From 4ab4f741069e9a8fac60a1f941ea3e7e0a944602 Mon Sep 17 00:00:00 2001 From: Calvin Buckley Date: Sun, 18 Jul 2021 13:53:08 -0300 Subject: Implement 68k FPU FATAN instruction (#8287) --- 3rdparty/softfloat/fpatan.c | 389 +++++++++++++++++++++++++++++++++++++ 3rdparty/softfloat/softfloat.h | 3 + scripts/src/3rdparty.lua | 1 + src/devices/cpu/m68000/m68kfpu.cpp | 7 + 4 files changed, 400 insertions(+) create mode 100644 3rdparty/softfloat/fpatan.c diff --git a/3rdparty/softfloat/fpatan.c b/3rdparty/softfloat/fpatan.c new file mode 100644 index 00000000000..a9a0afabf4f --- /dev/null +++ b/3rdparty/softfloat/fpatan.c @@ -0,0 +1,389 @@ +/*============================================================================ +This source file is an extension to the SoftFloat IEC/IEEE Floating-point +Arithmetic Package, Release 2b, written for Bochs (x86 achitecture simulator) +floating point emulation. + +THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE. Although reasonable effort has +been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT TIMES +RESULT IN INCORRECT BEHAVIOR. USE OF THIS SOFTWARE IS RESTRICTED TO PERSONS +AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ALL LOSSES, +COSTS, OR OTHER PROBLEMS THEY INCUR DUE TO THE SOFTWARE, AND WHO FURTHERMORE +EFFECTIVELY INDEMNIFY JOHN HAUSER AND THE INTERNATIONAL COMPUTER SCIENCE +INSTITUTE (possibly via similar legal warning) AGAINST ALL LOSSES, COSTS, OR +OTHER PROBLEMS INCURRED BY THEIR CUSTOMERS AND CLIENTS DUE TO THE SOFTWARE. + +Derivative works are acceptable, even for commercial purposes, so long as +(1) the source code for the derivative work includes prominent notice that +the work is derivative, and (2) the source code includes prominent notice with +these four paragraphs for those parts of this code that are retained. +=============================================================================*/ + +/*============================================================================ + * Written for Bochs (x86 achitecture simulator) by + * Stanislav Shwartsman [sshwarts at sourceforge net] + * Adapted for 3rdparty/softfloat in MAME by Calvin Buckley (05/2021) + * ==========================================================================*/ + +#define FLOAT128 + +#include "mamesf.h" +#include "softfloat.h" +//#include "softfloat-specialize" +#include "fpu_constant.h" + +/* XXX: These are common w/ fsincos/fyl2x; should be moved to common header? */ +#define packFloat_128(zHi, zLo) {(zHi), (zLo)} +#define packFloat2x128m(zHi, zLo) {(zHi), (zLo)} +#define PACK_FLOAT_128(hi,lo) packFloat2x128m(LIT64(hi),LIT64(lo)) +#define EXP_BIAS 0x3FFF + +/*---------------------------------------------------------------------------- +| Returns the fraction bits of the extended double-precision floating-point +| value `a'. +*----------------------------------------------------------------------------*/ + +INLINE bits64 extractFloatx80Frac( floatx80 a ) +{ + return a.low; + +} + +/*---------------------------------------------------------------------------- +| Returns the exponent bits of the extended double-precision floating-point +| value `a'. +*----------------------------------------------------------------------------*/ + +INLINE int32 extractFloatx80Exp( floatx80 a ) +{ + return a.high & 0x7FFF; + +} + +/*---------------------------------------------------------------------------- +| Returns the sign bit of the extended double-precision floating-point value +| `a'. +*----------------------------------------------------------------------------*/ + +INLINE flag extractFloatx80Sign( floatx80 a ) +{ + return a.high>>15; + +} + +/*---------------------------------------------------------------------------- +| Normalizes the subnormal extended double-precision floating-point value +| represented by the denormalized significand `aSig'. The normalized exponent +| and significand are stored at the locations pointed to by `zExpPtr' and +| `zSigPtr', respectively. +*----------------------------------------------------------------------------*/ + +INLINE void normalizeFloatx80Subnormal(uint64_t aSig, int32_t *zExpPtr, uint64_t *zSigPtr) +{ + int shiftCount = countLeadingZeros64(aSig); + *zSigPtr = aSig<>48 ) & 0x7FFF; + +} + +/* end copied */ + +#define FPATAN_ARR_SIZE 11 + +static const float128 float128_one = + packFloat_128(0x3fff000000000000U, 0x0000000000000000U); +static const float128 float128_sqrt3 = + packFloat_128(0x3fffbb67ae8584caU, 0xa73b25742d7078b8U); +static const floatx80 floatx80_one = packFloatx80(0, 0x3fff, 0x8000000000000000U); +static const floatx80 floatx80_pi = + packFloatx80(0, 0x4000, 0xc90fdaa22168c235U); + +static const float128 float128_pi2 = + packFloat_128(0x3fff921fb54442d1U, 0x8469898CC5170416U); +static const float128 float128_pi4 = + packFloat_128(0x3ffe921fb54442d1U, 0x8469898CC5170416U); +static const float128 float128_pi6 = + packFloat_128(0x3ffe0c152382d736U, 0x58465BB32E0F580FU); + +static float128 atan_arr[FPATAN_ARR_SIZE] = +{ + PACK_FLOAT_128(0x3fff000000000000, 0x0000000000000000), /* 1 */ + PACK_FLOAT_128(0xbffd555555555555, 0x5555555555555555), /* 3 */ + PACK_FLOAT_128(0x3ffc999999999999, 0x999999999999999a), /* 5 */ + PACK_FLOAT_128(0xbffc249249249249, 0x2492492492492492), /* 7 */ + PACK_FLOAT_128(0x3ffbc71c71c71c71, 0xc71c71c71c71c71c), /* 9 */ + PACK_FLOAT_128(0xbffb745d1745d174, 0x5d1745d1745d1746), /* 11 */ + PACK_FLOAT_128(0x3ffb3b13b13b13b1, 0x3b13b13b13b13b14), /* 13 */ + PACK_FLOAT_128(0xbffb111111111111, 0x1111111111111111), /* 15 */ + PACK_FLOAT_128(0x3ffae1e1e1e1e1e1, 0xe1e1e1e1e1e1e1e2), /* 17 */ + PACK_FLOAT_128(0xbffaaf286bca1af2, 0x86bca1af286bca1b), /* 19 */ + PACK_FLOAT_128(0x3ffa861861861861, 0x8618618618618618) /* 21 */ +}; + +extern float128 OddPoly(float128 x, float128 *arr, unsigned n); + +/* |x| < 1/4 */ +static float128 poly_atan(float128 x1) +{ +/* + // 3 5 7 9 11 13 15 17 + // x x x x x x x x + // atan(x) ~ x - --- + --- - --- + --- - ---- + ---- - ---- + ---- + // 3 5 7 9 11 13 15 17 + // + // 2 4 6 8 10 12 14 16 + // x x x x x x x x + // = x * [ 1 - --- + --- - --- + --- - ---- + ---- - ---- + ---- ] + // 3 5 7 9 11 13 15 17 + // + // 5 5 + // -- 4k -- 4k+2 + // p(x) = > C * x q(x) = > C * x + // -- 2k -- 2k+1 + // k=0 k=0 + // + // 2 + // atan(x) ~ x * [ p(x) + x * q(x) ] + // +*/ + return OddPoly(x1, atan_arr, FPATAN_ARR_SIZE); +} + +// ================================================= +// FPATAN Compute y * log (x) +// 2 +// ================================================= + +// +// Uses the following identities: +// +// 1. ---------------------------------------------------------- +// +// atan(-x) = -atan(x) +// +// 2. ---------------------------------------------------------- +// +// x + y +// atan(x) + atan(y) = atan -------, xy < 1 +// 1-xy +// +// x + y +// atan(x) + atan(y) = atan ------- + PI, x > 0, xy > 1 +// 1-xy +// +// x + y +// atan(x) + atan(y) = atan ------- - PI, x < 0, xy > 1 +// 1-xy +// +// 3. ---------------------------------------------------------- +// +// atan(x) = atan(INF) + atan(- 1/x) +// +// x-1 +// atan(x) = PI/4 + atan( ----- ) +// x+1 +// +// x * sqrt(3) - 1 +// atan(x) = PI/6 + atan( ----------------- ) +// x + sqrt(3) +// +// 4. ---------------------------------------------------------- +// 3 5 7 9 2n+1 +// x x x x n x +// atan(x) = x - --- + --- - --- + --- - ... + (-1) ------ + ... +// 3 5 7 9 2n+1 +// + +floatx80 floatx80_fpatan(floatx80 a, floatx80 b) +{ + uint64_t aSig = extractFloatx80Frac(a); + int32_t aExp = extractFloatx80Exp(a); + int aSign = extractFloatx80Sign(a); + uint64_t bSig = extractFloatx80Frac(b); + int32_t bExp = extractFloatx80Exp(b); + int bSign = extractFloatx80Sign(b); + + int zSign = aSign ^ bSign; + + if (bExp == 0x7FFF) + { + if ((uint64_t) (bSig<<1)) + return propagateFloatx80NaN(a, b); + + if (aExp == 0x7FFF) { + if ((uint64_t) (aSig<<1)) + return propagateFloatx80NaN(a, b); + + if (aSign) { /* return 3PI/4 */ + return roundAndPackFloatx80(80, bSign, + FLOATX80_3PI4_EXP, FLOAT_3PI4_HI, FLOAT_3PI4_LO); + } + else { /* return PI/4 */ + return roundAndPackFloatx80(80, bSign, + FLOATX80_PI4_EXP, FLOAT_PI_HI, FLOAT_PI_LO); + } + } + + if (aSig && (aExp == 0)) + float_raise(float_flag_denormal); + + /* return PI/2 */ + return roundAndPackFloatx80(80, bSign, FLOATX80_PI2_EXP, FLOAT_PI_HI, FLOAT_PI_LO); + } + if (aExp == 0x7FFF) + { + if ((uint64_t) (aSig<<1)) + return propagateFloatx80NaN(a, b); + + if (bSig && (bExp == 0)) + float_raise(float_flag_denormal); + +return_PI_or_ZERO: + + if (aSign) { /* return PI */ + return roundAndPackFloatx80(80, bSign, FLOATX80_PI_EXP, FLOAT_PI_HI, FLOAT_PI_LO); + } else { /* return 0 */ + return packFloatx80(bSign, 0, 0); + } + } + if (bExp == 0) + { + if (bSig == 0) { + if (aSig && (aExp == 0)) float_raise(float_flag_denormal); + goto return_PI_or_ZERO; + } + + float_raise(float_flag_denormal); + normalizeFloatx80Subnormal(bSig, &bExp, &bSig); + } + if (aExp == 0) + { + if (aSig == 0) /* return PI/2 */ + return roundAndPackFloatx80(80, bSign, FLOATX80_PI2_EXP, FLOAT_PI_HI, FLOAT_PI_LO); + + float_raise(float_flag_denormal); + normalizeFloatx80Subnormal(aSig, &aExp, &aSig); + } + + float_raise(float_flag_inexact); + + /* |a| = |b| ==> return PI/4 */ + if (aSig == bSig && aExp == bExp) + return roundAndPackFloatx80(80, bSign, FLOATX80_PI4_EXP, FLOAT_PI_HI, FLOAT_PI_LO); + + /* ******************************** */ + /* using float128 for approximation */ + /* ******************************** */ + + float128 a128 = normalizeRoundAndPackFloat128(0, aExp-0x10, aSig, 0); + float128 b128 = normalizeRoundAndPackFloat128(0, bExp-0x10, bSig, 0); + float128 x; + int swap = 0, add_pi6 = 0, add_pi4 = 0; + + if (aExp > bExp || (aExp == bExp && aSig > bSig)) + { + x = float128_div(b128, a128); + } + else { + x = float128_div(a128, b128); + swap = 1; + } + + int32_t xExp = extractFloat128Exp(x); + + if (xExp <= EXP_BIAS-40) + goto approximation_completed; + + if (x.high >= 0x3ffe800000000000U) // 3/4 < x < 1 + { + /* + arctan(x) = arctan((x-1)/(x+1)) + pi/4 + */ + float128 t1 = float128_sub(x, float128_one); + float128 t2 = float128_add(x, float128_one); + x = float128_div(t1, t2); + add_pi4 = 1; + } + else + { + /* argument correction */ + if (xExp >= 0x3FFD) // 1/4 < x < 3/4 + { + /* + arctan(x) = arctan((x*sqrt(3)-1)/(x+sqrt(3))) + pi/6 + */ + float128 t1 = float128_mul(x, float128_sqrt3); + float128 t2 = float128_add(x, float128_sqrt3); + x = float128_sub(t1, float128_one); + x = float128_div(x, t2); + add_pi6 = 1; + } + } + + x = poly_atan(x); + if (add_pi6) x = float128_add(x, float128_pi6); + if (add_pi4) x = float128_add(x, float128_pi4); + +approximation_completed: + if (swap) x = float128_sub(float128_pi2, x); + floatx80 result = float128_to_floatx80(x); + if (zSign) floatx80_chs(result); + int rSign = extractFloatx80Sign(result); + if (!bSign && rSign) + return floatx80_add(result, floatx80_pi); + if (bSign && !rSign) + return floatx80_sub(result, floatx80_pi); + return result; +} + +// The former function maps to x87 FPATAN, but we can simulate 68881 FATAN with +// it by simply hardcoding one here. +floatx80 floatx80_fatan(floatx80 a) +{ + return floatx80_fpatan(a, floatx80_one); +} diff --git a/3rdparty/softfloat/softfloat.h b/3rdparty/softfloat/softfloat.h index 6f4389b10bc..a97408c3222 100644 --- a/3rdparty/softfloat/softfloat.h +++ b/3rdparty/softfloat/softfloat.h @@ -244,6 +244,9 @@ int floatx80_fsin(floatx80 &a); int floatx80_fcos(floatx80 &a); int floatx80_ftan(floatx80 &a); +floatx80 floatx80_fpatan(floatx80 a, floatx80 b); +floatx80 floatx80_fatan(floatx80 a); + floatx80 floatx80_flognp1(floatx80 a); floatx80 floatx80_flogn(floatx80 a); floatx80 floatx80_flog2(floatx80 a); diff --git a/scripts/src/3rdparty.lua b/scripts/src/3rdparty.lua index f7aa6280533..e8b08df8f0c 100644 --- a/scripts/src/3rdparty.lua +++ b/scripts/src/3rdparty.lua @@ -197,6 +197,7 @@ end files { MAME_DIR .. "3rdparty/softfloat/softfloat.c", MAME_DIR .. "3rdparty/softfloat/fsincos.c", + MAME_DIR .. "3rdparty/softfloat/fpatan.c", MAME_DIR .. "3rdparty/softfloat/fyl2x.c", } diff --git a/src/devices/cpu/m68000/m68kfpu.cpp b/src/devices/cpu/m68000/m68kfpu.cpp index 7cd10e84b84..c265bf2b2f7 100644 --- a/src/devices/cpu/m68000/m68kfpu.cpp +++ b/src/devices/cpu/m68000/m68kfpu.cpp @@ -1454,6 +1454,13 @@ void m68000_base_device::fpgen_rm_reg(u16 w2) m_icount -= 594; // for MC68881 break; } + case 0x0a: // FATAN + { + m_fpr[dst] = floatx80_fatan (source); + SET_CONDITION_CODES(m_fpr[dst]); + m_icount -= 426; // for MC68881 + break; + } case 0x0e: // FSIN { m_fpr[dst] = source; -- cgit v1.2.3