -  void dump_info (fma_forest *);
> -
> -private:
> -  /* Prohibit copy construction.  */
> -  fma_node (const fma_node &);
> -
> -protected:
> -  /* Root node that lead to this node.  */
> -  fma_root_node *m_root;
> -
> -  /* The parent node of this node.  If the node belong to a chain with several
> -     parent nodes, the first one encountered in a depth-first search is chosen
> -     as canonical parent.  */
> -  fma_node *m_parent;
> -
> -  /* The list of child nodes.  If a chain contains several parent nodes, one is
> -     chosen as canonical parent and the others will have no children.  */
> -  std::list<fma_node *> *m_children;
> -
> -  /* The associated DU_HEAD chain that the insn represented by this object
> -     is (one of) the root of.  When a chain contains several roots, the non
> -     canonical ones have this field set to NULL.  */
> -  struct du_head *m_head;
> -
> -  /* The FMUL or FMADD/FMSUB instruction this object corresponds to.  */
> -  rtx_insn *m_insn;
> -};
> -
> -class fma_root_node : public fma_node
> -{
> -public:
> -  fma_root_node (func_fma_steering *, du_chain *, int);
> -
> -  fma_forest *get_forest ();
> -  void set_forest (fma_forest *);
> -  void dump_info (fma_forest *);
> -
> -private:
> -  /* The forest this node belonged to when it was created.  */
> -  fma_forest *m_forest;
> -};
> -
> -/* Class holding all data and methods relative to the FMA steering of a given
> -   function.  The FMA steering pass could then run in parallel for different
> -   functions.  */
> -
> -class func_fma_steering
> -{
> -public:
> -  func_fma_steering ();
> -  ~func_fma_steering ();
> -
> -  int get_fpu_balance ();
> -  void remove_forest (fma_forest *);
> -  bool put_node (fma_node *);
> -  void update_balance (int);
> -  fma_node *get_fma_node (rtx_insn *);
> -  void analyze_fma_fmul_insn (fma_forest *, du_chain *, du_head_p);
> -  void execute_fma_steering ();
> -
> -private:
> -  /* Prohibit copy construction.  */
> -  func_fma_steering (const func_fma_steering &);
> -
> -  void dfs (void (*) (fma_forest *), void (*) (fma_forest *, fma_root_node *),
> -	    void (*) (fma_forest *, fma_node *), bool);
> -  void analyze ();
> -  void rename_fma_trees ();
> -
> -  /* Mapping between FMUL or FMADD/FMSUB instructions and the associated
> -     fma_node object.  Used when analyzing an instruction that is a root of
> -     a chain to find if such an object was created because this instruction
> -     is also a use in another chain.  */
> -  hash_map<rtx_insn *, fma_node *> *m_insn_fma_head_map;
> -
> -  /* A list of all the forests in a given function.  */
> -  std::list<fma_forest *> m_fma_forests;
> -
> -  /* Balance of FMUL and FMADD/FMSUB instructions between the two FPU
> -     pipelines:
> -     < 0: more instruction dispatched to the first pipeline
> -     == 0: perfect balance
> -     > 0: more instruction dispatched to the second pipeline.  */
> -  int m_fpu_balance;
> -
> -  /* Identifier for the next forest created.  */
> -  int m_next_forest_id;
> -};
> -
> -/* Rename the register HEAD->regno in all the insns in the chain HEAD to any
> -   register not in the set UNAVAILABLE.  Adapted from rename_chains in
> -   regrename.cc.  */
> -
> -static bool
> -rename_single_chain (du_head_p head, HARD_REG_SET *unavailable)
> -{
> -  int best_new_reg;
> -  int n_uses = 0;
> -  struct du_chain *tmp;
> -  int reg = head->regno;
> -  enum reg_class super_class = NO_REGS;
> -
> -  if (head->cannot_rename)
> -    return false;
> -
> -  if (fixed_regs[reg] || global_regs[reg]
> -      || (frame_pointer_needed && reg == HARD_FRAME_POINTER_REGNUM))
> -    return false;
> -
> -  /* Iterate over elements in the chain in order to:
> -     1. Count number of uses, and narrow the set of registers we can
> -	use for renaming.
> -     2. Compute the superunion of register classes in this chain.  */
> -  for (tmp = head->first; tmp; tmp = tmp->next_use)
> -    {
> -      if (DEBUG_INSN_P (tmp->insn))
> -	continue;
> -      n_uses++;
> -      *unavailable |= ~reg_class_contents[tmp->cl];
> -      super_class = reg_class_superunion[(int) super_class][(int) tmp->cl];
> -    }
> -
> -  if (n_uses < 1)
> -    return false;
> -
> -  best_new_reg = find_rename_reg (head, super_class, unavailable, reg,
> -				  false);
> -
> -  if (dump_file)
> -    {
> -      fprintf (dump_file, "Register %s in insn %d", reg_names[reg],
> -	       INSN_UID (head->first->insn));
> -      if (head->call_abis)
> -	fprintf (dump_file, " crosses a call");
> -    }
> -
> -  if (best_new_reg == reg)
> -    {
> -      if (dump_file)
> -	fprintf (dump_file, "; no available better choice\n");
> -      return false;
> -    }
> -
> -  if (regrename_do_replace (head, best_new_reg))
> -    {
> -      if (dump_file)
> -	fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);
> -      df_set_regs_ever_live (best_new_reg, true);
> -    }
> -  else
> -    {
> -      if (dump_file)
> -	fprintf (dump_file, ", renaming as %s failed\n",
> -		 reg_names[best_new_reg]);
> -      return false;
> -    }
> -  return true;
> -}
> -
> -/* Return whether T is the attribute of a FMADD/FMSUB-like instruction.  */
> -
> -static bool
> -is_fmac_op (enum attr_type t)
> -{
> -  return (t == TYPE_FMACS) || (t == TYPE_FMACD) || (t == TYPE_NEON_FP_MLA_S);
> -}
> -
> -/* Return whether T is the attribute of a FMUL instruction.  */
> -
> -static bool
> -is_fmul_op (enum attr_type t)
> -{
> -  return (t == TYPE_FMULS) || (t == TYPE_FMULD) || (t == TYPE_NEON_FP_MUL_S);
> -}
> -
> -/* Return whether INSN is an FMUL (if FMUL_OK is true) or FMADD/FMSUB
> -   instruction.  */
> -
> -static bool
> -is_fmul_fmac_insn (rtx_insn *insn, bool fmul_ok)
> -{
> -  enum attr_type t;
> -
> -  if (!NONDEBUG_INSN_P (insn))
> -    return false;
> -
> -  if (recog_memoized (insn) < 0)
> -    return false;
> -
> -  /* Only consider chain(s) this instruction is a root of if this is an FMUL or
> -     FMADD/FMSUB instruction.  This allows to avoid browsing chains of all
> -     instructions for FMUL or FMADD/FMSUB in them.  */
> -  t = get_attr_type (insn);
> -  return is_fmac_op (t) || (fmul_ok && is_fmul_op (t));
> -}
> -
> -
> -/*
> - * Class fma_forest method definitions.
> - */
> -
> -fma_forest::fma_forest (func_fma_steering *fma_steer, fma_root_node *fma_root,
> -			int id)
> -{
> -      memset (this, 0, sizeof (*this));
> -      this->m_globals = fma_steer;
> -      this->m_roots = new std::list<fma_root_node *>;
> -      this->m_roots->push_back (fma_root);
> -      this->m_id = id;
> -}
> -
> -fma_forest::~fma_forest ()
> -{
> -  delete this->m_roots;
> -}
> -
> -int
> -fma_forest::get_id ()
> -{
> -  return this->m_id;
> -}
> -
> -std::list<fma_root_node *> *
> -fma_forest::get_roots ()
> -{
> -  return this->m_roots;
> -}
> -
> -func_fma_steering *
> -fma_forest::get_globals ()
> -{
> -  return this->m_globals;
> -}
> -
> -int
> -fma_forest::get_target_parity ()
> -{
> -  return this->m_target_parity;
> -}
> -
> -/* Act on the creation of NODE by updating statistics in FOREST and adding an
> -   entry for it in the func_fma_steering hashmap.  */
> -
> -void fma_forest::fma_node_created (fma_node *node)
> -{
> -  bool created = !this->m_globals->put_node (node);
> -
> -  gcc_assert (created);
> -  this->m_nb_nodes++;
> -}
> -
> -/* Merge REF_FOREST and OTHER_FOREST together, making REF_FOREST the canonical
> -   fma_forest object to represent both.  */
> -
> -void
> -fma_forest::merge_forest (fma_forest *other_forest)
> -{
> -  std::list<fma_root_node *> *other_roots;
> -  std::list<fma_root_node *>::iterator other_root_iter;
> -
> -  if (this == other_forest)
> -    return;
> -
> -  other_roots = other_forest->m_roots;
> -
> -  /* Update root nodes' pointer to forest.  */
> -  for (other_root_iter = other_roots->begin ();
> -       other_root_iter != other_roots->end (); ++other_root_iter)
> -    (*other_root_iter)->set_forest (this);
> -
> -  /* Remove other_forest from the list of forests and move its tree roots in
> -     the list of tree roots of ref_forest.  */
> -  this->m_globals->remove_forest (other_forest);
> -  this->m_roots->splice (this->m_roots->begin (), *other_roots);
> -  this->m_nb_nodes += other_forest->m_nb_nodes;
> -
> -  delete other_forest;
> -}
> -
> -/* Dump information about the forest FOREST.  */
> -
> -void
> -fma_forest::dump_info ()
> -{
> -  gcc_assert (dump_file);
> -
> -  fprintf (dump_file, "Forest #%d has %d nodes\n", this->m_id,
> -	   this->m_nb_nodes);
> -}
> -
> -/* Wrapper around fma_forest::dump_info for use as parameter of function
> -   pointer type in func_fma_steering::dfs.  */
> -
> -static void
> -dump_forest_info (fma_forest *forest)
> -{
> -  forest->dump_info ();
> -}
> -
> -/* Dispatch forest to the least utilized pipeline.  */
> -
> -void
> -fma_forest::dispatch ()
> -{
> -  this->m_target_parity = this->m_roots->front ()->get_parity ();
> -  int fpu_balance = this->m_globals->get_fpu_balance ();
> -  if (fpu_balance != 0)
