blob: cf68c94647a8232b83966464d1a503f8a403813f [file] [log] [blame]
// Function-related RTL SSA classes -*- C++ -*-
// Copyright (C) 2020-2021 Free Software Foundation, Inc.
// 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
// <>.
namespace rtl_ssa {
// SSA-related information about a function. It contains three levels
// of information, each in reverse postorder:
// - a list of extended basic blocks
// - a list of basic blocks
// - a list of instructions
// It also maintains a list of definitions of memory, and a list of
// definitions of each register.
// See doc/rtl.texi for more details about the way this information
// is organized and how changes to it are made.
class function_info
// The default obstack alignment takes long double into account.
// Since we have no use for that here, and since we allocate many
// relatively small objects, it's better to specify an alignment
// explicitly. The allocation routines assert that the alignment
// is enough for the objects being allocated.
// Because various structures use pointer_mux, we need at least 2 bytes
// of alignment.
static const size_t obstack_alignment = sizeof (void *);
// Construct SSA form for function FN.
function_info (function *fn);
~function_info ();
// Return a list of all the extended basic blocks in the function, in reverse
// postorder. The list includes the entry and exit blocks.
iterator_range<ebb_iterator> ebbs () const;
// Like ebbs (), but in the reverse order.
iterator_range<reverse_ebb_iterator> reverse_ebbs () const;
// Return a list of all the basic blocks in the function, in reverse
// postorder. The list includes the entry and exit blocks.
iterator_range<bb_iterator> bbs () const;
// Like bbs (), but in the reverse order.
iterator_range<reverse_bb_iterator> reverse_bbs () const;
// Return the SSA information for the basic block with index INDEX.
bb_info *bb (unsigned int index) const { return m_bbs[index]; }
// Return the SSA information for CFG_BB.
bb_info *bb (basic_block cfg_bb) const { return m_bbs[cfg_bb->index]; }
// Return a list of all the instructions in the function, in reverse
// postorder. The list includes both real and artificial instructions.
// Iterations over the list will pick up any new instructions that are
// inserted after the iterator's current instruction.
iterator_range<any_insn_iterator> all_insns () const;
// Like all_insns (), but in the reverse order.
// Iterations over the list will pick up any new instructions that are
// inserted before the iterator's current instruction.
iterator_range<reverse_any_insn_iterator> reverse_all_insns () const;
// Like all_insns (), but without the debug instructions.
iterator_range<nondebug_insn_iterator> nondebug_insns () const;
// Like reverse_all_insns (), but without the debug instructions.
reverse_nondebug_insns () const;
// Return the first and last instructions in insns ().
insn_info *first_insn () const { return m_first_insn; }
insn_info *last_insn () const { return m_last_insn; }
// Return a list of all definitions of memory, in reverse postorder.
// This includes both real stores by instructions and artificial
// definitions by things like phi nodes.
iterator_range<def_iterator> mem_defs () const;
// Return a list of all definitions of register REGNO, in reverse postorder.
// This includes both real stores by instructions and artificial
// definitions by things like phi nodes.
iterator_range<def_iterator> reg_defs (unsigned int regno) const;
// Check if all uses of register REGNO are either unconditionally undefined
// or use the same single dominating definition. Return the definition
// if so, otherwise return null.
set_info *single_dominating_def (unsigned int regno) const;
// Look for a definition of RESOURCE at INSN. Return the result of the
// search as a def_lookup; see the comments there for more details.
def_lookup find_def (resource_info resource, insn_info *insn);
// Return an RAII object that owns all temporary RTL SSA memory
// allocated during a change attempt. The object should remain in
// scope until the change has been aborted or successfully completed.
obstack_watermark new_change_attempt () { return &m_temp_obstack; }
// Make a best attempt to check whether the values used by USES are
// available on entry to BB, without solving a full dataflow problem.
// If all the values are already live on entry to BB or can be made
// available there, return a use_array that describes the uses as
// if they occured at the start of BB. These uses are purely temporary,
// and will not become permanent unless applied using change_insns.
// If the operation fails, return an invalid use_array.
// WATERMARK is a watermark returned by new_change_attempt ().
