freebsd-dev/sys/gnu/i386/fpemul/reg_u_sub.s
2002-05-13 12:55:30 +00:00

358 lines
8.2 KiB
ArmAsm

.file "reg_u_sub.S"
/*
* reg_u_sub.S
*
* Core floating point subtraction routine.
*
* Call from C as:
* void reg_u_sub(FPU_REG *arg1, FPU_REG *arg2, FPU_REG *answ,
* int control_w)
*
*
* Copyright (C) 1992,1993,1994
* W. Metzenthen, 22 Parker St, Ormond, Vic 3163,
* Australia. E-mail billm@vaxc.cc.monash.edu.au
* All rights reserved.
*
* This copyright notice covers the redistribution and use of the
* FPU emulator developed by W. Metzenthen. It covers only its use
* in the 386BSD, FreeBSD and NetBSD operating systems. Any other
* use is not permitted under this copyright.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must include information specifying
* that source code for the emulator is freely available and include
* either:
* a) an offer to provide the source code for a nominal distribution
* fee, or
* b) list at least two alternative methods whereby the source
* can be obtained, e.g. a publically accessible bulletin board
* and an anonymous ftp site from which the software can be
* downloaded.
* 3. All advertising materials specifically mentioning features or use of
* this emulator must acknowledge that it was developed by W. Metzenthen.
* 4. The name of W. Metzenthen may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* W. METZENTHEN BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*
* The purpose of this copyright, based upon the Berkeley copyright, is to
* ensure that the covered software remains freely available to everyone.
*
* The software (with necessary differences) is also available, but under
* the terms of the GNU copyleft, for the Linux operating system and for
* the djgpp ms-dos extender.
*
* W. Metzenthen June 1994.
*
*
* $FreeBSD$
*
*/
/*
| Kernel subtraction routine reg_u_sub(reg *arg1, reg *arg2, reg *answ).
| Takes two valid reg f.p. numbers (TW_Valid), which are
| treated as unsigned numbers,
| and returns their difference as a TW_Valid or TW_Zero f.p.
| number.
| The first number (arg1) must be the larger.
| The returned number is normalized.
| Basic checks are performed if PARANOID is defined.
*/
#include <gnu/i386/fpemul/fpu_asm.h>
.text
ENTRY(reg_u_sub)
pushl %ebp
movl %esp,%ebp
pushl %esi
pushl %edi
pushl %ebx
movl PARAM1,%esi /* source 1 */
movl PARAM2,%edi /* source 2 */
#ifdef DENORM_OPERAND
cmpl EXP_UNDER,EXP(%esi)
jg xOp1_not_denorm
call denormal_operand
orl %eax,%eax
jnz FPU_Arith_exit
xOp1_not_denorm:
cmpl EXP_UNDER,EXP(%edi)
jg xOp2_not_denorm
call denormal_operand
orl %eax,%eax
jnz FPU_Arith_exit
xOp2_not_denorm:
#endif /* DENORM_OPERAND */
/* xorl %ecx,%ecx */
movl EXP(%esi),%ecx
subl EXP(%edi),%ecx /* exp1 - exp2 */
#ifdef PARANOID
/* source 2 is always smaller than source 1 */
/* jc L_bugged */
js L_bugged_1
testl $0x80000000,SIGH(%edi) /* The args are assumed to be be normalized */
je L_bugged_2
testl $0x80000000,SIGH(%esi)
je L_bugged_2
#endif /* PARANOID */
/*--------------------------------------+
| Form a register holding the |
| smaller number |
+--------------------------------------*/
movl SIGH(%edi),%eax /* register ms word */
movl SIGL(%edi),%ebx /* register ls word */
movl PARAM3,%edi /* destination */
movl EXP(%esi),%edx
movl %edx,EXP(%edi) /* Copy exponent to destination */
movb SIGN(%esi),%dl
movb %dl,SIGN(%edi) /* Copy the sign from the first arg */
xorl %edx,%edx /* register extension */
/*--------------------------------------+
