minix/lib/libc/arch/sparc64/gen/divrem.m4
Ben Gras 2fe8fb192f Full switch to clang/ELF. Drop ack. Simplify.
There is important information about booting non-ack images in
docs/UPDATING. ack/aout-format images can't be built any more, and
booting clang/ELF-format ones is a little different. Updating to the
new boot monitor is recommended.

Changes in this commit:

	. drop boot monitor -> allowing dropping ack support
	. facility to copy ELF boot files to /boot so that old boot monitor
	  can still boot fairly easily, see UPDATING
	. no more ack-format libraries -> single-case libraries
	. some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases
	. drop several ack toolchain commands, but not all support
	  commands (e.g. aal is gone but acksize is not yet).
	. a few libc files moved to netbsd libc dir
	. new /bin/date as minix date used code in libc/
	. test compile fix
	. harmonize includes
	. /usr/lib is no longer special: without ack, /usr/lib plays no
	  kind of special bootstrapping role any more and bootstrapping
	  is done exclusively through packages, so releases depend even
	  less on the state of the machine making them now.
	. rename nbsd_lib* to lib*
	. reduce mtree
2012-02-14 14:52:02 +01:00

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7.6 KiB
Text

/* $NetBSD: divrem.m4,v 1.4 2003/08/07 16:42:27 agc Exp $ */
/*
* 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. 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
*/
#include <machine/asm.h>
#include <machine/trap.h>
/*
* Division and remainder, from Appendix E of the Sparc Version 8
* Architecture Manual, with fixes from Gordon Irlam.
*/
#if defined(LIBC_SCCS)
RCSID("$NetBSD: divrem.m4,v 1.4 2003/08/07 16:42:27 agc Exp $")
#endif
/*
* 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, `%g5')
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:')')
FUNC(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')