> -    this->m_target_parity = (fpu_balance < 0);
> -
> -  if (dump_file)
> -    fprintf (dump_file, "Target parity for forest #%d: %s\n", this->m_id,
> -	     this->m_target_parity ? "odd" : "even");
> -}
> -
> -/* Wrapper around fma_forest::dispatch for use as parameter of function pointer
> -   type in func_fma_steering::dfs.  */
> -
> -static void
> -dispatch_forest (fma_forest *forest)
> -{
> -  forest->dispatch ();
> -}
> -
> -fma_node::fma_node (fma_node *parent, du_chain *chain)
> -{
> -  memset (this, 0, sizeof (*this));
> -  this->m_parent = parent;
> -  this->m_children = new std::list<fma_node *>;
> -  this->m_insn = chain->insn;
> -  /* root_p () cannot be used to check for root before root is set.  */
> -  if (this->m_parent == this)
> -    this->m_root = static_cast<fma_root_node *> (parent);
> -  else
> -    {
> -      this->m_root = parent->m_root;
> -      this->get_forest ()->fma_node_created (this);
> -    }
> -}
> -
> -fma_node::~fma_node ()
> -{
> -  delete this->m_children;
> -}
> -
> -std::list<fma_node *> *
> -fma_node::get_children ()
> -{
> -  return this->m_children;
> -}
> -
> -rtx_insn *
> -fma_node::get_insn ()
> -{
> -  return this->m_insn;
> -}
> -
> -void
> -fma_node::set_head (du_head *head)
> -{
> -  gcc_assert (!this->m_head);
> -  this->m_head = head;
> -}
> -
> -/* Add a child to this node in the list of children.  */
> -
> -void
> -fma_node::add_child (fma_node *child)
> -{
> -  this->m_children->push_back (child);
> -}
> -
> -/* Return the parity of the destination register of the instruction represented
> -   by this node.  */
> -
> -int
> -fma_node::get_parity ()
> -{
> -  return this->m_head->regno % 2;
> -}
> -
> -/* Get the actual forest associated with a non root node as the one the node
> -   points to might have been merged into another one.  In that case the pointer
> -   in the root nodes are updated so we return the forest pointer of a root node
> -   pointed to by the initial forest.  Despite being a oneliner, this method is
> -   defined here as it references a method from fma_root_node.  */
> -
> -fma_forest *
> -fma_node::get_forest ()
> -{
> -  return this->m_root->get_forest ();
> -}
> -
> -/* Return whether a node is a root node.  */
> -
> -bool
> -fma_node::root_p ()
> -{
> -  return this->m_root == this;
> -}
> -
> -/* Dump information about the children of node FMA_NODE in forest FOREST.  */
> -
> -void
> -fma_node::dump_info (ATTRIBUTE_UNUSED fma_forest *forest)
> -{
> -  struct du_chain *chain;
> -  std::list<fma_node *>::iterator fma_child;
> -
> -  gcc_assert (dump_file);
> -
> -  if (this->get_children ()->empty ())
> -    return;
> -
> -  fprintf (dump_file, "Instruction(s)");
> -  for (chain = this->m_head->first; chain; chain = chain->next_use)
> -    {
> -      if (!is_fmul_fmac_insn (chain->insn, true))
> -	continue;
> -
> -      if (chain->loc != &SET_DEST (PATTERN (chain->insn)))
> -	continue;
> -
> -      fprintf (dump_file, " %d", INSN_UID (chain->insn));
> -    }
> -
> -  fprintf (dump_file, " is(are) accumulator dependency of instructions");
> -  for (fma_child = this->get_children ()->begin ();
> -       fma_child != this->get_children ()->end (); fma_child++)
> -    fprintf (dump_file, " %d", INSN_UID ((*fma_child)->m_insn));
> -  fprintf (dump_file, "\n");
> -}
> -
> -/* Wrapper around fma_node::dump_info for use as parameter of function pointer
> -   type in func_fma_steering::dfs.  */
> -
> -static void
> -dump_tree_node_info (fma_forest *forest, fma_node *node)
> -{
> -  node->dump_info (forest);
> -}
> -
> -/* Rename the destination register of a single FMUL or FMADD/FMSUB instruction
> -   represented by FMA_NODE to a register that respect the target parity for
> -   FOREST or with same parity of the instruction represented by its parent node
> -   if it has one.  */
> -
> -void
> -fma_node::rename (fma_forest *forest)
> -{
> -  int cur_parity, target_parity;
> -
> -  /* This is alternate root of a chain and thus has no children.  It will be
> -     renamed when processing the canonical root for that chain.  */
> -  if (!this->m_head)
> -    return;
> -
> -  target_parity = forest->get_target_parity ();
> -  if (this->m_parent)
> -    target_parity = this->m_parent->get_parity ();
> -  cur_parity = this->get_parity ();
> -
> -  /* Rename if parity differs.  */
> -  if (cur_parity != target_parity)
> -    {
> -      rtx_insn *insn = this->m_insn;
> -      HARD_REG_SET unavailable;
> -      machine_mode mode;
> -      int reg;
> -
> -      if (dump_file)
> -	{
> -	  unsigned cur_dest_reg = this->m_head->regno;
> -
> -	  fprintf (dump_file, "FMA or FMUL at insn %d but destination "
> -		   "register (%s) has different parity from expected to "
> -		   "maximize FPU pipeline utilization\n", INSN_UID (insn),
> -		   reg_names[cur_dest_reg]);
> -	}
> -
> -      /* Don't clobber traceback for noreturn functions.  */
> -      CLEAR_HARD_REG_SET (unavailable);
> -      if (frame_pointer_needed)
> -	{
> -	  add_to_hard_reg_set (&unavailable, Pmode, FRAME_POINTER_REGNUM);
> -	  add_to_hard_reg_set (&unavailable, Pmode, HARD_FRAME_POINTER_REGNUM);
> -	}
> -
> -      /* Exclude registers with wrong parity.  */
> -      mode = GET_MODE (SET_DEST (PATTERN (insn)));
> -      for (reg = cur_parity; reg < FIRST_PSEUDO_REGISTER; reg += 2)
> -	add_to_hard_reg_set (&unavailable, mode, reg);
> -
> -      if (!rename_single_chain (this->m_head, &unavailable))
> -	{
> -	  if (dump_file)
> -	    fprintf (dump_file, "Destination register of insn %d could not be "
> -		     "renamed. Dependent FMA insns will use this parity from "
> -		     "there on.\n", INSN_UID (insn));
> -	}
> -      else
> -	cur_parity = target_parity;
> -    }
> -
> -  forest->get_globals ()->update_balance (cur_parity);
> -}
> -
> -/* Wrapper around fma_node::dump_info for use as parameter of function pointer
> -   type in func_fma_steering::dfs.  */
> -
> -static void
> -rename_fma_node (fma_forest *forest, fma_node *node)
> -{
> -  node->rename (forest);
> -}
> -
> -fma_root_node::fma_root_node (func_fma_steering *globals, du_chain *chain,
> -			      int id) : fma_node (this, chain)
> -{
> -  this->m_forest = new fma_forest (globals, this, id);
> -  this->m_forest->fma_node_created (this);
> -}
> -
> -fma_forest *
> -fma_root_node::get_forest ()
> -{
> -  return this->m_forest;
> -}
> -
> -void
> -fma_root_node::set_forest (fma_forest *ref_forest)
> -{
> -  this->m_forest = ref_forest;
> -}
> -
> -/* Dump information about the roots of forest FOREST.  */
> -
> -void
> -fma_root_node::dump_info (fma_forest *forest)
> -{
> -  gcc_assert (dump_file);
> -
> -  if (this == forest->get_roots ()->front ())
> -    fprintf (dump_file, "Instruction(s) at root of forest #%d:",
> -	     forest->get_id ());
> -  fprintf (dump_file, " %d", INSN_UID (this->m_insn));
> -  if (this == forest->get_roots ()->back ())
> -    fprintf (dump_file, "\n");
> -}
> -
> -/* Wrapper around fma_root_node::dump_info for use as parameter of function
> -   pointer type in func_fma_steering::dfs.  */
> -
> -static void
> -dump_tree_root_info (fma_forest *forest, fma_root_node *node)
> -{
> -  node->dump_info (forest);
> -}
> -
> -func_fma_steering::func_fma_steering () : m_fpu_balance (0)
> -{
> -  this->m_insn_fma_head_map = new hash_map<rtx_insn *, fma_node *>;
> -  this->m_fma_forests.clear ();
> -  this->m_next_forest_id = 0;
> -}
> -
> -func_fma_steering::~func_fma_steering ()
> -{
> -  delete this->m_insn_fma_head_map;
> -}
> -
> -int
> -func_fma_steering::get_fpu_balance ()
> -{
> -  return this->m_fpu_balance;
> -}
> -
> -void
> -func_fma_steering::remove_forest (fma_forest *forest)
> -{
> -  this->m_fma_forests.remove (forest);
> -}
> -
> -/* Memorize the mapping of this instruction to its fma_node object and return
> -   whether such a mapping existed.  */
> -
> -bool
> -func_fma_steering::put_node (fma_node *node)
> -{
> -  return this->m_insn_fma_head_map->put (node->get_insn (), node);
> -}
> -
> -/* Update the current balance considering a node with the given PARITY.  */
> -
> -void
> -func_fma_steering::update_balance (int parity)
> -{
> -  this->m_fpu_balance = parity ? this->m_fpu_balance + 1
> -			       : this->m_fpu_balance - 1;
> -}
> -
> -/* Return whether an fma_node object exists for instruction INSN and, if not,
> -   allocate one in *RET.  */
> -
> -fma_node *
> -func_fma_steering::get_fma_node (rtx_insn *insn)
> -{
> -  fma_node **fma_slot;
> -
> -  fma_slot = this->m_insn_fma_head_map->get (insn);
> -  if (fma_slot)
> -    return *fma_slot;
> -  return NULL;
> -}
> -
> -/* Allocate and initialize fma_node objects for the FMUL or FMADD/FMSUB
> -   instruction in CHAIN->insn and its dependent FMADD/FMSUB instructions, all
> -   part of FOREST.  For the children, the associated head is left untouched
> -   (and thus null) as this function will be called again when considering the
> -   chain where they are def.  For the parent, the chain is given in HEAD.  */
> -
> -void
> -func_fma_steering::analyze_fma_fmul_insn (fma_forest *ref_forest,
