dist/gcc/reload.h

/* Communication between reload.cc, reload1.cc and the rest of compiler.
   Copyright (C) 1987-2022 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
<http://www.gnu.org/licenses/>.  */

#ifndef GCC_RELOAD_H
#define GCC_RELOAD_H

/* If secondary reloads are the same for inputs and outputs, define those
   macros here.  */

#ifdef SECONDARY_RELOAD_CLASS
#define SECONDARY_INPUT_RELOAD_CLASS(CLASS, MODE, X) \
  SECONDARY_RELOAD_CLASS (CLASS, MODE, X)
#define SECONDARY_OUTPUT_RELOAD_CLASS(CLASS, MODE, X) \
  SECONDARY_RELOAD_CLASS (CLASS, MODE, X)
#endif

extern int register_move_cost (machine_mode, reg_class_t, reg_class_t);
extern int memory_move_cost (machine_mode, reg_class_t, bool);
extern int memory_move_secondary_cost (machine_mode, reg_class_t, bool);

/* Maximum number of reloads we can need.  */
#define MAX_RELOADS (2 * MAX_RECOG_OPERANDS * (MAX_REGS_PER_ADDRESS + 1))

/* Encode the usage of a reload.  The following codes are supported:

   RELOAD_FOR_INPUT		reload of an input operand
   RELOAD_FOR_OUTPUT		likewise, for output
   RELOAD_FOR_INSN		a reload that must not conflict with anything
				used in the insn, but may conflict with
				something used before or after the insn
   RELOAD_FOR_INPUT_ADDRESS	reload for parts of the address of an object
				that is an input reload
   RELOAD_FOR_INPADDR_ADDRESS	reload needed for RELOAD_FOR_INPUT_ADDRESS
   RELOAD_FOR_OUTPUT_ADDRESS	like RELOAD_FOR INPUT_ADDRESS, for output
   RELOAD_FOR_OUTADDR_ADDRESS	reload needed for RELOAD_FOR_OUTPUT_ADDRESS
   RELOAD_FOR_OPERAND_ADDRESS	reload for the address of a non-reloaded
				operand; these don't conflict with
				any other addresses.
   RELOAD_FOR_OPADDR_ADDR	reload needed for RELOAD_FOR_OPERAND_ADDRESS
                                reloads; usually secondary reloads
   RELOAD_OTHER			none of the above, usually multiple uses
   RELOAD_FOR_OTHER_ADDRESS     reload for part of the address of an input
				that is marked RELOAD_OTHER.

   This used to be "enum reload_when_needed" but some debuggers have trouble
   with an enum tag and variable of the same name.  */

enum reload_type
{
  RELOAD_FOR_INPUT, RELOAD_FOR_OUTPUT, RELOAD_FOR_INSN,
  RELOAD_FOR_INPUT_ADDRESS, RELOAD_FOR_INPADDR_ADDRESS,
  RELOAD_FOR_OUTPUT_ADDRESS, RELOAD_FOR_OUTADDR_ADDRESS,
  RELOAD_FOR_OPERAND_ADDRESS, RELOAD_FOR_OPADDR_ADDR,
  RELOAD_OTHER, RELOAD_FOR_OTHER_ADDRESS
};

#ifdef GCC_INSN_CODES_H
/* Each reload is recorded with a structure like this.  */
struct reload
{
  /* The value to reload from */
  rtx in;
  /* Where to store reload-reg afterward if nec (often the same as
     reload_in)  */
  rtx out;

  /* The class of registers to reload into.  */
  enum reg_class rclass;

  /* The mode this operand should have when reloaded, on input.  */
  machine_mode inmode;
  /* The mode this operand should have when reloaded, on output.  */
  machine_mode outmode;

  /* The mode of the reload register.  */
  machine_mode mode;

  /* the largest number of registers this reload will require.  */
  unsigned int nregs;

  /* Positive amount to increment or decrement by if
     reload_in is a PRE_DEC, PRE_INC, POST_DEC, POST_INC.
     Ignored otherwise (don't assume it is zero).  */
  poly_int64_pod inc;
  /* A reg for which reload_in is the equivalent.
     If reload_in is a symbol_ref which came from
     reg_equiv_constant, then this is the pseudo
     which has that symbol_ref as equivalent.  */
  rtx in_reg;
  rtx out_reg;

