i386.md

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

  "* return output_fp_compare (insn, operands, 0, 0);"
  [(set_attr "type" "fcmp")
   (set_attr "mode" "XF")])

(define_insn "*cmpfp_2_xf_1"
  [(set (match_operand:HI 0 "register_operand" "=a")
	(unspec:HI
	  [(compare:CCFP
	     (match_operand:XF 1 "register_operand" "f")
	     (match_operand:XF 2 "register_operand" "f"))]
	  UNSPEC_FNSTSW))]
  "!TARGET_64BIT && TARGET_80387"
  "* return output_fp_compare (insn, operands, 2, 0);"
  [(set_attr "type" "multi")
   (set_attr "mode" "XF")])

(define_insn "*cmpfp_2_tf_1"
  [(set (match_operand:HI 0 "register_operand" "=a")
	(unspec:HI
	  [(compare:CCFP
	     (match_operand:TF 1 "register_operand" "f")
	     (match_operand:TF 2 "register_operand" "f"))]
	  UNSPEC_FNSTSW))]
  "TARGET_80387"
  "* return output_fp_compare (insn, operands, 2, 0);"
  [(set_attr "type" "multi")
   (set_attr "mode" "XF")])

(define_insn "*cmpfp_2u"
  [(set (reg:CCFPU 18)
	(compare:CCFPU
	  (match_operand 0 "register_operand" "f")
	  (match_operand 1 "register_operand" "f")))]
  "TARGET_80387
   && FLOAT_MODE_P (GET_MODE (operands[0]))
   && GET_MODE (operands[0]) == GET_MODE (operands[1])"
  "* return output_fp_compare (insn, operands, 0, 1);"
  [(set_attr "type" "fcmp")
   (set_attr "mode" "unknownfp")])

(define_insn "*cmpfp_2u_1"
  [(set (match_operand:HI 0 "register_operand" "=a")
	(unspec:HI
	  [(compare:CCFPU
	     (match_operand 1 "register_operand" "f")
	     (match_operand 2 "register_operand" "f"))]
	  UNSPEC_FNSTSW))]
  "TARGET_80387
   && FLOAT_MODE_P (GET_MODE (operands[1]))
   && GET_MODE (operands[1]) == GET_MODE (operands[2])"
  "* return output_fp_compare (insn, operands, 2, 1);"
  [(set_attr "type" "multi")
   (set_attr "mode" "unknownfp")])

;; Patterns to match the SImode-in-memory ficom instructions.
;;
;; %%% Play games with accepting gp registers, as otherwise we have to
;; force them to memory during rtl generation, which is no good.  We
;; can get rid of this once we teach reload to do memory input reloads 
;; via pushes.

(define_insn "*ficom_1"
  [(set (reg:CCFP 18)
	(compare:CCFP
	  (match_operand 0 "register_operand" "f,f")
	  (float (match_operand:SI 1 "nonimmediate_operand" "m,?r"))))]
  "0 && TARGET_80387 && FLOAT_MODE_P (GET_MODE (operands[0]))
   && GET_MODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == GET_MODE (operands[0])"
  "#")

;; Split the not-really-implemented gp register case into a
;; push-op-pop sequence.
;;
;; %%% This is most efficient, but am I gonna get in trouble
;; for separating cc0_setter and cc0_user?

(define_split
  [(set (reg:CCFP 18)
	(compare:CCFP
	  (match_operand:SF 0 "register_operand" "")
	  (float (match_operand:SI 1 "register_operand" ""))))]
  "0 && TARGET_80387 && reload_completed"
  [(set (mem:SI (pre_dec:SI (reg:SI 7))) (match_dup 1))
   (set (reg:CCFP 18) (compare:CCFP (match_dup 0) (match_dup 2)))
   (parallel [(set (match_dup 1) (mem:SI (reg:SI 7)))
              (set (reg:SI 7) (plus:SI (reg:SI 7) (const_int 4)))])]
  "operands[2] = gen_rtx_MEM (Pmode, stack_pointer_rtx);
   operands[2] = gen_rtx_FLOAT (GET_MODE (operands[0]), operands[2]);")

;; FP compares, step 2
;; Move the fpsw to ax.

