+++ /dev/null
-/*
- * Copyright (c) 1992, 1993
- * The Regents of the University of California. All rights reserved.
- *
- * This software was developed by the Computer Systems Engineering group
- * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
- * contributed to Berkeley.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- * must display the following acknowledgement:
- * This product includes software developed by the University of
- * California, Berkeley and its contributors.
- * 4. Neither the name of the University nor the names of its contributors
- * may be used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- *
- * from: Header: divrem.m4,v 1.4 92/06/25 13:23:57 torek Exp
- * $NetBSD: divrem.m4,v 1.4 1997/10/09 10:07:54 lukem Exp $
- */
-
-/*
- * Division and remainder, from Appendix E of the Sparc Version 8
- * Architecture Manual, with fixes from Gordon Irlam.
- */
-
-#if defined(LIBC_SCCS) && !defined(lint)
- .asciz "@(#)divrem.m4 8.1 (Berkeley) 6/4/93"
-#endif /* LIBC_SCCS and not lint */
-
-/*
- * Input: dividend and divisor in %o0 and %o1 respectively.
- *
- * m4 parameters:
- * NAME name of function to generate
- * OP OP=div => %o0 / %o1; OP=rem => %o0 % %o1
- * S S=true => signed; S=false => unsigned
- *
- * Algorithm parameters:
- * N how many bits per iteration we try to get (4)
- * WORDSIZE total number of bits (32)
- *
- * Derived constants:
- * TWOSUPN 2^N, for label generation (m4 exponentiation currently broken)
- * 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.
- */
-
-define(N, `4')
-define(TWOSUPN, `16')
-define(WORDSIZE, `32')
-define(TOPBITS, eval(WORDSIZE - N*((WORDSIZE-1)/N)))
-
-define(dividend, `%o0')
-define(divisor, `%o1')
-define(Q, `%o2')
-define(R, `%o3')
-define(ITER, `%o4')
-define(V, `%o5')
-
-/* m4 reminder: ifelse(a,b,c,d) => if a is b, then c, else d */
-define(T, `%g1')
-define(SC, `%g7')
-ifelse(S, `true', `define(SIGN, `%g6')')
-
-/*
- * This is the recursive definition for developing quotient digits.
- *
- * Parameters:
- * $1 the current depth, 1 <= $1 <= N
- * $2 the current accumulation of quotient bits
- * N max depth
- *
- * We add a new bit to $2 and either recurse or insert the bits in
- * the quotient. R, Q, and V are inputs and outputs as defined above;
- * the condition codes are expected to reflect the input R, and are
- * modified to reflect the output R.
- */
-define(DEVELOP_QUOTIENT_BITS,
-` ! depth $1, accumulated bits $2
- bl L.$1.eval(TWOSUPN+$2)
- srl V,1,V
- ! remainder is positive
- subcc R,V,R
- ifelse($1, N,
- ` b 9f
- add Q, ($2*2+1), Q
- ', ` DEVELOP_QUOTIENT_BITS(incr($1), `eval(2*$2+1)')')
-L.$1.eval(TWOSUPN+$2):
- ! remainder is negative
- addcc R,V,R
- ifelse($1, N,
- ` b 9f
- add Q, ($2*2-1), Q
- ', ` DEVELOP_QUOTIENT_BITS(incr($1), `eval(2*$2-1)')')
- ifelse($1, 1, `9:')')
-
-#define C_LABEL(name) name:
-
-#define C_SYMBOL_NAME(name) name
-
-#define ENTRY(name) \
- .global C_SYMBOL_NAME(name); \
- .align 4;\
- C_LABEL(name);\
- .type name,@function;
-
-#define END(name) \
- .size name, . - name
-
-#define ST_DIV0 0x02
-
-
-ENTRY(NAME)
-ifelse(S, `true',
-` ! compute sign of result; if neither is negative, no problem
- orcc divisor, dividend, %g0 ! either negative?
- bge 2f ! no, go do the divide
- ifelse(OP, `div',
- `xor divisor, dividend, SIGN',
- `mov dividend, SIGN') ! compute sign in any case
- tst divisor
- bge 1f
- tst dividend
- ! divisor is definitely negative; dividend might also be negative
- bge 2f ! if dividend not negative...
- neg divisor ! in any case, make divisor nonneg
-1: ! dividend is negative, divisor is nonnegative
- neg dividend ! make dividend nonnegative
-2:
-')
- ! Ready to divide. Compute size of quotient; scale comparand.
- orcc divisor, %g0, V
- bnz 1f
- mov dividend, R
-
- ! Divide by zero trap. If it returns, return 0 (about as
- ! wrong as possible, but that is what SunOS does...).
- t ST_DIV0
- retl
- clr %o0
-
-1:
- cmp R, V ! if divisor exceeds dividend, done
- blu Lgot_result ! (and algorithm fails otherwise)
- clr Q
- sethi %hi(1 << (WORDSIZE - TOPBITS - 1)), T
- cmp R, T
- blu Lnot_really_big
- clr ITER
-
- ! `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 V, T
- bgeu 3f
- mov 1, SC
- sll V, N, V
- b 1b
- inc ITER
-
- ! Now compute SC.
- 2: addcc V, V, V
- bcc Lnot_too_big
- inc SC
-
- ! We get here if the divisor overflowed while shifting.
- ! This means that R has the high-order bit set.
- ! Restore V and subtract from R.
- sll T, TOPBITS, T ! high order bit
- srl V, 1, V ! rest of V
- add V, T, V
- b Ldo_single_div
- dec SC
-
- Lnot_too_big:
- 3: cmp V, R
- 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) */
- ! V > R: went too far: back up 1 step
- ! srl V, 1, V
- ! dec SC
- ! do single-bit divide steps
- !
- ! We have to be careful here. We know that R >= V, so we can do the
- ! first divide step without thinking. BUT, the others are conditional,
- ! and are only done if R >= 0. Because both R and V 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:
- deccc SC
- bl Lend_regular_divide
- nop
- sub R, V, R
- mov 1, Q
- b Lend_single_divloop
- nop
- Lsingle_divloop:
- sll Q, 1, Q
- bl 1f
- srl V, 1, V
- ! R >= 0
- sub R, V, R
- b 2f
- inc Q
- 1: ! R < 0
- add R, V, R
- dec Q
- 2:
- Lend_single_divloop:
- deccc SC
- bge Lsingle_divloop
- tst R
- b,a Lend_regular_divide
-
-Lnot_really_big:
-1:
- sll V, N, V
- cmp V, R
- bleu 1b
- inccc ITER
- be Lgot_result
- dec ITER
-
- tst R ! set up for initial iteration
-Ldivloop:
- sll Q, N, Q
- DEVELOP_QUOTIENT_BITS(1, 0)
-Lend_regular_divide:
- deccc ITER
- bge Ldivloop
- tst R
- bl,a Lgot_result
- ! non-restoring fixup here (one instruction only!)
-ifelse(OP, `div',
-` dec Q
-', ` add R, divisor, R
-')
-
-Lgot_result:
-ifelse(S, `true',
-` ! check to see if answer should be < 0
- tst SIGN
- bl,a 1f
- ifelse(OP, `div', `neg Q', `neg R')
-1:')
- retl
- ifelse(OP, `div', `mov Q, %o0', `mov R, %o0')
-
-END(NAME)
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