diff options
Diffstat (limited to 'arch/x86/math-emu/reg_add_sub.c')
| -rw-r--r-- | arch/x86/math-emu/reg_add_sub.c | 374 |
1 files changed, 374 insertions, 0 deletions
diff --git a/arch/x86/math-emu/reg_add_sub.c b/arch/x86/math-emu/reg_add_sub.c new file mode 100644 index 0000000..7cd3b37 --- /dev/null +++ b/arch/x86/math-emu/reg_add_sub.c @@ -0,0 +1,374 @@ +/*---------------------------------------------------------------------------+ + | reg_add_sub.c | + | | + | Functions to add or subtract two registers and put the result in a third. | + | | + | Copyright (C) 1992,1993,1997 | + | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | + | E-mail billm@suburbia.net | + | | + | | + +---------------------------------------------------------------------------*/ + +/*---------------------------------------------------------------------------+ + | For each function, the destination may be any FPU_REG, including one of | + | the source FPU_REGs. | + | Each function returns 0 if the answer is o.k., otherwise a non-zero | + | value is returned, indicating either an exception condition or an | + | internal error. | + +---------------------------------------------------------------------------*/ + +#include "exception.h" +#include "reg_constant.h" +#include "fpu_emu.h" +#include "control_w.h" +#include "fpu_system.h" + +static +int add_sub_specials(FPU_REG const *a, u_char taga, u_char signa, + FPU_REG const *b, u_char tagb, u_char signb, + FPU_REG *dest, int deststnr, int control_w); + +/* + Operates on st(0) and st(n), or on st(0) and temporary data. + The destination must be one of the source st(x). + */ +int FPU_add(FPU_REG const *b, u_char tagb, int deststnr, int control_w) +{ + FPU_REG *a = &st(0); + FPU_REG *dest = &st(deststnr); + u_char signb = getsign(b); + u_char taga = FPU_gettag0(); + u_char signa = getsign(a); + u_char saved_sign = getsign(dest); + int diff, tag, expa, expb; + + if ( !(taga | tagb) ) + { + expa = exponent(a); + expb = exponent(b); + + valid_add: + /* Both registers are valid */ + if (!(signa ^ signb)) + { + /* signs are the same */ + tag = FPU_u_add(a, b, dest, control_w, signa, expa, expb); + } + else + { + /* The signs are different, so do a subtraction */ + diff = expa - expb; + if (!diff) + { + diff = a->sigh - b->sigh; /* This works only if the ms bits + are identical. */ + if (!diff) + { + diff = a->sigl > b->sigl; + if (!diff) + diff = -(a->sigl < b->sigl); + } + } + + if (diff > 0) + { + tag = FPU_u_sub(a, b, dest, control_w, signa, expa, expb); + } + else if ( diff < 0 ) + { + tag = FPU_u_sub(b, a, dest, control_w, signb, expb, expa); + } + else + { + FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); + /* sign depends upon rounding mode */ + setsign(dest, ((control_w & CW_RC) != RC_DOWN) + ? SIGN_POS : SIGN_NEG); + return TAG_Zero; + } + } + + if ( tag < 0 ) + { + setsign(dest, saved_sign); + return tag; + } + FPU_settagi(deststnr, tag); + return tag; + } + + if ( taga == TAG_Special ) + taga = FPU_Special(a); + if ( tagb == TAG_Special ) + tagb = FPU_Special(b); + + if ( ((taga == TAG_Valid) && (tagb == TW_Denormal)) + || ((taga == TW_Denormal) && (tagb == TAG_Valid)) + || ((taga == TW_Denormal) && (tagb == TW_Denormal)) ) + { + FPU_REG x, y; + + if ( denormal_operand() < 0 ) + return FPU_Exception; + + FPU_to_exp16(a, &x); + FPU_to_exp16(b, &y); + a = &x; + b = &y; + expa = exponent16(a); + expb = exponent16(b); + goto valid_add; + } + + if ( (taga == TW_NaN) || (tagb == TW_NaN) ) + { + if ( deststnr == 0 ) + return real_2op_NaN(b, tagb, deststnr, a); + else + return real_2op_NaN(a, taga, deststnr, a); + } + + return add_sub_specials(a, taga, signa, b, tagb, signb, + dest, deststnr, control_w); +} + + +/* Subtract b from a. (a-b) -> dest */ +int FPU_sub(int flags, int rm, int control_w) +{ + FPU_REG const *a, *b; + FPU_REG *dest; + u_char taga, tagb, signa, signb, saved_sign, sign; + int diff, tag = 0, expa, expb, deststnr; + + a = &st(0); + taga = FPU_gettag0(); + + deststnr = 0; + if ( flags & LOADED ) + { + b = (FPU_REG *)rm; + tagb = flags & 0x0f; + } + else + { + b = &st(rm); + tagb = FPU_gettagi(rm); + + if ( flags & DEST_RM ) + deststnr = rm; + } + + signa = getsign(a); + signb = getsign(b); + + if ( flags & REV ) + { + signa ^= SIGN_NEG; + signb ^= SIGN_NEG; + } + + dest = &st(deststnr); + saved_sign = getsign(dest); + + if ( !