> -					  du_chain *chain, du_head_p head)
> -{
> -  fma_forest *forest;
> -  fma_node *node = this->get_fma_node (chain->insn);
> -
> -  /* This is a root node.  */
> -  if (!node)
> -    {
> -      fma_root_node *root_node;
> -
> -      root_node = new fma_root_node (this, chain, this->m_next_forest_id++);
> -      forest = root_node->get_forest ();
> -      node = root_node;
> -
> -      /* Until proved otherwise, assume this root is not part of an existing
> -	 forest and thus add its forest to the list of forests.  */
> -      this->m_fma_forests.push_back (forest);
> -    }
> -  else
> -    forest = node->get_forest ();
> -
> -  node->set_head (head);
> -
> -  /* fma_node is part of a chain with several defs, one of them having already
> -     been processed.  The root of that already processed def is the canonical
> -     one and the root of fma_node is added to its forest.  No need to process
> -     the children nodes as they were already processed when the other def was
> -     processed.  */
> -  if (ref_forest)
> -    {
> -      ref_forest->merge_forest (forest);
> -      return;
> -    }
> -
> -  for (chain = head->first; chain; chain = chain->next_use)
> -    {
> -      fma_node *child_fma;
> -      rtx fma_rtx, *accum_rtx_p;
> -
> -      if (!is_fmul_fmac_insn (chain->insn, false))
> -	continue;
> -
> -      /* Get FMA rtx.  */
> -      fma_rtx = SET_SRC (PATTERN (chain->insn));
> -      /* FMA is negated.  */
> -      if (GET_CODE (fma_rtx) == NEG)
> -	fma_rtx = XEXP (fma_rtx, 0);
> -      /* Get accumulator rtx.  */
> -      accum_rtx_p = &XEXP (fma_rtx, 2);
> -      /* Accumulator is negated.  */
> -      if (!REG_P (*accum_rtx_p))
> -	accum_rtx_p = &XEXP (*accum_rtx_p, 0);
> -
> -      /* This du_chain structure is not for the accumulator register.  */
> -      if (accum_rtx_p != chain->loc)
> -	continue;
> -
> -      /* If object already created, this is a loop carried dependency.  We
> -	 don't include this object in the children as we want trees for
> -	 rename_fma_trees to not be an infinite loop.  */
> -      if (this->get_fma_node (chain->insn))
> -	continue;
> -
> -      child_fma = new fma_node (node, chain);
> -
> -      /* Memorize the mapping of this instruction to its fma_node object
> -	 as it will be processed for the chain starting at its destination
> -	 register later.  */
> -
> -      /* Link to siblings.  */
> -      node->add_child (child_fma);
> -    }
> -}
> -
> -/* Perform a depth-first search of the forests of fma_node in
> -   THIS->m_fma_forests, calling PROCESS_FOREST () on each fma_forest object in
> -   THIS->m_fma_forests list, PROCESS_ROOT () on each tree root and
> -   PROCESS_NODE () on each node.  If FREE is true, free all std::list in the
> -   same dfs.  */
> -
> -void
> -func_fma_steering::dfs (void (*process_forest) (fma_forest *),
> -			void (*process_root) (fma_forest *, fma_root_node *),
> -			void (*process_node) (fma_forest *, fma_node *),
> -			bool free)
> -{
> -  auto_vec<fma_node *> to_process;
> -  auto_vec<fma_node *> to_free;
> -  std::list<fma_forest *>::iterator forest_iter;
> -
> -  /* For each forest.  */
> -  for (forest_iter = this->m_fma_forests.begin ();
> -       forest_iter != this->m_fma_forests.end (); ++forest_iter)
> -    {
> -      std::list<fma_root_node *>::iterator root_iter;
> -
> -      if (process_forest)
> -	process_forest (*forest_iter);
> -
> -      /* For each tree root in this forest.  */
> -      for (root_iter = (*forest_iter)->get_roots ()->begin ();
> -	   root_iter != (*forest_iter)->get_roots ()->end (); ++root_iter)
> -	{
> -	  if (process_root)
> -	    process_root (*forest_iter, *root_iter);
> -	  to_process.safe_push (*root_iter);
> -	}
> -
> -      /* For each tree node in this forest.  */
> -      while (!to_process.is_empty ())
> -	{
> -	  fma_node *node;
> -	  std::list<fma_node *>::iterator child_iter;
> -
> -	  node = to_process.pop ();
> -
> -	  if (process_node)
> -	    process_node (*forest_iter, node);
> -
> -	  for (child_iter = node->get_children ()->begin ();
> -	       child_iter != node->get_children ()->end (); ++child_iter)
> -	    to_process.safe_push (*child_iter);
> -
> -	  /* Defer freeing so that the process_node callback can access the
> -	     parent and children of the node being processed.  */
> -	  if (free)
> -	    to_free.safe_push (node);
> -	}
> -
> -      if (free)
> -	{
> -	  delete *forest_iter;
> -
> -	  while (!to_free.is_empty ())
> -	    {
> -	      fma_node *node = to_free.pop ();
> -	      if (node->root_p ())
> -		delete static_cast<fma_root_node *> (node);
> -	      else
> -		delete node;
> -	    }
> -	}
> -    }
> -}
> -
> -/* Build the dependency trees of FMUL and FMADD/FMSUB instructions.  */
> -
> -void
> -func_fma_steering::analyze ()
> -{
> -  int i, n_blocks, *bb_dfs_preorder;
> -  basic_block bb;
> -  rtx_insn *insn;
> -
> -  bb_dfs_preorder = XNEWVEC (int, last_basic_block_for_fn (cfun));
> -  n_blocks = pre_and_rev_post_order_compute (bb_dfs_preorder, NULL, false);
> -
> -  /* Browse the graph of basic blocks looking for FMUL or FMADD/FMSUB
> -     instructions.  */
> -  for (i = 0; i < n_blocks; i++)
> -    {
> -      bb = BASIC_BLOCK_FOR_FN (cfun, bb_dfs_preorder[i]);
> -      FOR_BB_INSNS (bb, insn)
> -	{
> -	  operand_rr_info *dest_op_info;
> -	  struct du_chain *chain = NULL;
> -	  unsigned dest_regno;
> -	  fma_forest *forest = NULL;
> -	  du_head_p head = NULL;
> -	  int i;
> -
> -	  if (!is_fmul_fmac_insn (insn, true))
> -	    continue;
> -
> -	  /* Search the chain where this instruction is (one of) the root.  */
> -	  dest_op_info = insn_rr[INSN_UID (insn)].op_info;
> -	  dest_regno = REGNO (SET_DEST (PATTERN (insn)));
> -	  for (i = 0; i < dest_op_info->n_chains; i++)
> -	    {
> -	      /* The register tracked by this chain does not match the
> -		 destination register of insn.  */
> -	      if (dest_op_info->heads[i]->regno != dest_regno)
> -		continue;
> -
> -	      head = dest_op_info->heads[i];
> -	      /* The chain was merged in another, find the new head.  */
> -	      if (!head->first)
> -		head = regrename_chain_from_id (head->id);
> -
> -	      /* Search the chain element for this instruction and, if another
> -		 FMUL or FMADD/FMSUB instruction was already processed, note
> -		 the forest of its tree.  */
> -	      forest = NULL;
> -	      for (chain = head->first; chain; chain = chain->next_use)
> -		{
> -		  fma_node **fma_slot;
> -
> -		  if (!is_fmul_fmac_insn (chain->insn, true))
> -		    continue;
> -
> -		  /* This is a use, continue.  */
> -		  if (chain->loc != &SET_DEST (PATTERN (chain->insn)))
> -		    continue;
> -
> -		  if (chain->insn == insn)
> -		    break;
> -
> -		  fma_slot = this->m_insn_fma_head_map->get (chain->insn);
> -		  if (fma_slot && (*fma_slot)->get_children ())
> -		    forest = (*fma_slot)->get_forest ();
> -		}
> -	      if (chain)
> -		break;
> -	    }
> -
> -	  /* Due to implementation of regrename, dest register can slip away
> -	     from regrename's analysis.  As a result, there is no chain for
> -	     the destination register of insn.  We simply skip the insn even
> -	     it is a fmul/fmac instruction.  This can happen when the dest
> -	     register is also a source register of insn and one of the below
> -	     conditions is satisfied:
> -	       1) the source reg is setup in larger mode than this insn;
> -	       2) the source reg is uninitialized;
> -	       3) the source reg is passed in as parameter.  */
> -	  if (i < dest_op_info->n_chains)
> -	    this->analyze_fma_fmul_insn (forest, chain, head);
> -	}
> -    }
> -  free (bb_dfs_preorder);
> -
> -  if (dump_file)
> -    this->dfs (dump_forest_info, dump_tree_root_info, dump_tree_node_info,
> -	       false);
> -}
> -
> -/* Perform the renaming of all chains with FMUL or FMADD/FMSUB involved with
> -   the objective of keeping FPU pipeline balanced in term of instructions and
> -   having FMADD/FMSUB with dependencies on previous FMUL or FMADD/FMSUB be
> -   scheduled on the same pipeline.  */
> -
> -void
> -func_fma_steering::rename_fma_trees ()
> -{
> -  this->dfs (dispatch_forest, NULL, rename_fma_node, true);
> -
> -  if (dump_file && !this->m_fma_forests.empty ())
> -    {
> -      fprintf (dump_file, "Function %s has ", current_function_name ());
> -      if (this->m_fpu_balance == 0)
> -	fprintf (dump_file, "perfect balance of FMUL/FMA chains between the "
> -		 "two FPU pipelines\n");
> -      else if (this->m_fpu_balance > 0)
> -	fprintf (dump_file, "%d more FMUL/FMA chains scheduled on the second "
> -		 "FPU pipeline\n", this->m_fpu_balance);
> -      else /* this->m_fpu_balance < 0 */
> -	fprintf (dump_file, "%d more FMUL/FMA chains scheduled on the first "
> -		 "FPU pipeline\n", - this->m_fpu_balance);
> -    }
> -}
> -
> -/* Execute FMA steering pass.  */
> -
> -void
> -func_fma_steering::execute_fma_steering ()
> -{
> -  df_set_flags (DF_LR_RUN_DCE);
> -  df_note_add_problem ();
> -  df_analyze ();
> -  df_set_flags (DF_DEFER_INSN_RESCAN);
