207 lines
7.7 KiB
C++
207 lines
7.7 KiB
C++
/*============================================================================
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This source file is an extension to the SoftFloat IEC/IEEE Floating-point
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Arithmetic Package, Release 2b, written for Bochs (x86 achitecture simulator)
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floating point emulation.
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THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE. Although reasonable effort has
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been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT TIMES
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RESULT IN INCORRECT BEHAVIOR. USE OF THIS SOFTWARE IS RESTRICTED TO PERSONS
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AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ALL LOSSES,
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COSTS, OR OTHER PROBLEMS THEY INCUR DUE TO THE SOFTWARE, AND WHO FURTHERMORE
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EFFECTIVELY INDEMNIFY JOHN HAUSER AND THE INTERNATIONAL COMPUTER SCIENCE
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INSTITUTE (possibly via similar legal warning) AGAINST ALL LOSSES, COSTS, OR
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OTHER PROBLEMS INCURRED BY THEIR CUSTOMERS AND CLIENTS DUE TO THE SOFTWARE.
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Derivative works are acceptable, even for commercial purposes, so long as
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(1) the source code for the derivative work includes prominent notice that
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the work is derivative, and (2) the source code includes prominent notice with
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these four paragraphs for those parts of this code that are retained.
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=============================================================================*/
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/*============================================================================
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* Written for Bochs (x86 achitecture simulator) by
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* Stanislav Shwartsman [sshwarts at sourceforge net]
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* ==========================================================================*/
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#include "fpu_trans.h"
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#define USE_estimateDiv128To64
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#include "softfloat-helpers.h"
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#include "specialize.h" // for softfloat_propagateNaNExtF80UI
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/* executes single exponent reduction cycle */
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static uint64_t remainder_kernel(uint64_t aSig0, uint64_t bSig, int expDiff, uint64_t *zSig0, uint64_t *zSig1)
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{
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uint128 term, z;
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uint64_t aSig1 = 0;
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shortShift128Left(aSig1, aSig0, expDiff, &aSig1, &aSig0);
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uint64_t q = estimateDiv128To64(aSig1, aSig0, bSig);
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term = softfloat_mul64To128(bSig, q);
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z = softfloat_sub128(aSig1, aSig0, term.v64, term.v0);
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while ((int64_t) z.v64 < 0) {
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--q;
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z = softfloat_add128(z.v64, z.v0, 0, bSig);
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}
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*zSig0 = z.v0;
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*zSig1 = z.v64;
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return q;
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}
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static int do_fprem(floatx80 a, floatx80 b, floatx80 *r, uint64_t *q, int rounding_mode, struct softfloat_status_t *status)
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{
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/*----------------------------------------------------------------------------
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| The pattern for a default generated extended double-precision NaN.
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*----------------------------------------------------------------------------*/
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static const floatx80 floatx80_default_nan =
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packFloatx80(0, floatx80_default_nan_exp, floatx80_default_nan_fraction);
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int32_t aExp, bExp, zExp, expDiff;
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uint64_t aSig0, aSig1 = 0, bSig;
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int aSign;
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struct exp32_sig64 normExpSig;
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uint128 term;
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*q = 0;
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// handle unsupported extended double-precision floating encodings
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if (extF80_isUnsupported(a) || extF80_isUnsupported(b)) {
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softfloat_raiseFlags(status, softfloat_flag_invalid);
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*r = floatx80_default_nan;
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return -1;
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}
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aSig0 = extF80_fraction(a);
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aExp = extF80_exp(a);
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aSign = extF80_sign(a);
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bSig = extF80_fraction(b);
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bExp = extF80_exp(b);
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if (aExp == 0x7FFF) {
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if ((aSig0<<1) || ((bExp == 0x7FFF) && (bSig<<1))) {
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*r = softfloat_propagateNaNExtF80UI(a.signExp, a.signif, b.signExp, b.signif, status);
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return -1;
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}
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softfloat_raiseFlags(status, softfloat_flag_invalid);
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*r = floatx80_default_nan;
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return -1;
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}
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if (bExp == 0x7FFF) {
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if (bSig << 1) {
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*r = softfloat_propagateNaNExtF80UI(a.signExp, a.signif, b.signExp, b.signif, status);
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return -1;
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}
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if (! aExp && aSig0) {
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softfloat_raiseFlags(status, softfloat_flag_denormal);
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normExpSig = softfloat_normSubnormalExtF80Sig(aSig0);
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aExp = normExpSig.exp + 1;
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aSig0 = normExpSig.sig;
