xtensa.md

gcc-you can use this code to learn something about gcc, and inquire further into linux,

  if (!xtensa_expand_conditional_move (operands, 1)) FAIL;
  DONE;
}")

(define_insn "movsicc_internal0"
  [(set (match_operand:SI 0 "register_operand" "=a,a")
	(if_then_else:SI (match_operator 4 "branch_operator"
			   [(match_operand:SI 1 "register_operand" "r,r")
			    (const_int 0)])
			 (match_operand:SI 2 "register_operand" "r,0")
			 (match_operand:SI 3 "register_operand" "0,r")))]
  ""
  "*
{
  if (which_alternative == 0)
    {
      switch (GET_CODE (operands[4]))
	{
	case EQ:	return \"moveqz\\t%0, %2, %1\";
	case NE:	return \"movnez\\t%0, %2, %1\";
	case LT:	return \"movltz\\t%0, %2, %1\";
	case GE:	return \"movgez\\t%0, %2, %1\";
	default:	break;
	}
    }
  else
    {
      switch (GET_CODE (operands[4]))
	{
	case EQ:	return \"movnez\\t%0, %3, %1\";
	case NE:	return \"moveqz\\t%0, %3, %1\";
	case LT:	return \"movgez\\t%0, %3, %1\";
	case GE:	return \"movltz\\t%0, %3, %1\";
	default:	break;
	}
    }
  fatal_insn (\"unexpected cmov operator\", operands[4]);
  return \"\";
}"
  [(set_attr "type"	"move,move")
   (set_attr "mode"	"SI")
   (set_attr "length"	"3,3")])

(define_insn "movsicc_internal1"
  [(set (match_operand:SI 0 "register_operand" "=a,a")
	(if_then_else:SI (match_operator 4 "boolean_operator"
			   [(match_operand:CC 1 "register_operand" "b,b")
			    (const_int 0)])
			 (match_operand:SI 2 "register_operand" "r,0")
			 (match_operand:SI 3 "register_operand" "0,r")))]
  "TARGET_BOOLEANS"
  "*
{
  int isEq = (GET_CODE (operands[4]) == EQ);
  switch (which_alternative)
    {
    case 0:
      if (isEq) return \"movf\\t%0, %2, %1\";
      return \"movt\\t%0, %2, %1\";
    case 1:
      if (isEq) return \"movt\\t%0, %3, %1\";
      return \"movf\\t%0, %3, %1\";
    }
  abort ();
  return \"\";
}"
  [(set_attr "type"	"move,move")
   (set_attr "mode"	"SI")
   (set_attr "length"	"3,3")])

(define_insn "movsfcc_internal0"
  [(set (match_operand:SF 0 "register_operand" "=a,a,f,f")
	(if_then_else:SF (match_operator 4 "branch_operator"
			   [(match_operand:SI 1 "register_operand" "r,r,r,r")
			    (const_int 0)])
			 (match_operand:SF 2 "register_operand" "r,0,f,0")
			 (match_operand:SF 3 "register_operand" "0,r,0,f")))]
  ""
  "*
{
  if (which_alternative == 0)
    {
      switch (GET_CODE (operands[4]))
	{
	case EQ:	return \"moveqz\\t%0, %2, %1\";
	case NE:	return \"movnez\\t%0, %2, %1\";
	case LT:	return \"movltz\\t%0, %2, %1\";
	case GE:	return \"movgez\\t%0, %2, %1\";
	default:	break;
	}
    }
  else if (which_alternative == 1)
    {
      switch (GET_CODE (operands[4]))
	{
	case EQ:	return \"movnez\\t%0, %3, %1\";
	case NE:	return \"moveqz\\t%0, %3, %1\";
	case LT:	return \"movgez\\t%0, %3, %1\";
	case GE:	return \"movltz\\t%0, %3, %1\";
	default:	break;
	}
    }
  else if (which_alternative == 2)
    {
      switch (GET_CODE (operands[4]))
	{
	case EQ:	return \"moveqz.s %0, %2, %1\";
	case NE:	return \"movnez.s %0, %2, %1\";
	case LT:	return \"movltz.s %0, %2, %1\";
	case GE:	return \"movgez.s %0, %2, %1\";
	default:	break;
	}
    }
  else if (which_alternative == 3)
    {
      switch (GET_CODE (operands[4]))
	{
	case EQ:	return \"movnez.s %0, %3, %1\";
	case NE:	return \"moveqz.s %0, %3, %1\";
	case LT:	return \"movgez.s %0, %3, %1\";
	case GE:	return \"movltz.s %0, %3, %1\";
	default:	break;
	}
    }
  fatal_insn (\"unexpected cmov operator\", operands[4]);
  return \"\";
}"
  [(set_attr "type"	"move,move,move,move")
   (set_attr "mode"	"SF")
   (set_attr "length"	"3,3,3,3")])

