161 lines
5.2 KiB
C
161 lines
5.2 KiB
C
/*---------------------------------------------------------------------------+
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| poly_tan.c |
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| $Id: poly_tan.c,v 1.5 2003-05-15 16:19:39 sshwarts Exp $
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| Compute the tan of a FPU_REG, using a polynomial approximation. |
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| Copyright (C) 1992,1993,1994,1997,1999 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
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| Australia. E-mail billm@melbpc.org.au |
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+---------------------------------------------------------------------------*/
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#include "exception.h"
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#include "reg_constant.h"
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#include "fpu_emu.h"
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#include "fpu_system.h"
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#include "control_w.h"
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#include "poly.h"
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#define HiPOWERop 3 /* odd poly, positive terms */
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static const u64 oddplterm[HiPOWERop] =
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{
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BX_CONST64(0x0000000000000000),
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BX_CONST64(0x0051a1cf08fca228),
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BX_CONST64(0x0000000071284ff7)
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};
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#define HiPOWERon 2 /* odd poly, negative terms */
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static const u64 oddnegterm[HiPOWERon] =
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{
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BX_CONST64(0x1291a9a184244e80),
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BX_CONST64(0x0000583245819c21)
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};
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#define HiPOWERep 2 /* even poly, positive terms */
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static const u64 evenplterm[HiPOWERep] =
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{
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BX_CONST64(0x0e848884b539e888),
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BX_CONST64(0x00003c7f18b887da)
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};
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#define HiPOWERen 2 /* even poly, negative terms */
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static const u64 evennegterm[HiPOWERen] =
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{
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BX_CONST64(0xf1f0200fd51569cc),
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BX_CONST64(0x003afb46105c4432)
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};
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static const u64 twothirds = BX_CONST64(0xaaaaaaaaaaaaaaab);
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/*--- poly_tan() ------------------------------------------------------------+
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+---------------------------------------------------------------------------*/
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void poly_tan(FPU_REG *st0_ptr, int invert)
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{
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s32 exponent;
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Xsig argSq, argSqSq, accumulatoro, accumulatore, accum,
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argSignif;
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exponent = exponent(st0_ptr);
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#ifdef PARANOID
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if ( signnegative(st0_ptr) ) /* Can't hack a number < 0.0 */
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{ arith_invalid(0); return; } /* Need a positive number */
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#endif /* PARANOID */
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if ( (exponent >= 0)
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|| ((exponent == -1) && (st0_ptr->sigh > 0xc90fdaa2)) )
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{
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EXCEPTION(0x250);
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}
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else
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{
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argSignif.lsw = 0;
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XSIG_LL(accum) = XSIG_LL(argSignif) = significand(st0_ptr);
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if ( exponent < -1 )
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{
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/* shift the argument right by the required places */
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if ( FPU_shrx(&XSIG_LL(accum), -1-exponent) >= 0x80000000U )
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XSIG_LL(accum) ++; /* round up */
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}
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}
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XSIG_LL(argSq) = XSIG_LL(accum); argSq.lsw = accum.lsw;
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mul_Xsig_Xsig(&argSq, &argSq);
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XSIG_LL(argSqSq) = XSIG_LL(argSq); argSqSq.lsw = argSq.lsw;
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mul_Xsig_Xsig(&argSqSq, &argSqSq);
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/* Compute the negative terms for the numerator polynomial */
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accumulatoro.msw = accumulatoro.midw = accumulatoro.lsw = 0;
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polynomial_Xsig(&accumulatoro, &XSIG_LL(argSqSq), oddnegterm, HiPOWERon-1);
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mul_Xsig_Xsig(&accumulatoro, &argSq);
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negate_Xsig(&accumulatoro);
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/* Add the positive terms */
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polynomial_Xsig(&accumulatoro, &XSIG_LL(argSqSq), oddplterm, HiPOWERop-1);
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/* Compute the positive terms for the denominator polynomial */
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accumulatore.msw = accumulatore.midw = accumulatore.lsw = 0;
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polynomial_Xsig(&accumulatore, &XSIG_LL(argSqSq), evenplterm, HiPOWERep-1);
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mul_Xsig_Xsig(&accumulatore, &argSq);
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negate_Xsig(&accumulatore);
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/* Add the negative terms */
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polynomial_Xsig(&accumulatore, &XSIG_LL(argSqSq), evennegterm, HiPOWERen-1);
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/* Multiply by arg^2 */
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mul64_Xsig(&accumulatore, &XSIG_LL(argSignif));
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mul64_Xsig(&accumulatore, &XSIG_LL(argSignif));
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/* de-normalize and divide by 2 */
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shr_Xsig(&accumulatore, -2*(1+exponent) + 1);
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negate_Xsig(&accumulatore); /* This does 1 - accumulator */
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/* Now find the ratio. */
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if ( accumulatore.msw == 0 )
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{
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/* accumulatoro must contain 1.0 here, (actually, 0) but it
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really doesn't matter what value we use because it will
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have negligible effect in later calculations
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*/
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XSIG_LL(accum) = BX_CONST64(0x8000000000000000);
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accum.lsw = 0;
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}
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else
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{
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div_Xsig(&accumulatoro, &accumulatore, &accum);
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}
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/* Multiply by 1/3 * arg^3 */
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mul64_Xsig(&accum, &XSIG_LL(argSignif));
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mul64_Xsig(&accum, &XSIG_LL(argSignif));
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mul64_Xsig(&accum, &XSIG_LL(argSignif));
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mul64_Xsig(&accum, &twothirds);
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shr_Xsig(&accum, -2*(exponent+1));
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/* tan(arg) = arg + accum */
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add_two_Xsig(&accum, &argSignif, &exponent);
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if ( invert )
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{
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/* accum now contains tan(pi/2 - arg).
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Use tan(arg) = 1.0 / tan(pi/2 - arg)
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*/
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accumulatoro.lsw = accumulatoro.midw = 0;
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accumulatoro.msw = 0x80000000;
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div_Xsig(&accumulatoro, &accum, &accum);
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exponent = - exponent;
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}
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/* Transfer the result */
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exponent += round_Xsig(&accum);
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FPU_settag0(TAG_Valid);
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significand(st0_ptr) = XSIG_LL(accum);
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setexponent16(st0_ptr, exponent + EXTENDED_Ebias); /* Result is positive. */
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}
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