Reimplement bn_div_words, bn_add_words and bn_sub_words for VAX.
authorRichard Levitte <levitte@openssl.org>
Tue, 21 Nov 2000 23:32:38 +0000 (23:32 +0000)
committerRichard Levitte <levitte@openssl.org>
Tue, 21 Nov 2000 23:32:38 +0000 (23:32 +0000)
I'm a little bit nervous about bn_div_words, as I don't know what it's
supposed to return on overflow.  For now, I trust the rest of the
system to give it numbers that will not cause any overflow...

crypto/bn/asm/vms.mar

index ac9d57d..7e73fe8 100644 (file)
@@ -162,442 +162,236 @@ n=12 ;(AP)      n       by value (input)
        movl    #1,r0                   ; return SS$_NORMAL
        ret
 \f
-       .title  (generated)
-
-       .psect  code,nowrt
-
-.entry BN_DIV_WORDS,^m<r2,r3,r4,r5,r6,r7,r8,r9,r10>
-       subl2   #4,sp
-
-       clrl    r9
-       movl    #2,r8
-
-       tstl    12(ap)
-       bneq    noname.2
-       mnegl   #1,r10
-       brw     noname.3
-       tstl    r0
-       nop     
-noname.2:
-
-       pushl   12(ap)
-       calls   #1,BN_NUM_BITS_WORD
-       movl    r0,r7
-
-       cmpl    r7,#32
-       beql    noname.4
-       ashl    r7,#1,r2
-       cmpl    4(ap),r2
-       blequ   noname.4
-
-       pushl   r7
-       calls   #1,BN_DIV_WORDS_ABORT
-noname.4:
-
-       subl3   r7,#32,r7
-
-       movl    12(ap),r2
-       cmpl    4(ap),r2
-       blssu   noname.5
-       subl2   r2,4(ap)
-noname.5:
-
-       tstl    r7
-       beql    noname.6
-
-       ashl    r7,r2,12(ap)
-
-       ashl    r7,4(ap),r4
-       subl3   r7,#32,r3
-       subl3   r3,#32,r2
-       extzv   r3,r2,8(ap),r2
-       bisl3   r4,r2,4(ap)
-
-       ashl    r7,8(ap),8(ap)
-noname.6:
-
-       bicl3   #65535,12(ap),r2
-       extzv   #16,#16,r2,r5
-
-       bicl3   #-65536,12(ap),r6
-
-noname.7:
-
-       moval   4(ap),r2
-       movzwl  2(r2),r0
-       cmpl    r0,r5
-       bneq    noname.8
-
-       movzwl  #65535,r4
-       brb     noname.9
-noname.8:
-
-       clrl    r1
-       movl    (r2),r0
-       movl    r5,r2
-       bgeq    vcg.1
-       cmpl    r2,r0
-       bgtru   vcg.2
-       incl    r1
-       brb     vcg.2
-       nop     
-vcg.1:
-       ediv    r2,r0,r1,r0
-vcg.2:
-       movl    r1,r4
-noname.9:
-
-noname.10:
-
-       mull3   r5,r4,r0
-       subl3   r0,4(ap),r3
-
-       bicl3   #65535,r3,r0
-       bneq    noname.13
-       mull3   r6,r4,r2
-       ashl    #16,r3,r1
-       bicl3   #65535,8(ap),r0
-       extzv   #16,#16,r0,r0
-       addl2   r0,r1
-       cmpl    r2,r1
-       bgtru   noname.12
-noname.11:
-
-       brb     noname.13
-       nop     
-noname.12:
-
-       decl    r4
-       brb     noname.10
-noname.13:
-
-       mull3   r5,r4,r1
-
-       mull3   r6,r4,r0
-
-       extzv   #16,#16,r0,r3