(define_insn "movsfcc_internal1"
  [(set (match_operand:SF 0 "register_operand" "=a,a,f,f")
	(if_then_else:SF (match_operator 4 "boolean_operator"
			   [(match_operand:CC 1 "register_operand" "b,b,b,b")
			    (const_int 0)])
			 (match_operand:SF 2 "register_operand" "r,0,f,0")
			 (match_operand:SF 3 "register_operand" "0,r,0,f")))]
  "TARGET_BOOLEANS"
  "*
{
  int isEq = (GET_CODE (operands[4]) == EQ);
  switch (which_alternative)
    {
    case 0:
      if (isEq) return \"movf\\t%0, %2, %1\";
      return \"movt\\t%0, %2, %1\";
    case 1:
      if (isEq) return \"movt\\t%0, %3, %1\";
      return \"movf\\t%0, %3, %1\";
    case 2:
      if (isEq) return \"movf.s\\t%0, %2, %1\";
      return \"movt.s\\t%0, %2, %1\";
    case 3:
      if (isEq) return \"movt.s\\t%0, %3, %1\";
      return \"movf.s\\t%0, %3, %1\";
    }
  abort ();
  return \"\";
}"
  [(set_attr "type"	"move,move,move,move")
   (set_attr "mode"	"SF")
   (set_attr "length"	"3,3,3,3")])


;;
;;  ....................
;;
;;	FLOATING POINT COMPARISONS
;;
;;  ....................
;;

(define_insn "seq_sf"
  [(set (match_operand:CC 0 "register_operand" "=b")
	(eq:CC (match_operand:SF 1 "register_operand" "f")
	       (match_operand:SF 2 "register_operand" "f")))]
  "TARGET_HARD_FLOAT"
  "oeq.s\\t%0, %1, %2"
  [(set_attr "type"	"farith")
   (set_attr "mode"	"BL")
   (set_attr "length"	"3")])

(define_insn "slt_sf"
  [(set (match_operand:CC 0 "register_operand" "=b")
	(lt:CC (match_operand:SF 1 "register_operand" "f")
	       (match_operand:SF 2 "register_operand" "f")))]
  "TARGET_HARD_FLOAT"
  "olt.s\\t%0, %1, %2"
  [(set_attr "type"	"farith")
   (set_attr "mode"	"BL")
   (set_attr "length"	"3")])

(define_insn "sle_sf"
  [(set (match_operand:CC 0 "register_operand" "=b")
	(le:CC (match_operand:SF 1 "register_operand" "f")
	       (match_operand:SF 2 "register_operand" "f")))]
  "TARGET_HARD_FLOAT"
  "ole.s\\t%0, %1, %2"
  [(set_attr "type"	"farith")
   (set_attr "mode"	"BL")
   (set_attr "length"	"3")])


;;
;;  ....................
;;
;;	UNCONDITIONAL BRANCHES
;;
;;  ....................
;;

(define_insn "jump"
  [(set (pc)
	(label_ref (match_operand 0 "" "")))]
  ""
  "j\\t%l0"
  [(set_attr "type"	"jump")
   (set_attr "mode"	"none")
   (set_attr "length"	"3")])

(define_expand "indirect_jump"
  [(set (pc) (match_operand 0 "register_operand" ""))]
  ""
  "
{
  rtx dest = operands[0];
  if (GET_CODE (dest) != REG || GET_MODE (dest) != Pmode)
    operands[0] = copy_to_mode_reg (Pmode, dest);

  emit_jump_insn (gen_indirect_jump_internal (dest));
  DONE;
}")

(define_insn "indirect_jump_internal"
  [(set (pc) (match_operand:SI 0 "register_operand" "r"))]
  ""
  "jx\\t%0"
  [(set_attr "type"	"jump")
   (set_attr "mode"	"none")
   (set_attr "length"	"3")])


