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Diffstat (limited to 'arch/x86/math-emu/poly_atan.c')
| -rw-r--r-- | arch/x86/math-emu/poly_atan.c | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/arch/x86/math-emu/poly_atan.c b/arch/x86/math-emu/poly_atan.c new file mode 100644 index 000000000..7e7412c5a --- /dev/null +++ b/arch/x86/math-emu/poly_atan.c @@ -0,0 +1,209 @@ +// SPDX-License-Identifier: GPL-2.0 +/*---------------------------------------------------------------------------+ + | poly_atan.c | + | | + | Compute the arctan of a FPU_REG, using a polynomial approximation. | + | | + | Copyright (C) 1992,1993,1994,1997 | + | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | + | E-mail billm@suburbia.net | + | | + | | + +---------------------------------------------------------------------------*/ + +#include "exception.h" +#include "reg_constant.h" +#include "fpu_emu.h" +#include "fpu_system.h" +#include "status_w.h" +#include "control_w.h" +#include "poly.h" + +#define HIPOWERon 6 /* odd poly, negative terms */ +static const unsigned long long oddnegterms[HIPOWERon] = { + 0x0000000000000000LL, /* Dummy (not for - 1.0) */ + 0x015328437f756467LL, + 0x0005dda27b73dec6LL, + 0x0000226bf2bfb91aLL, + 0x000000ccc439c5f7LL, + 0x0000000355438407LL +}; + +#define HIPOWERop 6 /* odd poly, positive terms */ +static const unsigned long long oddplterms[HIPOWERop] = { +/* 0xaaaaaaaaaaaaaaabLL, transferred to fixedpterm[] */ + 0x0db55a71875c9ac2LL, + 0x0029fce2d67880b0LL, + 0x0000dfd3908b4596LL, + 0x00000550fd61dab4LL, + 0x0000001c9422b3f9LL, + 0x000000003e3301e1LL +}; + +static const unsigned long long denomterm = 0xebd9b842c5c53a0eLL; + +static const Xsig fixedpterm = MK_XSIG(0xaaaaaaaa, 0xaaaaaaaa, 0xaaaaaaaa); + +static const Xsig pi_signif = MK_XSIG(0xc90fdaa2, 0x2168c234, 0xc4c6628b); + +/*--- poly_atan() -----------------------------------------------------------+ + | | + +---------------------------------------------------------------------------*/ +void poly_atan(FPU_REG *st0_ptr, u_char st0_tag, + FPU_REG *st1_ptr, u_char st1_tag) +{ + u_char transformed, inverted, sign1, sign2; + int exponent; + long int dummy_exp; + Xsig accumulator, Numer, Denom, accumulatore, argSignif, argSq, argSqSq; + u_char tag; + + sign1 = getsign(st0_ptr); + sign2 = getsign(st1_ptr); + if (st0_tag == TAG_Valid) { + exponent = exponent(st0_ptr); + } else { + /* This gives non-compatible stack contents... */ + FPU_to_exp16(st0_ptr, st0_ptr); + exponent = exponent16(st0_ptr); + } + if (st1_tag == TAG_Valid) { + exponent -= exponent(st1_ptr); + } else { + /* This gives non-compatible stack contents... */ + FPU_to_exp16(st1_ptr, st1_ptr); + exponent -= exponent16(st1_ptr); + } + + if ((exponent < 0) || ((exponent == 0) && + ((st0_ptr->sigh < st1_ptr->sigh) || + ((st0_ptr->sigh == st1_ptr->sigh) && + (st0_ptr->sigl < st1_ptr->sigl))))) { + inverted = 1; + Numer.lsw = Denom.lsw = 0; + XSIG_LL(Numer) = significand(st0_ptr); + XSIG_LL(Denom) = significand(st1_ptr); + } else { + inverted = 0; + exponent = -exponent; + Numer.lsw = Denom.lsw = 0; + XSIG_LL(Numer) = significand(st1_ptr); + XSIG_LL(Denom) = significand(st0_ptr); + } + div_Xsig(&Numer, &Denom, &argSignif); + exponent += norm_Xsig(&argSignif); + + if ((exponent >= -1) + || ((exponent == -2) && (argSignif.msw > 0xd413ccd0))) { + /* The argument is greater than sqrt(2)-1 (=0.414213562...) */ + /* Convert the argument by an identity for atan */ + transformed = 1; + + if (exponent >= 0) { +#ifdef PARANOID + if (!