/* 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: exp.S,v 1.10 2007/01/14 15:08:17 dmix Exp $ */ #include "fp32def.h" #include "asmdef.h" /* float exp (float x); The exp() function returns the value of e (the base of natural logarithms) raised to the power of x. */ #define X2BIG 0x43000000 /* exp(-X2BIG) < 0x00000001 */ #define FL_1_LN2 0x3fb8aa3b /* 1 / ln(2) */ /* second arg for modf(), ldexp() functions. */ #define exp_lo r20 #define exp_hi r21 FUNCTION exp .L_nf: brne .L_nan .L_tb: brts .L_zr rjmp _U(__fp_inf) .L_zr: rjmp _U(__fp_zero) .L_nan: rjmp _U(__fp_nan) ENTRY exp ; split and analize A rcall _U(__fp_splitA) brcs .L_nf ; A is not a finite number cpi rA3, hhi8(X2BIG << 1) brsh .L_tb ; A is too big (in absolute value) ; save sign and jump to positive bld r0, 7 push r0 clt ; A = A / ln(2) ldi rB0, lo8(FL_1_LN2) ldi rB1, hi8(FL_1_LN2) ldi rB2, hlo8(FL_1_LN2 | 0x800000) ; hidden '1' ldi rB3, hhi8(FL_1_LN2 << 1) ; exponent rcall _U(__mulsf3_pse) ; split A into fraction and integral parts push r0 push r0 push r0 in exp_lo, SPL_IO_ADDR in exp_hi, SPH_IO_ADDR push r0 rcall _U(modf) ; calculate 2**(-x) for 0 <= x < 1 ldi ZL, lo8(.L_table) ldi ZH, hi8(.L_table) rcall _U(__fp_powser) ; get integral part pop exp_lo pop exp_hi pop ZL pop ZH ; cast to integer asr ZL rol ZL rol ZH breq 2f subi ZH, 0x7e ori ZL, 0x80 clr exp_lo 1: lsl ZL rol exp_lo dec ZH brne 1b ; negate and scale neg exp_lo sbc exp_hi, exp_hi 2: rcall _U(ldexp) ; inverse for positive arg. pop r0 sbrs r0, 7 rjmp _U(inverse) ret ENDFUNC PGM_SECTION .L_table: .byte 7 .byte 0x63,0x42,0x36,0xb7 ; -0.0000108635 .byte 0x9b,0xd8,0xa7,0x1a,0x39 ; 0.0001474911 .byte 0x68,0x56,0x18,0xae,0xba ; -0.0013282400 .byte 0xab,0x55,0x8c,0x1d,0x3c ; 0.0096159779 .byte 0xb7,0xcc,0x57,0x63,0xbd ; -0.0555036542 .byte 0x6d,0xed,0xfd,0x75,0x3e ; 0.2402264688 .byte 0xf6,0x17,0x72,0x31,0xbf ; -0.6931471802 .byte 0x00,0x00,0x00,0x80,0x3f ; 1.0000000000 .end