/* $NetBSD: ldexp.S,v 1.10 2014/09/17 11:01:05 joerg Exp $ */
/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Ralph Campbell.
*
* 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.
*/
#include <mips/asm.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
RCSID("from: @(#)ldexp.s 8.1 (Berkeley) 6/4/93")
#else
RCSID("$NetBSD: ldexp.S,v 1.10 2014/09/17 11:01:05 joerg Exp $")
#endif
#endif /* LIBC_SCCS and not lint */
#define DEXP_INF 0x7ff
#define DEXP_BIAS 1023
#define DEXP_MIN -1022
#define DEXP_MAX 1023
#define DFRAC_BITS 52
#define DIMPL_ONE 0x00100000
#define DLEAD_ZEROS 31 - 20
#define STICKYBIT 1
#define GUARDBIT 0x80000000
#define DSIGNAL_NAN 0x00040000
#define DQUIET_NAN0 0x0007ffff
#define DQUIET_NAN1 0xffffffff
/*
* double ldexp(x, N)
* double x; int N;
*
* Return x * (2**N), for integer values N.
*/
LEAF(ldexp)
mfc1 v1, $f13 # get MSW of x
mfc1 t3, $f12 # get LSW of x
sll t1, v1, 1 # get x exponent
srl t1, t1, 32 - 11
beq t1, DEXP_INF, 9f # is it a NAN or infinity?
beq t1, zero, 1f # zero or denormalized number?
addu t1, t1, a2 # scale exponent
sll v0, a2, 20 # position N for addition
bge t1, DEXP_INF, 8f # overflow?
addu v0, v0, v1 # multiply by (2**N)
ble t1, zero, 4f # underflow?
mtc1 v0, $f1 # save MSW of result
mtc1 t3, $f0 # save LSW of result
j ra
1:
sll t2, v1, 32 - 20 # get x fraction
srl t2, t2, 32 - 20
srl t0, v1, 31 # get x sign
bne t2, zero, 1f
beq t3, zero, 9f # result is zero
1:
/*
* Find out how many leading zero bits are in t2,t3 and put in t9.
*/
move v0, t2
move t9, zero
bne t2, zero, 1f
move v0, t3
addu t9, 32
1:
srl ta0, v0, 16
bne ta0, zero, 1f
addu t9, 16
sll v0, 16
1:
srl ta0, v0, 24
bne ta0, zero, 1f
addu t9, 8
sll v0, 8
1:
srl ta0, v0, 28
bne ta0, zero, 1f
addu t9, 4
sll v0, 4
1:
srl ta0, v0, 30
bne ta0, zero, 1f
addu t9, 2
sll v0, 2
1:
srl ta0, v0, 31
bne ta0, zero, 1f
addu t9, 1
/*
* Now shift t2,t3 the correct number of bits.
*/
1:
subu t9, t9, DLEAD_ZEROS # dont count normal leading zeros
li t1, DEXP_MIN + DEXP_BIAS
subu t1, t1, t9 # adjust exponent
addu t1, t1, a2 # scale exponent
li v0, 32
blt t9, v0, 1f
subu t9, t9, v0 # shift fraction left >= 32 bits
sll t2, t3, t9
move t3, zero
b 2f
1:
subu v0, v0, t9 # shift fraction left < 32 bits
sll t2, t2, t9
srl ta0, t3, v0
or t2, t2, ta0
sll t3, t3, t9
2:
bge t1, DEXP_INF, 8f # overflow?
ble t1, zero, 4f # underflow?
sll t2, t2, 32 - 20 # clear implied one bit
srl t2, t2, 32 - 20
3:
sll t1, t1, 31 - 11 # reposition exponent
sll t0, t0, 31 # reposition sign
or t0, t0, t1 # put result back together
or t0, t0, t2
mtc1 t0, $f1 # save MSW of result
mtc1 t3, $f0 # save LSW of result
j ra
4:
li v0, 0x80000000
ble t1, -52, 7f # is result too small for denorm?
sll t2, v1, 31 - 20 # clear exponent, extract fraction
or t2, t2, v0 # set implied one bit
blt t1, -30, 2f # will all bits in t3 be shifted out?
srl t2, t2, 31 - 20 # shift fraction back to normal position
subu t1, t1, 1
sll ta0, t2, t1 # shift right t2,t3 based on exponent
srl t8, t3, t1 # save bits shifted out
negu t1
srl t3, t3, t1
or t3, t3, ta0
srl t2, t2, t1
bge t8, zero, 1f # does result need to be rounded?
addu t3, t3, 1 # round result
sltu ta0, t3, 1
sll t8, t8, 1
addu t2, t2, ta0
bne t8, zero, 1f # round result to nearest
and t3, t3, ~1
1:
mtc1 t3, $f0 # save denormalized result (LSW)
mtc1 t2, $f1 # save denormalized result (MSW)
bge v1, zero, 1f # should result be negative?
neg.d $f0, $f0 # negate result
1:
j ra
2:
mtc1 zero, $f1 # exponent and upper fraction
addu t1, t1, 20 # compute amount to shift right by
sll t8, t2, t1 # save bits shifted out
negu t1
srl t3, t2, t1
bge t8, zero, 1f # does result need to be rounded?
addu t3, t3, 1 # round result
sltu ta0, t3, 1
sll t8, t8, 1
mtc1 ta0, $f1 # exponent and upper fraction
bne t8, zero, 1f # round result to nearest
and t3, t3, ~1
1:
mtc1 t3, $f0
bge v1, zero, 1f # is result negative?
neg.d $f0, $f0 # negate result
1:
j ra
7:
mtc1 zero, $f0 # result is zero
mtc1 zero, $f1
beq t0, zero, 1f # is result positive?
neg.d $f0, $f0 # negate result
1:
j ra
8:
li t1, 0x7ff00000 # result is infinity (MSW)
mtc1 t1, $f1
mtc1 zero, $f0 # result is infinity (LSW)
bge v1, zero, 1f # should result be negative infinity?
neg.d $f0, $f0 # result is negative infinity
1:
add.d $f0, $f0, $f0 # cause overflow faults if enabled
j ra
9:
mov.d $f0, $f12 # yes, result is just x
j ra
END(ldexp)