-
-       ashl    #16,r0,r2
-       bicl3   #65535,r2,r0
-
-       addl2   r3,r1
-
-       moval   8(ap),r3
-       cmpl    (r3),r0
-       bgequ   noname.15
-       incl    r1
-noname.15:
-
-       subl2   r0,(r3)
-
-       cmpl    4(ap),r1
-       bgequ   noname.16
-
-       addl2   12(ap),4(ap)
-
-       decl    r4
-noname.16:
-
-       subl2   r1,4(ap)
-
-       decl    r8
-       beql    noname.18
-noname.17:
-
-       ashl    #16,r4,r9
-
-       ashl    #16,4(ap),r2
-       movzwl  2(r3),r0
-       bisl2   r0,r2
-       bicl3   #0,r2,4(ap)
-
-       bicl3   #-65536,(r3),r0
-       ashl    #16,r0,(r3)
-       brw     noname.7
-       nop     
-noname.18:
+       .title  vax_bn_div_words  unsigned divide
+;
+; Richard Levitte 20-Nov-2000
+;
+; ULONG bn_div_words(ULONG h, ULONG l, ULONG d)
+; {
+;      return ((ULONG)((((ULLONG)h)<<32)|l) / (ULLONG)d);
+; }
+;
+; Using EDIV would be very easy, if it didn't do signed calculations.
+; Therefore, som extra things have to happen around it.  The way to
+; handle that is to shift all operands right one step (basically dividing
+; them by 2) and handle the different cases depending on what the lowest
+; bit of each operand was.
+;
+; To start with, let's define the following:
+;
+; a' = l & 1
+; a2 = <h,l> >> 1      # UNSIGNED shift!
+; b' = d & 1
+; b2 = d >> 1          # UNSIGNED shift!
+;
+; Now, use EDIV to calculate a quotient and a remainder:
+;
+; q'' = a2/b2
+; r'' = a2 - q''*b2
+;
+; If b' is 0, the quotient is already correct, we just need to adjust the
+; remainder:
+;
+; if (b' == 0)
+;   {
+;     r = 2*r'' + a'
+;     q = q''
+;   }
+;
+; If b' is 1, we need to do other adjustements.  The first thought is the
+; following (note that r' will not always have the right value, but an
+; adjustement follows further down):
+;
+; if (b' == 1)
+;   {
+;     q' = q''
+;     r' = a - q'*b
+;
+; However, one can note the folowing relationship:
+;
+;                         r'' = a2 - q''*b2
+;                  =>   2*r'' = 2*a2 - 2*q''*b2
+;                             = { a = 2*a2 + a', b = 2*b2 + b' = 2*b2 + 1,
+;                                 q' = q'' }
+;                             = a - a' - q'*(b - 1)
+;                             = a - q'*b - a' + q'
+;                             = r' - a' + q'
+;                  =>     r'  = 2*r'' - q' + a'
+;
+; This enables us to use r'' instead of discarding and calculating another
+; modulo:
+;
+; if (b' == 1)
+;   {
+;     q' = q''
+;     r' = (r'' << 1) - q' + a'
+;
+; Now, all we have to do is adjust r', because it might be < 0:
+;
+;     while (r' < 0)
+;       {
+;         r' = r' + b
+;         q' = q' - 1
+;       }
+;   }
+;
+; return q'
 
