i860.c

GCC编译器源代码

     instruction which precedes the loop, but we need to have it done
     two times before we enter the loop because of the bizarre semantics
     of the bla instruction.  */

  output_asm_insn ("adds %5,%2,%2", xoperands);

  /* Check for the case where the original count was less than or equal to
     zero.  Avoid going through the loop at all if the original count was
     indeed less than or equal to zero.  Note that we treat the count as
     if it were a signed 32-bit quantity here, rather than an unsigned one,
     even though we really shouldn't.  We have to do this because of the
     semantics of the `ble' instruction, which assume that the count is
     a signed 32-bit value.  Anyway, in practice it won't matter because
     nobody is going to try to do a memcpy() of more than half of the
     entire address space (i.e. 2 gigabytes) anyway.  */

  output_asm_insn ("bc .Le%3", xoperands);

  /* Make available a register which is a temporary.  */

  xoperands[6] = operands[6];

  /* Now the actual loop.
     In xoperands, elements 1 and 0 are the input and output vectors.
     Element 2 is the loop index.  Element 5 is the increment.  */

  output_asm_insn ("subs %1,%5,%1", xoperands);
  output_asm_insn ("bla %5,%2,.Lm%3", xoperands);
  output_asm_insn ("adds %0,%2,%6", xoperands);
  output_asm_insn ("\n.Lm%3:", xoperands);	    /* Label for bla above.  */
  output_asm_insn ("\n.Ls%3:",  xoperands);	    /* Loop start label. */
  output_asm_insn ("adds %5,%6,%6", xoperands);

  /* NOTE:  The code here which is supposed to handle the cases where the
     sources and destinations are known to start on a 4 or 2 byte boundary
     are currently broken.  They fail to do anything about the overflow
     bytes which might still need to be copied even after we have copied
     some number of words or halfwords.  Thus, for now we use the lowest
     common denominator, i.e. the code which just copies some number of
     totally unaligned individual bytes.  (See the calculation of
     chunk_size above.  */

  if (chunk_size == 4)
    {
      output_asm_insn ("ld.l %2(%1),%?r31", xoperands);
      output_asm_insn ("bla %5,%2,.Ls%3", xoperands);
      output_asm_insn ("st.l %?r31,8(%6)", xoperands);
    }
  else if (chunk_size == 2)
    {
      output_asm_insn ("ld.s %2(%1),%?r31", xoperands);
      output_asm_insn ("bla %5,%2,.Ls%3", xoperands);
      output_asm_insn ("st.s %?r31,4(%6)", xoperands);
    }
  else /* chunk_size == 1 */
    {
      output_asm_insn ("ld.b %2(%1),%?r31", xoperands);
      output_asm_insn ("bla %5,%2,.Ls%3", xoperands);
      output_asm_insn ("st.b %?r31,2(%6)", xoperands);
    }
  output_asm_insn ("\n.Le%3:", xoperands);	    /* Here if count <= 0.  */

  return "";
}

/* Output a delayed branch insn with the delay insn in its
   branch slot.  The delayed branch insn template is in TEMPLATE,
   with operands OPERANDS.  The insn in its delay slot is INSN.

   As a special case, since we know that all memory transfers are via
   ld/st insns, if we see a (MEM (SYMBOL_REF ...)) we divide the memory
   reference around the branch as

	orh ha%x,%?r0,%?r31
	b ...
	ld/st l%x(%?r31),...

   As another special case, we handle loading (SYMBOL_REF ...) and
   other large constants around branches as well:

	orh h%x,%?r0,%0
	b ...
	or l%x,%0,%1

   */

char *
output_delayed_branch (template, operands, insn)
     char *template;
     rtx *operands;
     rtx insn;
{
  rtx src = XVECEXP (PATTERN (insn), 0, 1);
  rtx dest = XVECEXP (PATTERN (insn), 0, 0);