> -
> -  regrename_init (true);
> -  regrename_analyze (NULL);
> -  this->analyze ();
> -  this->rename_fma_trees ();
> -  regrename_finish ();
> -}
> -
> -const pass_data pass_data_fma_steering =
> -{
> -  RTL_PASS, /* type */
> -  "fma_steering", /* name */
> -  OPTGROUP_NONE, /* optinfo_flags */
> -  TV_NONE, /* tv_id */
> -  0, /* properties_required */
> -  0, /* properties_provided */
> -  0, /* properties_destroyed */
> -  0, /* todo_flags_start */
> -  TODO_df_finish, /* todo_flags_finish */
> -};
> -
> -class pass_fma_steering : public rtl_opt_pass
> -{
> -public:
> -  pass_fma_steering (gcc::context *ctxt)
> -    : rtl_opt_pass (pass_data_fma_steering, ctxt)
> -  {}
> -
> -  /* opt_pass methods: */
> -  virtual bool gate (function *)
> -    {
> -      return (aarch64_tune_params.extra_tuning_flags
> -	      & AARCH64_EXTRA_TUNE_RENAME_FMA_REGS)
> -	      && optimize >= 2;
> -    }
> -
> -  virtual unsigned int execute (function *)
> -    {
> -      func_fma_steering *fma_steering = new func_fma_steering;
> -      fma_steering->execute_fma_steering ();
> -      delete fma_steering;
> -      return 0;
> -    }
> -
> -}; // class pass_fma_steering
> -
> -/* Create a new fma steering pass instance.  */
> -
> -rtl_opt_pass *
> -make_pass_fma_steering (gcc::context *ctxt)
> -{
> -  return new pass_fma_steering (ctxt);
> -}
> diff --git a/gcc/config/aarch64/t-aarch64 b/gcc/config/aarch64/t-aarch64
> index 5aa7780994834a1ae3424b23e77679d7e1e187ed..0bde167cc043f358fa7131504a44eb185f1864aa 100644
> --- a/gcc/config/aarch64/t-aarch64
> +++ b/gcc/config/aarch64/t-aarch64
> @@ -151,15 +151,6 @@ aarch64-d.o: $(srcdir)/config/aarch64/aarch64-d.cc
>  
>  PASSES_EXTRA += $(srcdir)/config/aarch64/aarch64-passes.def
>  
> -cortex-a57-fma-steering.o: $(srcdir)/config/aarch64/cortex-a57-fma-steering.cc \
> -    $(CONFIG_H) $(SYSTEM_H) $(TM_H) $(REGS_H) insn-config.h $(RTL_BASE_H) \
> -    dominance.h cfg.h cfganal.h $(BASIC_BLOCK_H) $(INSN_ATTR_H) $(RECOG_H) \
> -    output.h hash-map.h $(DF_H) $(OBSTACK_H) $(TARGET_H) $(RTL_H) \
> -    $(CONTEXT_H) $(TREE_PASS_H) regrename.h \
> -    $(srcdir)/config/aarch64/aarch64-protos.h
> -	$(COMPILER) -c $(ALL_COMPILERFLAGS) $(ALL_CPPFLAGS) $(INCLUDES) \
> -		$(srcdir)/config/aarch64/cortex-a57-fma-steering.cc
> -
>  aarch64-speculation.o: $(srcdir)/config/aarch64/aarch64-speculation.cc \
>      $(CONFIG_H) \
>      $(SYSTEM_H) \
> diff --git a/gcc/config/aarch64/tuning_models/cortexa57.h b/gcc/config/aarch64/tuning_models/cortexa57.h
> index 8da7fa9d80df983c640c1870d2f4de6c35808760..8df67f4c512e3e3f38d92d4e18a0763ac9d23648 100644
> --- a/gcc/config/aarch64/tuning_models/cortexa57.h
> +++ b/gcc/config/aarch64/tuning_models/cortexa57.h
> @@ -99,7 +99,7 @@ static const struct tune_params cortexa57_tunings =
>    2,	/* min_div_recip_mul_df.  */
>    0,	/* max_case_values.  */
>    tune_params::AUTOPREFETCHER_WEAK,	/* autoprefetcher_model.  */
> -  (AARCH64_EXTRA_TUNE_RENAME_FMA_REGS),	/* tune_flags.  */
> +  (AARCH64_EXTRA_TUNE_NONE),	/* tune_flags.  */
>    &generic_prefetch_tune,
>    AARCH64_LDP_STP_POLICY_ALWAYS,   /* ldp_policy_model.  */
>    AARCH64_LDP_STP_POLICY_ALWAYS    /* stp_policy_model.  */
  

> On 10 Jan 2025, at 15:30, Richard Sandiford <richard.sandiford@arm.com> wrote:
> 
> Wilco Dijkstra <Wilco.Dijkstra@arm.com> writes:
>> As a minor cleanup remove Cortex-A57 FMA steering pass.  Since Cortex-A57 is
>> pretty old, there isn't any benefit of keeping this.
>> 
>> Passes regress & bootstrap, OK for commit?
>> 
>> gcc:
>> * config.gcc (extra_objs): Remove cortex-a57-fma-steering.o.
>> * config/aarch64/aarch64-passes.def: Remove pass_fma_steering. 
>> * config/aarch64/aarch64-protos.h: Remove make_pass_fma_steering.
>> * config/aarch64/aarch64-tuning-flags.def (RENAME_FMA_REGS): Remove. 
>> * config/aarch64/cortex-a57-fma-steering.cc: Delete file.
>> * config/aarch64/t-aarch64: Remove cortex-a57-fma-steering.o rules. 
>> * config/aarch64/tuning_models/cortexa57.h (cortexa57_tunings):
>>        Remove RENAME_FMA_REGS tuning.
> 
> This would probably be a reasonable compromise if the pass ever became a
> maintenance burden.  But I'm not sure the pass is a burden at the moment.
> TBH, I don't remember having had to think about it for years :)
> 
> So IMO we should keep the pass, but reconsider removing it if in future
> it requires non-trivial effort to keep working.
> 
> That said, the fact the patch requires no testsuite changes suggests
> that the pass could easily become ineffective without anyone noticing.
> So I won't object if other maintainers are in favour.

We still have Cortex-A57-based products out there that can potentially use newer compilers.
So I’d be in favor for keeping the pass in as long as it’s not too much of a maintenance burden.

Thanks,
Kyrill

> 
> Thanks,
> Richard
> 
>> 
>> ---
>> 
>> diff --git a/gcc/config.gcc b/gcc/config.gcc
>> index 55e37146ee0356b67b8a1a09d263eccdf69cd91a..97ef3ae77fb97b347ba43e55f7a05f5438a96a43 100644
>> --- a/gcc/config.gcc
>> +++ b/gcc/config.gcc
>> @@ -350,7 +350,7 @@ aarch64*-*-*)
>> c_target_objs="aarch64-c.o"
>> cxx_target_objs="aarch64-c.o"
>> d_target_objs="aarch64-d.o"
>> - extra_objs="aarch64-builtins.o aarch-common.o aarch64-sve-builtins.o aarch64-sve-builtins-shapes.o aarch64-sve-builtins-base.o aarch64-sve-builtins-sve2.o aarch64-sve-builtins-sme.o cortex-a57-fma-steering.o aarch64-speculation.o aarch-bti-insert.o aarch64-cc-fusion.o aarch64-early-ra.o aarch64-ldp-fusion.o"
>> + extra_objs="aarch64-builtins.o aarch-common.o aarch64-sve-builtins.o aarch64-sve-builtins-shapes.o aarch64-sve-builtins-base.o aarch64-sve-builtins-sve2.o aarch64-sve-builtins-sme.o aarch64-speculation.o aarch-bti-insert.o aarch64-cc-fusion.o aarch64-early-ra.o aarch64-ldp-fusion.o"
>> target_gtfiles="\$(srcdir)/config/aarch64/aarch64-protos.h \$(srcdir)/config/aarch64/aarch64-builtins.h \$(srcdir)/config/aarch64/aarch64-builtins.cc \$(srcdir)/config/aarch64/aarch64-sve-builtins.h \$(srcdir)/config/aarch64/aarch64-sve-builtins.cc"
>> target_has_targetm_common=yes
>> ;;
>> diff --git a/gcc/config/aarch64/aarch64-passes.def b/gcc/config/aarch64/aarch64-passes.def
>> index 9cf9d3e13b2cb0d0bf9c34439785e8ca704230fe..d80b9c6f39c3b56aa6251a81590172f70b31e01e 100644
>> --- a/gcc/config/aarch64/aarch64-passes.def
>> +++ b/gcc/config/aarch64/aarch64-passes.def
>> @@ -19,7 +19,6 @@
>>    <http://www.gnu.org/licenses/>.  */
>> 
>> INSERT_PASS_BEFORE (pass_sched, 1, pass_aarch64_early_ra);
>> -INSERT_PASS_AFTER (pass_regrename, 1, pass_fma_steering);
>> INSERT_PASS_BEFORE (pass_reorder_blocks, 1, pass_track_speculation);
>> INSERT_PASS_BEFORE (pass_late_thread_prologue_and_epilogue, 1, pass_switch_pstate_sm);
>> INSERT_PASS_BEFORE (pass_late_thread_prologue_and_epilogue, 1, pass_late_track_speculation);
>> diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
>> index fa7bc8029be04f6530d2aee2ead4d754ba3b2550..afdf7d01adb3bdafd15d0422c3b2dfd680383bef 100644
>> --- a/gcc/config/aarch64/aarch64-protos.h
>> +++ b/gcc/config/aarch64/aarch64-protos.h
>> @@ -1199,7 +1199,6 @@ std::string aarch64_get_extension_string_for_isa_flags (aarch64_feature_flags,
>> aarch64_feature_flags);
>> 
>> rtl_opt_pass *make_pass_aarch64_early_ra (gcc::context *);
>> -rtl_opt_pass *make_pass_fma_steering (gcc::context *);
>> rtl_opt_pass *make_pass_track_speculation (gcc::context *);
>> rtl_opt_pass *make_pass_late_track_speculation (gcc::context *);
>> rtl_opt_pass *make_pass_insert_bti (gcc::context *ctxt);
>> diff --git a/gcc/config/aarch64/aarch64-tuning-flags.def b/gcc/config/aarch64/aarch64-tuning-flags.def
>> index 1feff3beb348f45c254c5a7c346a1a9674dee362..b1ab068f4073f459e829503f59c9de236cffb63a 100644
>> --- a/gcc/config/aarch64/aarch64-tuning-flags.def
>> +++ b/gcc/config/aarch64/aarch64-tuning-flags.def
>> @@ -28,8 +28,6 @@
>>      INTERNAL_NAME gives the internal name suitable for appending to
>>      AARCH64_TUNE_ to give an enum name. */
>> 
>> -AARCH64_EXTRA_TUNING_OPTION ("rename_fma_regs", RENAME_FMA_REGS)
>> -
>> /* Some of the optional shift to some arthematic instructions are
>>    considered cheap.  Logical shift left <=4 with or without a
>>    zero extend are considered cheap.  Sign extend; non logical shift left
>> diff --git a/gcc/config/aarch64/cortex-a57-fma-steering.cc b/gcc/config/aarch64/cortex-a57-fma-steering.cc
>> deleted file mode 100644
>> index fd6da66d855e36cd023b5343c392cd2f7f062d1b..0000000000000000000000000000000000000000
>> --- a/gcc/config/aarch64/cortex-a57-fma-steering.cc
>> +++ /dev/null
>> @@ -1,1096 +0,0 @@
>> -/* FMA steering optimization pass for Cortex-A57.
>> -   Copyright (C) 2015-2025 Free Software Foundation, Inc.
>> -   Contributed by ARM Ltd.
>> -
>> -   This file is part of GCC.
>> -
>> -   GCC is free software; you can redistribute it and/or modify it
>> -   under the terms of the GNU General Public License as published by
>> -   the Free Software Foundation; either version 3, or (at your option)
>> -   any later version.
