Virtual Reality Homebrewer's Handbook/vr.iso/vr386/miscmath.asm

Assembly Source File | 1996-03-19 | 10KB | 571 lines

    TITLE    MISCMATH - VARIOUS MATH IN ASSEMBLER

    COMMENT $

// Routines to do various math that can't be done in C.
// Some are just for efficiency, and could be done in C with
// a true 32-bit compiler.  Others use 64-bit intermediate results.

// All code by Dave Stampe, last updated 23/12/93

/*
 This code is part of the VR-386 project, created by Dave Stampe.
 VR-386 is a desendent of REND386, created by Dave Stampe and
 Bernie Roehl.  Almost all the code has been rewritten by Dave
 Stampre for VR-386.

 Copyright (c) 1994 by Dave Stampe:
 May be freely used to write software for release into the public domain
 or for educational use; all commercial endeavours MUST contact Dave Stampe
 ([e-mail]) for permission to incorporate any part of
 this software or source code into their products!  Usually there is no
 charge for under 50-100 items for low-cost or shareware products, and terms
 are reasonable.  Any royalties are used for development, so equipment is
 often acceptable payment.

 ATTRIBUTION:  If you use any part of this source code or the libraries
 in your projects, you must give attribution to VR-386 and Dave Stampe,
 and any other authors in your documentation, source code, and at startup
 of your program.  Let's keep the freeware ball rolling!

 DEVELOPMENT: VR-386 is a effort to develop the process started by
 REND386, improving programmer access by rewriting the code and supplying
 a standard API.  If you write improvements, add new functions rather
 than rewriting current functions.  This will make it possible to
 include you improved code in the next API release.  YOU can help advance
 VR-386.  Comments on the API are welcome.

 CONTACT: [e-mail]
*/
        $

    .MODEL large

; # define XFSC 536870912   /* 2**29 for shifting xform coeffs to long */


    .DATA

_longmath_overflow    dd 0    ;; overflow/high dword return

    .CODE INTMATH


MULT29     MACRO a,b                 ; multiply <3.29> -> eax
    mov    eax,DWORD PTR a
    imul    DWORD PTR b
    shrd    eax,edx,29
    adc    eax,0
    ENDM

MMULT29 MACRO a,b,c               ; multiply 3 of <3.29> -> eax
    mov    eax,DWORD PTR a
    imul    DWORD PTR b
    shrd    eax,edx,29
    adc    eax,0
    imul    DWORD PTR c
    shrd    eax,edx,29
    adc    eax,0
    ENDM

DOTPROD    MACRO a,b,c,x,y,z,p      ; dot product plus p, accum in ecx:ebx
    mov    eax,a            ; result in eax
    imul    DWORD PTR x
    mov    ecx,edx
    mov    ebx,eax
    mov    eax,b
    imul    DWORD PTR y
    add    ebx,eax
    adc    ecx,edx
    mov    eax,c
    imul    DWORD PTR z
    add    eax,ebx
    adc    edx,ecx
    shrd    eax,edx,29
    adc    eax,p
    ENDM

;/****************** MISC. MATH SUPPORT **********/



;long m_mult(long a, long b)    /* perform mult. by matrix element         */
;{                              /* where either a or b is in <3.29> format */

a    equ    [bp+8]          ; arguments
b    equ    [bp+12]

    PUBLIC    _m_mult

_m_mult    proc    far

    .386
    push    ebp
    mov    ebp,esp

    MULT29    a,b

    shld    edx,eax,16    ; return in dx:ax

    mov    esp,ebp
    pop    ebp
    ret

_m_mult    endp


;long m2_mult(long a, long b, long c)    /* perform mult. by matrix element         */
;{                              /* where a and b is in <3.29> format */

a    equ    [bp+8]          ; arguments
b    equ    [bp+12]
b    equ    [bp+16]

    PUBLIC    _m_mult

_m2_mult    proc    far

    .386
    push    ebp
    mov    ebp,esp

    MMULT29    a,b,c

    shld    edx,eax,16    ; return in dx:ax

    mov    esp,ebp
    pop    ebp
    ret

_m2_mult    endp




;long divide_29(long a, long b) /* perform divide, result in <3.29> format */
;{                              /* up to user to test for  overflow          */

a    equ    DWORD PTR [bp+8]          ; arguments
b    equ    DWORD PTR [bp+12]