-       bisl2   r4,r9
+h=4 ;(AP)      h       by value (input)
+l=8 ;(AP)      l       by value (input)
+d=12 ;(AP)     d       by value (input)
 
-       movl    r9,r10
+aprim=r5
+a2=r6
+a20=r6
+a21=r7
+bprim=r8
+b2=r9
+qprim=r10      ; initially used as q''
+rprim=r11      ; initially used as r''
 
-noname.3:
-       movl    r10,r0
-       ret     
-       tstl    r0
 
-\f
        .psect  code,nowrt
 
-.entry BN_ADD_WORDS,^m<r2,r3,r4,r5,r6,r7>
-
-       tstl    16(ap)
-       bgtr    noname.21
-       clrl    r7
-       brw     noname.22
-noname.21:
-
-       clrl    r4
-
-       tstl    r0
-noname.23:
-
-       movl    8(ap),r6
-       addl3   r4,(r6),r2
-
-       bicl2   #0,r2
-
-       clrl    r0
-       cmpl    r2,r4
-       bgequ   vcg.3
-       incl    r0
-vcg.3:
-       movl    r0,r4
-
-       movl    12(ap),r5
-       addl3   (r5),r2,r1
-       bicl2   #0,r1
-
-       clrl    r0
-       cmpl    r1,r2
-       bgequ   vcg.4
-       incl    r0
-vcg.4:
-       addl2   r0,r4
-
-       movl    4(ap),r3
-       movl    r1,(r3)
-
-       decl    16(ap)
-       bgtr    gen.1
-       brw     noname.25
-gen.1:
-noname.24:
-
-       addl3   r4,4(r6),r2
-
-       bicl2   #0,r2
-
-       clrl    r0
-       cmpl    r2,r4
-       bgequ   vcg.5
-       incl    r0
-vcg.5:
-       movl    r0,r4
-
-       addl3   4(r5),r2,r1
-       bicl2   #0,r1
-
-       clrl    r0
-       cmpl    r1,r2
-       bgequ   vcg.6
-       incl    r0
-vcg.6:
-       addl2   r0,r4
-
-       movl    r1,4(r3)
-
-       decl    16(ap)
-       bleq    noname.25
-noname.26:
-
-       addl3   r4,8(r6),r2
-
-       bicl2   #0,r2
-
-       clrl    r0
-       cmpl    r2,r4
-       bgequ   vcg.7
-       incl    r0
-vcg.7:
-       movl    r0,r4
-
-       addl3   8(r5),r2,r1
-       bicl2   #0,r1
-
-       clrl    r0
-       cmpl    r1,r2
-       bgequ   vcg.8
-       incl    r0
-vcg.8:
-       addl2   r0,r4
-
-       movl    r1,8(r3)
-
-       decl    16(ap)
-       bleq    noname.25
-noname.27:
-
-       addl3   r4,12(r6),r2
-
-       bicl2   #0,r2
-
-       clrl    r0
-       cmpl    r2,r4
-       bgequ   vcg.9
-       incl    r0
-vcg.9:
-       movl    r0,r4
-
-       addl3   12(r5),r2,r1
-       bicl2   #0,r1
-
-       clrl    r0
-       cmpl    r1,r2
-       bgequ   vcg.10
-       incl    r0
-vcg.10:
-       addl2   r0,r4
+.entry bn_div_words,^m<r2,r3,r4,r5,r6,r7,r8,r9,r10,r11>
+       movl    l(ap),r2
+       movl    h(ap),r3
+       movl    d(ap),r4
+
+       movl    #0,aprim
+       movl    #0,bprim
+       movl    #0,r0
+
+       rotl    #-1,r2,a20      ; a20 = l >> 1 (almost)
+       rotl    #-1,r3,a21      ; a21 = h >> 1 (almost)
+       rotl    #-1,r4,b2       ; b2 = d >> 1 (almost)
+
+       tstl    a20
+       bgeq    1$
+       xorl2   #^X80000000,a20 ; fixup a20 so highest bit is 0
+       incl    aprim           ; a' = 1
+1$:
+       tstl    a21
+       bgeq    2$
+       xorl2   #^X80000000,a20 ; fixup a20 so highest bit is 1,
+                               ; since that's what was lowest in a21
+       xorl2   #^X80000000,a21 ; fixup a21 so highest bit is 1
+2$:
+       tstl    b2
+       bgeq    666$            ; Uh-oh, the divisor is 0...
+       bgrt    3$
+       xorl2   #^X80000000,b2  ; fixup b2 so highest bit is 1
+       incl    bprim
+3$:
+       tstl    b2
+       bneq    4$              ; if b2 is 0, we know that bprim is 1
+       tstl    a21
+       bneq    666$            ; if higher half isn't 0, we overflow
+       movl    r0,a20          ; otherwise, we have our result
+       brb     42$
+4$:
+       ediv    b2,a2,qprim,rprim
+
+       tstl    bprim
+       bneq    5$              ; If b' != 0, go to the other part
+;      addl3   rprim,rprim,r1
+;      addl2   aprim,r1
+       brb     42$
+5$:
+       ash     #1,rprim,rprim
+       subl2   qprim,rprim
+       addl2   aprim,rprim
+       bgeq    7$
+6$:
+       decl    qprim
+       addl2   r4,rprim
+       blss    6$
+7$:
+;      movl    rprim,r1
+42$:
+       movl    qprim,r0
+666$:
+       ret
+\f
+       .title  vax_bn_add_words  unsigned add of two arrays
+;
+; Richard Levitte 20-Nov-2000
+;
+; ULONG bn_add_words(ULONG r[], ULONG a[], ULONG b[], int n) {
+;      ULONG c = 0;
+;      int i;
+;      for (i = 0; i < n; i++) <c,r[i]> = a[i] + b[i] + c;
+;      return(c);
+; }
 
