i386.md

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

	      (const_string "imov")
	    (and (eq_attr "alternative" "1,2")
		 (match_operand:HI 1 "aligned_operand" ""))
	      (const_string "imov")
	    (and (ne (symbol_ref "TARGET_MOVX")
		     (const_int 0))
		 (eq_attr "alternative" "0,2"))
	      (const_string "imovx")
	   ]
	   (const_string "imov")))
    (set (attr "mode")
      (cond [(eq_attr "type" "imovx")
	       (const_string "SI")
	     (and (eq_attr "alternative" "1,2")
		  (match_operand:HI 1 "aligned_operand" ""))
	       (const_string "SI")
	     (and (eq_attr "alternative" "0")
		  (ior (eq (symbol_ref "TARGET_PARTIAL_REG_STALL")
			   (const_int 0))
		       (eq (symbol_ref "TARGET_HIMODE_MATH")
			   (const_int 0))))
	       (const_string "SI")
	    ]
	    (const_string "HI")))])

;; Stores and loads of ax to arbitary constant address.
;; We fake an second form of instruction to force reload to load address
;; into register when rax is not available
(define_insn "*movabshi_1_rex64"
  [(set (mem:HI (match_operand:DI 0 "x86_64_movabs_operand" "i,r"))
	(match_operand:HI 1 "nonmemory_operand" "a,er"))]
  "TARGET_64BIT && ix86_check_movabs (insn, 0)"
  "@
   movabs{w}\t{%1, %P0|%P0, %1}
   mov{w}\t{%1, %a0|%a0, %1}"
  [(set_attr "type" "imov")
   (set_attr "modrm" "0,*")
   (set_attr "length_address" "8,0")
   (set_attr "length_immediate" "0,*")
   (set_attr "memory" "store")
   (set_attr "mode" "HI")])

(define_insn "*movabshi_2_rex64"
  [(set (match_operand:HI 0 "register_operand" "=a,r")
        (mem:HI (match_operand:DI 1 "x86_64_movabs_operand" "i,r")))]
  "TARGET_64BIT && ix86_check_movabs (insn, 1)"
  "@
   movabs{w}\t{%P1, %0|%0, %P1}
   mov{w}\t{%a1, %0|%0, %a1}"
  [(set_attr "type" "imov")
   (set_attr "modrm" "0,*")
   (set_attr "length_address" "8,0")
   (set_attr "length_immediate" "0")
   (set_attr "memory" "load")
   (set_attr "mode" "HI")])

(define_insn "*swaphi_1"
  [(set (match_operand:HI 0 "register_operand" "+r")
	(match_operand:HI 1 "register_operand" "+r"))
   (set (match_dup 1)
	(match_dup 0))]
  "TARGET_PARTIAL_REG_STALL"
  "xchg{w}\t%1, %0"
  [(set_attr "type" "imov")
   (set_attr "pent_pair" "np")
   (set_attr "mode" "HI")
   (set_attr "modrm" "0")
   (set_attr "ppro_uops" "few")])

(define_insn "*swaphi_2"
  [(set (match_operand:HI 0 "register_operand" "+r")
	(match_operand:HI 1 "register_operand" "+r"))
   (set (match_dup 1)
	(match_dup 0))]
  "! TARGET_PARTIAL_REG_STALL"
  "xchg{l}\t%k1, %k0"
  [(set_attr "type" "imov")
   (set_attr "pent_pair" "np")
   (set_attr "mode" "SI")
   (set_attr "modrm" "0")
   (set_attr "ppro_uops" "few")])

(define_expand "movstricthi"
  [(set (strict_low_part (match_operand:HI 0 "nonimmediate_operand" ""))
	(match_operand:HI 1 "general_operand" ""))]
  "! TARGET_PARTIAL_REG_STALL || optimize_size"
{
  /* Don't generate memory->memory moves, go through a register */
  if (GET_CODE (operands[0]) == MEM && GET_CODE (operands[1]) == MEM)
    operands[1] = force_reg (HImode, operands[1]);
})

(define_insn "*movstricthi_1"
  [(set (strict_low_part (match_operand:HI 0 "nonimmediate_operand" "+rm,r"))
	(match_operand:HI 1 "general_operand" "rn,m"))]
  "(! TARGET_PARTIAL_REG_STALL || optimize_size)
   && (GET_CODE (operands[0]) != MEM || GET_CODE (operands[1]) != MEM)"
  "mov{w}\t{%1, %0|%0, %1}"
  [(set_attr "type" "imov")
   (set_attr "mode" "HI")])