  /* Used in find_reload_regs to record the allocated register.  */
  int regno;
  /* This is the register to reload into.  If it is zero when `find_reloads'
     returns, you must find a suitable register in the class specified by
     reload_reg_class, and store here an rtx for that register with mode from
     reload_inmode or reload_outmode.  */
  rtx reg_rtx;
  /* The operand number being reloaded.  This is used to group related reloads
     and need not always be equal to the actual operand number in the insn,
     though it current will be; for in-out operands, it is one of the two
     operand numbers.  */
  int opnum;

  /* Gives the reload number of a secondary input reload, when needed;
     otherwise -1.  */
  int secondary_in_reload;
  /* Gives the reload number of a secondary output reload, when needed;
     otherwise -1.  */
  int secondary_out_reload;
  /* If a secondary input reload is required, gives the INSN_CODE that uses the
     secondary reload as a scratch register, or CODE_FOR_nothing if the
     secondary reload register is to be an intermediate register.  */
  enum insn_code secondary_in_icode;
  /* Likewise, for a secondary output reload.  */
  enum insn_code secondary_out_icode;

  /* Classifies reload as needed either for addressing an input reload,
     addressing an output, for addressing a non-reloaded mem ref, or for
     unspecified purposes (i.e., more than one of the above).  */
  enum reload_type when_needed;

  /* Nonzero for an optional reload.  Optional reloads are ignored unless the
     value is already sitting in a register.  */
  unsigned int optional:1;
  /* nonzero if this reload shouldn't be combined with another reload.  */
  unsigned int nocombine:1;
  /* Nonzero if this is a secondary register for one or more reloads.  */
  unsigned int secondary_p:1;
  /* Nonzero if this reload must use a register not already allocated to a
     group.  */
  unsigned int nongroup:1;
};

extern struct reload rld[MAX_RELOADS];
extern int n_reloads;
#endif

/* Target-dependent globals.  */
struct target_reload {
  /* Nonzero if indirect addressing is supported when the innermost MEM is
     of the form (MEM (SYMBOL_REF sym)).  It is assumed that the level to
     which these are valid is the same as spill_indirect_levels, above.  */
  bool x_indirect_symref_ok;

  /* Nonzero if indirect addressing is supported on the machine; this means
     that spilling (REG n) does not require reloading it into a register in
     order to do (MEM (REG n)) or (MEM (PLUS (REG n) (CONST_INT c))).  The
     value indicates the level of indirect addressing supported, e.g., two
     means that (MEM (MEM (REG n))) is also valid if (REG n) does not get
     a hard register.  */
  unsigned char x_spill_indirect_levels;

  /* True if caller-save has been reinitialized.  */
  bool x_caller_save_initialized_p;

  /* Modes for each hard register that we can save.  The smallest mode is wide
     enough to save the entire contents of the register.  When saving the
     register because it is live we first try to save in multi-register modes.
     If that is not possible the save is done one register at a time.  */
  machine_mode (x_regno_save_mode
		     [FIRST_PSEUDO_REGISTER]
		     [MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1]);

  /* Nonzero if an address (plus (reg frame_pointer) (reg ...)) is valid
     in the given mode.  */
  bool x_double_reg_address_ok[MAX_MACHINE_MODE];

  /* We will only make a register eligible for caller-save if it can be
     saved in its widest mode with a simple SET insn as long as the memory
     address is valid.  We record the INSN_CODE is those insns here since
     when we emit them, the addresses might not be valid, so they might not
     be recognized.  */
  int x_cached_reg_save_code[FIRST_PSEUDO_REGISTER][MAX_MACHINE_MODE];
  int x_cached_reg_restore_code[FIRST_PSEUDO_REGISTER][MAX_MACHINE_MODE];
};

extern struct target_reload default_target_reload;
#if SWITCHABLE_TARGET
extern struct target_reload *this_target_reload;
#else
#define this_target_reload (&default_target_reload)
#endif

#define indirect_symref_ok \
  (this_target_reload->x_indirect_symref_ok)
#define double_reg_address_ok \
  (this_target_reload->x_double_reg_address_ok)
#define caller_save_initialized_p \
  (this_target_reload->x_caller_save_initialized_p)

/* Register equivalences.  Indexed by register number.  */
struct reg_equivs_t
{
  /* The constant value to which pseudo reg N is equivalent,
     or zero if pseudo reg N is not equivalent to a constant.
     find_reloads looks at this in order to replace pseudo reg N
     with the constant it stands for.  */
  rtx constant;

  /* An invariant value to which pseudo reg N is equivalent.
     eliminate_regs_in_insn uses this to replace pseudos in particular
     contexts.  */
  rtx invariant;