(define_insn "x86_fnstsw_1"
  [(set (match_operand:HI 0 "register_operand" "=a")
	(unspec:HI [(reg 18)] UNSPEC_FNSTSW))]
  "TARGET_80387"
  "fnstsw\t%0"
  [(set_attr "length" "2")
   (set_attr "mode" "SI")
   (set_attr "unit" "i387")
   (set_attr "ppro_uops" "few")])

;; FP compares, step 3
;; Get ax into flags, general case.

(define_insn "x86_sahf_1"
  [(set (reg:CC 17)
	(unspec:CC [(match_operand:HI 0 "register_operand" "a")] UNSPEC_SAHF))]
  "!TARGET_64BIT"
  "sahf"
  [(set_attr "length" "1")
   (set_attr "athlon_decode" "vector")
   (set_attr "mode" "SI")
   (set_attr "ppro_uops" "one")])

;; Pentium Pro can do steps 1 through 3 in one go.

(define_insn "*cmpfp_i"
  [(set (reg:CCFP 17)
	(compare:CCFP (match_operand 0 "register_operand" "f")
		      (match_operand 1 "register_operand" "f")))]
  "TARGET_80387 && TARGET_CMOVE
   && !SSE_FLOAT_MODE_P (GET_MODE (operands[0]))
   && FLOAT_MODE_P (GET_MODE (operands[0]))
   && GET_MODE (operands[0]) == GET_MODE (operands[0])"
  "* return output_fp_compare (insn, operands, 1, 0);"
  [(set_attr "type" "fcmp")
   (set_attr "mode" "unknownfp")
   (set_attr "athlon_decode" "vector")])

(define_insn "*cmpfp_i_sse"
  [(set (reg:CCFP 17)
	(compare:CCFP (match_operand 0 "register_operand" "f#x,x#f")
		      (match_operand 1 "nonimmediate_operand" "f#x,xm#f")))]
  "TARGET_80387
   && SSE_FLOAT_MODE_P (GET_MODE (operands[0]))
   && GET_MODE (operands[0]) == GET_MODE (operands[0])"
  "* return output_fp_compare (insn, operands, 1, 0);"
  [(set_attr "type" "fcmp,ssecmp")
   (set_attr "mode" "unknownfp")
   (set_attr "athlon_decode" "vector")])

(define_insn "*cmpfp_i_sse_only"
  [(set (reg:CCFP 17)
	(compare:CCFP (match_operand 0 "register_operand" "x")
		      (match_operand 1 "nonimmediate_operand" "xm")))]
  "SSE_FLOAT_MODE_P (GET_MODE (operands[0]))
   && GET_MODE (operands[0]) == GET_MODE (operands[0])"
  "* return output_fp_compare (insn, operands, 1, 0);"
  [(set_attr "type" "ssecmp")
   (set_attr "mode" "unknownfp")
   (set_attr "athlon_decode" "vector")])

(define_insn "*cmpfp_iu"
  [(set (reg:CCFPU 17)
	(compare:CCFPU (match_operand 0 "register_operand" "f")
		       (match_operand 1 "register_operand" "f")))]
  "TARGET_80387 && TARGET_CMOVE
   && !SSE_FLOAT_MODE_P (GET_MODE (operands[0]))
   && FLOAT_MODE_P (GET_MODE (operands[0]))
   && GET_MODE (operands[0]) == GET_MODE (operands[1])"
  "* return output_fp_compare (insn, operands, 1, 1);"
  [(set_attr "type" "fcmp")
   (set_attr "mode" "unknownfp")
   (set_attr "athlon_decode" "vector")])

(define_insn "*cmpfp_iu_sse"
  [(set (reg:CCFPU 17)
	(compare:CCFPU (match_operand 0 "register_operand" "f#x,x#f")
		       (match_operand 1 "nonimmediate_operand" "f#x,xm#f")))]
  "TARGET_80387
   && SSE_FLOAT_MODE_P (GET_MODE (operands[0]))
   && GET_MODE (operands[0]) == GET_MODE (operands[1])"
  "* return output_fp_compare (insn, operands, 1, 1);"
  [(set_attr "type" "fcmp,ssecmp")
   (set_attr "mode" "unknownfp")
   (set_attr "athlon_decode" "vector")])

(define_insn "*cmpfp_iu_sse_only"
  [(set (reg:CCFPU 17)
	(compare:CCFPU (match_operand 0 "register_operand" "x")
		       (match_operand 1 "nonimmediate_operand" "xm")))]
  "SSE_FLOAT_MODE_P (GET_MODE (operands[0]))
   && GET_MODE (operands[0]) == GET_MODE (operands[1])"
  "* return output_fp_compare (insn, operands, 1, 1);"
  [(set_attr "type" "ssecmp")
   (set_attr "mode" "unknownfp")
   (set_attr "athlon_decode" "vector")])

;; Move instructions.