>> -
>> -   GCC is distributed in the hope that it will be useful, but
>> -   WITHOUT ANY WARRANTY; without even the implied warranty of
>> -   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> -   General Public License for more details.
>> -
>> -   You should have received a copy of the GNU General Public License
>> -   along with GCC; see the file COPYING3.  If not see
>> -   <http://www.gnu.org/licenses/>.  */
>> -
>> -#define IN_TARGET_CODE 1
>> -
>> -#include "config.h"
>> -#define INCLUDE_LIST
>> -#include "system.h"
>> -#include "coretypes.h"
>> -#include "backend.h"
>> -#include "target.h"
>> -#include "rtl.h"
>> -#include "df.h"
>> -#include "insn-config.h"
>> -#include "regs.h"
>> -#include "memmodel.h"
>> -#include "emit-rtl.h"
>> -#include "recog.h"
>> -#include "cfganal.h"
>> -#include "insn-attr.h"
>> -#include "context.h"
>> -#include "tree-pass.h"
>> -#include "function-abi.h"
>> -#include "regrename.h"
>> -#include "aarch64-protos.h"
>> -
>> -/* For better performance, the destination of FMADD/FMSUB instructions should
>> -   have the same parity as their accumulator register if the accumulator
>> -   contains the result of a previous FMUL or FMADD/FMSUB instruction if
>> -   targetting Cortex-A57 processors.  Performance is also increased by
>> -   otherwise keeping a good balance in the parity of the destination register
>> -   of FMUL or FMADD/FMSUB.
>> -
>> -   This pass ensure that registers are renamed so that these conditions hold.
>> -   We reuse the existing register renaming facility from regrename.cc to build
>> -   dependency chains and expose candidate registers for renaming.
>> -
>> -
>> -   The algorithm has three steps:
>> -
>> -   First, the functions of the register renaming pass are called.  These
>> -   analyze the instructions and produce a list of def/use chains of
>> -   instructions.
>> -
>> -   Next, this information is used to build trees of multiply and
>> -   multiply-accumulate instructions.  The roots of these trees are any
>> -   multiply, or any multiply-accumulate whose accumulator is not dependent on
>> -   a multiply or multiply-accumulate instruction.  A child is added to the
>> -   tree where a dependency chain exists between the result of the parent
>> -   instruction and the accumulator operand of the child, as in the diagram
>> -   below:
>> -
>> - fmul s2, s0, s1
>> - / \
>> -   fmadd s0, s1, s1, s2   fmadd s4, s1, s1 s2
>> -    |
>> -   fmadd s3, s1, s1, s0
>> -
>> -   Trees made of a single instruction are permitted.
>> -
>> -   Finally, renaming is performed.  The parity of the destination register at
>> -   the root of a tree is checked against the current balance of multiply and
>> -   multiply-accumulate on each pipeline.  If necessary, the root of a tree is
>> -   renamed, in which case the rest of the tree is then renamed to keep the same
>> -   parity in the destination registers of all instructions in the tree.  */
>> -
>> -
>> -
>> -/* Forward declarations.  */
>> -class fma_node;
>> -class fma_root_node;
>> -class func_fma_steering;
>> -
>> -/* Dependencies between FMUL or FMADD/FMSUB instructions and subsequent
>> -   FMADD/FMSUB instructions form a graph.  This is because alternatives can
>> -   make a register be set by several FMUL or FMADD/FMSUB instructions in
>> -   different basic blocks and because of loops.  For ease of browsing, the
>> -   connected components of this graph are broken up into forests of trees.
>> -   Forests are represented by fma_forest objects, contained in the fma_forests
>> -   list.  Using a separate object for the forests allows for a better use of
>> -   memory as there is some information that is global to each forest, such as
>> -   the number of FMSUB and FMADD/FMSUB instructions currently scheduled on each
>> -   floating-point execution pipelines.  */
>> -
>> -class fma_forest
>> -{
>> -public:
>> -  fma_forest (func_fma_steering *, fma_root_node *, int);
>> -  ~fma_forest ();
>> -
>> -  int get_id ();
>> -  std::list<fma_root_node *> *get_roots ();
>> -  func_fma_steering *get_globals ();
>> -  int get_target_parity ();
>> -  void fma_node_created (fma_node *);
>> -  void merge_forest (fma_forest *);
>> -  void dump_info ();
>> -  void dispatch ();
>> -
>> -private:
>> -  /* Prohibit copy construction.  */
>> -  fma_forest (const fma_forest &);
>> -
>> -  /* The list of roots that form this forest.  */
>> -  std::list<fma_root_node *> *m_roots;
>> -
>> -  /* Target parity the destination register of all FMUL and FMADD/FMSUB
>> -     instructions in this forest should have.  */
>> -  int m_target_parity;
>> -
>> -  /* Link to the instance of func_fma_steering holding data related to the
>> -     FMA steering of the current function (cfun).  */
>> -  func_fma_steering *m_globals;
>> -
>> -  /* Identifier for the forest (used for dumps).  */
>> -  int m_id;
>> -
>> -  /* Total number of nodes in the forest (for statistics).  */
>> -  int m_nb_nodes;
>> -};
>> -
>> -class fma_node
>> -{
>> -public:
>> -  fma_node (fma_node *parent, du_chain *chain);
>> -  ~fma_node ();
>> -
>> -  bool root_p ();
>> -  fma_forest *get_forest ();
>> -  std::list<fma_node *> *get_children ();
>> -  rtx_insn *get_insn ();
>> -  void add_child (fma_node *);
>> -  int get_parity ();
>> -  void set_head (du_head *);
>> -  void rename (fma_forest *);
>> -  void dump_info (fma_forest *);
>> -
>> -private:
>> -  /* Prohibit copy construction.  */
>> -  fma_node (const fma_node &);
>> -
>> -protected:
>> -  /* Root node that lead to this node.  */
>> -  fma_root_node *m_root;
>> -
>> -  /* The parent node of this node.  If the node belong to a chain with several
>> -     parent nodes, the first one encountered in a depth-first search is chosen
>> -     as canonical parent.  */
>> -  fma_node *m_parent;
>> -
>> -  /* The list of child nodes.  If a chain contains several parent nodes, one is
>> -     chosen as canonical parent and the others will have no children.  */
>> -  std::list<fma_node *> *m_children;
>> -
>> -  /* The associated DU_HEAD chain that the insn represented by this object
>> -     is (one of) the root of.  When a chain contains several roots, the non
>> -     canonical ones have this field set to NULL.  */
>> -  struct du_head *m_head;
>> -
>> -  /* The FMUL or FMADD/FMSUB instruction this object corresponds to.  */
>> -  rtx_insn *m_insn;
>> -};
>> -
>> -class fma_root_node : public fma_node
>> -{
>> -public:
>> -  fma_root_node (func_fma_steering *, du_chain *, int);
>> -
>> -  fma_forest *get_forest ();
>> -  void set_forest (fma_forest *);
>> -  void dump_info (fma_forest *);
>> -
>> -private:
>> -  /* The forest this node belonged to when it was created.  */
>> -  fma_forest *m_forest;
>> -};
>> -
>> -/* Class holding all data and methods relative to the FMA steering of a given
>> -   function.  The FMA steering pass could then run in parallel for different
>> -   functions.  */
>> -
>> -class func_fma_steering
>> -{
>> -public:
>> -  func_fma_steering ();
>> -  ~func_fma_steering ();
>> -
>> -  int get_fpu_balance ();
>> -  void remove_forest (fma_forest *);
>> -  bool put_node (fma_node *);
>> -  void update_balance (int);
>> -  fma_node *get_fma_node (rtx_insn *);
>> -  void analyze_fma_fmul_insn (fma_forest *, du_chain *, du_head_p);
>> -  void execute_fma_steering ();
>> -
>> -private:
>> -  /* Prohibit copy construction.  */
>> -  func_fma_steering (const func_fma_steering &);
>> -
>> -  void dfs (void (*) (fma_forest *), void (*) (fma_forest *, fma_root_node *),
>> -    void (*) (fma_forest *, fma_node *), bool);
>> -  void analyze ();
>> -  void rename_fma_trees ();
>> -
>> -  /* Mapping between FMUL or FMADD/FMSUB instructions and the associated
>> -     fma_node object.  Used when analyzing an instruction that is a root of
>> -     a chain to find if such an object was created because this instruction
>> -     is also a use in another chain.  */
>> -  hash_map<rtx_insn *, fma_node *> *m_insn_fma_head_map;
>> -
>> -  /* A list of all the forests in a given function.  */
>> -  std::list<fma_forest *> m_fma_forests;
>> -
>> -  /* Balance of FMUL and FMADD/FMSUB instructions between the two FPU
>> -     pipelines:
>> -     < 0: more instruction dispatched to the first pipeline
>> -     == 0: perfect balance
>> -     > 0: more instruction dispatched to the second pipeline.  */
>> -  int m_fpu_balance;
>> -
>> -  /* Identifier for the next forest created.  */
>> -  int m_next_forest_id;
>> -};
>> -
>> -/* Rename the register HEAD->regno in all the insns in the chain HEAD to any
>> -   register not in the set UNAVAILABLE.  Adapted from rename_chains in
>> -   regrename.cc.  */
>> -
>> -static bool
>> -rename_single_chain (du_head_p head, HARD_REG_SET *unavailable)
>> -{
>> -  int best_new_reg;
>> -  int n_uses = 0;
>> -  struct du_chain *tmp;
>> -  int reg = head->regno;
>> -  enum reg_class super_class = NO_REGS;
>> -
>> -  if (head->cannot_rename)
>> -    return false;
>> -
>> -  if (fixed_regs[reg] || global_regs[reg]
>> -      || (frame_pointer_needed && reg == HARD_FRAME_POINTER_REGNUM))
>> -    return false;
>> -
>> -  /* Iterate over elements in the chain in order to:
>> -     1. Count number of uses, and narrow the set of registers we can
>> - use for renaming.