(taga | tagb) ) + { + expa = exponent(a); + expb = exponent(b); + + valid_subtract: + /* Both registers are valid */ + + diff = expa - expb; + + if (!diff) + { + diff = a->sigh - b->sigh; /* Works only if ms bits are identical */ + if (!diff) + { + diff = a->sigl > b->sigl; + if (!diff) + diff = -(a->sigl < b->sigl); + } + } + + switch ( (((int)signa)*2 + signb) / SIGN_NEG ) + { + case 0: /* P - P */ + case 3: /* N - N */ + if (diff > 0) + { + /* |a| > |b| */ + tag = FPU_u_sub(a, b, dest, control_w, signa, expa, expb); + } + else if ( diff == 0 ) + { + FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); + + /* sign depends upon rounding mode */ + setsign(dest, ((control_w & CW_RC) != RC_DOWN) + ? SIGN_POS : SIGN_NEG); + return TAG_Zero; + } + else + { + sign = signa ^ SIGN_NEG; + tag = FPU_u_sub(b, a, dest, control_w, sign, expb, expa); + } + break; + case 1: /* P - N */ + tag = FPU_u_add(a, b, dest, control_w, SIGN_POS, expa, expb); + break; + case 2: /* N - P */ + tag = FPU_u_add(a, b, dest, control_w, SIGN_NEG, expa, expb); + break; +#ifdef PARANOID + default: + EXCEPTION(EX_INTERNAL|0x111); + return -1; +#endif + } + if ( tag < 0 ) + { + setsign(dest, saved_sign); + return tag; + } + FPU_settagi(deststnr, tag); + return tag; + } + + if ( taga == TAG_Special ) + taga = FPU_Special(a); + if ( tagb == TAG_Special ) + tagb = FPU_Special(b); + + if ( ((taga == TAG_Valid) && (tagb == TW_Denormal)) + || ((taga == TW_Denormal) && (tagb == TAG_Valid)) + || ((taga == TW_Denormal) && (tagb == TW_Denormal)) ) + { + FPU_REG x, y; + + if ( denormal_operand() < 0 ) + return FPU_Exception; + + FPU_to_exp16(a, &x); + FPU_to_exp16(b, &y); + a = &x; + b = &y; + expa = exponent16(a); + expb = exponent16(b); + + goto valid_subtract; + } + + if ( (taga == TW_NaN) || (tagb == TW_NaN) ) + { + FPU_REG const *d1, *d2; + if ( flags & REV ) + { + d1 = b; + d2 = a; + } + else + { + d1 = a; + d2 = b; + } + if ( flags & LOADED ) + return real_2op_NaN(b, tagb, deststnr, d1); + if ( flags & DEST_RM ) + return real_2op_NaN(a, taga, deststnr, d2); + else + return real_2op_NaN(b, tagb, deststnr, d2); + } + + return add_sub_specials(a, taga, signa, b, tagb, signb ^ SIGN_NEG, + dest, deststnr, control_w); +} + + +static +int add_sub_specials(FPU_REG const *a, u_char taga, u_char signa, + FPU_REG const *b, u_char tagb, u_char signb, + FPU_REG *dest, int deststnr, int control_w) +{ + if ( ((taga == TW_Denormal) || (tagb == TW_Denormal)) + && (denormal_operand() < 0) ) + return FPU_Exception; + + if (taga == TAG_Zero) + { + if (tagb == TAG_Zero) + { + /* Both are zero, result will be zero. */ + u_char different_signs = signa ^ signb; + + FPU_copy_to_regi(a, TAG_Zero, deststnr); + if ( different_signs ) + { + /* Signs are different. */ + /* Sign of answer depends upon rounding mode. */ + setsign(dest, ((control_w & CW_RC) != RC_DOWN) + ? SIGN_POS : SIGN_NEG); + } + else + setsign(dest, signa); /* signa may differ from the sign of a. */ + return TAG_Zero; + } + else + { + reg_copy(b, dest); + if ( (tagb == TW_Denormal) && (b->sigh & 0x80000000) ) + { + /* A pseudoDenormal, convert it. */ + addexponent(dest, 1); + tagb = TAG_Valid; + } + else if ( tagb > TAG_Empty ) + tagb = TAG_Special; + setsign(dest, signb); /* signb may differ from the sign of b. */ + FPU_settagi(deststnr, tagb); + return tagb; + } + } + else if (tagb == TAG_Zero) + { + reg_copy(a, dest); + if ( (taga == TW_Denormal) && (a->sigh & 0x80000000) ) + { + /* A pseudoDenormal */ + addexponent(dest, 1); + taga = TAG_Valid; + } + else if ( taga > TAG_Empty ) + taga = TAG_Special; + setsign(dest, signa); /* signa may differ from the sign of a. */ + FPU_settagi(deststnr, taga); + return taga; + } + else if (taga == TW_Infinity) + { + if ( (tagb != TW_Infinity) || (signa == signb) ) + { + FPU_copy_to_regi(a, TAG_Special, deststnr); + setsign(dest, signa); /* signa may differ from the sign of a. */ + return taga; + } + /* Infinity-Infinity is undefined. */ + return arith_invalid(deststnr); + } + else if (tagb == TW_Infinity) + { + FPU_copy_to_regi(b, TAG_Special, deststnr); + setsign(dest, signb); /* signb may differ from the sign of b. */ + return tagb; + } + +#ifdef PARANOID + EXCEPTION(EX_INTERNAL|0x101); +#endif + + return FPU_Exception; +} + |
