bfin.c

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/* The Blackfin code generation auxiliary output file.
   Copyright (C) 2005  Free Software Foundation, Inc.
   Contributed by Analog Devices.

   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 2, 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 COPYING.  If not, write to
   the Free Software Foundation, 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "rtl.h"
#include "regs.h"
#include "hard-reg-set.h"
#include "real.h"
#include "insn-config.h"
#include "insn-codes.h"
#include "conditions.h"
#include "insn-flags.h"
#include "output.h"
#include "insn-attr.h"
#include "tree.h"
#include "flags.h"
#include "except.h"
#include "function.h"
#include "input.h"
#include "target.h"
#include "target-def.h"
#include "expr.h"
#include "toplev.h"
#include "recog.h"
#include "ggc.h"
#include "integrate.h"
#include "cgraph.h"
#include "langhooks.h"
#include "bfin-protos.h"
#include "tm-preds.h"
#include "gt-bfin.h"

/* Test and compare insns in bfin.md store the information needed to
   generate branch and scc insns here.  */
rtx bfin_compare_op0, bfin_compare_op1;

/* RTX for condition code flag register and RETS register */
extern GTY(()) rtx bfin_cc_rtx;
extern GTY(()) rtx bfin_rets_rtx;
rtx bfin_cc_rtx, bfin_rets_rtx;

int max_arg_registers = 0;

/* Arrays used when emitting register names.  */
const char *short_reg_names[]  =  SHORT_REGISTER_NAMES;
const char *high_reg_names[]   =  HIGH_REGISTER_NAMES;
const char *dregs_pair_names[] =  DREGS_PAIR_NAMES;
const char *byte_reg_names[]   =  BYTE_REGISTER_NAMES;

static int arg_regs[] = FUNCTION_ARG_REGISTERS;

/* Nonzero if -mshared-library-id was given.  */
static int bfin_lib_id_given;

static void
bfin_globalize_label (FILE *stream, const char *name)
{
  fputs (".global ", stream);
  assemble_name (stream, name);
  fputc (';',stream);
  fputc ('\n',stream);
}

static void 
output_file_start (void) 
{
  FILE *file = asm_out_file;
  int i;

  fprintf (file, ".file \"%s\";\n", input_filename);
  
  for (i = 0; arg_regs[i] >= 0; i++)
    ;
  max_arg_registers = i;	/* how many arg reg used  */
}

/* Called early in the compilation to conditionally modify
   fixed_regs/call_used_regs.  */

void 
conditional_register_usage (void)
{
  /* initialize condition code flag register rtx */
  bfin_cc_rtx = gen_rtx_REG (BImode, REG_CC);
  bfin_rets_rtx = gen_rtx_REG (Pmode, REG_RETS);
}

/* Examine machine-dependent attributes of function type FUNTYPE and return its
   type.  See the definition of E_FUNKIND.  */

static e_funkind funkind (tree funtype)
{
  tree attrs = TYPE_ATTRIBUTES (funtype);
  if (lookup_attribute ("interrupt_handler", attrs))
    return INTERRUPT_HANDLER;
  else if (lookup_attribute ("exception_handler", attrs))
    return EXCPT_HANDLER;
  else if (lookup_attribute ("nmi_handler", attrs))
    return NMI_HANDLER;
  else
    return SUBROUTINE;
}

/* Legitimize PIC addresses.  If the address is already position-independent,
   we return ORIG.  Newly generated position-independent addresses go into a
   reg.  This is REG if nonzero, otherwise we allocate register(s) as
   necessary.  PICREG is the register holding the pointer to the PIC offset
   table.  */

rtx
legitimize_pic_address (rtx orig, rtx reg, rtx picreg)
{
  rtx addr = orig;
  rtx new = orig;

  if (GET_CODE (addr) == SYMBOL_REF || GET_CODE (addr) == LABEL_REF)
    {
      if (GET_CODE (addr) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (addr))
	reg = new = orig;
      else
	{
	  if (reg == 0)
	    {
	      gcc_assert (!no_new_pseudos);
	      reg = gen_reg_rtx (Pmode);
	    }

	  if (flag_pic == 2)
	    {
	      emit_insn (gen_movsi_high_pic (reg, addr));
	      emit_insn (gen_movsi_low_pic (reg, reg, addr));
	      emit_insn (gen_addsi3 (reg, reg, picreg));
	      new = gen_const_mem (Pmode, reg);
	    }
	  else
	    {
	      rtx tmp = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, addr),
					UNSPEC_MOVE_PIC);
	      new = gen_const_mem (Pmode,
				   gen_rtx_PLUS (Pmode, picreg, tmp));
	    }
	  emit_move_insn (reg, new);
	}
      if (picreg == pic_offset_table_rtx)
	current_function_uses_pic_offset_table = 1;
      return reg;
    }

  else if (GET_CODE (addr) == CONST || GET_CODE (addr) == PLUS)
    {
      rtx base;

      if (GET_CODE (addr) == CONST)
	{
	  addr = XEXP (addr, 0);
	  gcc_assert (GET_CODE (addr) == PLUS);
	}

