| /*---------------------------------------------------------------------------+ |
| | poly_tan.c | |
| | | |
| | Compute the tan of a FPU_REG, using a polynomial approximation. | |
| | | |
| | Copyright (C) 1992,1993 | |
| | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, | |
| | Australia. E-mail apm233m@vaxc.cc.monash.edu.au | |
| | | |
| | | |
| +---------------------------------------------------------------------------*/ |
| |
| #include "exception.h" |
| #include "reg_constant.h" |
| #include "fpu_emu.h" |
| #include "control_w.h" |
| |
| |
| #define HIPOWERop 3 /* odd poly, positive terms */ |
| static unsigned short oddplterms[HIPOWERop][4] = |
| { |
| { 0x846a, 0x42d1, 0xb544, 0x921f}, |
| { 0x6fb2, 0x0215, 0x95c0, 0x099c}, |
| { 0xfce6, 0x0cc8, 0x1c9a, 0x0000} |
| }; |
| |
| #define HIPOWERon 2 /* odd poly, negative terms */ |
| static unsigned short oddnegterms[HIPOWERon][4] = |
| { |
| { 0x6906, 0xe205, 0x25c8, 0x8838}, |
| { 0x1dd7, 0x3fe3, 0x944e, 0x002c} |
| }; |
| |
| #define HIPOWERep 2 /* even poly, positive terms */ |
| static unsigned short evenplterms[HIPOWERep][4] = |
| { |
| { 0xdb8f, 0x3761, 0x1432, 0x2acf}, |
| { 0x16eb, 0x13c1, 0x3099, 0x0003} |
| }; |
| |
| #define HIPOWERen 2 /* even poly, negative terms */ |
| static unsigned short evennegterms[HIPOWERen][4] = |
| { |
| { 0x3a7c, 0xe4c5, 0x7f87, 0x2945}, |
| { 0x572b, 0x664c, 0xc543, 0x018c} |
| }; |
| |
| |
| /*--- poly_tan() ------------------------------------------------------------+ |
| | | |
| +---------------------------------------------------------------------------*/ |
| void poly_tan(FPU_REG *arg, FPU_REG *y_reg, int invert) |
| { |
| short exponent; |
| FPU_REG odd_poly, even_poly, pos_poly, neg_poly; |
| FPU_REG argSq; |
| unsigned long long arg_signif, argSqSq; |
| |
| |
| exponent = arg->exp - EXP_BIAS; |
| |
| #ifdef PARANOID |
| if ( arg->sign != 0 ) /* Can't hack a number < 0.0 */ |
| { arith_invalid(y_reg); return; } /* Need a positive number */ |
| #endif PARANOID |
| |
| arg_signif = significand(arg); |
| if ( exponent < -1 ) |
| { |
| /* shift the argument right by the required places */ |
| if ( shrx(&arg_signif, -1-exponent) >= 0x80000000U ) |
| arg_signif++; /* round up */ |
| } |
| |
| mul64(&arg_signif, &arg_signif, &significand(&argSq)); |
| mul64(&significand(&argSq), &significand(&argSq), &argSqSq); |
| |
| /* will be a valid positive nr with expon = 0 */ |
| *(short *)&(pos_poly.sign) = 0; |
| pos_poly.exp = EXP_BIAS; |
| |
| /* Do the basic fixed point polynomial evaluation */ |
| polynomial(&pos_poly.sigl, (unsigned *)&argSqSq, oddplterms, HIPOWERop-1); |
| |
| /* will be a valid positive nr with expon = 0 */ |
| *(short *)&(neg_poly.sign) = 0; |
| neg_poly.exp = EXP_BIAS; |
| |
| /* Do the basic fixed point polynomial evaluation */ |
| polynomial(&neg_poly.sigl, (unsigned *)&argSqSq, oddnegterms, HIPOWERon-1); |
| mul64(&significand(&argSq), &significand(&neg_poly), |
| &significand(&neg_poly)); |
| |
| /* Subtract the mantissas */ |
| significand(&pos_poly) -= significand(&neg_poly); |
| |
| /* Convert to 64 bit signed-compatible */ |
| pos_poly.exp -= 1; |
| |
| reg_move(&pos_poly, &odd_poly); |
| normalize(&odd_poly); |
| |
| reg_mul(&odd_poly, arg, &odd_poly, FULL_PRECISION); |
| /* Complete the odd polynomial. */ |
| reg_u_add(&odd_poly, arg, &odd_poly, FULL_PRECISION); |
| |
| /* will be a valid positive nr with expon = 0 */ |
| *(short *)&(pos_poly.sign) = 0; |
| pos_poly.exp = EXP_BIAS; |
| |
| /* Do the basic fixed point polynomial evaluation */ |
| polynomial(&pos_poly.sigl, (unsigned *)&argSqSq, evenplterms, HIPOWERep-1); |
| mul64(&significand(&argSq), |
| &significand(&pos_poly), &significand(&pos_poly)); |
| |
| /* will be a valid positive nr with expon = 0 */ |
| *(short *)&(neg_poly.sign) = 0; |
| neg_poly.exp = EXP_BIAS; |
| |
| /* Do the basic fixed point polynomial evaluation */ |
| polynomial(&neg_poly.sigl, (unsigned *)&argSqSq, evennegterms, HIPOWERen-1); |
| |
| /* Subtract the mantissas */ |
| significand(&neg_poly) -= significand(&pos_poly); |
| /* and multiply by argSq */ |
| |
| /* Convert argSq to a valid reg number */ |
| *(short *)&(argSq.sign) = 0; |
| argSq.exp = EXP_BIAS - 1; |
| normalize(&argSq); |
| |
| /* Convert to 64 bit signed-compatible */ |
| neg_poly.exp -= 1; |
| |
| reg_move(&neg_poly, &even_poly); |
| normalize(&even_poly); |
| |
| reg_mul(&even_poly, &argSq, &even_poly, FULL_PRECISION); |
| reg_add(&even_poly, &argSq, &even_poly, FULL_PRECISION); |
| /* Complete the even polynomial */ |
| reg_sub(&CONST_1, &even_poly, &even_poly, FULL_PRECISION); |
| |
| /* Now ready to copy the results */ |
| if ( invert ) |
| { reg_div(&even_poly, &odd_poly, y_reg, FULL_PRECISION); } |
| else |
| { reg_div(&odd_poly, &even_poly, y_reg, FULL_PRECISION); } |
| |
| } |