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/* Copyright (c) 2002 Michael Stumpf <mistumpf@de.pepperl-fuchs.com>
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Copyright (c) 2006 Dmitry Xmelkov
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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 are met:
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* 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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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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* Neither the name of the copyright holders nor the names of
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND 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 COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE. */
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/* $Id: fp_rempio2.S,v 1.1 2007/01/14 14:58:04 dmix Exp $ */
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/* <non_standart> __fp_rempio2 (float x);
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The __fp_rempio2() function computes the remainder of dividing
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absolute value of x by Pi/2. The return value is x - n*Pi/2, where
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n is the quotient of abs(x)/(Pi/2), rounded towards zero to an integer.
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rA3.rA2.rA1.rA0.rAE - flt40_t remainder
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#define HI40_PIO2 0x3FC90FDA /* (flt40_t) Pi/2 */
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#define LO40_PIO2 0xA2
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#define MNT32_PIO2 0xC90FDAA2 /* mantissa of Pi/2, 32 bits */
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#define SPLIT_PIO2 0x7FC80FDA /* split(HI40_PIO2) */
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; split and check finite
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brcs 0b ; only finite numbers are valid
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; init division result ('com' at the end)
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ldi rB1, hi8(SPLIT_PIO2 + 1)
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ldi rB2, hlo8(SPLIT_PIO2 + 1)
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ldi rB3, hhi8(SPLIT_PIO2 + 1)
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cpi rA0, lo8(SPLIT_PIO2 + 1)
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brlo .L_pack ; A < Pi/2 ==> return A
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clr ZH ; highest A byte
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subi rA3, hhi8(HI40_PIO2 << 1) ; ilogb(A) - ilogb(B)
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subi rAE, lo8(MNT32_PIO2)
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sbci rA0, hi8(MNT32_PIO2)
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sbci rA1, hlo8(MNT32_PIO2)
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sbci rA2, hhi8(MNT32_PIO2)
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subi rAE, lo8(-MNT32_PIO2)
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sbci rA0, hi8(-MNT32_PIO2)
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sbci rA1, hlo8(-MNT32_PIO2)
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sbci rA2, hhi8(-MNT32_PIO2)
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/* FIXME: Is it possible to obtain a zero value in rA2.1.0.E ?
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I do't known. So, there is a check in exponent decrement. */
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ldi rA3, hhi8((HI40_PIO2 << 1) - 0x01000000)
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removed
libm/fplib/fp_rempio2.S