      if (XEXP (addr, 0) == picreg)
	return orig;

      if (reg == 0)
	{
	  gcc_assert (!no_new_pseudos);
	  reg = gen_reg_rtx (Pmode);
	}

      base = legitimize_pic_address (XEXP (addr, 0), reg, picreg);
      addr = legitimize_pic_address (XEXP (addr, 1),
				     base == reg ? NULL_RTX : reg,
				     picreg);

      if (GET_CODE (addr) == CONST_INT)
	{
	  gcc_assert (! reload_in_progress && ! reload_completed);
	  addr = force_reg (Pmode, addr);
	}

      if (GET_CODE (addr) == PLUS && CONSTANT_P (XEXP (addr, 1)))
	{
	  base = gen_rtx_PLUS (Pmode, base, XEXP (addr, 0));
	  addr = XEXP (addr, 1);
	}

      return gen_rtx_PLUS (Pmode, base, addr);
    }

  return new;
}

/* Stack frame layout. */

/* Compute the number of DREGS to save with a push_multiple operation.
   This could include registers that aren't modified in the function,
   since push_multiple only takes a range of registers.
   If IS_INTHANDLER, then everything that is live must be saved, even
   if normally call-clobbered.  */

static int
n_dregs_to_save (bool is_inthandler)
{
  unsigned i;

  for (i = REG_R0; i <= REG_R7; i++)
    {
      if (regs_ever_live[i] && (is_inthandler || ! call_used_regs[i]))
	return REG_R7 - i + 1;

      if (current_function_calls_eh_return)
	{
	  unsigned j;
	  for (j = 0; ; j++)
	    {
	      unsigned test = EH_RETURN_DATA_REGNO (j);
	      if (test == INVALID_REGNUM)
		break;
	      if (test == i)
		return REG_R7 - i + 1;
	    }
	}

    }
  return 0;
}

/* Like n_dregs_to_save, but compute number of PREGS to save.  */

static int
n_pregs_to_save (bool is_inthandler)
{
  unsigned i;

  for (i = REG_P0; i <= REG_P5; i++)
    if ((regs_ever_live[i] && (is_inthandler || ! call_used_regs[i]))
	|| (i == PIC_OFFSET_TABLE_REGNUM
	    && (current_function_uses_pic_offset_table
		|| (TARGET_ID_SHARED_LIBRARY && ! current_function_is_leaf))))
      return REG_P5 - i + 1;
  return 0;
}

/* Determine if we are going to save the frame pointer in the prologue.  */

static bool
must_save_fp_p (void)
{
  return frame_pointer_needed || regs_ever_live[REG_FP];
}

static bool
stack_frame_needed_p (void)
{
  /* EH return puts a new return address into the frame using an
     address relative to the frame pointer.  */
  if (current_function_calls_eh_return)
    return true;
  return frame_pointer_needed;
}

/* Emit code to save registers in the prologue.  SAVEALL is nonzero if we
   must save all registers; this is used for interrupt handlers.
   SPREG contains (reg:SI REG_SP).  IS_INTHANDLER is true if we're doing
   this for an interrupt (or exception) handler.  */

static void
expand_prologue_reg_save (rtx spreg, int saveall, bool is_inthandler)
{
  int ndregs = saveall ? 8 : n_dregs_to_save (is_inthandler);
  int npregs = saveall ? 6 : n_pregs_to_save (is_inthandler);
  int dregno = REG_R7 + 1 - ndregs;
  int pregno = REG_P5 + 1 - npregs;
  int total = ndregs + npregs;
  int i;
  rtx pat, insn, val;

  if (total == 0)
    return;

  val = GEN_INT (-total * 4);
  pat = gen_rtx_PARALLEL (VOIDmode, rtvec_alloc (total + 2));
  XVECEXP (pat, 0, 0) = gen_rtx_UNSPEC (VOIDmode, gen_rtvec (1, val),
					UNSPEC_PUSH_MULTIPLE);
  XVECEXP (pat, 0, total + 1) = gen_rtx_SET (VOIDmode, spreg,
					     gen_rtx_PLUS (Pmode, spreg,
							   val));
  RTX_FRAME_RELATED_P (XVECEXP (pat, 0, total + 1)) = 1;
  for (i = 0; i < total; i++)
    {
      rtx memref = gen_rtx_MEM (word_mode,
				gen_rtx_PLUS (Pmode, spreg,
					      GEN_INT (- i * 4 - 4)));
      rtx subpat;
      if (ndregs > 0)
	{
	  subpat = gen_rtx_SET (VOIDmode, memref, gen_rtx_REG (word_mode,
							       dregno++));
	  ndregs--;
	}
      else
	{
	  subpat = gen_rtx_SET (VOIDmode, memref, gen_rtx_REG (word_mode,
							       pregno++));
	  npregs++;
	}
      XVECEXP (pat, 0, i + 1) = subpat;
      RTX_FRAME_RELATED_P (subpat) = 1;
    }
  insn = emit_insn (pat);
  RTX_FRAME_RELATED_P (insn) = 1;
}