-       movl    r1,12(r3)
+r=4 ;(AP)      r       by reference (output)
+a=8 ;(AP)      a       by reference (input)
+b=12 ;(AP)     b       by reference (input)
+n=16 ;(AP)     n       by value (input)
 
-       decl    16(ap)
-       bleq    noname.25
-noname.28:
 
-       addl3   #16,r6,8(ap)
+       .psect  code,nowrt
 
-       addl3   #16,r5,12(ap)
+.entry bn_add_words,^m<r2,r3,r4,r5,r6>
 
-       addl3   #16,r3,4(ap)
-       brw     noname.23
-       tstl    r0
-noname.25:
+       moval   @r(ap),r2
+       moval   @a(ap),r3
+       moval   @b(ap),r4
+       movl    n(ap),r5        ; assumed >0 by C code
+       clrl    r0              ; c
 
-       movl    r4,r7
+       tstl    r5              ; carry = 0
+       bleq    666$
 
-noname.22:
-       movl    r7,r0
-       ret     
-       nop     
+0$:
+       movl    (r3)+,r6        ; carry untouched
+       addwc   (r4)+,r6        ; carry used and touched
+       movl    r6,(r2)+        ; carry untouched
+       sobgtr  r5,0$           ; carry untouched
 
+       addwc   #0,r0
+666$:
+       ret
 \f
+       .title  vax_bn_sub_words  unsigned add of two arrays
+;
+; Richard Levitte 20-Nov-2000
+;
+; ULONG bn_sub_words(ULONG r[], ULONG a[], ULONG b[], int n) {
+;      ULONG c = 0;
+;      int i;
+;      for (i = 0; i < n; i++) <c,r[i]> = a[i] - b[i] - c;
+;      return(c);
+; }
 
-;r=4 ;(AP)
-;a=8 ;(AP)
-;b=12 ;(AP)
-;n=16 ;(AP)    n       by value (input)
+r=4 ;(AP)      r       by reference (output)
+a=8 ;(AP)      a       by reference (input)
+b=12 ;(AP)     b       by reference (input)
+n=16 ;(AP)     n       by value (input)
 
-       .psect  code,nowrt
 
-.entry BN_SUB_WORDS,^m<r2,r3,r4,r5,r6,r7>
+       .psect  code,nowrt
 
-       clrl    r6
+.entry bn_sub_words,^m<r2,r3,r4,r5,r6>
 
-       tstl    16(ap)
-       bgtr    noname.31
-       clrl    r7
-       brw     noname.32
-       tstl    r0
-noname.31:
+       moval   @r(ap),r2
+       moval   @a(ap),r3
+       moval   @b(ap),r4
+       movl    n(ap),r5        ; assumed >0 by C code
+       clrl    r0              ; c
 