// WILL_BE_DEBUG_USES is true if the returned use_array will be
// used only for debug instructions.
use_array make_uses_available (obstack_watermark &watermark,
use_array uses, bb_info *bb,
bool will_be_debug_uses);
// If CHANGE doesn't already clobber REGNO, try to add such a clobber,
// limiting the movement range in order to make the clobber valid.
// When determining whether REGNO is live, ignore accesses made by an
// instruction I if IGNORE (I) is true. The caller then assumes the
// responsibility of ensuring that CHANGE and I are placed in a valid order.
// Return true on success. Leave CHANGE unmodified when returning false.
// WATERMARK is a watermark returned by new_change_attempt ().
template<typename IgnorePredicate>
bool add_regno_clobber (obstack_watermark &watermark, insn_change &change,
unsigned int regno, IgnorePredicate ignore);
// Return true if change_insns will be able to perform the changes
// described by CHANGES.
bool verify_insn_changes (array_slice<insn_change *const> changes);
// Perform all the changes in CHANGES, keeping the instructions in the
// order specified by the CHANGES array. On return, the SSA information
// remains up-to-date. The same is true for instruction-level DF
// information, although the block-level DF information might be
// marked dirty.
void change_insns (array_slice<insn_change *> changes);
// Like change_insns, but for a single change CHANGE.
void change_insn (insn_change &change);
// If the changes that have been made to instructions require updates
// to the CFG, perform those updates now. Return true if something changed.
// If it did:
// - The SSA information is now invalid and needs to be recomputed.
// - Dominance information is no longer available (in either direction).
// - The caller will need to call cleanup_cfg at some point.
// ??? We could probably update the SSA information for simple updates,
// but currently nothing would benefit. These late CFG changes are
// relatively rare anyway, since gimple optimisers should remove most
// unnecessary control flow.
bool perform_pending_updates ();
// Print the contents of the function to PP.
void print (pretty_printer *pp) const;
class bb_phi_info;
class build_info;
class bb_walker;
// Return an RAII object that owns all objects allocated by
// allocate_temp during its lifetime.
obstack_watermark temp_watermark () { return &m_temp_obstack; }
template<typename T, typename... Ts>
T *allocate (Ts... args);
template<typename T, typename... Ts>
T *allocate_temp (Ts... args);
access_array temp_access_array (access_array accesses);
clobber_group *need_clobber_group (clobber_info *);
def_node *need_def_node (def_info *);
def_splay_tree need_def_splay_tree (def_info *);
use_info *make_use_available (use_info *, bb_info *, bool);
def_array insert_temp_clobber (obstack_watermark &, insn_info *,
unsigned int, def_array);
void insert_def_before (def_info *, def_info *);
void insert_def_after (def_info *, def_info *);
void remove_def_from_list (def_info *);
void add_clobber (clobber_info *, clobber_group *);
void remove_clobber (clobber_info *, clobber_group *);
void prepend_clobber_to_group (clobber_info *, clobber_group *);
void append_clobber_to_group (clobber_info *, clobber_group *);
void merge_clobber_groups (clobber_info *, clobber_info *,
def_info *);
clobber_info *split_clobber_group (clobber_group *, insn_info *);
void append_def (def_info *);
void add_def (def_info *);
void remove_def (def_info *);
void need_use_splay_tree (set_info *);
static void insert_use_before (use_info *, use_info *);
static void insert_use_after (use_info *, use_info *);
void add_use (use_info *);
void remove_use (use_info *);
insn_info::order_node *need_order_node (insn_info *);
void add_insn_after (insn_info *, insn_info *);
void append_insn (insn_info *);
void remove_insn (insn_info *);
insn_info *append_artificial_insn (bb_info *, rtx_insn * = nullptr);
void start_insn_accesses ();
void finish_insn_accesses (insn_info *);
use_info *create_reg_use (build_info &, insn_info *, resource_info);
void record_use (build_info &, insn_info *, rtx_obj_reference);
