Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/* $Id: sdiv.S,v 1.6 1996/10/02 17:37:00 davem Exp $

 * sdiv.S:      This routine was taken from glibc-1.09 and is covered

 *              by the GNU Library General Public License Version 2.

 */

/* This file is generated from divrem.m4; DO NOT EDIT! */

/*

 * Division and remainder, from Appendix E of the Sparc Version 8

 * Architecture Manual, with fixes from Gordon Irlam.

 */

/*

 * Input: dividend and divisor in %o0 and %o1 respectively.

 *

 * m4 parameters:

 *  .div        name of function to generate

 *  div         div=div => %o0 / %o1; div=rem => %o0 % %o1

 *  true                true=true => signed; true=false => unsigned

 *

 * Algorithm parameters:

 *  N           how many bits per iteration we try to get (4)

 *  WORDSIZE    total number of bits (32)

 *

 * Derived constants:

 *  TOPBITS     number of bits in the top decade of a number

 *

 * Important variables:

 *  Q           the partial quotient under development (initially 0)

 *  R           the remainder so far, initially the dividend

 *  ITER        number of main division loop iterations required;

 *              equal to ceil(log2(quotient) / N).  Note that this

 *              is the log base (2^N) of the quotient.

 *  V           the current comparand, initially divisor*2^(ITER*N-1)

 *

 * Cost:

 *  Current estimate for non-large dividend is

 *      ceil(log2(quotient) / N) * (10 + 7N/2) + C

 *  A large dividend is one greater than 2^(31-TOPBITS) and takes a

 *  different path, as the upper bits of the quotient must be developed

 *  one bit at a time.

 */

        .globl .div

        .globl _Div

.div:

_Div:   /* needed for export */

        ! compute sign of result; if neither is negative, no problem

        orcc    %o1, %o0, %g0   ! either negative?

        bge     2f                      ! no, go do the divide

         xor    %o1, %o0, %g2   ! compute sign in any case

        tst     %o1

        bge     1f

         tst    %o0

        ! %o1 is definitely negative; %o0 might also be negative

        bge     2f                      ! if %o0 not negative...

         sub    %g0, %o1, %o1   ! in any case, make %o1 nonneg

1:      ! %o0 is negative, %o1 is nonnegative

        sub     %g0, %o0, %o0   ! make %o0 nonnegative

2:

        ! Ready to divide.  Compute size of quotient; scale comparand.

        orcc    %o1, %g0, %o5

        bne     1f

         mov    %o0, %o3

                ! Divide by zero trap.  If it returns, return 0 (about as

                ! wrong as possible, but that is what SunOS does...).

                ta      ST_DIV0

                retl

                 clr    %o0

1:

        cmp     %o3, %o5                        ! if %o1 exceeds %o0, done

        blu     Lgot_result             ! (and algorithm fails otherwise)

         clr    %o2

        sethi   %hi(1 << (32 - 4 - 1)), %g1

        cmp     %o3, %g1

        blu     Lnot_really_big

         clr    %o4

        ! Here the dividend is >= 2**(31-N) or so.  We must be careful here,

        ! as our usual N-at-a-shot divide step will cause overflow and havoc.

        ! The number of bits in the result here is N*ITER+SC, where SC <= N.

        ! Compute ITER in an unorthodox manner: know we need to shift V into

        ! the top decade: so do not even bother to compare to R.

        1:

                cmp     %o5, %g1

                bgeu    3f

                 mov    1, %g7

                sll     %o5, 4, %o5

                b       1b

                 add    %o4, 1, %o4

        ! Now compute %g7.

        2:

                addcc   %o5, %o5, %o5

                bcc     Lnot_too_big

                 add    %g7, 1, %g7

                ! We get here if the %o1 overflowed while shifting.

                ! This means that %o3 has the high-order bit set.

                ! Restore %o5 and subtract from %o3.

                sll     %g1, 4, %g1     ! high order bit

                srl     %o5, 1, %o5             ! rest of %o5

                add     %o5, %g1, %o5

                b       Ldo_single_div

                 sub    %g7, 1, %g7

        Lnot_too_big:

        3:

                cmp     %o5, %o3

                blu     2b

                 nop

                be      Ldo_single_div

                 nop

        /* NB: these are commented out in the V8-Sparc manual as well */

        /* (I do not understand this) */

        ! %o5 > %o3: went too far: back up 1 step

        !       srl     %o5, 1, %o5

        !       dec     %g7

        ! do single-bit divide steps

        !

        ! We have to be careful here.  We know that %o3 >= %o5, so we can do the

        ! first divide step without thinking.  BUT, the others are conditional,

        ! and are only done if %o3 >= 0.  Because both %o3 and %o5 may have the high-

        ! order bit set in the first step, just falling into the regular

        ! division loop will mess up the first time around.

        ! So we unroll slightly...