(define_insn "*movstricthi_xor"
  [(set (strict_low_part (match_operand:HI 0 "register_operand" "+r"))
	(match_operand:HI 1 "const0_operand" "i"))
   (clobber (reg:CC 17))]
  "reload_completed
   && ((!TARGET_USE_MOV0 && !TARGET_PARTIAL_REG_STALL) || optimize_size)"
  "xor{w}\t{%0, %0|%0, %0}"
  [(set_attr "type" "alu1")
   (set_attr "mode" "HI")
   (set_attr "length_immediate" "0")])

(define_expand "movqi"
  [(set (match_operand:QI 0 "nonimmediate_operand" "")
	(match_operand:QI 1 "general_operand" ""))]
  ""
  "ix86_expand_move (QImode, operands); DONE;")

;; emit_push_insn when it calls move_by_pieces requires an insn to
;; "push a byte".  But actually we use pushw, which has the effect
;; of rounding the amount pushed up to a halfword.

(define_insn "*pushqi2"
  [(set (match_operand:QI 0 "push_operand" "=X,X")
	(match_operand:QI 1 "nonmemory_no_elim_operand" "n,r"))]
  "!TARGET_64BIT"
  "@
   push{w}\t{|word ptr }%1
   push{w}\t%w1"
  [(set_attr "type" "push")
   (set_attr "mode" "HI")])

;; For 64BIT abi we always round up to 8 bytes.
(define_insn "*pushqi2_rex64"
  [(set (match_operand:QI 0 "push_operand" "=X")
	(match_operand:QI 1 "nonmemory_no_elim_operand" "qi"))]
  "TARGET_64BIT"
  "push{q}\t%q1"
  [(set_attr "type" "push")
   (set_attr "mode" "QI")])

;; Situation is quite tricky about when to choose full sized (SImode) move
;; over QImode moves.  For Q_REG -> Q_REG move we use full size only for
;; partial register dependency machines (such as AMD Athlon), where QImode
;; moves issue extra dependency and for partial register stalls machines
;; that don't use QImode patterns (and QImode move cause stall on the next
;; instruction).
;;
;; For loads of Q_REG to NONQ_REG we use full sized moves except for partial
;; register stall machines with, where we use QImode instructions, since
;; partial register stall can be caused there.  Then we use movzx.
(define_insn "*movqi_1"
  [(set (match_operand:QI 0 "nonimmediate_operand" "=q,q ,q ,r,r ,?r,m")
	(match_operand:QI 1 "general_operand"      " q,qn,qm,q,rn,qm,qn"))]
  "GET_CODE (operands[0]) != MEM || GET_CODE (operands[1]) != MEM"
{
  switch (get_attr_type (insn))
    {
    case TYPE_IMOVX:
      if (!ANY_QI_REG_P (operands[1]) && GET_CODE (operands[1]) != MEM)
	abort ();
      return "movz{bl|x}\t{%1, %k0|%k0, %1}";
    default:
      if (get_attr_mode (insn) == MODE_SI)
        return "mov{l}\t{%k1, %k0|%k0, %k1}";
      else
        return "mov{b}\t{%1, %0|%0, %1}";
    }
}
  [(set (attr "type")
     (cond [(and (eq_attr "alternative" "3")
		 (ior (eq (symbol_ref "TARGET_PARTIAL_REG_STALL")
			  (const_int 0))
		      (eq (symbol_ref "TARGET_QIMODE_MATH")
			  (const_int 0))))
	      (const_string "imov")
	    (eq_attr "alternative" "3,5")
	      (const_string "imovx")
	    (and (ne (symbol_ref "TARGET_MOVX")
		     (const_int 0))
		 (eq_attr "alternative" "2"))
	      (const_string "imovx")
	   ]
	   (const_string "imov")))
   (set (attr "mode")
      (cond [(eq_attr "alternative" "3,4,5")
	       (const_string "SI")
	     (eq_attr "alternative" "6")
	       (const_string "QI")
	     (eq_attr "type" "imovx")
	       (const_string "SI")
	     (and (eq_attr "type" "imov")
		  (and (eq_attr "alternative" "0,1,2")
		       (ne (symbol_ref "TARGET_PARTIAL_REG_DEPENDENCY")
			   (const_int 0))))
	       (const_string "SI")
	     ;; Avoid partial register stalls when not using QImode arithmetic
	     (and (eq_attr "type" "imov")
		  (and (eq_attr "alternative" "0,1,2")
		       (and (ne (symbol_ref "TARGET_PARTIAL_REG_STALL")
				(const_int 0))
			    (eq (symbol_ref "TARGET_QIMODE_MATH")
				(const_int 0)))))
	       (const_string "SI")
	   ]
	   (const_string "QI")))])