    PUBLIC    _divide_29

_divide_29    proc    far

    .386
    push    ebp
    mov    ebp,esp

    mov    eax,a
    cdq
    shld    edx,eax,29
    shl    eax,29

    idiv    b

    shld    edx,eax,16    ; return in dx:ax

    mov    esp,ebp
    pop    ebp
    ret

_divide_29    endp


;long divide_long(long ahi, long alo, long b)

a    equ    DWORD PTR [bp+8]          ; arguments
b    equ    DWORD PTR [bp+12]
b    equ    DWORD PTR [bp+16]

    PUBLIC    _divide_long

_divide_long    proc    far

    .386
    push    ebp
    mov    ebp,esp

    mov    eax,alo
    mov    edx,ahi

    idiv    b
    mov    _longmath_overflow,edx

    shld    edx,eax,16    ; return in dx:ax

    mov    esp,ebp
    pop    ebp
    ret

_divide_long    endp


;long mult_long(long a, long b) /* perform multiply on longs         */

a    equ    DWORD PTR [bp+8]          ; arguments
b    equ    DWORD PTR [bp+12]

    PUBLIC    _mult_long

_mult_long    proc    far

    .386
    push    ebp
    mov    ebp,esp

    mov    eax,a
    imul    b
    mov    _longmath_overflow,edx

    shld    edx,eax,16    ; return in dx:ax

    mov    esp,ebp
    pop    ebp
    ret

_mult_long    endp



;    // shifts 32-bit signed number left or right (>0 is left, <0 is right)
;extern long_shift32(long a, int shift);

a    equ    DWORD PTR [bp+8]          ; arguments
shift    equ    WORD PTR [bp+12]

    PUBLIC    _long_shift32

_long_shift32    proc    far

    .386
    push    ebp
    mov    ebp,esp

    mov    eax,a
    cdq
    mov    cx,shift
    or    cx,cx
    jge    left_shift32

    neg    cx
    shrd    eax,edx,cl
    shr    edx,cl
    adc    eax,0
    adc    edx,0
    mov    _longmath_overflow,edx
    jmp    done_shift32

left_shift32:
    shld    edx,eax,cl
    shl    eax,cl
    mov    _longmath_overflow,edx

done_shift32:
    shld    edx,eax,16    ; return in dx:ax and eax

    mov    esp,ebp
    pop    ebp
    ret

_long_shift32    endp




;    // shifts 64-bit signed number left or right (>0 is left, <0 is right)
;    // msdword of result is returned in longmath_overflow
;extern long_shift64(long ahi, long alo, int shift);

ahi    equ    DWORD PTR [bp+8]          ; arguments
alo    equ    DWORD PTR [bp+12]
shift    equ    WORD PTR  [bp+16]

    PUBLIC    _long_shift64

_long_shift64    proc    far

    .386
    push    ebp
    mov    ebp,esp

    mov    edx,ahi
    mov    eax,alo
    mov    cx,shift
    or    cx,cx
    jge    left_shift64

    neg    cx
    shrd    eax,edx,cl
    shr    edx,cl
    adc    eax,0
    adc    edx,0
    mov    _longmath_overflow,edx
    jmp    done_shift64

left_shift64:
    shld    edx,eax,cl
    shl    eax,cl
    mov    _longmath_overflow,edx

done_shift64:
    shld    edx,eax,16    ; return in dx:ax and eax

    mov    esp,ebp
    pop    ebp
    ret

_long_shift64    endp



;long mulmuldiv(long a, long b) /* perform (a*b)/c with 64-bit intermediate */
;{                              /* up to user to test for  overflow  */

a    equ    DWORD PTR [bp+8]          ; arguments
b    equ    DWORD PTR [bp+12]
c    equ    DWORD PTR [bp+16]

    PUBLIC    _mulmuldiv

_mulmuldiv    proc    far

    .386
    push    ebp
    mov    ebp,esp

    mov    eax,a
    imul    b
    idiv    c
    mov    _longmath_overflow,edx

    shld    edx,eax,16    ; return in dx:ax

    mov    esp,ebp
    pop    ebp
    ret

_mulmuldiv    endp



;long dot_prod_29(long a, long b, long c, long x, long y, long z)
; /* computes (Ax + By + Cz)>>29 */

a    equ    [bp+8]          ; arguments
b    equ    [bp+12]
c    equ    [bp+16]
x    equ    [bp+20]
y    equ    [bp+24]
z    equ    [bp+28]

