/* Copyright (c) 2002 Michael Stumpf Copyright (c) 2006 Dmitry Xmelkov All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * 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. * Neither the name of the copyright holders nor the names of contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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. */ /* $Id: fp_rempio2.S,v 1.1 2007/01/14 14:58:04 dmix Exp $ */ #include "fp32def.h" #include "asmdef.h" /* __fp_rempio2 (float x); The __fp_rempio2() function computes the remainder of dividing absolute value of x by Pi/2. The return value is x - n*Pi/2, where n is the quotient of abs(x)/(Pi/2), rounded towards zero to an integer. Output: rA3.rA2.rA1.rA0.rAE - flt40_t remainder ZL - low byte of n */ #define HI40_PIO2 0x3FC90FDA /* (flt40_t) Pi/2 */ #define LO40_PIO2 0xA2 #define MNT32_PIO2 0xC90FDAA2 /* mantissa of Pi/2, 32 bits */ #define SPLIT_PIO2 0x7FC90FDA /* split(HI40_PIO2) */ FUNCTION __fp_rempio2 0: rjmp _U(__fp_nan) ENTRY __fp_rempio2 ; split and check finite rcall _U(__fp_splitA) brcs 0b ; only finite numbers are valid clt ; ignore a sign ; init division result ('com' at the end) ldi ZL, -1 ; compare A with Pi/2 clr rAE ldi rB1, hi8(SPLIT_PIO2 + 1) ldi rB2, hlo8(SPLIT_PIO2 + 1) ldi rB3, hhi8(SPLIT_PIO2 + 1) cpi rA0, lo8(SPLIT_PIO2 + 1) cpc rA1, rB1 cpc rA2, rB2 cpc rA3, rB3 brlo .L_pack ; A < Pi/2 ==> return A ; prepare loop clr ZH ; highest A byte subi rA3, hhi8(HI40_PIO2 << 1) ; ilogb(A) - ilogb(B) .Loop: subi rAE, lo8(MNT32_PIO2) sbci rA0, hi8(MNT32_PIO2) sbci rA1, hlo8(MNT32_PIO2) sbci rA2, hhi8(MNT32_PIO2) sbci ZH, 0 brpl 5f subi rAE, lo8(-MNT32_PIO2) sbci rA0, hi8(-MNT32_PIO2) sbci rA1, hlo8(-MNT32_PIO2) sbci rA2, hhi8(-MNT32_PIO2) sbci ZH, -1 sec 5: rol ZL subi rA3, 1 brlo 6f lsl rAE rol rA0 rol rA1 rol rA2 rol ZH rjmp .Loop 6: ; normalize /* FIXME: Is it possible to obtain a zero value in rA2.1.0.E ? I do't known. So, there is a check in exponent decrement. */ ldi rA3, hhi8((HI40_PIO2 << 1) - 0x01000000) 7: tst rA2 brmi 8f lsl rAE rol rA0 rol rA1 rol rA2 dec rA3 brne 7b 8: inc rA3 .L_pack: com ZL rjmp _U(__fp_mpack) ENDFUNC