-noname.33:
+       tstl    r5              ; carry = 0
+       bleq    666$
 
-       movl    8(ap),r5
-       movl    (r5),r1
-       movl    12(ap),r4
-       movl    (r4),r2
-
-       movl    4(ap),r3
-       subl3   r2,r1,r0
-       subl2   r6,r0
-       bicl3   #0,r0,(r3)
-
-       cmpl    r1,r2
-       beql    noname.34
-       clrl    r0
-       cmpl    r1,r2
-       bgequ   vcg.11
-       incl    r0
-vcg.11:
-       movl    r0,r6
-noname.34:
-
-       decl    16(ap)
-       bgtr    gen.2
-       brw     noname.36
-gen.2:
-noname.35:
-
-       movl    4(r5),r2
-       movl    4(r4),r1
-
-       subl3   r1,r2,r0
-       subl2   r6,r0
-       bicl3   #0,r0,4(r3)
-
-       cmpl    r2,r1
-       beql    noname.37
-       clrl    r0
-       cmpl    r2,r1
-       bgequ   vcg.12
-       incl    r0
-vcg.12:
-       movl    r0,r6
-noname.37:
-
-       decl    16(ap)
-       bleq    noname.36
-noname.38:
-
-       movl    8(r5),r1
-       movl    8(r4),r2
-
-       subl3   r2,r1,r0
-       subl2   r6,r0
-       bicl3   #0,r0,8(r3)
-
-       cmpl    r1,r2
-       beql    noname.39
-       clrl    r0
-       cmpl    r1,r2
-       bgequ   vcg.13
-       incl    r0
-vcg.13:
-       movl    r0,r6
-noname.39:
-
-       decl    16(ap)
-       bleq    noname.36
-noname.40:
-
-       movl    12(r5),r1
-       movl    12(r4),r2
-
-       subl3   r2,r1,r0
-       subl2   r6,r0
-       bicl3   #0,r0,12(r3)
-
-       cmpl    r1,r2
-       beql    noname.41
-       clrl    r0
-       cmpl    r1,r2
-       bgequ   vcg.14
-       incl    r0
-vcg.14:
-       movl    r0,r6
-noname.41:
-
-       decl    16(ap)
-       bleq    noname.36
-noname.42:
-
-       addl3   #16,r5,8(ap)
-
-       addl3   #16,r4,12(ap)
-
-       addl3   #16,r3,4(ap)
-       brw     noname.33
-       tstl    r0
-noname.36:
-
-       movl    r6,r7
-
-noname.32:
-       movl    r7,r0
-       ret     
-       nop     
+0$:
+       movl    (r3)+,r6        ; carry untouched
+       sbwc    (r4)+,r6        ; carry used and touched
+       movl    r6,(r2)+        ; carry untouched
+       sobgtr  r5,0$           ; carry untouched
 
+       addwc   #0,r0
+666$:
+       ret
 \f
 
 ;r=4 ;(AP)
@@ -6614,82 +6408,4 @@ noname.610:
        ret     
 
 ; For now, the code below doesn't work, so I end this prematurely.
-.end
-
-       .title  vax_bn_div64    division 64/32=>32
-; 
-; r.l. 16-jan-1998
-;
-; unsigned int bn_div64(unsigned long h, unsigned long l, unsigned long d)
-;      return <h,l>/d;
-;
-
-       .psect  code,nowrt
-
-h=4 ;(AP)      by value (input)
-l=8 ;(AP)      by value (input)
-d=12 ;(AP)     by value (input)
-
-.entry bn_div64,^m<r2,r3,r4,r5,r6,r7,r8,r9>
-
-       movl    l(ap),r2        ; l
-       movl    h(ap),r3        ; h
-       movl    d(ap),r4        ; d
-       clrl    r5              ; q
-       clrl    r6              ; r
-
-       ; Treat "negative" specially
-       tstl    r3
-       blss    30$
-
-       tstl    r4
-       beql    90$
-
-       ediv    r4,r2,r5,r6
-       bvs     666$
-
-       movl    r5,r0
-       ret
-
-30$:
-       ; The theory here is to do some harmless shifting and a little
-       ; bit of rounding (brackets are to designate when decimals are
-       ; cut off):
-       ;
-       ;       result = 2 * [ ([<h,0>/2] + [d/2]) / d ] + [ l / d ]
-
-       movl    #0,r7
-       movl    r3,r8           ; copy h
-       ashq    #-1,r7,r7       ; [<h,0>/2] => <r8,r7>
-       bicl2   #^X80000000,r8  ; Remove "sign"
-
-       movl    r4,r9           ; copy d
-       ashl    #-1,r9,r9       ; [d/2] => r9
-       bicl2   #^X80000000,r9  ; Remove "sign"
-
-       addl2   r9,r7
-       adwc    #0,r8           ; [<h,0>/2] + [d/2] => <r8,r7>
-
-       ediv    r4,r7,r5,r6     ; [ ([<h,0>/2] + [d/2]) / d ] => <r5,r6>
-       bvs     666$
-
-       movl    #0,r6
-       ashq    #1,r5,r5        ; 2 * [ ([<h,0>/2] + [d/2]) / d ] => r5
-
-       movl    #0,r3
-       ediv    r4,r2,r8,r9     ; [ l / d ] => <r8,r9>
-
-       addl2   r8,r5           ;
-       bcs     666$
-
-       movl    r5,r0
-       ret
-               
-90$:
-       movl    #-1,r0
-       ret
-
-666$:
-
-       
 .end