/* SPDX-License-Identifier: GPL-2.0 */
        .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
SYM_FUNC_START(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 */
SYM_FUNC_END(FPU_u_add)