((exponent == 0) && + (argSignif.lsw == 0) && (argSignif.midw == 0) && + (argSignif.msw == 0x80000000))) { + EXCEPTION(EX_INTERNAL | 0x104); /* There must be a logic error */ + return; + } +#endif /* PARANOID */ + argSignif.msw = 0; /* Make the transformed arg -> 0.0 */ + } else { + Numer.lsw = Denom.lsw = argSignif.lsw; + XSIG_LL(Numer) = XSIG_LL(Denom) = XSIG_LL(argSignif); + + if (exponent < -1) + shr_Xsig(&Numer, -1 - exponent); + negate_Xsig(&Numer); + + shr_Xsig(&Denom, -exponent); + Denom.msw |= 0x80000000; + + div_Xsig(&Numer, &Denom, &argSignif); + + exponent = -1 + norm_Xsig(&argSignif); + } + } else { + transformed = 0; + } + + argSq.lsw = argSignif.lsw; + argSq.midw = argSignif.midw; + argSq.msw = argSignif.msw; + mul_Xsig_Xsig(&argSq, &argSq); + + argSqSq.lsw = argSq.lsw; + argSqSq.midw = argSq.midw; + argSqSq.msw = argSq.msw; + mul_Xsig_Xsig(&argSqSq, &argSqSq); + + accumulatore.lsw = argSq.lsw; + XSIG_LL(accumulatore) = XSIG_LL(argSq); + + shr_Xsig(&argSq, 2 * (-1 - exponent - 1)); + shr_Xsig(&argSqSq, 4 * (-1 - exponent - 1)); + + /* Now have argSq etc with binary point at the left + .1xxxxxxxx */ + + /* Do the basic fixed point polynomial evaluation */ + accumulator.msw = accumulator.midw = accumulator.lsw = 0; + polynomial_Xsig(&accumulator, &XSIG_LL(argSqSq), + oddplterms, HIPOWERop - 1); + mul64_Xsig(&accumulator, &XSIG_LL(argSq)); + negate_Xsig(&accumulator); + polynomial_Xsig(&accumulator, &XSIG_LL(argSqSq), oddnegterms, + HIPOWERon - 1); + negate_Xsig(&accumulator); + add_two_Xsig(&accumulator, &fixedpterm, &dummy_exp); + + mul64_Xsig(&accumulatore, &denomterm); + shr_Xsig(&accumulatore, 1 + 2 * (-1 - exponent)); + accumulatore.msw |= 0x80000000; + + div_Xsig(&accumulator, &accumulatore, &accumulator); + + mul_Xsig_Xsig(&accumulator, &argSignif); + mul_Xsig_Xsig(&accumulator, &argSq); + + shr_Xsig(&accumulator, 3); + negate_Xsig(&accumulator); + add_Xsig_Xsig(&accumulator, &argSignif); + + if (transformed) { + /* compute pi/4 - accumulator */ + shr_Xsig(&accumulator, -1 - exponent); + negate_Xsig(&accumulator); + add_Xsig_Xsig(&accumulator, &pi_signif); + exponent = -1; + } + + if (inverted) { + /* compute pi/2 - accumulator */ + shr_Xsig(&accumulator, -exponent); + negate_Xsig(&accumulator); + add_Xsig_Xsig(&accumulator, &pi_signif); + exponent = 0; + } + + if (sign1) { + /* compute pi - accumulator */ + shr_Xsig(&accumulator, 1 - exponent); + negate_Xsig(&accumulator); + add_Xsig_Xsig(&accumulator, &pi_signif); + exponent = 1; + } + + exponent += round_Xsig(&accumulator); + + significand(st1_ptr) = XSIG_LL(accumulator); + setexponent16(st1_ptr, exponent); + + tag = FPU_round(st1_ptr, 1, 0, FULL_PRECISION, sign2); + FPU_settagi(1, tag); + + set_precision_flag_up(); /* We do not really know if up or down, + use this as the default. */ + +} |