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/*---------------------------------------------------------------------------+
 |  reg_norm.S                                                               |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1995,1997                                    |
 |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
 |                       Australia.  E-mail billm@suburbia.net               |
 |                                                                           |
 | Normalize the value in a FPU_REG.                                         |
 |                                                                           |
 | Call from C as:                                                           |
 |    int FPU_normalize(FPU_REG *n)                                          |
 |                                                                           |
 |    int FPU_normalize_nuo(FPU_REG *n)                                      |
 |                                                                           |
 |    Return value is the tag of the answer, or-ed with FPU_Exception if     |
 |    one was raised, or -1 on internal error.                               |
 |                                                                           |
 +---------------------------------------------------------------------------*/

#include "fpu_emu.h"


.text
ENTRY(FPU_normalize)
        pushl   %ebp
        movl    %esp,%ebp
        pushl   %ebx

        movl    PARAM1,%ebx

        movl    SIGH(%ebx),%edx
        movl    SIGL(%ebx),%eax

        orl     %edx,%edx       /* ms bits */
        js      L_done          /* Already normalized */
        jnz     L_shift_1       /* Shift left 1 - 31 bits */

        orl     %eax,%eax
        jz      L_zero          /* The contents are zero */

        movl    %eax,%edx
        xorl    %eax,%eax
        subw    $32,EXP(%ebx)   /* This can cause an underflow */

/* We need to shift left by 1 - 31 bits */
L_shift_1:
        bsrl    %edx,%ecx       /* get the required shift in %ecx */
        subl    $31,%ecx
        negl    %ecx
        shld    %cl,%eax,%edx
        shl     %cl,%eax
        subw    %cx,EXP(%ebx)   /* This can cause an underflow */

        movl    %edx,SIGH(%ebx)
        movl    %eax,SIGL(%ebx)

L_done:
        cmpw    EXP_OVER,EXP(%ebx)
        jge     L_overflow

        cmpw    EXP_UNDER,EXP(%ebx)
        jle     L_underflow

L_exit_valid:
        movl    TAG_Valid,%eax

        /* Convert the exponent to 80x87 form. */
        addw    EXTENDED_Ebias,EXP(%ebx)
        andw    $0x7fff,EXP(%ebx)

L_exit:
        popl    %ebx
        leave
        ret


L_zero:
        movw    $0,EXP(%ebx)
        movl    TAG_Zero,%eax
        jmp     L_exit

L_underflow:
        /* Convert the exponent to 80x87 form. */
        addw    EXTENDED_Ebias,EXP(%ebx)
        push    %ebx
        call    SYMBOL_NAME(arith_underflow)
        pop     %ebx
        jmp     L_exit

L_overflow:
        /* Convert the exponent to 80x87 form. */
        addw    EXTENDED_Ebias,EXP(%ebx)
        push    %ebx
        call    SYMBOL_NAME(arith_overflow)
        pop     %ebx
        jmp     L_exit



/* Normalise without reporting underflow or overflow */
ENTRY(FPU_normalize_nuo)
        pushl   %ebp
        movl    %esp,%ebp
        pushl   %ebx

        movl    PARAM1,%ebx

        movl    SIGH(%ebx),%edx
        movl    SIGL(%ebx),%eax

        orl     %edx,%edx       /* ms bits */
        js      L_exit_nuo_valid        /* Already normalized */
        jnz     L_nuo_shift_1   /* Shift left 1 - 31 bits */

        orl     %eax,%eax
        jz      L_exit_nuo_zero         /* The contents are zero */

        movl    %eax,%edx
        xorl    %eax,%eax
        subw    $32,EXP(%ebx)   /* This can cause an underflow */

/* We need to shift left by 1 - 31 bits */
L_nuo_shift_1:
        bsrl    %edx,%ecx       /* get the required shift in %ecx */
        subl    $31,%ecx
        negl    %ecx
        shld    %cl,%eax,%edx
        shl     %cl,%eax
        subw    %cx,EXP(%ebx)   /* This can cause an underflow */

        movl    %edx,SIGH(%ebx)
        movl    %eax,SIGL(%ebx)

L_exit_nuo_valid:
        movl    TAG_Valid,%eax

        popl    %ebx
        leave
        ret

L_exit_nuo_zero:
        movl    TAG_Zero,%eax
        movw    EXP_UNDER,EXP(%ebx)

        popl    %ebx
        leave
        ret