220 lines
6.0 KiB
ArmAsm
220 lines
6.0 KiB
ArmAsm
/* $NetBSD: ldexp.S,v 1.8 2003/08/07 16:42:15 agc Exp $ */
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/*-
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Ralph Campbell.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <machine/asm.h>
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__FBSDID("$FreeBSD$");
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#if defined(LIBC_SCCS) && !defined(lint)
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ASMSTR("from: @(#)ldexp.s 8.1 (Berkeley) 6/4/93")
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ASMSTR("$NetBSD: ldexp.S,v 1.8 2003/08/07 16:42:15 agc Exp $")
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#endif /* LIBC_SCCS and not lint */
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#ifdef __ABICALLS__
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.abicalls
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#endif
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#define DEXP_INF 0x7ff
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#define DEXP_BIAS 1023
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#define DEXP_MIN -1022
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#define DEXP_MAX 1023
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#define DFRAC_BITS 52
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#define DIMPL_ONE 0x00100000
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#define DLEAD_ZEROS 31 - 20
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#define STICKYBIT 1
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#define GUARDBIT 0x80000000
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#define DSIGNAL_NAN 0x00040000
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#define DQUIET_NAN0 0x0007ffff
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#define DQUIET_NAN1 0xffffffff
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/*
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* double ldexp(x, N)
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* double x; int N;
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*
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* Return x * (2**N), for integer values N.
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*/
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LEAF(ldexp)
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mfc1 v1, $f13 # get MSW of x
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mfc1 t3, $f12 # get LSW of x
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sll t1, v1, 1 # get x exponent
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srl t1, t1, 32 - 11
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beq t1, DEXP_INF, 9f # is it a NAN or infinity?
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beq t1, zero, 1f # zero or denormalized number?
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addu t1, t1, a2 # scale exponent
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sll v0, a2, 20 # position N for addition
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bge t1, DEXP_INF, 8f # overflow?
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addu v0, v0, v1 # multiply by (2**N)
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ble t1, zero, 4f # underflow?
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mtc1 v0, $f1 # save MSW of result
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mtc1 t3, $f0 # save LSW of result
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j ra
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1:
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sll t2, v1, 32 - 20 # get x fraction
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srl t2, t2, 32 - 20
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srl t0, v1, 31 # get x sign
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bne t2, zero, 1f
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beq t3, zero, 9f # result is zero
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1:
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/*
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* Find out how many leading zero bits are in t2,t3 and put in t9.
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*/
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move v0, t2
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move t9, zero
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bne t2, zero, 1f
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move v0, t3
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addu t9, 32
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1:
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srl ta0, v0, 16
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bne ta0, zero, 1f
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addu t9, 16
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sll v0, 16
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1:
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srl ta0, v0, 24
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bne ta0, zero, 1f
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addu t9, 8
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sll v0, 8
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1:
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srl ta0, v0, 28
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bne ta0, zero, 1f
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addu t9, 4
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sll v0, 4
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1:
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srl ta0, v0, 30
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bne ta0, zero, 1f
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addu t9, 2
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sll v0, 2
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1:
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srl ta0, v0, 31
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bne ta0, zero, 1f
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addu t9, 1
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/*
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* Now shift t2,t3 the correct number of bits.
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*/
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1:
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subu t9, t9, DLEAD_ZEROS # dont count normal leading zeros
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li t1, DEXP_MIN + DEXP_BIAS
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subu t1, t1, t9 # adjust exponent
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addu t1, t1, a2 # scale exponent
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li v0, 32
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blt t9, v0, 1f
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subu t9, t9, v0 # shift fraction left >= 32 bits
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sll t2, t3, t9
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move t3, zero
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b 2f
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1:
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subu v0, v0, t9 # shift fraction left < 32 bits
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sll t2, t2, t9
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srl ta0, t3, v0
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or t2, t2, ta0
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sll t3, t3, t9
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2:
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bge t1, DEXP_INF, 8f # overflow?
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ble t1, zero, 4f # underflow?
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sll t2, t2, 32 - 20 # clear implied one bit
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srl t2, t2, 32 - 20
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3:
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sll t1, t1, 31 - 11 # reposition exponent
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sll t0, t0, 31 # reposition sign
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or t0, t0, t1 # put result back together
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or t0, t0, t2
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mtc1 t0, $f1 # save MSW of result
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mtc1 t3, $f0 # save LSW of result
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j ra
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4:
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li v0, 0x80000000
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ble t1, -52, 7f # is result too small for denorm?
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sll t2, v1, 31 - 20 # clear exponent, extract fraction
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or t2, t2, v0 # set implied one bit
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blt t1, -30, 2f # will all bits in t3 be shifted out?
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srl t2, t2, 31 - 20 # shift fraction back to normal position
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subu t1, t1, 1
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sll ta0, t2, t1 # shift right t2,t3 based on exponent
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srl t8, t3, t1 # save bits shifted out
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negu t1
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srl t3, t3, t1
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or t3, t3, ta0
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srl t2, t2, t1
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bge t8, zero, 1f # does result need to be rounded?
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addu t3, t3, 1 # round result
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sltu ta0, t3, 1
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sll t8, t8, 1
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addu t2, t2, ta0
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bne t8, zero, 1f # round result to nearest
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and t3, t3, ~1
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1:
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mtc1 t3, $f0 # save denormalized result (LSW)
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mtc1 t2, $f1 # save denormalized result (MSW)
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bge v1, zero, 1f # should result be negative?
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neg.d $f0, $f0 # negate result
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1:
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j ra
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2:
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mtc1 zero, $f1 # exponent and upper fraction
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addu t1, t1, 20 # compute amount to shift right by
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sll t8, t2, t1 # save bits shifted out
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negu t1
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srl t3, t2, t1
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bge t8, zero, 1f # does result need to be rounded?
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addu t3, t3, 1 # round result
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sltu ta0, t3, 1
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sll t8, t8, 1
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mtc1 ta0, $f1 # exponent and upper fraction
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bne t8, zero, 1f # round result to nearest
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and t3, t3, ~1
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1:
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mtc1 t3, $f0
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bge v1, zero, 1f # is result negative?
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neg.d $f0, $f0 # negate result
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1:
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j ra
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7:
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mtc1 zero, $f0 # result is zero
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mtc1 zero, $f1
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beq t0, zero, 1f # is result positive?
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neg.d $f0, $f0 # negate result
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1:
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j ra
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8:
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li t1, 0x7ff00000 # result is infinity (MSW)
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mtc1 t1, $f1
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mtc1 zero, $f0 # result is infinity (LSW)
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bge v1, zero, 1f # should result be negative infinity?
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neg.d $f0, $f0 # result is negative infinity
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1:
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add.d $f0, $f0 # cause overflow faults if enabled
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j ra
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9:
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mov.d $f0, $f12 # yes, result is just x
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j ra
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END(ldexp)
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