    PUBLIC    _dot_prod_29

_dot_prod_29    proc    far

    .386
    push    ebp
    mov    ebp,esp

    push    esi
    push    edi
    push    ecx

    DOTPROD a,b,c,x,y,z,0

    shld    edx,eax,16    ; return dx:ax

    pop    edi
    pop    esi

    mov    esp,ebp
    pop    ebp
    ret

_dot_prod_29    endp



;long scale_16(long s, long a, long x)    /* perform scaling by 16.16 number */


s    equ    [bp+8]          ; arguments
a     equ    [bp+12]
x     equ    [bp+16]

    PUBLIC    _scale_16

_scale_16     proc    far

    .386
    push    ebp
    mov    ebp,esp

    mov    eax,DWORD PTR x
    add     eax,DWORD PTR a
    imul    DWORD PTR s
    shrd    eax,edx,16
    adc    eax,0

    shld    edx,eax,16    ; return in eax and dx:ax

    mov    esp,ebp
    pop    ebp
    ret

_scale_16  endp


;long calc_scale_16(long a, long b, long s)   /* compute 16.16 scaling factor */

a    equ    [bp+8]          ; arguments
b     equ    [bp+12]
s     equ    [bp+16]

    PUBLIC    _calc_scale_16

_calc_scale_16    proc    far

    .386
    push    ebp
    mov    ebp,esp

    xor    eax,eax        ; return 0 for divide error
    mov    ebx,DWORD PTR a
    sub    ebx,DWORD PTR b
    je    cdiv
    mov    eax, DWORD PTR s
    cdq
    shld    edx,eax,17
    shl    eax,17
    idiv  ebx
cdiv:
    shld    edx,eax,16    ; return in eax and dx:ax

    mov    esp,ebp
    pop    ebp
    ret

_calc_scale_16    endp






;long plane_y(long a, long b, long c, long d, long x, long z)
;         /* used to compute floor/ceiling of areas */

a    equ    [bp+8]          ; arguments
b     equ    [bp+12]
c     equ    [bp+16]
d     equ    [bp+20]
x     equ    [bp+24]
z     equ    [bp+28]

    PUBLIC    _plane_y

_plane_y    proc    far

    .386
    push    ebp
    mov    ebp,esp
            ;* computes (Ax + Cz + D)/-B */
    push    esi
    push    edi

    xor    eax,eax
    test    DWORD PTR b,-1
    je    divzero

    mov    eax,a
    imul    DWORD PTR x
    mov    esi,eax
    mov    edi,edx

    mov    eax,c
    imul    DWORD PTR z
    add    esi,eax
    adc    edi,edx

    mov    eax,DWORD PTR d
    cdq
    add    eax,esi
    adc    edx,edi
    idiv    DWORD PTR b
divzero:
    shld    edx,eax,16    ; return in eax and dx:ax
    pop    edi
    pop    esi

    mov    esp,ebp
    pop    ebp
    ret

_plane_y    endp




;/************* 32 BIT CITY-BLOCK DISTANCE *************/

;/* returns abs(x1-x2) + abs(y1-y2) + abs(z1-z2) */

;long big_dist(long x1, long y1, long z1,
;           long x2, long y2, long z2 )

x1    equ    [bp+8]          ; arguments
y1    equ    [bp+12]
z1    equ    [bp+16]
x2    equ    [bp+20]
y2    equ    [bp+24]
z2    equ    [bp+28]

    PUBLIC    _big_dist

_big_dist    proc    far

    .386
    push    ebp
    mov    ebp,esp

    push    ecx

    mov     eax,x1
    sub    eax,x2
    cdq
    xor    eax,edx
    sub    eax,edx
    mov    ecx,eax

    mov     eax,y1
    sub    eax,y2
    cdq
    xor    eax,edx
    sub    eax,edx
    add    ecx,eax

    mov     eax,z1
    sub    eax,z2
    cdq
    xor    eax,edx
    sub    eax,edx
    add    eax,ecx

    shld    edx,eax,16    ; return in eax and dx:ax

    pop    ecx

    mov    esp,ebp
    pop    ebp
    ret

_big_dist    endp




    end