| Shift the temporary register |
| right the required number of |
| places. |
+--------------------------------------*/
L_shift_r:
cmpl $32,%ecx /* shrd only works for 0..31 bits */
jnc L_more_than_31
/* less than 32 bits */
shrd %cl,%ebx,%edx
shrd %cl,%eax,%ebx
shr %cl,%eax
jmp L_shift_done
L_more_than_31:
cmpl $64,%ecx
jnc L_more_than_63
subb $32,%cl
jz L_exactly_32
shrd %cl,%eax,%edx
shr %cl,%eax
orl %ebx,%ebx
jz L_more_31_no_low /* none of the lowest bits is set */
orl $1,%edx /* record the fact in the extension */
L_more_31_no_low:
movl %eax,%ebx
xorl %eax,%eax
jmp L_shift_done
L_exactly_32:
movl %ebx,%edx
movl %eax,%ebx
xorl %eax,%eax
jmp L_shift_done
L_more_than_63:
cmpw $65,%cx
jnc L_more_than_64
/* Shift right by 64 bits */
movl %eax,%edx
orl %ebx,%ebx
jz L_more_63_no_low
orl $1,%edx
jmp L_more_63_no_low
L_more_than_64:
jne L_more_than_65
/* Shift right by 65 bits */
/* Carry is clear if we get here */
movl %eax,%edx
rcrl %edx
jnc L_shift_65_nc
orl $1,%edx
jmp L_more_63_no_low
L_shift_65_nc:
orl %ebx,%ebx
jz L_more_63_no_low
orl $1,%edx
jmp L_more_63_no_low
L_more_than_65:
movl $1,%edx /* The shifted nr always at least one '1' */
L_more_63_no_low:
xorl %ebx,%ebx
xorl %eax,%eax
L_shift_done:
L_subtr:
/*------------------------------+
| Do the subtraction |
+------------------------------*/
xorl %ecx,%ecx
subl %edx,%ecx
movl %ecx,%edx
movl SIGL(%esi),%ecx
sbbl %ebx,%ecx
movl %ecx,%ebx
movl SIGH(%esi),%ecx
sbbl %eax,%ecx
movl %ecx,%eax
#ifdef PARANOID
/* We can never get a borrow */
jc L_bugged
#endif /* PARANOID */
/*--------------------------------------+
| Normalize the result |
+--------------------------------------*/
testl $0x80000000,%eax
jnz L_round /* no shifting needed */
orl %eax,%eax
jnz L_shift_1 /* shift left 1 - 31 bits */
orl %ebx,%ebx
jnz L_shift_32 /* shift left 32 - 63 bits */
/* A rare case, the only one which is non-zero if we got here
// is: 1000000 .... 0000
// -0111111 .... 1111 1
// --------------------
// 0000000 .... 0000 1 */
cmpl $0x80000000,%edx
jnz L_must_be_zero
/* Shift left 64 bits */
subl $64,EXP(%edi)
movl %edx,%eax
jmp L_store
L_must_be_zero:
#ifdef PARANOID
orl %edx,%edx
jnz L_bugged_3
#endif /* PARANOID */
/* The result is zero */
movb TW_Zero,TAG(%edi)
movl $0,EXP(%edi) /* exponent */
movl $0,SIGL(%edi)
movl $0,SIGH(%edi)
jmp L_exit /* Does not underflow */
L_shift_32:
movl %ebx,%eax
movl %edx,%ebx
movl $0,%edx
subl $32,EXP(%edi) /* Can get underflow here */
/* We need to shift left by 1 - 31 bits */
L_shift_1:
bsrl %eax,%ecx /* get the required shift in %ecx */
subl $31,%ecx
negl %ecx
shld %cl,%ebx,%eax
shld %cl,%edx,%ebx
shl %cl,%edx
subl %ecx,EXP(%edi) /* Can get underflow here */
L_round:
jmp FPU_round /* Round the result */
#ifdef PARANOID
L_bugged_1:
pushl EX_INTERNAL|0x206
call EXCEPTION
pop %ebx
jmp L_exit
L_bugged_2:
pushl EX_INTERNAL|0x209
call EXCEPTION
pop %ebx
jmp L_exit
L_bugged_3:
pushl EX_INTERNAL|0x210
call EXCEPTION
pop %ebx
jmp L_exit
L_bugged_4:
pushl EX_INTERNAL|0x211
call EXCEPTION
pop %ebx
jmp L_exit
L_bugged:
pushl EX_INTERNAL|0x212
call EXCEPTION
pop %ebx
jmp L_exit
#endif /* PARANOID */
L_store:
/*------------------------------+
| Store the result |
+------------------------------*/
movl %eax,SIGH(%edi)
movl %ebx,SIGL(%edi)
movb TW_Valid,TAG(%edi) /* Set the tags to TW_Valid */
cmpl EXP_UNDER,EXP(%edi)
jle L_underflow
L_exit:
popl %ebx
popl %edi
popl %esi
leave
ret
L_underflow:
push %edi
call arith_underflow
pop %ebx
jmp L_exit