;; General case of fullword move.

(define_expand "movsi"
  [(set (match_operand:SI 0 "nonimmediate_operand" "")
	(match_operand:SI 1 "general_operand" ""))]
  ""
  "ix86_expand_move (SImode, operands); DONE;")

;; Push/pop instructions.  They are separate since autoinc/dec is not a
;; general_operand.
;;
;; %%% We don't use a post-inc memory reference because x86 is not a 
;; general AUTO_INC_DEC host, which impacts how it is treated in flow.
;; Changing this impacts compiler performance on other non-AUTO_INC_DEC
;; targets without our curiosities, and it is just as easy to represent
;; this differently.

(define_insn "*pushsi2"
  [(set (match_operand:SI 0 "push_operand" "=<")
	(match_operand:SI 1 "general_no_elim_operand" "ri*m"))]
  "!TARGET_64BIT"
  "push{l}\t%1"
  [(set_attr "type" "push")
   (set_attr "mode" "SI")])

;; For 64BIT abi we always round up to 8 bytes.
(define_insn "*pushsi2_rex64"
  [(set (match_operand:SI 0 "push_operand" "=X")
	(match_operand:SI 1 "nonmemory_no_elim_operand" "ri"))]
  "TARGET_64BIT"
  "push{q}\t%q1"
  [(set_attr "type" "push")
   (set_attr "mode" "SI")])

(define_insn "*pushsi2_prologue"
  [(set (match_operand:SI 0 "push_operand" "=<")
	(match_operand:SI 1 "general_no_elim_operand" "ri*m"))
   (clobber (mem:BLK (scratch)))]
  "!TARGET_64BIT"
  "push{l}\t%1"
  [(set_attr "type" "push")
   (set_attr "mode" "SI")])

(define_insn "*popsi1_epilogue"
  [(set (match_operand:SI 0 "nonimmediate_operand" "=r*m")
	(mem:SI (reg:SI 7)))
   (set (reg:SI 7)
	(plus:SI (reg:SI 7) (const_int 4)))
   (clobber (mem:BLK (scratch)))]
  "!TARGET_64BIT"
  "pop{l}\t%0"
  [(set_attr "type" "pop")
   (set_attr "mode" "SI")])

(define_insn "popsi1"
  [(set (match_operand:SI 0 "nonimmediate_operand" "=r*m")
	(mem:SI (reg:SI 7)))
   (set (reg:SI 7)
	(plus:SI (reg:SI 7) (const_int 4)))]
  "!TARGET_64BIT"
  "pop{l}\t%0"
  [(set_attr "type" "pop")
   (set_attr "mode" "SI")])

(define_insn "*movsi_xor"
  [(set (match_operand:SI 0 "register_operand" "=r")
	(match_operand:SI 1 "const0_operand" "i"))
   (clobber (reg:CC 17))]
  "reload_completed && (!TARGET_USE_MOV0 || optimize_size)"
  "xor{l}\t{%0, %0|%0, %0}"
  [(set_attr "type" "alu1")
   (set_attr "mode" "SI")
   (set_attr "length_immediate" "0")])

(define_insn "*movsi_or"
  [(set (match_operand:SI 0 "register_operand" "=r")
	(match_operand:SI 1 "immediate_operand" "i"))
   (clobber (reg:CC 17))]
  "reload_completed && GET_CODE (operands[1]) == CONST_INT
   && INTVAL (operands[1]) == -1
   && (TARGET_PENTIUM || optimize_size)"
{
  operands[1] = constm1_rtx;
  return "or{l}\t{%1, %0|%0, %1}";
}
  [(set_attr "type" "alu1")
   (set_attr "mode" "SI")
   (set_attr "length_immediate" "1")])