>> -     2. Compute the superunion of register classes in this chain.  */
>> -  for (tmp = head->first; tmp; tmp = tmp->next_use)
>> -    {
>> -      if (DEBUG_INSN_P (tmp->insn))
>> - continue;
>> -      n_uses++;
>> -      *unavailable |= ~reg_class_contents[tmp->cl];
>> -      super_class = reg_class_superunion[(int) super_class][(int) tmp->cl];
>> -    }
>> -
>> -  if (n_uses < 1)
>> -    return false;
>> -
>> -  best_new_reg = find_rename_reg (head, super_class, unavailable, reg,
>> -  false);
>> -
>> -  if (dump_file)
>> -    {
>> -      fprintf (dump_file, "Register %s in insn %d", reg_names[reg],
>> -       INSN_UID (head->first->insn));
>> -      if (head->call_abis)
>> - fprintf (dump_file, " crosses a call");
>> -    }
>> -
>> -  if (best_new_reg == reg)
>> -    {
>> -      if (dump_file)
>> - fprintf (dump_file, "; no available better choice\n");
>> -      return false;
>> -    }
>> -
>> -  if (regrename_do_replace (head, best_new_reg))
>> -    {
>> -      if (dump_file)
>> - fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);
>> -      df_set_regs_ever_live (best_new_reg, true);
>> -    }
>> -  else
>> -    {
>> -      if (dump_file)
>> - fprintf (dump_file, ", renaming as %s failed\n",
>> - reg_names[best_new_reg]);
>> -      return false;
>> -    }
>> -  return true;
>> -}
>> -
>> -/* Return whether T is the attribute of a FMADD/FMSUB-like instruction.  */
>> -
>> -static bool
>> -is_fmac_op (enum attr_type t)
>> -{
>> -  return (t == TYPE_FMACS) || (t == TYPE_FMACD) || (t == TYPE_NEON_FP_MLA_S);
>> -}
>> -
>> -/* Return whether T is the attribute of a FMUL instruction.  */
>> -
>> -static bool
>> -is_fmul_op (enum attr_type t)
>> -{
>> -  return (t == TYPE_FMULS) || (t == TYPE_FMULD) || (t == TYPE_NEON_FP_MUL_S);
>> -}
>> -
>> -/* Return whether INSN is an FMUL (if FMUL_OK is true) or FMADD/FMSUB
>> -   instruction.  */
>> -
>> -static bool
>> -is_fmul_fmac_insn (rtx_insn *insn, bool fmul_ok)
>> -{
>> -  enum attr_type t;
>> -
>> -  if (!NONDEBUG_INSN_P (insn))
>> -    return false;
>> -
>> -  if (recog_memoized (insn) < 0)
>> -    return false;
>> -
>> -  /* Only consider chain(s) this instruction is a root of if this is an FMUL or
>> -     FMADD/FMSUB instruction.  This allows to avoid browsing chains of all
>> -     instructions for FMUL or FMADD/FMSUB in them.  */
>> -  t = get_attr_type (insn);
>> -  return is_fmac_op (t) || (fmul_ok && is_fmul_op (t));
>> -}
>> -
>> -
>> -/*
>> - * Class fma_forest method definitions.
>> - */
>> -
>> -fma_forest::fma_forest (func_fma_steering *fma_steer, fma_root_node *fma_root,
>> - int id)
>> -{
>> -      memset (this, 0, sizeof (*this));
>> -      this->m_globals = fma_steer;
>> -      this->m_roots = new std::list<fma_root_node *>;
>> -      this->m_roots->push_back (fma_root);
>> -      this->m_id = id;
>> -}
>> -
>> -fma_forest::~fma_forest ()
>> -{
>> -  delete this->m_roots;
>> -}
>> -
>> -int
>> -fma_forest::get_id ()
>> -{
>> -  return this->m_id;
>> -}
>> -
>> -std::list<fma_root_node *> *
>> -fma_forest::get_roots ()
>> -{
>> -  return this->m_roots;
>> -}
>> -
>> -func_fma_steering *
>> -fma_forest::get_globals ()
>> -{
>> -  return this->m_globals;
>> -}
>> -
>> -int
>> -fma_forest::get_target_parity ()
>> -{
>> -  return this->m_target_parity;
>> -}
>> -
>> -/* Act on the creation of NODE by updating statistics in FOREST and adding an
>> -   entry for it in the func_fma_steering hashmap.  */
>> -
>> -void fma_forest::fma_node_created (fma_node *node)
>> -{
>> -  bool created = !this->m_globals->put_node (node);
>> -
>> -  gcc_assert (created);
>> -  this->m_nb_nodes++;
>> -}
>> -
>> -/* Merge REF_FOREST and OTHER_FOREST together, making REF_FOREST the canonical
>> -   fma_forest object to represent both.  */
>> -
>> -void
>> -fma_forest::merge_forest (fma_forest *other_forest)
>> -{
>> -  std::list<fma_root_node *> *other_roots;
>> -  std::list<fma_root_node *>::iterator other_root_iter;
>> -
>> -  if (this == other_forest)
>> -    return;
>> -
>> -  other_roots = other_forest->m_roots;
>> -
>> -  /* Update root nodes' pointer to forest.  */
>> -  for (other_root_iter = other_roots->begin ();
>> -       other_root_iter != other_roots->end (); ++other_root_iter)
>> -    (*other_root_iter)->set_forest (this);
>> -
>> -  /* Remove other_forest from the list of forests and move its tree roots in
>> -     the list of tree roots of ref_forest.  */
>> -  this->m_globals->remove_forest (other_forest);
>> -  this->m_roots->splice (this->m_roots->begin (), *other_roots);
>> -  this->m_nb_nodes += other_forest->m_nb_nodes;
>> -
>> -  delete other_forest;
>> -}
>> -
>> -/* Dump information about the forest FOREST.  */
>> -
>> -void
>> -fma_forest::dump_info ()
>> -{
>> -  gcc_assert (dump_file);
>> -
>> -  fprintf (dump_file, "Forest #%d has %d nodes\n", this->m_id,
>> -   this->m_nb_nodes);
>> -}
>> -
>> -/* Wrapper around fma_forest::dump_info for use as parameter of function
>> -   pointer type in func_fma_steering::dfs.  */
>> -
>> -static void
>> -dump_forest_info (fma_forest *forest)
>> -{
>> -  forest->dump_info ();
>> -}
>> -
>> -/* Dispatch forest to the least utilized pipeline.  */
>> -
>> -void
>> -fma_forest::dispatch ()
>> -{
>> -  this->m_target_parity = this->m_roots->front ()->get_parity ();
>> -  int fpu_balance = this->m_globals->get_fpu_balance ();
>> -  if (fpu_balance != 0)
>> -    this->m_target_parity = (fpu_balance < 0);
>> -
>> -  if (dump_file)
>> -    fprintf (dump_file, "Target parity for forest #%d: %s\n", this->m_id,
>> -     this->m_target_parity ? "odd" : "even");
>> -}
>> -
>> -/* Wrapper around fma_forest::dispatch for use as parameter of function pointer
>> -   type in func_fma_steering::dfs.  */
>> -
>> -static void
>> -dispatch_forest (fma_forest *forest)
>> -{
>> -  forest->dispatch ();
>> -}
>> -
>> -fma_node::fma_node (fma_node *parent, du_chain *chain)
>> -{
>> -  memset (this, 0, sizeof (*this));
>> -  this->m_parent = parent;
>> -  this->m_children = new std::list<fma_node *>;
>> -  this->m_insn = chain->insn;
>> -  /* root_p () cannot be used to check for root before root is set.  */
>> -  if (this->m_parent == this)
>> -    this->m_root = static_cast<fma_root_node *> (parent);
>> -  else
>> -    {
>> -      this->m_root = parent->m_root;
>> -      this->get_forest ()->fma_node_created (this);
>> -    }
>> -}
>> -
>> -fma_node::~fma_node ()
>> -{
>> -  delete this->m_children;
>> -}
>> -
>> -std::list<fma_node *> *
>> -fma_node::get_children ()
>> -{
>> -  return this->m_children;
>> -}
>> -
>> -rtx_insn *
>> -fma_node::get_insn ()
>> -{
>> -  return this->m_insn;
>> -}
>> -
>> -void
>> -fma_node::set_head (du_head *head)
>> -{
>> -  gcc_assert (!this->m_head);
>> -  this->m_head = head;
>> -}
>> -
>> -/* Add a child to this node in the list of children.  */
>> -
>> -void
>> -fma_node::add_child (fma_node *child)
>> -{
>> -  this->m_children->push_back (child);
>> -}
>> -
>> -/* Return the parity of the destination register of the instruction represented
>> -   by this node.  */
>> -
>> -int
>> -fma_node::get_parity ()
>> -{
>> -  return this->m_head->regno % 2;
>> -}
>> -
>> -/* Get the actual forest associated with a non root node as the one the node
>> -   points to might have been merged into another one.  In that case the pointer
>> -   in the root nodes are updated so we return the forest pointer of a root node
>> -   pointed to by the initial forest.  Despite being a oneliner, this method is
>> -   defined here as it references a method from fma_root_node.  */
>> -
>> -fma_forest *
>> -fma_node::get_forest ()
>> -{
>> -  return this->m_root->get_forest ();
>> -}
>> -
>> -/* Return whether a node is a root node.  */
>> -
>> -bool
>> -fma_node::root_p ()
>> -{
>> -  return this->m_root == this;
>> -}
>> -
>> -/* Dump information about the children of node FMA_NODE in forest FOREST.  */
>> -
>> -void
>> -fma_node::dump_info (ATTRIBUTE_UNUSED fma_forest *forest)
>> -{
>> -  struct du_chain *chain;
>> -  std::list<fma_node *>::iterator fma_child;
>> -
>> -  gcc_assert (dump_file);
>> -
>> -  if (this->get_children ()->empty ())
>> -    return;
>> -
>> -  fprintf (dump_file, "Instruction(s)");
>> -  for (chain = this->m_head->first; chain; chain = chain->next_use)
>> -    {
>> -      if (!is_fmul_fmac_insn (chain->insn, true))
>> - continue;
>> -
>> -      if (chain->loc != &SET_DEST (PATTERN (chain->insn)))
>> - continue;
>> -
>> -      fprintf (dump_file, " %d", INSN_UID (chain->insn));
>> -    }
>> -
>> -  fprintf (dump_file, " is(are) accumulator dependency of instructions");
>> -  for (fma_child = this->get_children ()->begin ();
>> -       fma_child != this->get_children ()->end (); fma_child++)
>> -    fprintf (dump_file, " %d", INSN_UID ((*fma_child)->m_insn));
>> -  fprintf (dump_file, "\n");
>> -}
>> -
>> -/* Wrapper around fma_node::dump_info for use as parameter of function pointer
>> -   type in func_fma_steering::dfs.  */
>> -
>> -static void
>> -dump_tree_node_info (fma_forest *forest, fma_node *node)
>> -{
>> -  node->dump_info (forest);