(define_expand "tablejump"
  [(use (match_operand:SI 0 "register_operand" ""))
   (use (label_ref (match_operand 1 "" "")))]
   ""
   "
{
  rtx target = operands[0];
  if (flag_pic)
    {
      /* For PIC, the table entry is relative to the start of the table. */
      rtx label = gen_reg_rtx (SImode);
      target = gen_reg_rtx (SImode);
      emit_move_insn (label, gen_rtx_LABEL_REF (SImode, operands[1]));
      emit_insn (gen_addsi3 (target, operands[0], label));
    }
  emit_jump_insn (gen_tablejump_internal (target, operands[1]));
  DONE;
}")

(define_insn "tablejump_internal"
  [(set (pc)
	(match_operand:SI 0 "register_operand" "r"))
   (use (label_ref (match_operand 1 "" "")))]
  ""
  "jx\\t%0"
  [(set_attr "type"	"jump")
   (set_attr "mode"	"none")
   (set_attr "length"	"3")])


;;
;;  ....................
;;
;;	FUNCTION CALLS
;;
;;  ....................
;;

(define_expand "sym_PLT"
  [(const (unspec [(match_operand:SI 0 "" "")] UNSPEC_PLT))]
  ""
  "")

(define_expand "call"
  [(call (match_operand 0 "memory_operand" "")
	 (match_operand 1 "" ""))]
  ""
  "
{
  rtx addr = XEXP (operands[0], 0);
  if (flag_pic && GET_CODE (addr) == SYMBOL_REF && !SYMBOL_REF_FLAG (addr))
    addr = gen_sym_PLT (addr);
  if (!call_insn_operand (addr, VOIDmode))
    XEXP (operands[0], 0) = copy_to_mode_reg (Pmode, addr);
}")

(define_insn "call_internal"
  [(call (mem (match_operand:SI 0 "call_insn_operand" "n,i,r"))
	 (match_operand 1 "" "i,i,i"))]
  ""
  "*
    return xtensa_emit_call (0, operands);
  "
  [(set_attr "type"	"call")
   (set_attr "mode"	"none")
   (set_attr "length"	"3")])

(define_expand "call_value"
  [(set (match_operand 0 "register_operand" "")
	(call (match_operand 1 "memory_operand" "")
	      (match_operand 2 "" "")))]
  ""
  "
{
  rtx addr = XEXP (operands[1], 0);
  if (flag_pic && GET_CODE (addr) == SYMBOL_REF && !SYMBOL_REF_FLAG (addr))
    addr = gen_sym_PLT (addr);
  if (!call_insn_operand (addr, VOIDmode))
    XEXP (operands[1], 0) = copy_to_mode_reg (Pmode, addr);
}")

;; cannot combine constraints for operand 0 into "afvb"
;; reload.c:find_reloads seems to assume that grouped constraints somehow
;; specify related register classes, and when they don't the constraints
;; fail to match. By not grouping the constraints, we get the correct
;; behavior.
(define_insn "call_value_internal"
   [(set (match_operand 0 "register_operand" "=af,af,af,v,v,v,b,b,b")
         (call (mem (match_operand:SI 1 "call_insn_operand"
					"n,i,r,n,i,r,n,i,r"))
               (match_operand 2 "" "i,i,i,i,i,i,i,i,i")))]
  ""
  "*
    return xtensa_emit_call (1, operands);
  "
  [(set_attr "type"	"call")
   (set_attr "mode"	"none")
   (set_attr "length"	"3")])

(define_insn "return"
  [(return)
   (use (reg:SI A0_REG))]
  "reload_completed"
  "*
{
  return (TARGET_DENSITY ? \"retw.n\" : \"retw\");
}"
  [(set_attr "type"	"jump")
   (set_attr "mode"	"none")
   (set_attr "length"	"2")])


;;
;;  ....................
;;
;;	MISC.
;;
;;  ....................
;;

(define_insn "nop"
  [(const_int 0)]
  ""
  "*
{
  return (TARGET_DENSITY ? \"nop.n\" : \"nop\");
}"
  [(set_attr "type"	"nop")
   (set_attr "mode"	"none")
   (set_attr "length"	"3")])

