150 lines
4.5 KiB
C
150 lines
4.5 KiB
C
/*---------------------------------------------------------------------------+
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| poly_sin.c |
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| Computation of an approximation of the sin function by a polynomial |
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| Copyright (C) 1992,1993,1994 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
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| Australia. E-mail billm@vaxc.cc.monash.edu.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 "control_w.h"
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#define HIPOWER 5
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static unsigned short const lterms[HIPOWER][4] =
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{
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{ 0x846a, 0x42d1, 0xb544, 0x921f},
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{ 0xe110, 0x75aa, 0xbc67, 0x1466},
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{ 0x503d, 0xa43f, 0x83c1, 0x000a},
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{ 0x8f9d, 0x7a19, 0x00f4, 0x0000},
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{ 0xda03, 0x06aa, 0x0000, 0x0000},
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};
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static unsigned short const negterms[HIPOWER][4] =
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{
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{ 0x95ed, 0x2df2, 0xe731, 0xa55d},
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{ 0xd159, 0xe62b, 0xd2cc, 0x0132},
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{ 0x6342, 0xe9fb, 0x3c60, 0x0000},
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{ 0x6256, 0xdf5a, 0x0002, 0x0000},
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{ 0xf279, 0x000b, 0x0000, 0x0000},
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};
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/*--- poly_sine() -----------------------------------------------------------+
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+---------------------------------------------------------------------------*/
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void poly_sine(FPU_REG const *arg, FPU_REG *result)
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{
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short exponent;
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FPU_REG fixed_arg, arg_sqrd, arg_to_4, accum, negaccum;
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exponent = arg->exp - EXP_BIAS;
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if ( arg->tag == TW_Zero )
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{
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/* Return 0.0 */
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reg_move(&CONST_Z, result);
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return;
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}
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#ifdef PARANOID
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if ( arg->sign != 0 ) /* Can't hack a number < 0.0 */
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{
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EXCEPTION(EX_Invalid);
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reg_move(&CONST_QNaN, result);
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return;
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}
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if ( exponent >= 0 ) /* Can't hack a number > 1.0 */
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{
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if ( (exponent == 0) && (arg->sigl == 0) && (arg->sigh == 0x80000000) )
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{
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reg_move(&CONST_1, result);
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return;
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}
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EXCEPTION(EX_Invalid);
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reg_move(&CONST_QNaN, result);
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return;
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}
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#endif PARANOID
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fixed_arg.sigl = arg->sigl;
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fixed_arg.sigh = arg->sigh;
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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 ( shrx(&(fixed_arg.sigl), -1-exponent) >= 0x80000000U )
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significand(&fixed_arg)++; /* round up */
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}
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mul64(&significand(&fixed_arg), &significand(&fixed_arg),
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&significand(&arg_sqrd));
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mul64(&significand(&arg_sqrd), &significand(&arg_sqrd),
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&significand(&arg_to_4));
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/* will be a valid positive nr with expon = 0 */
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*(short *)&(accum.sign) = 0;
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accum.exp = 0;
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/* Do the basic fixed point polynomial evaluation */
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polynomial(&(accum.sigl), &(arg_to_4.sigl), lterms, HIPOWER-1);
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/* will be a valid positive nr with expon = 0 */
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*(short *)&(negaccum.sign) = 0;
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negaccum.exp = 0;
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/* Do the basic fixed point polynomial evaluation */
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polynomial(&(negaccum.sigl), &(arg_to_4.sigl), negterms, HIPOWER-1);
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mul64(&significand(&arg_sqrd), &significand(&negaccum),
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&significand(&negaccum));
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/* Subtract the mantissas */
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significand(&accum) -= significand(&negaccum);
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/* Convert to 64 bit signed-compatible */
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accum.exp = EXP_BIAS - 1 + accum.exp;
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reg_move(&accum, result);
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normalize(result);
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reg_mul(result, arg, result, FULL_PRECISION);
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reg_u_add(result, arg, result, FULL_PRECISION);
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if ( result->exp >= EXP_BIAS )
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{
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/* A small overflow may be possible... but an illegal result. */
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if ( (result->exp > EXP_BIAS) /* Larger or equal 2.0 */
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|| (result->sigl > 1) /* Larger than 1.0+msb */
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|| (result->sigh != 0x80000000) /* Much > 1.0 */
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)
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{
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#ifdef DEBUGGING
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RE_ENTRANT_CHECK_OFF;
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printk("\nEXP=%d, MS=%08x, LS=%08x\n", result->exp,
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result->sigh, result->sigl);
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RE_ENTRANT_CHECK_ON;
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#endif DEBUGGING
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EXCEPTION(EX_INTERNAL|0x103);
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}
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#ifdef DEBUGGING
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RE_ENTRANT_CHECK_OFF;
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printk("\n***CORRECTING ILLEGAL RESULT*** in poly_sin() computation\n");
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printk("EXP=%d, MS=%08x, LS=%08x\n", result->exp,
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result->sigh, result->sigl);
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RE_ENTRANT_CHECK_ON;
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#endif DEBUGGING
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result->sigl = 0; /* Truncate the result to 1.00 */
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}
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}
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