>> -}
>> -
>> -/* Rename the destination register of a single FMUL or FMADD/FMSUB instruction
>> -   represented by FMA_NODE to a register that respect the target parity for
>> -   FOREST or with same parity of the instruction represented by its parent node
>> -   if it has one.  */
>> -
>> -void
>> -fma_node::rename (fma_forest *forest)
>> -{
>> -  int cur_parity, target_parity;
>> -
>> -  /* This is alternate root of a chain and thus has no children.  It will be
>> -     renamed when processing the canonical root for that chain.  */
>> -  if (!this->m_head)
>> -    return;
>> -
>> -  target_parity = forest->get_target_parity ();
>> -  if (this->m_parent)
>> -    target_parity = this->m_parent->get_parity ();
>> -  cur_parity = this->get_parity ();
>> -
>> -  /* Rename if parity differs.  */
>> -  if (cur_parity != target_parity)
>> -    {
>> -      rtx_insn *insn = this->m_insn;
>> -      HARD_REG_SET unavailable;
>> -      machine_mode mode;
>> -      int reg;
>> -
>> -      if (dump_file)
>> - {
>> -  unsigned cur_dest_reg = this->m_head->regno;
>> -
>> -  fprintf (dump_file, "FMA or FMUL at insn %d but destination "
>> -   "register (%s) has different parity from expected to "
>> -   "maximize FPU pipeline utilization\n", INSN_UID (insn),
>> -   reg_names[cur_dest_reg]);
>> - }
>> -
>> -      /* Don't clobber traceback for noreturn functions.  */
>> -      CLEAR_HARD_REG_SET (unavailable);
>> -      if (frame_pointer_needed)
>> - {
>> -  add_to_hard_reg_set (&unavailable, Pmode, FRAME_POINTER_REGNUM);
>> -  add_to_hard_reg_set (&unavailable, Pmode, HARD_FRAME_POINTER_REGNUM);
>> - }
>> -
>> -      /* Exclude registers with wrong parity.  */
>> -      mode = GET_MODE (SET_DEST (PATTERN (insn)));
>> -      for (reg = cur_parity; reg < FIRST_PSEUDO_REGISTER; reg += 2)
>> - add_to_hard_reg_set (&unavailable, mode, reg);
>> -
>> -      if (!rename_single_chain (this->m_head, &unavailable))
>> - {
>> -  if (dump_file)
>> -    fprintf (dump_file, "Destination register of insn %d could not be "
>> -     "renamed. Dependent FMA insns will use this parity from "
>> -     "there on.\n", INSN_UID (insn));
>> - }
>> -      else
>> - cur_parity = target_parity;
>> -    }
>> -
>> -  forest->get_globals ()->update_balance (cur_parity);
>> -}
>> -
>> -/* Wrapper around fma_node::dump_info for use as parameter of function pointer
>> -   type in func_fma_steering::dfs.  */
>> -
>> -static void
>> -rename_fma_node (fma_forest *forest, fma_node *node)
>> -{
>> -  node->rename (forest);
>> -}
>> -
>> -fma_root_node::fma_root_node (func_fma_steering *globals, du_chain *chain,
>> -      int id) : fma_node (this, chain)
>> -{
>> -  this->m_forest = new fma_forest (globals, this, id);
>> -  this->m_forest->fma_node_created (this);
>> -}
>> -
>> -fma_forest *
>> -fma_root_node::get_forest ()
>> -{
>> -  return this->m_forest;
>> -}
>> -
>> -void
>> -fma_root_node::set_forest (fma_forest *ref_forest)
>> -{
>> -  this->m_forest = ref_forest;
>> -}
>> -
>> -/* Dump information about the roots of forest FOREST.  */
>> -
>> -void
>> -fma_root_node::dump_info (fma_forest *forest)
>> -{
>> -  gcc_assert (dump_file);
>> -
>> -  if (this == forest->get_roots ()->front ())
>> -    fprintf (dump_file, "Instruction(s) at root of forest #%d:",
>> -     forest->get_id ());
>> -  fprintf (dump_file, " %d", INSN_UID (this->m_insn));
>> -  if (this == forest->get_roots ()->back ())
>> -    fprintf (dump_file, "\n");
>> -}
>> -
>> -/* Wrapper around fma_root_node::dump_info for use as parameter of function
>> -   pointer type in func_fma_steering::dfs.  */
>> -
>> -static void
>> -dump_tree_root_info (fma_forest *forest, fma_root_node *node)
>> -{
>> -  node->dump_info (forest);
>> -}
>> -
>> -func_fma_steering::func_fma_steering () : m_fpu_balance (0)
>> -{
>> -  this->m_insn_fma_head_map = new hash_map<rtx_insn *, fma_node *>;
>> -  this->m_fma_forests.clear ();
>> -  this->m_next_forest_id = 0;
>> -}
>> -
>> -func_fma_steering::~func_fma_steering ()
>> -{
>> -  delete this->m_insn_fma_head_map;
>> -}
>> -
>> -int
>> -func_fma_steering::get_fpu_balance ()
>> -{
>> -  return this->m_fpu_balance;
>> -}
>> -
>> -void
>> -func_fma_steering::remove_forest (fma_forest *forest)
>> -{
>> -  this->m_fma_forests.remove (forest);
>> -}
>> -
>> -/* Memorize the mapping of this instruction to its fma_node object and return
>> -   whether such a mapping existed.  */
>> -
>> -bool
>> -func_fma_steering::put_node (fma_node *node)
>> -{
>> -  return this->m_insn_fma_head_map->put (node->get_insn (), node);
>> -}
>> -
>> -/* Update the current balance considering a node with the given PARITY.  */
>> -
>> -void
>> -func_fma_steering::update_balance (int parity)
>> -{
>> -  this->m_fpu_balance = parity ? this->m_fpu_balance + 1
>> -       : this->m_fpu_balance - 1;
>> -}
>> -
>> -/* Return whether an fma_node object exists for instruction INSN and, if not,
>> -   allocate one in *RET.  */
>> -
>> -fma_node *
>> -func_fma_steering::get_fma_node (rtx_insn *insn)
>> -{
>> -  fma_node **fma_slot;
>> -
>> -  fma_slot = this->m_insn_fma_head_map->get (insn);
>> -  if (fma_slot)
>> -    return *fma_slot;
>> -  return NULL;
>> -}
>> -
>> -/* Allocate and initialize fma_node objects for the FMUL or FMADD/FMSUB
>> -   instruction in CHAIN->insn and its dependent FMADD/FMSUB instructions, all
>> -   part of FOREST.  For the children, the associated head is left untouched
>> -   (and thus null) as this function will be called again when considering the
>> -   chain where they are def.  For the parent, the chain is given in HEAD.  */
>> -
>> -void
>> -func_fma_steering::analyze_fma_fmul_insn (fma_forest *ref_forest,
>> -  du_chain *chain, du_head_p head)
>> -{
>> -  fma_forest *forest;
>> -  fma_node *node = this->get_fma_node (chain->insn);
>> -
>> -  /* This is a root node.  */
>> -  if (!node)
>> -    {
>> -      fma_root_node *root_node;
>> -
>> -      root_node = new fma_root_node (this, chain, this->m_next_forest_id++);
>> -      forest = root_node->get_forest ();
>> -      node = root_node;
>> -
>> -      /* Until proved otherwise, assume this root is not part of an existing
>> - forest and thus add its forest to the list of forests.  */
>> -      this->m_fma_forests.push_back (forest);
>> -    }
>> -  else
>> -    forest = node->get_forest ();
>> -
>> -  node->set_head (head);
>> -
>> -  /* fma_node is part of a chain with several defs, one of them having already
>> -     been processed.  The root of that already processed def is the canonical
>> -     one and the root of fma_node is added to its forest.  No need to process
>> -     the children nodes as they were already processed when the other def was
>> -     processed.  */
>> -  if (ref_forest)
>> -    {
>> -      ref_forest->merge_forest (forest);
>> -      return;
>> -    }
>> -
>> -  for (chain = head->first; chain; chain = chain->next_use)
>> -    {
>> -      fma_node *child_fma;
>> -      rtx fma_rtx, *accum_rtx_p;
>> -
>> -      if (!is_fmul_fmac_insn (chain->insn, false))
>> - continue;
>> -
>> -      /* Get FMA rtx.  */
>> -      fma_rtx = SET_SRC (PATTERN (chain->insn));
>> -      /* FMA is negated.  */
>> -      if (GET_CODE (fma_rtx) == NEG)
>> - fma_rtx = XEXP (fma_rtx, 0);
>> -      /* Get accumulator rtx.  */
>> -      accum_rtx_p = &XEXP (fma_rtx, 2);
>> -      /* Accumulator is negated.  */
>> -      if (!REG_P (*accum_rtx_p))
>> - accum_rtx_p = &XEXP (*accum_rtx_p, 0);
>> -
>> -      /* This du_chain structure is not for the accumulator register.  */
>> -      if (accum_rtx_p != chain->loc)
>> - continue;
>> -
>> -      /* If object already created, this is a loop carried dependency.  We
>> - don't include this object in the children as we want trees for
>> - rename_fma_trees to not be an infinite loop.  */
>> -      if (this->get_fma_node (chain->insn))
>> - continue;
>> -
>> -      child_fma = new fma_node (node, chain);
>> -
>> -      /* Memorize the mapping of this instruction to its fma_node object
>> - as it will be processed for the chain starting at its destination
>> - register later.  */
>> -
>> -      /* Link to siblings.  */
>> -      node->add_child (child_fma);
>> -    }
>> -}
>> -
>> -/* Perform a depth-first search of the forests of fma_node in
>> -   THIS->m_fma_forests, calling PROCESS_FOREST () on each fma_forest object in
>> -   THIS->m_fma_forests list, PROCESS_ROOT () on each tree root and
>> -   PROCESS_NODE () on each node.  If FREE is true, free all std::list in the
>> -   same dfs.  */
>> -
>> -void
>> -func_fma_steering::dfs (void (*process_forest) (fma_forest *),
>> - void (*process_root) (fma_forest *, fma_root_node *),
>> - void (*process_node) (fma_forest *, fma_node *),
>> - bool free)
>> -{
>> -  auto_vec<fma_node *> to_process;
>> -  auto_vec<fma_node *> to_free;
>> -  std::list<fma_forest *>::iterator forest_iter;
>> -
>> -  /* For each forest.  */
>> -  for (forest_iter = this->m_fma_forests.begin ();
>> -       forest_iter != this->m_fma_forests.end (); ++forest_iter)
>> -    {
>> -      std::list<fma_root_node *>::iterator root_iter;
