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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.
* 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: modf.s,v 1.3 92/06/20 00:00:54 torek Exp
*/
#if defined(LIBC_SCCS) && !defined(lint)
.asciz "@(#)modf.s 8.1 (Berkeley) 6/4/93"
#if 0
.asciz "$NetBSD: modf.S,v 1.2 2000/07/23 07:12:22 eeh Exp $"
#endif
#endif /* LIBC_SCCS and not lint */
#include <machine/asm.h>
__FBSDID("$FreeBSD$");
#include "assym.s"
/*
* 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 + SPOFF - 4] saved %fsr
* 4@[%fp + SPOFF - 8] new %fsr with rounding set to `towards 0'
* 8@[%fp + SPOFF - 16] space for moving between %i and %f registers
* Register usage:
* %f0:f1 double val;
* %l0 scratch
* %l1 sign bit (0x80000000)
* %i1 double *iptr;
* %f2:f3 `magic number' 2^52, in fpu registers
* %f4:f5 double v, in fpu registers
* %f6:f7 double temp.
*/
.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, -CCFSZ - 16, %sp
PIC_PROLOGUE(%l6, %l7)
/*
* First, compute v = abs(val)
*/
fabsd %f0, %f4 ! %f4:f5 = v
fcmped %fcc1, %f0, %f4 ! %fcc1 = (val == abs(val))
SET(.Lmagic, %l7, %l0)
ldd [%l0], %f2
/*
* Is %f4:f5 >= %f2:f3 ? If so, it is all integer bits.
* It is probably less, though.
*/
fcmped %f4, %f2
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 + SPOFF - 4] ! %l5 = current FSR mode
set FSR_RD_MASK, %l3 ! %l3 = rounding direction mask
ld [%fp + SPOFF - 4], %l5
set FSR_RD_RD_Z, %l4
andn %l5, %l3, %l6
or %l6, %l4, %l6 ! round towards zero, please
and %l5, %l3, %l5 ! save original rounding mode
st %l6, [%fp + SPOFF - 8]
ld [%fp + SPOFF - 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 + SPOFF - 4]
ld [%fp + SPOFF - 4], %l6
andn %l6, %l3, %l6 ! %l6 = %fsr & ~FSR_RD_MASK;
or %l5, %l6, %l5 ! %l5 |= %l6;
st %l5, [%fp + SPOFF - 4]
ld [%fp + SPOFF - 4], %fsr ! restore %fsr, leaving accrued stuff
/*
* Now insert the original sign in %f4:f5.
* %fcc1 should still have the results of (val == abs(val))
* from above, so we use a conditional move on %fcc1 to:
*
* %f4 = (val == abs(val)) ? %f4 : -%f4
*
*/
fnegd %f4, %f6
fmovdnz %fcc1, %f6, %f4
1:
/*
* The value in %f4:f5 is now the integer portion of the original
* argument. We need to store this in *ival (%i1), subtract it
* from the original value argument (%d0), and return the result.
*/
std %f4, [%i1] ! *ival = %f4:f5;
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.
*/
SET(.L0, %l7, %l0)
std %f0, [%i1] ! *ival = val;
ldd [%l0], %f0 ! return 0.0;
ret
restore
END(modf)
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