void record_call_clobbers (build_info &, insn_info *, rtx_call_insn *);
void record_def (build_info &, insn_info *, rtx_obj_reference);
void add_insn_to_block (build_info &, rtx_insn *);
void add_reg_unused_notes (insn_info *);
void add_live_out_use (bb_info *, set_info *);
set_info *live_out_value (bb_info *, set_info *);
void append_phi (ebb_info *, phi_info *);
void remove_phi (phi_info *);
void delete_phi (phi_info *);
void replace_phi (phi_info *, set_info *);
phi_info *create_phi (ebb_info *, resource_info, access_info **,
unsigned int);
phi_info *create_degenerate_phi (ebb_info *, set_info *);
bb_info *create_bb_info (basic_block);
void append_bb (bb_info *);
insn_info *add_placeholder_after (insn_info *);
void possibly_queue_changes (insn_change &);
void finalize_new_accesses (insn_change &);
void apply_changes_to_insn (insn_change &);
void init_function_data ();
void calculate_potential_phi_regs (build_info &);
void place_phis (build_info &);
void create_ebbs (build_info &);
void add_entry_block_defs (build_info &);
void calculate_ebb_live_in_for_debug (build_info &);
void add_phi_nodes (build_info &);
void add_artificial_accesses (build_info &, df_ref_flags);
void add_block_contents (build_info &);
void record_block_live_out (build_info &);
void start_block (build_info &, bb_info *);
void end_block (build_info &, bb_info *);
void populate_phi_inputs (build_info &);
void process_all_blocks ();
void simplify_phi_setup (phi_info *, set_info **, bitmap);
void simplify_phi_propagate (phi_info *, set_info **, bitmap, bitmap);
void simplify_phis ();
// The function that this object describes.
function *m_fn;
// The lowest (negative) in-use artificial insn uid minus one.
int m_next_artificial_uid;
// The highest in-use phi uid plus one.
unsigned int m_next_phi_uid;
// The highest in-use register number plus one.
unsigned int m_num_regs;
// M_DEFS[R] is the first definition of register R - 1 in a reverse
// postorder traversal of the function, or null if the function has
// no definition of R. Applying last () gives the last definition of R.
// M_DEFS[0] is for memory; MEM_REGNO + 1 == 0.
auto_vec<def_info *> m_defs;
// M_BBS[BI] gives the SSA information about the block with index BI.
auto_vec<bb_info *> m_bbs;
// An obstack used to allocate the main RTL SSA information.
obstack m_obstack;
// An obstack used for temporary work, such as while building up a list
// of possible instruction changes.
obstack m_temp_obstack;
// The start of each obstack, so that all memory in them can be freed.
char *m_obstack_start;
char *m_temp_obstack_start;
// The entry and exit blocks.
bb_info *m_first_bb;
bb_info *m_last_bb;
// The first and last instructions in a reverse postorder traversal
// of the function.
insn_info *m_first_insn;
insn_info *m_last_insn;
// The last nondebug instruction in the list of instructions.
// This is only different from m_last_insn when building the initial
// SSA information; after that, the last instruction is always a
// BB end instruction.
insn_info *m_last_nondebug_insn;
// Temporary working state when building up lists of definitions and uses.
// Keeping them around should reduce the number of unnecessary reallocations.
auto_vec<access_info *> m_temp_defs;
auto_vec<access_info *> m_temp_uses;
// A list of phis that are no longer in use. Their uids are still unique
// and so can be recycled.
phi_info *m_free_phis;
// A list of instructions that have been changed in ways that need
// further processing later, such as removing dead instructions or
// altering the CFG.
auto_vec<insn_info *> m_queued_insn_updates;
// The INSN_UIDs of all instructions in M_QUEUED_INSN_UPDATES.
auto_bitmap m_queued_insn_update_uids;
// A basic_block is in this bitmap if we need to call purge_dead_edges
// on it. As with M_QUEUED_INSN_UPDATES, these updates are queued until
// a convenient point.
auto_bitmap m_need_to_purge_dead_edges;
void pp_function (pretty_printer *, const function_info *);
void dump (FILE *, const rtl_ssa::function_info *);
void DEBUG_FUNCTION debug (const rtl_ssa::function_info *);