(define_insn "*movsi_1"
  [(set (match_operand:SI 0 "nonimmediate_operand" "=r,m,!*y,!rm,!*y,!*Y,!*Y,!rm")
	(match_operand:SI 1 "general_operand" "rinm,rin,rm,*y,*y,*Y,rm,*Y"))]
  "GET_CODE (operands[0]) != MEM || GET_CODE (operands[1]) != MEM"
{
  switch (get_attr_type (insn))
    {
    case TYPE_SSEMOV:
      if (get_attr_mode (insn) == MODE_TI)
        return "movdqa\t{%1, %0|%0, %1}";
      return "movd\t{%1, %0|%0, %1}";

    case TYPE_MMXMOV:
      if (get_attr_mode (insn) == MODE_DI)
	return "movq\t{%1, %0|%0, %1}";
      return "movd\t{%1, %0|%0, %1}";

    case TYPE_LEA:
      return "lea{l}\t{%1, %0|%0, %1}";

    default:
      if (flag_pic && !LEGITIMATE_PIC_OPERAND_P (operands[1]))
	abort();
      return "mov{l}\t{%1, %0|%0, %1}";
    }
}
  [(set (attr "type")
     (cond [(eq_attr "alternative" "2,3,4")
	      (const_string "mmxmov")
	    (eq_attr "alternative" "5,6,7")
	      (const_string "ssemov")
	    (and (ne (symbol_ref "flag_pic") (const_int 0))
		 (match_operand:SI 1 "symbolic_operand" ""))
	      (const_string "lea")
	   ]
	   (const_string "imov")))
   (set_attr "mode" "SI,SI,SI,SI,DI,TI,SI,SI")])

;; 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 "*movabssi_1_rex64"
  [(set (mem:SI (match_operand:DI 0 "x86_64_movabs_operand" "i,r"))
	(match_operand:SI 1 "nonmemory_operand" "a,er"))]
  "TARGET_64BIT && ix86_check_movabs (insn, 0)"
  "@
   movabs{l}\t{%1, %P0|%P0, %1}
   mov{l}\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" "SI")])

(define_insn "*movabssi_2_rex64"
  [(set (match_operand:SI 0 "register_operand" "=a,r")
        (mem:SI (match_operand:DI 1 "x86_64_movabs_operand" "i,r")))]
  "TARGET_64BIT && ix86_check_movabs (insn, 1)"
  "@
   movabs{l}\t{%P1, %0|%0, %P1}
   mov{l}\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" "SI")])

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

(define_expand "movhi"
  [(set (match_operand:HI 0 "nonimmediate_operand" "")
        (match_operand:HI 1 "general_operand" ""))]
  ""
  "ix86_expand_move (HImode, operands); DONE;")

(define_insn "*pushhi2"
  [(set (match_operand:HI 0 "push_operand" "=<,<")
	(match_operand:HI 1 "general_no_elim_operand" "n,r*m"))]
  "!TARGET_64BIT"
  "@
   push{w}\t{|WORD PTR }%1
   push{w}\t%1"
  [(set_attr "type" "push")
   (set_attr "mode" "HI")])

;; For 64BIT abi we always round up to 8 bytes.
(define_insn "*pushhi2_rex64"
  [(set (match_operand:HI 0 "push_operand" "=X")
	(match_operand:HI 1 "nonmemory_no_elim_operand" "ri"))]
  "TARGET_64BIT"
  "push{q}\t%q1"
  [(set_attr "type" "push")
   (set_attr "mode" "QI")])

(define_insn "*movhi_1"
  [(set (match_operand:HI 0 "nonimmediate_operand" "=r,r,r,m")
	(match_operand:HI 1 "general_operand" "r,rn,rm,rn"))]
  "GET_CODE (operands[0]) != MEM || GET_CODE (operands[1]) != MEM"
{
  switch (get_attr_type (insn))
    {
    case TYPE_IMOVX:
      /* movzwl is faster than movw on p2 due to partial word stalls,
	 though not as fast as an aligned movl.  */
      return "movz{wl|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{w}\t{%1, %0|%0, %1}";
    }
}
  [(set (attr "type")
     (cond [(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))))