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kernel add
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|
.file "reg_u_add.S"
/*---------------------------------------------------------------------------+
| reg_u_add.S |
| |
| Add two valid (TAG_Valid) FPU_REG numbers, of the same sign, and put the |
| result in a destination FPU_REG. |
| |
| Copyright (C) 1992,1993,1995,1997 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
| E-mail billm@suburbia.net |
| |
| Call from C as: |
| int FPU_u_add(FPU_REG *arg1, FPU_REG *arg2, FPU_REG *answ, |
| int control_w) |
| Return value is the tag of the answer, or-ed with FPU_Exception if |
| one was raised, or -1 on internal error. |
| |
+---------------------------------------------------------------------------*/
/*
| Kernel addition routine FPU_u_add(reg *arg1, reg *arg2, reg *answ).
| Takes two valid reg f.p. numbers (TAG_Valid), which are
| treated as unsigned numbers,
| and returns their sum as a TAG_Valid or TAG_Special f.p. number.
| The returned number is normalized.
| Basic checks are performed if PARANOID is defined.
*/
#include "exception.h"
#include "fpu_emu.h"
#include "control_w.h"
.text
ENTRY(FPU_u_add)
pushl %ebp
movl %esp,%ebp
pushl %esi
pushl %edi
pushl %ebx
movl PARAM1,%esi /* source 1 */
movl PARAM2,%edi /* source 2 */
movl PARAM6,%ecx
movl %ecx,%edx
subl PARAM7,%ecx /* exp1 - exp2 */
jge L_arg1_larger
/* num1 is smaller */
movl SIGL(%esi),%ebx
movl SIGH(%esi),%eax
movl %edi,%esi
movl PARAM7,%edx
negw %cx
jmp L_accum_loaded
L_arg1_larger:
/* num1 has larger or equal exponent */
movl SIGL(%edi),%ebx
movl SIGH(%edi),%eax
L_accum_loaded:
movl PARAM3,%edi /* destination */
movw %dx,EXP(%edi) /* Copy exponent to destination */
xorl %edx,%edx /* clear the extension */
#ifdef PARANOID
testl $0x80000000,%eax
je L_bugged
testl $0x80000000,SIGH(%esi)
je L_bugged
#endif /* PARANOID */
/* The number to be shifted is in %eax:%ebx:%edx */
cmpw $32,%cx /* 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:
cmpw $64,%cx
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
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:
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:
/* Now do the addition */
addl SIGL(%esi),%ebx
adcl SIGH(%esi),%eax
jnc L_round_the_result
/* Overflow, adjust the result */
rcrl $1,%eax
rcrl $1,%ebx
rcrl $1,%edx
jnc L_no_bit_lost
orl $1,%edx
L_no_bit_lost:
incw EXP(%edi)
L_round_the_result:
jmp fpu_reg_round /* Round the result */
#ifdef PARANOID
/* If we ever get here then we have problems! */
L_bugged:
pushl EX_INTERNAL|0x201
call EXCEPTION
pop %ebx
movl $-1,%eax
jmp L_exit
L_exit:
popl %ebx
popl %edi
popl %esi
leave
ret
#endif /* PARANOID */
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