  /* A memory location to which pseudo reg N is equivalent,
     prior to any register elimination (such as frame pointer to stack
     pointer).  Depending on whether or not it is a valid address, this value
     is transferred to either equiv_address or equiv_mem.  */
  rtx memory_loc;

  /* The address of stack slot to which pseudo reg N is equivalent.
     This is used when the address is not valid as a memory address
     (because its displacement is too big for the machine.)  */
  rtx address;

  /* The memory slot to which pseudo reg N is equivalent,
     or zero if pseudo reg N is not equivalent to a memory slot.  */
  rtx mem;

  /* An EXPR_LIST of REG_EQUIVs containing MEMs with
     alternate representations of the location of pseudo reg N.  */
  rtx_expr_list *alt_mem_list;

  /* The list of insns that initialized reg N from its equivalent
     constant or memory slot.  */
  rtx_insn_list *init;
};

#define reg_equiv_constant(ELT) \
  (*reg_equivs)[(ELT)].constant
#define reg_equiv_invariant(ELT) \
  (*reg_equivs)[(ELT)].invariant
#define reg_equiv_memory_loc(ELT) \
  (*reg_equivs)[(ELT)].memory_loc
#define reg_equiv_address(ELT) \
  (*reg_equivs)[(ELT)].address
#define reg_equiv_mem(ELT) \
  (*reg_equivs)[(ELT)].mem
#define reg_equiv_alt_mem_list(ELT) \
  (*reg_equivs)[(ELT)].alt_mem_list
#define reg_equiv_init(ELT) \
  (*reg_equivs)[(ELT)].init

extern vec<reg_equivs_t, va_gc> *reg_equivs;

/* All the "earlyclobber" operands of the current insn
   are recorded here.  */
extern int n_earlyclobbers;
extern rtx reload_earlyclobbers[MAX_RECOG_OPERANDS];

/* Save the number of operands.  */
extern int reload_n_operands;

/* First uid used by insns created by reload in this function.
   Used in find_equiv_reg.  */
extern int reload_first_uid;

extern int num_not_at_initial_offset;

#if defined HARD_CONST && defined CLEAR_REG_SET
/* This structure describes instructions which are relevant for reload.
   Apart from all regular insns, this also includes CODE_LABELs, since they
   must be examined for register elimination.  */
class insn_chain
{
public:
  /* Links to the neighbor instructions.  */
  class insn_chain *next, *prev;

  /* Link through a chains set up by calculate_needs_all_insns, containing
     all insns that need reloading.  */
  class insn_chain *next_need_reload;

  /* The rtx of the insn.  */
  rtx_insn *insn;

  /* The basic block this insn is in.  */
  int block;

  /* Nonzero if find_reloads said the insn requires reloading.  */
  unsigned int need_reload:1;
  /* Nonzero if find_reloads needs to be run during reload_as_needed to
     perform modifications on any operands.  */
  unsigned int need_operand_change:1;
  /* Nonzero if eliminate_regs_in_insn said it requires eliminations.  */
  unsigned int need_elim:1;
  /* Nonzero if this insn was inserted by perform_caller_saves.  */
  unsigned int is_caller_save_insn:1;

  /* Register life information: record all live hard registers, and
     all live pseudos that have a hard register.  This set also
     contains pseudos spilled by IRA.  */
  bitmap_head live_throughout;
  bitmap_head dead_or_set;

  /* Copies of the global variables computed by find_reloads.  */
  struct reload *rld;
  int n_reloads;

  /* Indicates which registers have already been used for spills.  */
  HARD_REG_SET used_spill_regs;
};

/* A chain of insn_chain structures to describe all non-note insns in
   a function.  */
extern class insn_chain *reload_insn_chain;

/* Allocate a new insn_chain structure.  */
extern class insn_chain *new_insn_chain (void);
#endif

#if defined HARD_CONST
extern void compute_use_by_pseudos (HARD_REG_SET *, bitmap);
#endif

/* Functions from reload.cc:  */

extern reg_class_t secondary_reload_class (bool, reg_class_t,
					   machine_mode, rtx);

#ifdef GCC_INSN_CODES_H
extern enum reg_class scratch_reload_class (enum insn_code);
#endif

/* Return a memory location that will be used to copy X in mode MODE.
   If we haven't already made a location for this mode in this insn,
   call find_reloads_address on the location being returned.  */
extern rtx get_secondary_mem (rtx, machine_mode, int, enum reload_type);

/* Clear any secondary memory locations we've made.  */
extern void clear_secondary_mem (void);

