diff options
Diffstat (limited to 'arch/mips/math-emu/ieee754sp.c')
| -rw-r--r-- | arch/mips/math-emu/ieee754sp.c | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/arch/mips/math-emu/ieee754sp.c b/arch/mips/math-emu/ieee754sp.c new file mode 100644 index 000000000..0b6267bc8 --- /dev/null +++ b/arch/mips/math-emu/ieee754sp.c @@ -0,0 +1,196 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* IEEE754 floating point arithmetic + * single precision + */ +/* + * MIPS floating point support + * Copyright (C) 1994-2000 Algorithmics Ltd. + */ + +#include <linux/compiler.h> + +#include "ieee754sp.h" + +int ieee754sp_class(union ieee754sp x) +{ + COMPXSP; + EXPLODEXSP; + return xc; +} + +static inline int ieee754sp_isnan(union ieee754sp x) +{ + return ieee754_class_nan(ieee754sp_class(x)); +} + +static inline int ieee754sp_issnan(union ieee754sp x) +{ + int qbit; + + assert(ieee754sp_isnan(x)); + qbit = (SPMANT(x) & SP_MBIT(SP_FBITS - 1)) == SP_MBIT(SP_FBITS - 1); + return ieee754_csr.nan2008 ^ qbit; +} + + +/* + * Raise the Invalid Operation IEEE 754 exception + * and convert the signaling NaN supplied to a quiet NaN. + */ +union ieee754sp __cold ieee754sp_nanxcpt(union ieee754sp r) +{ + assert(ieee754sp_issnan(r)); + + ieee754_setcx(IEEE754_INVALID_OPERATION); + if (ieee754_csr.nan2008) { + SPMANT(r) |= SP_MBIT(SP_FBITS - 1); + } else { + SPMANT(r) &= ~SP_MBIT(SP_FBITS - 1); + if (!ieee754sp_isnan(r)) + SPMANT(r) |= SP_MBIT(SP_FBITS - 2); + } + + return r; +} + +static unsigned int ieee754sp_get_rounding(int sn, unsigned int xm) +{ + /* inexact must round of 3 bits + */ + if (xm & (SP_MBIT(3) - 1)) { + switch (ieee754_csr.rm) { + case FPU_CSR_RZ: + break; + case FPU_CSR_RN: + xm += 0x3 + ((xm >> 3) & 1); + /* xm += (xm&0x8)?0x4:0x3 */ + break; + case FPU_CSR_RU: /* toward +Infinity */ + if (!sn) /* ?? */ + xm += 0x8; + break; + case FPU_CSR_RD: /* toward -Infinity */ + if (sn) /* ?? */ + xm += 0x8; + break; + } + } + return xm; +} + + +/* generate a normal/denormal number with over,under handling + * sn is sign + * xe is an unbiased exponent + * xm is 3bit extended precision value. + */ +union ieee754sp ieee754sp_format(int sn, int xe, unsigned int xm) +{ + assert(xm); /* we don't gen exact zeros (probably should) */ + + assert((xm >> (SP_FBITS + 1 + 3)) == 0); /* no excess */ + assert(xm & (SP_HIDDEN_BIT << 3)); + + if (xe < SP_EMIN) { + /* strip lower bits */ + int es = SP_EMIN - xe; + + if (ieee754_csr.nod) { + ieee754_setcx(IEEE754_UNDERFLOW); + ieee754_setcx(IEEE754_INEXACT); + + switch(ieee754_csr.rm) { + case FPU_CSR_RN: + case FPU_CSR_RZ: + return ieee754sp_zero(sn); + case FPU_CSR_RU: /* toward +Infinity */ + if (sn == 0) + return ieee754sp_min(0); + else + return ieee754sp_zero(1); + case FPU_CSR_RD: /* toward -Infinity */ + if (sn == 0) + return ieee754sp_zero(0); + else + return ieee754sp_min(1); + } + } + + if (xe == SP_EMIN - 1 && + ieee754sp_get_rounding(sn, xm) >> (SP_FBITS + 1 + 3)) + { + /* Not tiny after rounding */ + ieee754_setcx(IEEE754_INEXACT); + xm = ieee754sp_get_rounding(sn, xm); + xm >>= 1; + /* Clear grs bits */ + xm &= ~(SP_MBIT(3) - 1); + xe++; + } else { + /* sticky right shift es bits + */ + xm = XSPSRS(xm, es); + xe += es; + assert((xm & (SP_HIDDEN_BIT << 3)) == 0); + assert(xe == SP_EMIN); + } + } + if (xm & (SP_MBIT(3) - 1)) { + ieee754_setcx(IEEE754_INEXACT); + if ((xm & (SP_HIDDEN_BIT << 3)) == 0) { + ieee754_setcx(IEEE754_UNDERFLOW); + } + + /* inexact must round of 3 bits + */ + xm = ieee754sp_get_rounding(sn, xm); + /* adjust exponent for rounding add overflowing + */ + if (xm >> (SP_FBITS + 1 + 3)) { + /* add causes mantissa overflow */ + xm >>= 1; + xe++; + } + } + /* strip grs bits */ + xm >>= 3; + + assert((xm >> (SP_FBITS + 1)) == 0); /* no excess */ + assert(xe >= SP_EMIN); + + if (xe > SP_EMAX) { + ieee754_setcx(IEEE754_OVERFLOW); + ieee754_setcx(IEEE754_INEXACT); + /* -O can be table indexed by (rm,sn) */ + switch (ieee754_csr.rm) { + case FPU_CSR_RN: + return ieee754sp_inf(sn); + case FPU_CSR_RZ: + return ieee754sp_max(sn); + case FPU_CSR_RU: /* toward +Infinity */ + if (sn == 0) + return ieee754sp_inf(0); + else + return ieee754sp_max(1); + case FPU_CSR_RD: /* toward -Infinity */ + if (sn == 0) + return ieee754sp_max(0); + else + return ieee754sp_inf(1); + } + } + /* gen norm/denorm/zero */ + + if ((xm & SP_HIDDEN_BIT) == 0) { + /* we underflow (tiny/zero) */ + assert(xe == SP_EMIN); + if (ieee754_csr.mx & IEEE754_UNDERFLOW) + ieee754_setcx(IEEE754_UNDERFLOW); + return buildsp(sn, SP_EMIN - 1 + SP_EBIAS, xm); + } else { + assert((xm >> (SP_FBITS + 1)) == 0); /* no excess */ + assert(xm & SP_HIDDEN_BIT); + + return buildsp(sn, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT); + } +} |