(define_expand "nonlocal_goto"
  [(match_operand:SI 0 "general_operand" "")
   (match_operand:SI 1 "general_operand" "")
   (match_operand:SI 2 "general_operand" "")
   (match_operand:SI 3 "" "")]
  ""
  "
{
  xtensa_expand_nonlocal_goto (operands);
  DONE;
}")

;; Setting up a frame pointer is tricky for Xtensa because GCC doesn't
;; know if a frame pointer is required until the reload pass, and
;; because there may be an incoming argument value in the hard frame
;; pointer register (a7). If there is an incoming argument in that
;; register, the "set_frame_ptr" insn gets inserted immediately after
;; the insn that copies the incoming argument to a pseudo or to the
;; stack.  This serves several purposes here: (1) it keeps the
;; optimizer from copy-propagating or scheduling the use of a7 as an
;; incoming argument away from the beginning of the function; (2) we
;; can use a post-reload splitter to expand away the insn if a frame
;; pointer is not required, so that the post-reload scheduler can do
;; the right thing; and (3) it makes it easy for xtensa_reorg() to
;; search for this insn to determine whether it should add a new insn
;; to set up the frame pointer.

(define_insn "set_frame_ptr"
  [(set (reg:SI A7_REG) (unspec_volatile [(const_int 0)] UNSPECV_SET_FP))]
  ""
  "*
{
  if (frame_pointer_needed)
    return \"mov\\ta7, sp\";
  return \"\";
}"
  [(set_attr "type"	"move")
   (set_attr "mode"	"SI")
   (set_attr "length"	"3")])

;; Post-reload splitter to remove fp assignment when it's not needed.
(define_split
  [(set (reg:SI A7_REG) (unspec_volatile [(const_int 0)] UNSPECV_SET_FP))]
  "reload_completed && !frame_pointer_needed"
  [(unspec [(const_int 0)] UNSPEC_NOP)]
  "")

;; The preceding splitter needs something to split the insn into;
;; things start breaking if the result is just a "use" so instead we
;; generate the following insn.
(define_insn "*unspec_nop"
  [(unspec [(const_int 0)] UNSPEC_NOP)]
  ""
  ""
  [(set_attr "type"	"nop")
   (set_attr "mode"	"none")
   (set_attr "length"	"0")])

;; The fix_return_addr pattern sets the high 2 bits of an address in a
;; register to match the high bits of the current PC.

(define_insn "fix_return_addr"
  [(set (match_operand:SI 0 "register_operand" "=a")
	(unspec:SI [(match_operand:SI 1 "register_operand" "r")]
		   UNSPEC_RET_ADDR))
   (clobber (match_scratch:SI 2 "=r"))
   (clobber (match_scratch:SI 3 "=r"))]
  ""
  "mov\\t%2, a0\;call0\\t0f\;.align\\t4\;0:\;mov\\t%3, a0\;mov\\ta0, %2\;\
srli\\t%3, %3, 30\;slli\\t%0, %1, 2\;ssai\\t2\;src\\t%0, %3, %0"
  [(set_attr "type"	"multi")
   (set_attr "mode"	"SI")
   (set_attr "length"	"24")])


;;
;;  ....................
;;
;;	BOOLEANS
;;
;;  ....................
;;

;; branch patterns

(define_insn "*booltrue"
  [(set (pc)
	(if_then_else (match_operator 2 "boolean_operator"
			 [(match_operand:CC 0 "register_operand" "b")
			  (const_int 0)])
		      (label_ref (match_operand 1 "" ""))
		      (pc)))]
  "TARGET_BOOLEANS"
  "*
{
  if (GET_CODE (operands[2]) == EQ)
    return \"bf\\t%0, %1\";
  else
    return \"bt\\t%0, %1\";
}"
  [(set_attr "type"	"jump")
   (set_attr "mode"	"none")
   (set_attr "length"	"3")])

(define_insn "*boolfalse"
  [(set (pc)
	(if_then_else (match_operator 2 "boolean_operator"
			 [(match_operand:CC 0 "register_operand" "b")
			  (const_int 0)])
		      (pc)
		      (label_ref (match_operand 1 "" ""))))]
  "TARGET_BOOLEANS"
  "*
{
  if (GET_CODE (operands[2]) == EQ)
    return \"bt\\t%0, %1\";
  else
    return \"bf\\t%0, %1\";
}"
  [(set_attr "type"	"jump")
   (set_attr "mode"	"none")
   (set_attr "length"	"3")])