/* Transfer all replacements that used to be in reload FROM to be in
   reload TO.  */
extern void transfer_replacements (int, int);

/* IN_RTX is the value loaded by a reload that we now decided to inherit,
   or a subpart of it.  If we have any replacements registered for IN_RTX,
   cancel the reloads that were supposed to load them.
   Return nonzero if we canceled any reloads.  */
extern int remove_address_replacements (rtx in_rtx);

/* Like rtx_equal_p except that it allows a REG and a SUBREG to match
   if they are the same hard reg, and has special hacks for
   autoincrement and autodecrement.  */
extern int operands_match_p (rtx, rtx);

/* Return 1 if altering OP will not modify the value of CLOBBER.  */
extern int safe_from_earlyclobber (rtx, rtx);

/* Search the body of INSN for values that need reloading and record them
   with push_reload.  REPLACE nonzero means record also where the values occur
   so that subst_reloads can be used.  */
extern int find_reloads (rtx_insn *, int, int, int, short *);

/* Compute the sum of X and Y, making canonicalizations assumed in an
   address, namely: sum constant integers, surround the sum of two
   constants with a CONST, put the constant as the second operand, and
   group the constant on the outermost sum.  */
extern rtx form_sum (machine_mode, rtx, rtx);

/* Substitute into the current INSN the registers into which we have reloaded
   the things that need reloading.  */
extern void subst_reloads (rtx_insn *);

/* Make a copy of any replacements being done into X and move those copies
   to locations in Y, a copy of X.  We only look at the highest level of
   the RTL.  */
extern void copy_replacements (rtx, rtx);

/* Change any replacements being done to *X to be done to *Y */
extern void move_replacements (rtx *x, rtx *y);

/* If LOC was scheduled to be replaced by something, return the replacement.
   Otherwise, return *LOC.  */
extern rtx find_replacement (rtx *);

/* Nonzero if modifying X will affect IN.  */
extern int reg_overlap_mentioned_for_reload_p (rtx, rtx);

/* Check the insns before INSN to see if there is a suitable register
   containing the same value as GOAL.  */
extern rtx find_equiv_reg (rtx, rtx_insn *, enum reg_class, int, short *,
			   int, machine_mode);

/* Return 1 if register REGNO is the subject of a clobber in insn INSN.  */
extern int regno_clobbered_p (unsigned int, rtx_insn *, machine_mode, int);

/* Return 1 if X is an operand of an insn that is being earlyclobbered.  */
extern int earlyclobber_operand_p (rtx);

/* Record one reload that needs to be performed.  */
extern int push_reload (rtx, rtx, rtx *, rtx *, enum reg_class,
			machine_mode, machine_mode,
			int, int, int, enum reload_type);

/* Functions in reload1.cc:  */

/* Initialize the reload pass once per compilation.  */
extern void init_reload (void);

/* The reload pass itself.  */
extern bool reload (rtx_insn *, int);

/* Mark the slots in regs_ever_live for the hard regs
   used by pseudo-reg number REGNO.  */
extern void mark_home_live (int);

/* Scan X and replace any eliminable registers (such as fp) with a
   replacement (such as sp), plus an offset.  */
extern rtx eliminate_regs (rtx, machine_mode, rtx);
extern bool elimination_target_reg_p (rtx);

/* Called from the register allocator to estimate costs of eliminating
   invariant registers.  */
extern void calculate_elim_costs_all_insns (void);

/* Deallocate the reload register used by reload number R.  */
extern void deallocate_reload_reg (int r);

/* Functions in caller-save.cc:  */

/* Initialize for caller-save.  */
extern void init_caller_save (void);

/* Initialize save areas by showing that we haven't allocated any yet.  */
extern void init_save_areas (void);

/* Allocate save areas for any hard registers that might need saving.  */
extern void setup_save_areas (void);

/* Find the places where hard regs are live across calls and save them.  */
extern void save_call_clobbered_regs (void);

/* Replace (subreg (reg)) with the appropriate (reg) for any operands.  */
extern void cleanup_subreg_operands (rtx_insn *);

/* Debugging support.  */
extern void debug_reload_to_stream (FILE *);
extern void debug_reload (void);

/* Compute the actual register we should reload to, in case we're
   reloading to/from a register that is wider than a word.  */
extern rtx reload_adjust_reg_for_mode (rtx, machine_mode);

/* Allocate or grow the reg_equiv tables, initializing new entries to 0.  */
extern void grow_reg_equivs (void);

#endif /* GCC_RELOAD_H */