  /* See if we are doing some branch together with setting some register
     to some 32-bit value which does (or may) have some of the high-order
     16 bits set.  If so, we need to set the register in two stages.  One
     stage must be done before the branch, and the other one can be done
     in the delay slot.  */

  if ( (GET_CODE (src) == CONST_INT
	&& ((unsigned) INTVAL (src) & (unsigned) 0xffff0000) != (unsigned) 0)
      || (GET_CODE (src) == SYMBOL_REF)
      || (GET_CODE (src) == LABEL_REF)
      || (GET_CODE (src) == CONST))
    {
      rtx xoperands[2];
      xoperands[0] = dest;
      xoperands[1] = src;

      CC_STATUS_PARTIAL_INIT;
      /* Output the `orh' insn.  */
      output_asm_insn ("orh %H1,%?r0,%0", xoperands);

      /* Output the branch instruction next.  */
      output_asm_insn (template, operands);

      /* Now output the `or' insn.  */
      output_asm_insn ("or %L1,%0,%0", xoperands);
    }
  else if ((GET_CODE (src) == MEM
	    && CONSTANT_ADDRESS_P (XEXP (src, 0)))
	   || (GET_CODE (dest) == MEM
	       && CONSTANT_ADDRESS_P (XEXP (dest, 0))))
    {
      rtx xoperands[2];
      char *split_template;
      xoperands[0] = dest;
      xoperands[1] = src;

      /* Output the `orh' insn.  */
      if (GET_CODE (src) == MEM)
	{
	  if (! ((cc_prev_status.flags & CC_KNOW_HI_R31)
		 && (cc_prev_status.flags & CC_HI_R31_ADJ)
		 && cc_prev_status.mdep == XEXP (operands[1], 0)))
	    {
	      CC_STATUS_INIT;
	      output_asm_insn ("orh %h1,%?r0,%?r31", xoperands);
	    }
	  split_template = load_opcode (GET_MODE (dest),
					"%L1(%?r31),%0", dest);
	}
      else
	{
	  if (! ((cc_prev_status.flags & CC_KNOW_HI_R31)
		 && (cc_prev_status.flags & CC_HI_R31_ADJ)
		 && cc_prev_status.mdep == XEXP (operands[0], 0)))
	    {
	      CC_STATUS_INIT;
	      output_asm_insn ("orh %h0,%?r0,%?r31", xoperands);
	    }
	  split_template = store_opcode (GET_MODE (dest),
					 "%r1,%L0(%?r31)", src);
	}

      /* Output the branch instruction next.  */
      output_asm_insn (template, operands);

      /* Now output the load or store.
	 No need to do a CC_STATUS_INIT, because we are branching anyway.  */
      output_asm_insn (split_template, xoperands);
    }
  else
    {
      int insn_code_number;
      rtx pat = gen_rtx (SET, VOIDmode, dest, src);
      rtx delay_insn = gen_rtx (INSN, VOIDmode, 0, 0, 0, pat, -1, 0, 0);
      int i;

      /* Output the branch instruction first.  */
      output_asm_insn (template, operands);

      /* Now recognize the insn which we put in its delay slot.
	 We must do this after outputting the branch insn,
	 since operands may just be a pointer to `recog_operand'.  */
      INSN_CODE (delay_insn) = insn_code_number = recog (pat, delay_insn);
      if (insn_code_number == -1)
	abort ();

      for (i = 0; i < insn_n_operands[insn_code_number]; i++)
	{
	  if (GET_CODE (recog_operand[i]) == SUBREG)
	    recog_operand[i] = alter_subreg (recog_operand[i]);
	}

      insn_extract (delay_insn);
      if (! constrain_operands (insn_code_number, 1))
	fatal_insn_not_found (delay_insn);

      template = insn_template[insn_code_number];
      if (template == 0)
	template = (*insn_outfun[insn_code_number]) (recog_operand, delay_insn);
      output_asm_insn (template, recog_operand);
    }
  CC_STATUS_INIT;
  return "";
}

/* Output a newly constructed insn DELAY_INSN.  */
char *
output_delay_insn (delay_insn)
     rtx delay_insn;
{
  char *template;
  int insn_code_number;
  int i;

  /* Now recognize the insn which we put in its delay slot.
     We must do this after outputting the branch insn,
     since operands may just be a pointer to `recog_operand'.  */
  insn_code_number = recog_memoized (delay_insn);
  if (insn_code_number == -1)
    abort ();

