275 строки
6.0 KiB
ArmAsm
275 строки
6.0 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
|
|
.file "reg_u_sub.S"
|
|
/*---------------------------------------------------------------------------+
|
|
| reg_u_sub.S |
|
|
| |
|
|
| Core floating point subtraction routine. |
|
|
| |
|
|
| 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_sub(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 subtraction routine FPU_u_sub(reg *arg1, reg *arg2, reg *answ).
|
|
| Takes two valid reg f.p. numbers (TAG_Valid), which are
|
|
| treated as unsigned numbers,
|
|
| and returns their difference as a TAG_Valid or TAG_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 "exception.h"
|
|
#include "fpu_emu.h"
|
|
#include "control_w.h"
|
|
|
|
.text
|
|
SYM_FUNC_START(FPU_u_sub)
|
|
pushl %ebp
|
|
movl %esp,%ebp
|
|
pushl %esi
|
|
pushl %edi
|
|
pushl %ebx
|
|
|
|
movl PARAM1,%esi /* source 1 */
|
|
movl PARAM2,%edi /* source 2 */
|
|
|
|
movl PARAM6,%ecx
|
|
subl PARAM7,%ecx /* exp1 - exp2 */
|
|
|
|
#ifdef PARANOID
|
|
/* source 2 is always smaller than source 1 */
|
|
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 PARAM6,%edx
|
|
movw %dx,EXP(%edi) /* Copy exponent to destination */
|
|
|
|
xorl %edx,%edx /* register extension */
|
|
|
|
/*--------------------------------------+
|
|
| Shift the temporary register |
|
|
| right the required number of |
|
|
| places. |
|
|
+--------------------------------------*/
|
|
|
|
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
|
|
|
|
/* 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 */
|
|
subw $64,EXP(%edi)
|
|
xchg %edx,%eax
|
|
jmp fpu_reg_round
|
|
|
|
L_must_be_zero:
|
|
#ifdef PARANOID
|
|
orl %edx,%edx
|
|
jnz L_bugged_3
|
|
#endif /* PARANOID */
|
|
|
|
/* The result is zero */
|
|
movw $0,EXP(%edi) /* exponent */
|
|
movl $0,SIGL(%edi)
|
|
movl $0,SIGH(%edi)
|
|
movl TAG_Zero,%eax
|
|
jmp L_exit
|
|
|
|
L_shift_32:
|
|
movl %ebx,%eax
|
|
movl %edx,%ebx
|
|
movl $0,%edx
|
|
subw $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
|
|
subw %cx,EXP(%edi) /* Can get underflow here */
|
|
|
|
L_round:
|
|
jmp fpu_reg_round /* Round the result */
|
|
|
|
|
|
#ifdef PARANOID
|
|
L_bugged_1:
|
|
pushl EX_INTERNAL|0x206
|
|
call EXCEPTION
|
|
pop %ebx
|
|
jmp L_error_exit
|
|
|
|
L_bugged_2:
|
|
pushl EX_INTERNAL|0x209
|
|
call EXCEPTION
|
|
pop %ebx
|
|
jmp L_error_exit
|
|
|
|
L_bugged_3:
|
|
pushl EX_INTERNAL|0x210
|
|
call EXCEPTION
|
|
pop %ebx
|
|
jmp L_error_exit
|
|
|
|
L_bugged_4:
|
|
pushl EX_INTERNAL|0x211
|
|
call EXCEPTION
|
|
pop %ebx
|
|
jmp L_error_exit
|
|
|
|
L_bugged:
|
|
pushl EX_INTERNAL|0x212
|
|
call EXCEPTION
|
|
pop %ebx
|
|
jmp L_error_exit
|
|
|
|
L_error_exit:
|
|
movl $-1,%eax
|
|
|
|
#endif /* PARANOID */
|
|
|
|
L_exit:
|
|
popl %ebx
|
|
popl %edi
|
|
popl %esi
|
|
leave
|
|
ret
|
|
SYM_FUNC_END(FPU_u_sub)
|