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*r = (a.signif & BX_CONST64(0x8000000000000000)) ? packToExtF80(aSign, aExp, aSig0) : a;
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return 0;
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}
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*r = a;
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return 0;
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}
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if (! bExp) {
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if (! bSig) {
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softfloat_raiseFlags(status, softfloat_flag_invalid);
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*r = floatx80_default_nan;
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return -1;
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}
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softfloat_raiseFlags(status, softfloat_flag_denormal);
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normExpSig = softfloat_normSubnormalExtF80Sig(bSig);
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bExp = normExpSig.exp + 1;
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bSig = normExpSig.sig;
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}
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if (! aExp) {
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if (! aSig0) {
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*r = a;
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return 0;
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}
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softfloat_raiseFlags(status, softfloat_flag_denormal);
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normExpSig = softfloat_normSubnormalExtF80Sig(aSig0);
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aExp = normExpSig.exp + 1;
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aSig0 = normExpSig.sig;
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}
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expDiff = aExp - bExp;
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int overflow = 0;
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if (expDiff >= 64) {
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int n = (expDiff & 0x1f) | 0x20;
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remainder_kernel(aSig0, bSig, n, &aSig0, &aSig1);
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zExp = aExp - n;
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overflow = 1;
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}
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else {
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zExp = bExp;
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if (expDiff < 0) {
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if (expDiff < -1) {
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*r = (a.signif & BX_CONST64(0x8000000000000000)) ? packToExtF80(aSign, aExp, aSig0) : a;
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return 0;
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}
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shortShift128Right(aSig0, 0, 1, &aSig0, &aSig1);
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expDiff = 0;
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}
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if (expDiff > 0) {
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*q = remainder_kernel(aSig0, bSig, expDiff, &aSig0, &aSig1);
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}
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else {
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if (bSig <= aSig0) {
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aSig0 -= bSig;
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*q = 1;
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}
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}
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if (rounding_mode == softfloat_round_near_even) {
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uint64_t term0, term1;
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shortShift128Right(bSig, 0, 1, &term0, &term1);
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if (! softfloat_lt128(aSig0, aSig1, term0, term1)) {
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int lt = softfloat_lt128(term0, term1, aSig0, aSig1);
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int eq = softfloat_eq128(aSig0, aSig1, term0, term1);
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if ((eq && ((*q) & 1)) || lt) {
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aSign = !aSign;
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++(*q);
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}
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if (lt) {
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term = softfloat_sub128(bSig, 0, aSig0, aSig1);
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aSig0 = term.v64;
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aSig1 = term.v0;
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}
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}
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}
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}
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*r = softfloat_normRoundPackToExtF80(aSign, zExp, aSig0, aSig1, 80, status);
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return overflow;
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}
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/*----------------------------------------------------------------------------
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| Returns the remainder of the extended double-precision floating-point value
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| `a' with respect to the corresponding value `b'. The operation is performed
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| according to the IEC/IEEE Standard for Binary Floating-Point Arithmetic.
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*----------------------------------------------------------------------------*/
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int floatx80_ieee754_remainder(floatx80 a, floatx80 b, floatx80 *r, uint64_t *q, struct softfloat_status_t *status)
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{
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return do_fprem(a, b, r, q, softfloat_round_near_even, status);
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}
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/*----------------------------------------------------------------------------
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| Returns the remainder of the extended double-precision floating-point value
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| `a' with respect to the corresponding value `b'. Unlike previous function
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| the function does not compute the remainder specified in the IEC/IEEE
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| Standard for Binary Floating-Point Arithmetic. This function operates
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| differently from the previous function in the way that it rounds the
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| quotient of 'a' divided by 'b' to an integer.
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*----------------------------------------------------------------------------*/
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int floatx80_remainder(floatx80 a, floatx80 b, floatx80 *r, uint64_t *q, struct softfloat_status_t *status)
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{
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return do_fprem(a, b, r, q, softfloat_round_to_zero, status);
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}
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