  /* Extract the operands of this delay insn.  */
  INSN_CODE (delay_insn) = insn_code_number;
  insn_extract (delay_insn);

  /* It is possible that this insn has not been properly scanned by final
     yet.  If this insn's operands don't appear in the peephole's
     actual operands, then they won't be fixed up by final, so we
     make sure they get fixed up here.  -- This is a kludge.  */
  for (i = 0; i < insn_n_operands[insn_code_number]; i++)
    {
      if (GET_CODE (recog_operand[i]) == SUBREG)
	recog_operand[i] = alter_subreg (recog_operand[i]);
    }

#ifdef REGISTER_CONSTRAINTS
  if (! constrain_operands (insn_code_number))
    abort ();
#endif

  cc_prev_status = cc_status;

  /* Update `cc_status' for this instruction.
     The instruction's output routine may change it further.
     If the output routine for a jump insn needs to depend
     on the cc status, it should look at cc_prev_status.  */

  NOTICE_UPDATE_CC (PATTERN (delay_insn), delay_insn);

  /* Now get the template for what this insn would
     have been, without the branch.  */

  template = insn_template[insn_code_number];
  if (template == 0)
    template = (*insn_outfun[insn_code_number]) (recog_operand, delay_insn);
  output_asm_insn (template, recog_operand);
  return "";
}

/* Special routine to convert an SFmode value represented as a
   CONST_DOUBLE into its equivalent unsigned long bit pattern.
   We convert the value from a double precision floating-point
   value to single precision first, and thence to a bit-wise
   equivalent unsigned long value.  This routine is used when
   generating an immediate move of an SFmode value directly
   into a general register because the svr4 assembler doesn't
   grok floating literals in instruction operand contexts.  */

unsigned long
sfmode_constant_to_ulong (x)
     rtx x;
{
  REAL_VALUE_TYPE d;
  union { float f; unsigned long i; } u2;

  if (GET_CODE (x) != CONST_DOUBLE || GET_MODE (x) != SFmode)
    abort ();

#if TARGET_FLOAT_FORMAT != HOST_FLOAT_FORMAT
 error IEEE emulation needed
#endif
  REAL_VALUE_FROM_CONST_DOUBLE (d, x);
  u2.f = d;
  return u2.i;
}

/* This function generates the assembly code for function entry.
   The macro FUNCTION_PROLOGUE in i860.h is defined to call this function.

   ASM_FILE is a stdio stream to output the code to.
   SIZE is an int: how many units of temporary storage to allocate.

   Refer to the array `regs_ever_live' to determine which registers
   to save; `regs_ever_live[I]' is nonzero if register number I
   is ever used in the function.  This macro is responsible for
   knowing which registers should not be saved even if used.

   NOTE: `frame_lower_bytes' is the count of bytes which will lie
   between the new `fp' value and the new `sp' value after the
   prologue is done.  `frame_upper_bytes' is the count of bytes
   that will lie between the new `fp' and the *old* `sp' value
   after the new `fp' is setup (in the prologue).  The upper
   part of each frame always includes at least 2 words (8 bytes)
   to hold the saved frame pointer and the saved return address.

   The svr4 ABI for the i860 now requires that the values of the
   stack pointer and frame pointer registers be kept aligned to
   16-byte boundaries at all times.  We obey that restriction here.

   The svr4 ABI for the i860 is entirely vague when it comes to specifying
   exactly where the "preserved" registers should be saved.  The native
   svr4 C compiler I now have doesn't help to clarify the requirements
   very much because it is plainly out-of-date and non-ABI-compliant
   (in at least one important way, i.e. how it generates function
   epilogues).

   The native svr4 C compiler saves the "preserved" registers (i.e.
   r4-r15 and f2-f7) in the lower part of a frame (i.e. at negative
   offsets from the frame pointer).

   Previous versions of GCC also saved the "preserved" registers in the
   "negative" part of the frame, but they saved them using positive
   offsets from the (adjusted) stack pointer (after it had been adjusted
   to allocate space for the new frame).  That's just plain wrong
   because if the current function calls alloca(), the stack pointer
   will get moved, and it will be impossible to restore the registers
   properly again after that.