>> -
>> -      if (process_forest)
>> - process_forest (*forest_iter);
>> -
>> -      /* For each tree root in this forest.  */
>> -      for (root_iter = (*forest_iter)->get_roots ()->begin ();
>> -   root_iter != (*forest_iter)->get_roots ()->end (); ++root_iter)
>> - {
>> -  if (process_root)
>> -    process_root (*forest_iter, *root_iter);
>> -  to_process.safe_push (*root_iter);
>> - }
>> -
>> -      /* For each tree node in this forest.  */
>> -      while (!to_process.is_empty ())
>> - {
>> -  fma_node *node;
>> -  std::list<fma_node *>::iterator child_iter;
>> -
>> -  node = to_process.pop ();
>> -
>> -  if (process_node)
>> -    process_node (*forest_iter, node);
>> -
>> -  for (child_iter = node->get_children ()->begin ();
>> -       child_iter != node->get_children ()->end (); ++child_iter)
>> -    to_process.safe_push (*child_iter);
>> -
>> -  /* Defer freeing so that the process_node callback can access the
>> -     parent and children of the node being processed.  */
>> -  if (free)
>> -    to_free.safe_push (node);
>> - }
>> -
>> -      if (free)
>> - {
>> -  delete *forest_iter;
>> -
>> -  while (!to_free.is_empty ())
>> -    {
>> -      fma_node *node = to_free.pop ();
>> -      if (node->root_p ())
>> - delete static_cast<fma_root_node *> (node);
>> -      else
>> - delete node;
>> -    }
>> - }
>> -    }
>> -}
>> -
>> -/* Build the dependency trees of FMUL and FMADD/FMSUB instructions.  */
>> -
>> -void
>> -func_fma_steering::analyze ()
>> -{
>> -  int i, n_blocks, *bb_dfs_preorder;
>> -  basic_block bb;
>> -  rtx_insn *insn;
>> -
>> -  bb_dfs_preorder = XNEWVEC (int, last_basic_block_for_fn (cfun));
>> -  n_blocks = pre_and_rev_post_order_compute (bb_dfs_preorder, NULL, false);
>> -
>> -  /* Browse the graph of basic blocks looking for FMUL or FMADD/FMSUB
>> -     instructions.  */
>> -  for (i = 0; i < n_blocks; i++)
>> -    {
>> -      bb = BASIC_BLOCK_FOR_FN (cfun, bb_dfs_preorder[i]);
>> -      FOR_BB_INSNS (bb, insn)
>> - {
>> -  operand_rr_info *dest_op_info;
>> -  struct du_chain *chain = NULL;
>> -  unsigned dest_regno;
>> -  fma_forest *forest = NULL;
>> -  du_head_p head = NULL;
>> -  int i;
>> -
>> -  if (!is_fmul_fmac_insn (insn, true))
>> -    continue;
>> -
>> -  /* Search the chain where this instruction is (one of) the root.  */
>> -  dest_op_info = insn_rr[INSN_UID (insn)].op_info;
>> -  dest_regno = REGNO (SET_DEST (PATTERN (insn)));
>> -  for (i = 0; i < dest_op_info->n_chains; i++)
>> -    {
>> -      /* The register tracked by this chain does not match the
>> - destination register of insn.  */
>> -      if (dest_op_info->heads[i]->regno != dest_regno)
>> - continue;
>> -
>> -      head = dest_op_info->heads[i];
>> -      /* The chain was merged in another, find the new head.  */
>> -      if (!head->first)
>> - head = regrename_chain_from_id (head->id);
>> -
>> -      /* Search the chain element for this instruction and, if another
>> - FMUL or FMADD/FMSUB instruction was already processed, note
>> - the forest of its tree.  */
>> -      forest = NULL;
>> -      for (chain = head->first; chain; chain = chain->next_use)
>> - {
>> -  fma_node **fma_slot;
>> -
>> -  if (!is_fmul_fmac_insn (chain->insn, true))
>> -    continue;
>> -
>> -  /* This is a use, continue.  */
>> -  if (chain->loc != &SET_DEST (PATTERN (chain->insn)))
>> -    continue;
>> -
>> -  if (chain->insn == insn)
>> -    break;
>> -
>> -  fma_slot = this->m_insn_fma_head_map->get (chain->insn);
>> -  if (fma_slot && (*fma_slot)->get_children ())
>> -    forest = (*fma_slot)->get_forest ();
>> - }
>> -      if (chain)
>> - break;
>> -    }
>> -
>> -  /* Due to implementation of regrename, dest register can slip away
>> -     from regrename's analysis.  As a result, there is no chain for
>> -     the destination register of insn.  We simply skip the insn even
>> -     it is a fmul/fmac instruction.  This can happen when the dest
>> -     register is also a source register of insn and one of the below
>> -     conditions is satisfied:
>> -       1) the source reg is setup in larger mode than this insn;
>> -       2) the source reg is uninitialized;
>> -       3) the source reg is passed in as parameter.  */
>> -  if (i < dest_op_info->n_chains)
>> -    this->analyze_fma_fmul_insn (forest, chain, head);
>> - }
>> -    }
>> -  free (bb_dfs_preorder);
>> -
>> -  if (dump_file)
>> -    this->dfs (dump_forest_info, dump_tree_root_info, dump_tree_node_info,
>> -       false);
>> -}
>> -
>> -/* Perform the renaming of all chains with FMUL or FMADD/FMSUB involved with
>> -   the objective of keeping FPU pipeline balanced in term of instructions and
>> -   having FMADD/FMSUB with dependencies on previous FMUL or FMADD/FMSUB be
>> -   scheduled on the same pipeline.  */
>> -
>> -void
>> -func_fma_steering::rename_fma_trees ()
>> -{
>> -  this->dfs (dispatch_forest, NULL, rename_fma_node, true);
>> -
>> -  if (dump_file && !this->m_fma_forests.empty ())
>> -    {
>> -      fprintf (dump_file, "Function %s has ", current_function_name ());
>> -      if (this->m_fpu_balance == 0)
>> - fprintf (dump_file, "perfect balance of FMUL/FMA chains between the "
>> - "two FPU pipelines\n");
>> -      else if (this->m_fpu_balance > 0)
>> - fprintf (dump_file, "%d more FMUL/FMA chains scheduled on the second "
>> - "FPU pipeline\n", this->m_fpu_balance);
>> -      else /* this->m_fpu_balance < 0 */
>> - fprintf (dump_file, "%d more FMUL/FMA chains scheduled on the first "
>> - "FPU pipeline\n", - this->m_fpu_balance);
>> -    }
>> -}
>> -
>> -/* Execute FMA steering pass.  */
>> -
>> -void
>> -func_fma_steering::execute_fma_steering ()
>> -{
>> -  df_set_flags (DF_LR_RUN_DCE);
>> -  df_note_add_problem ();
>> -  df_analyze ();
>> -  df_set_flags (DF_DEFER_INSN_RESCAN);
>> -
>> -  regrename_init (true);
>> -  regrename_analyze (NULL);
>> -  this->analyze ();
>> -  this->rename_fma_trees ();
>> -  regrename_finish ();
>> -}
>> -
>> -const pass_data pass_data_fma_steering =
>> -{
>> -  RTL_PASS, /* type */
>> -  "fma_steering", /* name */
>> -  OPTGROUP_NONE, /* optinfo_flags */
>> -  TV_NONE, /* tv_id */
>> -  0, /* properties_required */
>> -  0, /* properties_provided */
>> -  0, /* properties_destroyed */
>> -  0, /* todo_flags_start */
>> -  TODO_df_finish, /* todo_flags_finish */
>> -};
>> -
>> -class pass_fma_steering : public rtl_opt_pass
>> -{
>> -public:
>> -  pass_fma_steering (gcc::context *ctxt)
>> -    : rtl_opt_pass (pass_data_fma_steering, ctxt)
>> -  {}
>> -
>> -  /* opt_pass methods: */
>> -  virtual bool gate (function *)
>> -    {
>> -      return (aarch64_tune_params.extra_tuning_flags
>> -      & AARCH64_EXTRA_TUNE_RENAME_FMA_REGS)
>> -      && optimize >= 2;
>> -    }
>> -
>> -  virtual unsigned int execute (function *)
>> -    {
>> -      func_fma_steering *fma_steering = new func_fma_steering;
>> -      fma_steering->execute_fma_steering ();
>> -      delete fma_steering;
>> -      return 0;
>> -    }
>> -
>> -}; // class pass_fma_steering
>> -
>> -/* Create a new fma steering pass instance.  */
>> -
>> -rtl_opt_pass *
>> -make_pass_fma_steering (gcc::context *ctxt)
>> -{
>> -  return new pass_fma_steering (ctxt);
>> -}
>> diff --git a/gcc/config/aarch64/t-aarch64 b/gcc/config/aarch64/t-aarch64
>> index 5aa7780994834a1ae3424b23e77679d7e1e187ed..0bde167cc043f358fa7131504a44eb185f1864aa 100644
>> --- a/gcc/config/aarch64/t-aarch64
>> +++ b/gcc/config/aarch64/t-aarch64
>> @@ -151,15 +151,6 @@ aarch64-d.o: $(srcdir)/config/aarch64/aarch64-d.cc
>> 
>> PASSES_EXTRA += $(srcdir)/config/aarch64/aarch64-passes.def
>> 
>> -cortex-a57-fma-steering.o: $(srcdir)/config/aarch64/cortex-a57-fma-steering.cc \
>> -    $(CONFIG_H) $(SYSTEM_H) $(TM_H) $(REGS_H) insn-config.h $(RTL_BASE_H) \
>> -    dominance.h cfg.h cfganal.h $(BASIC_BLOCK_H) $(INSN_ATTR_H) $(RECOG_H) \
>> -    output.h hash-map.h $(DF_H) $(OBSTACK_H) $(TARGET_H) $(RTL_H) \
>> -    $(CONTEXT_H) $(TREE_PASS_H) regrename.h \
>> -    $(srcdir)/config/aarch64/aarch64-protos.h
>> - $(COMPILER) -c $(ALL_COMPILERFLAGS) $(ALL_CPPFLAGS) $(INCLUDES) \
>> - $(srcdir)/config/aarch64/cortex-a57-fma-steering.cc
>> -
>> aarch64-speculation.o: $(srcdir)/config/aarch64/aarch64-speculation.cc \
>>     $(CONFIG_H) \
>>     $(SYSTEM_H) \
>> diff --git a/gcc/config/aarch64/tuning_models/cortexa57.h b/gcc/config/aarch64/tuning_models/cortexa57.h
>> index 8da7fa9d80df983c640c1870d2f4de6c35808760..8df67f4c512e3e3f38d92d4e18a0763ac9d23648 100644
>> --- a/gcc/config/aarch64/tuning_models/cortexa57.h
>> +++ b/gcc/config/aarch64/tuning_models/cortexa57.h
>> @@ -99,7 +99,7 @@ static const struct tune_params cortexa57_tunings =
>>   2, /* min_div_recip_mul_df.  */
>>   0, /* max_case_values.  */
>>   tune_params::AUTOPREFETCHER_WEAK, /* autoprefetcher_model.  */
>> -  (AARCH64_EXTRA_TUNE_RENAME_FMA_REGS), /* tune_flags.  */
>> +  (AARCH64_EXTRA_TUNE_NONE), /* tune_flags.  */
>>   &generic_prefetch_tune,
>>   AARCH64_LDP_STP_POLICY_ALWAYS,   /* ldp_policy_model.  */
>>   AARCH64_LDP_STP_POLICY_ALWAYS    /* stp_policy_model.  */