        Ldo_single_div:

                subcc   %g7, 1, %g7

                bl      Lend_regular_divide

                 nop

                sub     %o3, %o5, %o3

                mov     1, %o2

                b       Lend_single_divloop

                 nop

        Lsingle_divloop:

                sll     %o2, 1, %o2

                bl      1f

                 srl    %o5, 1, %o5

                ! %o3 >= 0

                sub     %o3, %o5, %o3

                b       2f

                 add    %o2, 1, %o2

        1:      ! %o3 < 0

                add     %o3, %o5, %o3

                sub     %o2, 1, %o2

        2:

        Lend_single_divloop:

                subcc   %g7, 1, %g7

                bge     Lsingle_divloop

                 tst    %o3

                b,a     Lend_regular_divide

Lnot_really_big:

1:

        sll     %o5, 4, %o5

        cmp     %o5, %o3

        bleu    1b

         addcc  %o4, 1, %o4

        be      Lgot_result

         sub    %o4, 1, %o4

        tst     %o3     ! set up for initial iteration

Ldivloop:

        sll     %o2, 4, %o2

                ! depth 1, accumulated bits 0

        bl      L.1.16

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

                        ! depth 2, accumulated bits 1

        bl      L.2.17

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

                        ! depth 3, accumulated bits 3

        bl      L.3.19

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

                        ! depth 4, accumulated bits 7

        bl      L.4.23

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

        b       9f

         add    %o2, (7*2+1), %o2

L.4.23:

        ! remainder is negative

        addcc   %o3,%o5,%o3

        b       9f

         add    %o2, (7*2-1), %o2

L.3.19:

        ! remainder is negative

        addcc   %o3,%o5,%o3

                        ! depth 4, accumulated bits 5

        bl      L.4.21

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

        b       9f

         add    %o2, (5*2+1), %o2

L.4.21:

        ! remainder is negative

        addcc   %o3,%o5,%o3

        b       9f

         add    %o2, (5*2-1), %o2

L.2.17:

        ! remainder is negative

        addcc   %o3,%o5,%o3

                        ! depth 3, accumulated bits 1

        bl      L.3.17

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

                        ! depth 4, accumulated bits 3

        bl      L.4.19

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

        b       9f

         add    %o2, (3*2+1), %o2

L.4.19:

        ! remainder is negative

        addcc   %o3,%o5,%o3

        b       9f

         add    %o2, (3*2-1), %o2

L.3.17:

        ! remainder is negative

        addcc   %o3,%o5,%o3

                        ! depth 4, accumulated bits 1

        bl      L.4.17

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

        b       9f

         add    %o2, (1*2+1), %o2

L.4.17:

        ! remainder is negative

        addcc   %o3,%o5,%o3

        b       9f

         add    %o2, (1*2-1), %o2

L.1.16:

        ! remainder is negative

        addcc   %o3,%o5,%o3

                        ! depth 2, accumulated bits -1

        bl      L.2.15

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

                        ! depth 3, accumulated bits -1

        bl      L.3.15

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

                        ! depth 4, accumulated bits -1

        bl      L.4.15

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

        b       9f

         add    %o2, (-1*2+1), %o2

L.4.15:

        ! remainder is negative

        addcc   %o3,%o5,%o3

        b       9f

         add    %o2, (-1*2-1), %o2

L.3.15:

        ! remainder is negative

        addcc   %o3,%o5,%o3

                        ! depth 4, accumulated bits -3

        bl      L.4.13

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

        b       9f

         add    %o2, (-3*2+1), %o2

L.4.13:

        ! remainder is negative

        addcc   %o3,%o5,%o3

        b       9f

         add    %o2, (-3*2-1), %o2

L.2.15:

        ! remainder is negative

        addcc   %o3,%o5,%o3

                        ! depth 3, accumulated bits -3

        bl      L.3.13

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

                        ! depth 4, accumulated bits -5

        bl      L.4.11

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

        b       9f

         add    %o2, (-5*2+1), %o2

L.4.11:

        ! remainder is negative

        addcc   %o3,%o5,%o3

        b       9f

         add    %o2, (-5*2-1), %o2

L.3.13:

        ! remainder is negative

        addcc   %o3,%o5,%o3

                        ! depth 4, accumulated bits -7

        bl      L.4.9

         srl    %o5,1,%o5

        ! remainder is positive

        subcc   %o3,%o5,%o3

        b       9f

         add    %o2, (-7*2+1), %o2

L.4.9:

        ! remainder is negative

        addcc   %o3,%o5,%o3

        b       9f

         add    %o2, (-7*2-1), %o2

        9:

Lend_regular_divide:

        subcc   %o4, 1, %o4

        bge     Ldivloop

         tst    %o3

        bl,a    Lgot_result

        ! non-restoring fixup here (one instruction only!)

        sub     %o2, 1, %o2

Lgot_result:

        ! check to see if answer should be < 0

        tst     %g2

        bl,a    1f

         sub %g0, %o2, %o2

1:

        retl

         mov %o2, %o0

        .globl  .div_patch

.div_patch:

        sra     %o0, 0x1f, %o2

        wr      %o2, 0x0, %y

        nop

        nop

        nop

        sdivcc  %o0, %o1, %o0

        bvs,a   1f

         xnor   %o0, %g0, %o0

1:      retl

         nop