diff options
Diffstat (limited to 'kernel/arch/x86/math-emu/reg_mul.c')
| -rw-r--r-- | kernel/arch/x86/math-emu/reg_mul.c | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/kernel/arch/x86/math-emu/reg_mul.c b/kernel/arch/x86/math-emu/reg_mul.c new file mode 100644 index 000000000..36c37f71f --- /dev/null +++ b/kernel/arch/x86/math-emu/reg_mul.c @@ -0,0 +1,115 @@ +/*---------------------------------------------------------------------------+ + | reg_mul.c | + | | + | Multiply one FPU_REG by another, put the result in a destination FPU_REG. | + | | + | Copyright (C) 1992,1993,1997 | + | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | + | E-mail billm@suburbia.net | + | | + | Returns the tag of the result if no exceptions or errors occurred. | + | | + +---------------------------------------------------------------------------*/ + +/*---------------------------------------------------------------------------+ + | The destination may be any FPU_REG, including one of the source FPU_REGs. | + +---------------------------------------------------------------------------*/ + +#include "fpu_emu.h" +#include "exception.h" +#include "reg_constant.h" +#include "fpu_system.h" + +/* + Multiply two registers to give a register result. + The sources are st(deststnr) and (b,tagb,signb). + The destination is st(deststnr). + */ +/* This routine must be called with non-empty source registers */ +int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w) +{ + FPU_REG *a = &st(deststnr); + FPU_REG *dest = a; + u_char taga = FPU_gettagi(deststnr); + u_char saved_sign = getsign(dest); + u_char sign = (getsign(a) ^ getsign(b)); + int tag; + + if (!(taga | tagb)) { + /* Both regs Valid, this should be the most common case. */ + + tag = + FPU_u_mul(a, b, dest, control_w, sign, + exponent(a) + exponent(b)); + 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); + tag = FPU_u_mul(&x, &y, dest, control_w, sign, + exponent16(&x) + exponent16(&y)); + if (tag < 0) { + setsign(dest, saved_sign); + return tag; + } + FPU_settagi(deststnr, tag); + return tag; + } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) { + if (((tagb == TW_Denormal) || (taga == TW_Denormal)) + && (denormal_operand() < 0)) + return FPU_Exception; + + /* Must have either both arguments == zero, or + one valid and the other zero. + The result is therefore zero. */ + FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); + /* The 80486 book says that the answer is +0, but a real + 80486 behaves this way. + IEEE-754 apparently says it should be this way. */ + setsign(dest, sign); + return TAG_Zero; + } + /* Must have infinities, NaNs, etc */ + else if ((taga == TW_NaN) || (tagb == TW_NaN)) { + return real_2op_NaN(b, tagb, deststnr, &st(0)); + } else if (((taga == TW_Infinity) && (tagb == TAG_Zero)) + || ((tagb == TW_Infinity) && (taga == TAG_Zero))) { + return arith_invalid(deststnr); /* Zero*Infinity is invalid */ + } else if (((taga == TW_Denormal) || (tagb == TW_Denormal)) + && (denormal_operand() < 0)) { + return FPU_Exception; + } else if (taga == TW_Infinity) { + FPU_copy_to_regi(a, TAG_Special, deststnr); + setsign(dest, sign); + return TAG_Special; + } else if (tagb == TW_Infinity) { + FPU_copy_to_regi(b, TAG_Special, deststnr); + setsign(dest, sign); + return TAG_Special; + } +#ifdef PARANOID + else { + EXCEPTION(EX_INTERNAL | 0x102); + return FPU_Exception; + } +#endif /* PARANOID */ + + return 0; +} |