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/*
* 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.
*/
#if defined(LIBC_SCCS)
.text
.asciz "$OpenBSD: modf.S,v 1.4 2003/06/02 20:18:32 millert Exp $"
#endif /* LIBC_SCCS */
#include "DEFS.h"
#include <machine/fsr.h>
/*
* double modf(double val, double *iptr)
*
* Returns the fractional part of `val', storing the integer part of
* `val' in *iptr. Both *iptr and the return value have the same sign
* as `val'.
*
* Method:
*
* We use the fpu's normalization hardware to compute the integer portion
* of the double precision argument. Sun IEEE double precision numbers
* have 52 bits of mantissa, 11 bits of exponent, and one bit of sign,
* with the sign occupying bit 31 of word 0, and the exponent bits 30:20
* of word 0. Thus, values >= 2^52 are by definition integers.
*
* If we take a value that is in the range [+0..2^52) and add 2^52, all
* of the fractional bits fall out and all of the integer bits are summed
* with 2^52. If we then subtract 2^52, we get those integer bits back.
* This must be done with rounding set to `towards 0' or `towards -inf'.
* `Toward -inf' fails when the value is 0 (we get -0 back)....
*
* Note that this method will work anywhere, but is machine dependent in
* various aspects.
*
* Stack usage:
* 4@[%fp - 4] saved %fsr
* 4@[%fp - 8] new %fsr with rounding set to `towards 0'
* 8@[%fp - 16] space for moving between %i and %f registers
* Register usage:
* %i0%i1 double val;
* %l0 scratch
* %l1 sign bit (0x80000000)
* %i2 double *iptr;
* %f2:f3 `magic number' 2^52, in fpu registers
* %f4:f5 double v, in fpu registers
*/
.align 8
Lmagic:
.word 0x43300000 ! sign = 0, exponent = 52 + 1023, mantissa = 0
.word 0 ! (i.e., .double 0r4503599627370496e+00)
L0:
.word 0 ! 0.0
.word 0
ENTRY(modf)
save %sp, -64-16, %sp
/*
* First, compute v = abs(val) by clearing sign bit,
* and then set up the fpu registers. This would be
* much easier if we could do alu operations on fpu registers!
*/
sethi %hi(0x80000000), %l1 ! sign bit
andn %i0, %l1, %l0
st %l0, [%fp - 16]
#ifdef PIC
PICCY_SET(Lmagic, %l0, %o7)
ldd [%l0], %f2
#else
sethi %hi(Lmagic), %l0
ldd [%l0 + %lo(Lmagic)], %f2
#endif
st %i1, [%fp - 12]
ldd [%fp - 16], %f4 ! %f4:f5 = v
/*
* Is %f4:f5 >= %f2:f3 ? If so, it is all integer bits.
* It is probably less, though.
*/
fcmped %f4, %f2
nop ! fpop2 delay
fbuge Lbig ! if >= (or unordered), go out
nop
/*
* v < 2^52, so add 2^52, then subtract 2^52, but do it all
* with rounding set towards zero. We leave any enabled
* traps enabled, but change the rounding mode. This might
* not be so good. Oh well....
*/
st %fsr, [%fp - 4] ! %l5 = current FSR mode
set FSR_RD, %l3 ! %l3 = rounding direction mask
ld [%fp - 4], %l5
set FSR_RD_RZ << FSR_RD_SHIFT, %l4
andn %l5, %l3, %l6
or %l6, %l4, %l6 ! round towards zero, please
and %l5, %l3, %l5 ! save original rounding mode
st %l6, [%fp - 8]
ld [%fp - 8], %fsr
faddd %f4, %f2, %f4 ! %f4:f5 += 2^52
fsubd %f4, %f2, %f4 ! %f4:f5 -= 2^52
/*
* Restore %fsr, but leave exceptions accrued.
*/
st %fsr, [%fp - 4]
ld [%fp - 4], %l6
andn %l6, %l3, %l6 ! %l6 = %fsr & ~FSR_RD;
or %l5, %l6, %l5 ! %l5 |= %l6;
st %l5, [%fp - 4]
ld [%fp - 4], %fsr ! restore %fsr, leaving accrued stuff
/*
* Now insert the original sign in %f4:f5.
* This is a lot of work, so it is conditional here.
*/
btst %l1, %i0
be 1f
nop
st %f4, [%fp - 16]
ld [%fp - 16], %g1
or %l1, %g1, %g1
st %g1, [%fp - 16]
ld [%fp - 16], %f4
1:
/*
* The value in %f4:f5 is now the integer portion of the original
* argument. We need to store this in *ival (%i2), subtract it
* from the original value argument (%i0:i1), and return the result.
*/
std %f4, [%i2] ! *ival = %f4:f5;
std %i0, [%fp - 16]
ldd [%fp - 16], %f0 ! %f0:f1 = val;
fsubd %f0, %f4, %f0 ! %f0:f1 -= %f4:f5;
ret
restore
Lbig:
/*
* We get here if the original comparison of %f4:f5 (v) to
* %f2:f3 (2^52) came out `greater or unordered'. In this
* case the integer part is the original value, and the
* fractional part is 0.
*/
#ifdef PIC
PICCY_SET(L0, %l0, %o7)
std %f0, [%i2] ! *ival = val;
ldd [%l0], %f0 ! return 0.0;
#else
sethi %hi(L0), %l0
std %f0, [%i2] ! *ival = val;
ldd [%l0 + %lo(L0)], %f0 ! return 0.0;
#endif
ret
restore
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