(define_expand "reload_outqi"
  [(parallel [(match_operand:QI 0 "" "=m")
              (match_operand:QI 1 "register_operand" "r")
              (match_operand:QI 2 "register_operand" "=&q")])]
  ""
{
  rtx op0, op1, op2;
  op0 = operands[0]; op1 = operands[1]; op2 = operands[2];

  if (reg_overlap_mentioned_p (op2, op0))
    abort ();
  if (! q_regs_operand (op1, QImode))
    {
      emit_insn (gen_movqi (op2, op1));
      op1 = op2;
    }
  emit_insn (gen_movqi (op0, op1));
  DONE;
})

(define_insn "*swapqi"
  [(set (match_operand:QI 0 "register_operand" "+r")
	(match_operand:QI 1 "register_operand" "+r"))
   (set (match_dup 1)
	(match_dup 0))]
  ""
  "xchg{b}\t%1, %0"
  [(set_attr "type" "imov")
   (set_attr "pent_pair" "np")
   (set_attr "mode" "QI")
   (set_attr "modrm" "0")
   (set_attr "ppro_uops" "few")])

(define_expand "movstrictqi"
  [(set (strict_low_part (match_operand:QI 0 "nonimmediate_operand" ""))
	(match_operand:QI 1 "general_operand" ""))]
  "! TARGET_PARTIAL_REG_STALL || optimize_size"
{
  /* Don't generate memory->memory moves, go through a register.  */
  if (GET_CODE (operands[0]) == MEM && GET_CODE (operands[1]) == MEM)
    operands[1] = force_reg (QImode, operands[1]);
})

(define_insn "*movstrictqi_1"
  [(set (strict_low_part (match_operand:QI 0 "nonimmediate_operand" "+qm,q"))
	(match_operand:QI 1 "general_operand" "*qn,m"))]
  "(! TARGET_PARTIAL_REG_STALL || optimize_size)
   && (GET_CODE (operands[0]) != MEM || GET_CODE (operands[1]) != MEM)"
  "mov{b}\t{%1, %0|%0, %1}"
  [(set_attr "type" "imov")
   (set_attr "mode" "QI")])

(define_insn "*movstrictqi_xor"
  [(set (strict_low_part (match_operand:QI 0 "q_regs_operand" "+q"))
	(match_operand:QI 1 "const0_operand" "i"))
   (clobber (reg:CC 17))]
  "reload_completed && (!TARGET_USE_MOV0 || optimize_size)"
  "xor{b}\t{%0, %0|%0, %0}"
  [(set_attr "type" "alu1")
   (set_attr "mode" "QI")
   (set_attr "length_immediate" "0")])

(define_insn "*movsi_extv_1"
  [(set (match_operand:SI 0 "register_operand" "=R")
	(sign_extract:SI (match_operand 1 "ext_register_operand" "Q")
			 (const_int 8)
			 (const_int 8)))]
  ""
  "movs{bl|x}\t{%h1, %0|%0, %h1}"
  [(set_attr "type" "imovx")
   (set_attr "mode" "SI")])

(define_insn "*movhi_extv_1"
  [(set (match_operand:HI 0 "register_operand" "=R")
	(sign_extract:HI (match_operand 1 "ext_register_operand" "Q")
			 (const_int 8)
			 (const_int 8)))]
  ""
  "movs{bl|x}\t{%h1, %k0|%k0, %h1}"
  [(set_attr "type" "imovx")
   (set_attr "mode" "SI")])

(define_insn "*movqi_extv_1"
  [(set (match_operand:QI 0 "nonimmediate_operand" "=Qm,?r")
        (sign_extract:QI (match_operand 1 "ext_register_operand" "Q,Q")
                         (const_int 8)
                         (const_int 8)))]
  "!TARGET_64BIT"
{
  switch (get_attr_type (insn))
    {
    case TYPE_IMOVX:
      return "movs{bl|x}\t{%h1, %k0|%k0, %h1}";
    default:
      return "mov{b}\t{%h1, %0|%0, %h1}";
    }
}
  [(set (attr "type")
     (if_then_else (and (match_operand:QI 0 "register_operand" "")
			(ior (not (match_operand:QI 0 "q_regs_operand" ""))
			     (ne (symbol_ref "TARGET_MOVX")
				 (const_int 0))))
	(const_string "imovx")
	(const_string "imov")))
   (set (attr "mode")
     (if_then_else (eq_attr "type" "imovx")
	(const_string "SI")
	(const_string "QI")))])

