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- /* rem.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:
- * .rem name of function to generate
- * rem rem=div => %o0 / %o1; rem=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 .rem
- .rem:
- ! 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, %g6 ! 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!)
- add %o3, %o1, %o3
-
-
- Lgot_result:
-
- retl
- mov %o3, %o0
-
