www.pudn.com > system.rar > fd_cmp16.asm

;****************************************************************************** 
;* FD_CMP16.ASM  - 16 BIT STATE -  v2.54                                      * 
;* Copyright (c) 1996-2004 Texas Instruments Incorporated                     * 
;****************************************************************************** 
  
;**************************************************************************** 
;* FD$CMP - COMPARE TWO IEEE 754 FORMAT DOUBLE PRECISION FLOATING POINT  
;*          NUMBERS, SETTING THE STATUS ON THE RESULT. 
;* 
;**************************************************************************** 
;* 
;*   o INPUT OP1 IS IN r0:r1 
;*   o INPUT OP2 IS IN r2:r3 
;*   o INPUTS ARE NOT DESTROYED 
;* 
;*   o SIGNALLING NOT-A-NUMBER (SNaN) AND QUIET NOT-A-NUMBER (QNaN) 
;*     ARE TREATED AS INFINITY 
;*   o +0 == -0 
;* 
;*   o IF COMPUTING THE RESULT INVOLVES INFINITIES, THE FOLLOWING TABLE 
;*     SUMMARIZES THE EFFECTIVE RESULT 
;*                   +----------+----------+----------+  
;*                   + OP2 !INF | OP2 -INF + OP2 +INF + 
;*        +----------+==========+==========+==========+  
;*        + OP1 !INF +    -     |   +INF   +   -INF   + 
;*        +----------+----------+----------+----------+  
;*        + OP1 -INF +   -INF   |    -0    +   -INF   + 
;*        +----------+----------+----------+----------+  
;*        + OP1 +INF +   +INF   |   +INF   +    +0    + 
;*        +----------+----------+----------+----------+ 
;* 
;*   o THE RESULT OF THE COMPARE IS COMPUTED USING INTEGER SUBRACT IF THE 
;*     SIGN OF THE INPUTS IS THE SAME.  THE TABLE SUMMARIZES THE  
;*     IMPLEMENTATION. 
;*                 +-----------+-----------+  
;*                 +   OP2 +   |   OP2 -   + 
;*        +--------+===========+===========+  
;*        + OP1 +  + OP1 - OP2 |    OP1    +  
;*        +--------+-----------+-----------+  
;*        + OP1 -  +    OP1    | OP2 - OP1 +  
;*        +--------+-----------+-----------+  
;* 
;*   o THE FOLLOWING STATUS BITS ARE SET ON THE RESULT 
;*     o Z=1,N=0,V=0  IFF 0 
;*     o Z=0,N=1,V=0  IFF - 
;*     o Z=0,N=0,V=0  IFF + 
;* 
;**************************************************************************** 
;* 
;* +------------------------------------------------------------------+ 
;* | DOUBLE PRECISION FLOATING POINT FORMAT                           | 
;* |   64-bit representation                                          | 
;* |   31 30      20 19                  0                            | 
;* |   +-+----------+---------------------+                           | 
;* |   |S|     E    |        M1           |                           | 
;* |   +-+----------+---------------------+                           | 
;* |                                                                  | 
;* |   31                                0                            | 
;* |   +----------------------------------+                           | 
;* |   |             M2                   |                           | 
;* |   +----------------------------------+                           | 
;* |                                                                  | 
;* |     SIGN FIELD    :          0 - POSITIVE VALUE               | 
;* |                                 1 - NEGATIVE VALUE               | 
;* |                                                                  | 
;* |     EXPONENT FIELD: 0000000000 - ZERO IFF M == 0              | 
;* |            0000000001..1111111110 - EXPONENT VALUE(1023 BIAS)    | 
;* |                        1111111111 - INFINITY                     | 
;* |                                                                  | 
;* |     MANTISSA FIELDS:  FRACTIONAL MAGNITUDE WITH IMPLIED 1 | 
;* +------------------------------------------------------------------+ 
;* 
;**************************************************************************** 
         .state16 
 
         .global FD$CMP 
 
tmp	.set	r4 
tmp2	.set	r5 
 
FD$CMP: .asmfunc stack_usage(8) 
	PUSH	{r4, r5}		; 
 
	CMP	r0, r2			; HANDLE THE CASE OF BOTH INPUTS EQUAL  
	BNE	$1			; 
	CMP	r1, r3			; 
	BEQ	exit			; 
 
$1:	MOV	tmp, r1			; 
	ORR	tmp, r3			; HANDLE THE CASE OF BOTH INPUTS BEING 
	BNE	$2			; ZERO 
	MOV	tmp, r0			; 
	ORR	tmp, r2			; 
	LSL	tmp, tmp, #1		; 
	CMP	tmp, #0x0		; 
	BEQ	exit			; 
 
$2:	LSL	tmp, r0, #1		; TEST OP1 == 0 
	ORR	tmp, r1			;  
	BNE	$3			; 
 
	CMP	tmp, r2			; OP1 == 0, DISREGARD SIGN OF OP1 
	POP	{r4, r5}		; WHEN COMPUTING RESULT STATUS 
	MOV	pc, lr			; 
 
$3:	LSL	tmp, r0, #1		; CHECK INPUT #1 FOR INFINITY 
	ASR	tmp, tmp, #21		; 
	ADD	tmp, tmp, #1		; 
	BNE	$4			; 
	LSL	tmp, r2, #1		; CHECK INPUT #2 FOR INFINITY 
	ASR	tmp, tmp, #21		; 
	ADD	tmp, tmp, #1		; 
	BNE	$4			; 
 
	LSR	tmp, r2, #31		; HANDLE THE CASE OF BOTH INPUTS 
	LSR	tmp2, r0, #31		; BEING INFINITE 
	SUB	tmp, tmp, tmp2		; 
        POP	{r4, r5}		; 
	MOV	pc, lr			; 
 
$4:	CMP	r2, #0			; CHECK OP2'S SIGN 
	BMI	$6			; 
 
	CMP	r0, #0			; OP2 IS POSITIVE.  IF OP1 IS NEGATIVE, 
	BMI	exit			; THE RESULT IS OP1 
	CMP	r0, r2			; ELSE THE RESULT IS OP1 - OP2 
        BNE	exit			; 
	MOV	tmp, r1			; MAKE SURE WE SET THE N BIT CORRECTLY 
	EOR	tmp, r3			; 
	BMI	$5			; 
	CMP	r1, r3			; 
	POP	{r4, r5}		; 
	MOV	pc, lr			; 
$5:	CMP	r3, #0			; 
	POP	{r4, r5}		; 
	MOV	pc, lr			; 
 
$6:	CMP	r0, #0			; OP2 IS NEGATIVE.  IF OP1 IS POSITIVE, 
	BPL	exit			; THE RESULT IS OP1 
	CMP	r2, r0			; ELSE THE RESULT IS OP2 - OP1 
	BNE	exit			; 
	MOV	tmp, r1			; MAKE SURE WE SET THE N BIT CORRECTLY 
	EOR	tmp, r3			; 
	BMI	$7			; 
	CMP	r3, r1			; 
	POP	{r4, r5}		; 
	MOV	pc, lr			; 
$7:	CMP	r1, #0			; 
exit:	POP	{r4, r5}		; 
	MOV	pc, lr			; 
 
	.endasmfunc 
 
	.end