/* Copyright (c) 2007 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: lround.S,v 1.2 2007/12/01 02:12:54 dmix Exp $ */ #include "fp32def.h" #include "asmdef.h" /* long lround (double A); The lround() function rounds A to the nearest integer, but rounds halfway cases away from zero (instead of to the nearest even integer). This function is similar to round() function, but it differs in type of return value and in that an overflow is possible. Return: The rounded long integer value. If A is infinite, NaN or an overflow was, this realization returns the LONG_MIN value (0x80000000). Algorithm roughly: - split - shift mantissa according to exponent - add 0.5 to round - restore the sign Objections to saturation are listen in __fixunssfsi.S file. */ ENTRY lround rcall _U(__fp_splitA) brcs .L_err ; A is finite subi rA3, 126 ; exponent field of 0.5 brlo .L_zr ; A is too small ; fabs(A) >= 0x0.800000p+00 subi rA3, 24 brlo 2f ; shtft to right and round breq .L_sign ; no shift ; fabs(A) >= 0x0.800000p+25 cpi rA3, 8 brsh .L_err ; A is too big ; 0x0.800000p+25 <= fabs(A) <= 0x0.ffffffp+31 --> shift to left by 1..7 mov r0, rA3 ; shift counter clr rA3 ; MSB ; rA3.2.1.0 <<= r0 1: lsl rA0 rol rA1 rol rA2 rol rA3 dec r0 brne 1b rjmp .L_sign ; quick shift to right by 8 5: mov r0, rA0 ; save for possible round mov rA0, rA1 mov rA1, rA2 clr rA2 subi rA3, -8 brne 2f lsl r0 ; restore C rjmp 4f ; and round ; 0x0.800000p+00 <= fabs(A) <= 0x0.ffffffp+23 ; Shift A to right by 1 (rA3 == -1) .. 24 (rA3 == -24) positions and ; round. 2: cpi rA3, -7 brlt 5b ; shift to right by 1..7 (slow) 3: lsr rA2 ror rA1 ror rA0 ; --> C inc rA3 ; C is not changed brne 3b ; Round. Now flag C is set if fractional is >= 0.5 4: adc rA0, r1 adc rA1, r1 adc rA2, r1 ; rA2 was <= 0x7f, so rA3 will not changed ; restore the sign and return .L_sign: brtc 6f com rA3 com rA2 com rA1 neg rA0 sbci rA1, -1 sbci rA2, -1 sbci rA3, -1 6: ret .L_err: set ; force return 0x80000000 rjmp _U(__fp_szero) .L_zr: rjmp _U(__fp_zero) ; return 0x00000000 ENDFUNC