/* Emit code to restore registers in the epilogue.  SAVEALL is nonzero if we
   must save all registers; this is used for interrupt handlers.
   SPREG contains (reg:SI REG_SP).  IS_INTHANDLER is true if we're doing
   this for an interrupt (or exception) handler.  */

static void
expand_epilogue_reg_restore (rtx spreg, bool saveall, bool is_inthandler)
{
  int ndregs = saveall ? 8 : n_dregs_to_save (is_inthandler);
  int npregs = saveall ? 6 : n_pregs_to_save (is_inthandler);
  int total = ndregs + npregs;
  int i, regno;
  rtx pat, insn;

  if (total == 0)
    return;

  pat = gen_rtx_PARALLEL (VOIDmode, rtvec_alloc (total + 1));
  XVECEXP (pat, 0, 0) = gen_rtx_SET (VOIDmode, spreg,
				     gen_rtx_PLUS (Pmode, spreg,
						   GEN_INT (total * 4)));

  if (npregs > 0)
    regno = REG_P5 + 1;
  else
    regno = REG_R7 + 1;

  for (i = 0; i < total; i++)
    {
      rtx addr = (i > 0
		  ? gen_rtx_PLUS (Pmode, spreg, GEN_INT (i * 4))
		  : spreg);
      rtx memref = gen_rtx_MEM (word_mode, addr);

      regno--;
      XVECEXP (pat, 0, i + 1)
	= gen_rtx_SET (VOIDmode, gen_rtx_REG (word_mode, regno), memref);

      if (npregs > 0)
	{
	  if (--npregs == 0)
	    regno = REG_R7 + 1;
	}
    }

  insn = emit_insn (pat);
  RTX_FRAME_RELATED_P (insn) = 1;
}

/* Perform any needed actions needed for a function that is receiving a
   variable number of arguments.

   CUM is as above.

   MODE and TYPE are the mode and type of the current parameter.

   PRETEND_SIZE is a variable that should be set to the amount of stack
   that must be pushed by the prolog to pretend that our caller pushed
   it.

   Normally, this macro will push all remaining incoming registers on the
   stack and set PRETEND_SIZE to the length of the registers pushed.  

   Blackfin specific :
   - VDSP C compiler manual (our ABI) says that a variable args function
     should save the R0, R1 and R2 registers in the stack.
   - The caller will always leave space on the stack for the
     arguments that are passed in registers, so we dont have
     to leave any extra space.
   - now, the vastart pointer can access all arguments from the stack.  */

static void
setup_incoming_varargs (CUMULATIVE_ARGS *cum,
			enum machine_mode mode ATTRIBUTE_UNUSED,
			tree type ATTRIBUTE_UNUSED, int *pretend_size,
			int no_rtl)
{
  rtx mem;
  int i;

  if (no_rtl)
    return;

  /* The move for named arguments will be generated automatically by the
     compiler.  We need to generate the move rtx for the unnamed arguments
     if they are in the first 3 words.  We assume at least 1 named argument
     exists, so we never generate [ARGP] = R0 here.  */

  for (i = cum->words + 1; i < max_arg_registers; i++)
    {
      mem = gen_rtx_MEM (Pmode,
			 plus_constant (arg_pointer_rtx, (i * UNITS_PER_WORD)));
      emit_move_insn (mem, gen_rtx_REG (Pmode, i));
    }

  *pretend_size = 0;
}

/* Value should be nonzero if functions must have frame pointers.
   Zero means the frame pointer need not be set up (and parms may
   be accessed via the stack pointer) in functions that seem suitable.  */

int
bfin_frame_pointer_required (void) 
{
  e_funkind fkind = funkind (TREE_TYPE (current_function_decl));

  if (fkind != SUBROUTINE)
    return 1;

  /* We turn on -fomit-frame-pointer if -momit-leaf-frame-pointer is used,
     so we have to override it for non-leaf functions.  */
  if (TARGET_OMIT_LEAF_FRAME_POINTER && ! current_function_is_leaf)
    return 1;

  return 0;
}

/* Return the number of registers pushed during the prologue.  */

static int
n_regs_saved_by_prologue (void)
{
  e_funkind fkind = funkind (TREE_TYPE (current_function_decl));
  bool is_inthandler = fkind != SUBROUTINE;
  tree attrs = TYPE_ATTRIBUTES (TREE_TYPE (current_function_decl));
  bool all = (lookup_attribute ("saveall", attrs) != NULL_TREE
	      || (is_inthandler && !current_function_is_leaf));
  int ndregs = all ? 8 : n_dregs_to_save (is_inthandler);
  int npregs = all ? 6 : n_pregs_to_save (is_inthandler);  
  int n = ndregs + npregs;

  if (all || stack_frame_needed_p ())
    /* We use a LINK instruction in this case.  */
    n += 2;
  else
    {
      if (must_save_fp_p ())
	n++;
      if (! current_function_is_leaf)
	n++;
    }

  if (fkind != SUBROUTINE)
    {
      int i;

      /* Increment once for ASTAT.  */
      n++;

      /* RETE/X/N.  */