   Both compilers handled parameter registers (i.e. r16-r27 and f8-f15)
   by copying their values either into various "preserved" registers or
   into stack slots in the lower part of the current frame (as seemed
   appropriate, depending upon subsequent usage of these values).

   Here we want to save the preserved registers at some offset from the
   frame pointer register so as to avoid any possible problems arising
   from calls to alloca().  We can either save them at small positive
   offsets from the frame pointer, or at small negative offsets from
   the frame pointer.  If we save them at small negative offsets from
   the frame pointer (i.e. in the lower part of the frame) then we
   must tell the rest of GCC (via STARTING_FRAME_OFFSET) exactly how
   many bytes of space we plan to use in the lower part of the frame
   for this purpose.  Since other parts of the compiler reference the
   value of STARTING_FRAME_OFFSET long before final() calls this function,
   we would have to go ahead and assume the worst-case storage requirements
   for saving all of the "preserved" registers (and use that number, i.e.
   `80', to define STARTING_FRAME_OFFSET) if we wanted to save them in
   the lower part of the frame.  That could potentially be very wasteful,
   and that wastefulness could really hamper people compiling for embedded
   i860 targets with very tight limits on stack space.  Thus, we choose
   here to save the preserved registers in the upper part of the
   frame, so that we can decide at the very last minute how much (or how
   little) space we must allocate for this purpose.

   To satisfy the needs of the svr4 ABI "tdesc" scheme, preserved
   registers must always be saved so that the saved values of registers
   with higher numbers are at higher addresses.  We obey that restriction
   here.

   There are two somewhat different ways that you can generate prologues
   here... i.e. pedantically ABI-compliant, and the "other" way.  The
   "other" way is more consistent with what is currently generated by the
   "native" svr4 C compiler for the i860.  That's important if you want
   to use the current (as of 8/91) incarnation of svr4 SDB for the i860.
   The SVR4 SDB for the i860 insists on having function prologues be
   non-ABI-compliant!

   To get fully ABI-compliant prologues, define I860_STRICT_ABI_PROLOGUES
   in the i860svr4.h file.  (By default this is *not* defined).

   The differences between the ABI-compliant and non-ABI-compliant prologues
   are that (a) the ABI version seems to require the use of *signed*
   (rather than unsigned) adds and subtracts, and (b) the ordering of
   the various steps (e.g. saving preserved registers, saving the
   return address, setting up the new frame pointer value) is different.

   For strict ABI compliance, it seems to be the case that the very last
   thing that is supposed to happen in the prologue is getting the frame
   pointer set to its new value (but only after everything else has
   already been properly setup).  We do that here, but only if the symbol
   I860_STRICT_ABI_PROLOGUES is defined.
*/

#ifndef STACK_ALIGNMENT
#define STACK_ALIGNMENT	16
#endif

extern char call_used_regs[];
extern int leaf_function_p ();

char *current_function_original_name;

static int must_preserve_r1;
static unsigned must_preserve_bytes;

void
function_prologue (asm_file, local_bytes)
     register FILE *asm_file;
     register unsigned local_bytes;
{
  register unsigned frame_lower_bytes;
  register unsigned frame_upper_bytes;
  register unsigned total_fsize;
  register unsigned preserved_reg_bytes = 0;
  register unsigned i;
  register unsigned preserved_so_far = 0;

  must_preserve_r1 = (optimize < 2 || ! leaf_function_p ());
  must_preserve_bytes = 4 + (must_preserve_r1 ? 4 : 0);

  /* Count registers that need preserving.  Ignore r0.  It never needs
     preserving.  */

  for (i = 1; i < FIRST_PSEUDO_REGISTER; i++)
    {
      if (regs_ever_live[i] && ! call_used_regs[i])
        preserved_reg_bytes += 4;
    }

  /* Round-up the frame_lower_bytes so that it's a multiple of 16. */

  frame_lower_bytes = (local_bytes + STACK_ALIGNMENT - 1) & -STACK_ALIGNMENT;

  /* The upper part of each frame will contain the saved fp,
     the saved r1, and stack slots for all of the other "preserved"
     registers that we find we will need to save & restore. */