(define_insn "*movqi_extv_1_rex64"
  [(set (match_operand:QI 0 "register_operand" "=Q,?R")
        (sign_extract:QI (match_operand 1 "ext_register_operand" "Q,Q")
                         (const_int 8)
                         (const_int 8)))]
  "TARGET_64BIT"
{
  switch (get_attr_type (insn))
    {
    case TYPE_IMOVX:
      return "movs{bl|x}\t{%h1, %k0|%k0, %h1}";
    default:
      return "mov{b}\t{%h1, %0|%0, %h1}";
    }
}
  [(set (attr "type")
     (if_then_else (and (match_operand:QI 0 "register_operand" "")
			(ior (not (match_operand:QI 0 "q_regs_operand" ""))
			     (ne (symbol_ref "TARGET_MOVX")
				 (const_int 0))))
	(const_string "imovx")
	(const_string "imov")))
   (set (attr "mode")
     (if_then_else (eq_attr "type" "imovx")
	(const_string "SI")
	(const_string "QI")))])

;; Stores and loads of ax to arbitary constant address.
;; We fake an second form of instruction to force reload to load address
;; into register when rax is not available
(define_insn "*movabsqi_1_rex64"
  [(set (mem:QI (match_operand:DI 0 "x86_64_movabs_operand" "i,r"))
	(match_operand:QI 1 "nonmemory_operand" "a,er"))]
  "TARGET_64BIT && ix86_check_movabs (insn, 0)"
  "@
   movabs{b}\t{%1, %P0|%P0, %1}
   mov{b}\t{%1, %a0|%a0, %1}"
  [(set_attr "type" "imov")
   (set_attr "modrm" "0,*")
   (set_attr "length_address" "8,0")
   (set_attr "length_immediate" "0,*")
   (set_attr "memory" "store")
   (set_attr "mode" "QI")])

(define_insn "*movabsqi_2_rex64"
  [(set (match_operand:QI 0 "register_operand" "=a,r")
        (mem:QI (match_operand:DI 1 "x86_64_movabs_operand" "i,r")))]
  "TARGET_64BIT && ix86_check_movabs (insn, 1)"
  "@
   movabs{b}\t{%P1, %0|%0, %P1}
   mov{b}\t{%a1, %0|%0, %a1}"
  [(set_attr "type" "imov")
   (set_attr "modrm" "0,*")
   (set_attr "length_address" "8,0")
   (set_attr "length_immediate" "0")
   (set_attr "memory" "load")
   (set_attr "mode" "QI")])

(define_insn "*movsi_extzv_1"
  [(set (match_operand:SI 0 "register_operand" "=R")
	(zero_extract:SI (match_operand 1 "ext_register_operand" "Q")
			 (const_int 8)
			 (const_int 8)))]
  ""
  "movz{bl|x}\t{%h1, %0|%0, %h1}"
  [(set_attr "type" "imovx")
   (set_attr "mode" "SI")])

(define_insn "*movqi_extzv_2"
  [(set (match_operand:QI 0 "nonimmediate_operand" "=Qm,?R")
        (subreg:QI (zero_extract:SI (match_operand 1 "ext_register_operand" "Q,Q")
				    (const_int 8)
				    (const_int 8)) 0))]
  "!TARGET_64BIT"
{
  switch (get_attr_type (insn))
    {
    case TYPE_IMOVX:
      return "movz{bl|x}\t{%h1, %k0|%k0, %h1}";
    default:
      return "mov{b}\t{%h1, %0|%0, %h1}";
    }
}
  [(set (attr "type")
     (if_then_else (and (match_operand:QI 0 "register_operand" "")
			(ior (not (match_operand:QI 0 "q_regs_operand" ""))
			     (ne (symbol_ref "TARGET_MOVX")
				 (const_int 0))))
	(const_string "imovx")
	(const_string "imov")))
   (set (attr "mode")
     (if_then_else (eq_attr "type" "imovx")
	(const_string "SI")
	(const_string "QI")))])

(define_insn "*movqi_extzv_2_rex64"