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[FAST486]

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Fix several division related problems:
- In UnsignedDivMod128, fix the leading zero calculation for 128-bit numbers.
- In Fast486FpuDivide, there's no need to increase the exponent by 64 (adding zeros
at the end of a number after the decimal point changes nothing).
- FDIV/FDIVR were reversed


svn path=/trunk/; revision=67820
This commit is contained in:
Aleksandar Andrejevic 2015-05-18 12:17:40 +00:00
parent ec471e2759
commit de0880752b
1 changed files with 6 additions and 7 deletions
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13
reactos/lib/fast486/fpu.c
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@ -203,9 +203,9 @@ UnsignedDivMod128(ULONGLONG DividendLow,
* Calculate the number of significant bits the current * Calculate the number of significant bits the current
* divisor has more than the original divisor * divisor has more than the original divisor
*/ */
Bits = CountLeadingZeros64(Divisor) + 64; Bits = CountLeadingZeros64(Divisor);
Bits -= (CurrentHigh > 0ULL) ? CountLeadingZeros64(CurrentHigh) : 64; if (CurrentHigh > 0ULL) Bits -= CountLeadingZeros64(CurrentHigh);
Bits -= (CurrentLow > 0ULL) ? CountLeadingZeros64(CurrentLow) : 64; else Bits -= CountLeadingZeros64(CurrentLow);
if (Bits) if (Bits)
{ {
@ -923,11 +923,10 @@ Fast486FpuDivide(PFAST486_STATE State,
} }
/* Calculate the exponent of the result */ /* Calculate the exponent of the result */
Exponent = (LONG)FirstOperand->Exponent - (LONG)SecondOperand->Exponent - 64; Exponent = (LONG)FirstOperand->Exponent - (LONG)SecondOperand->Exponent - 1;
/* Divide the two mantissas */ /* Divide the two mantissas */
Remainder = UnsignedDivMod128(0ULL, Remainder = UnsignedDivMod128(0ULL,
/* Notice the 64 above - this is the high part */
FirstOperand->Mantissa, FirstOperand->Mantissa,
SecondOperand->Mantissa, SecondOperand->Mantissa,
&QuotientLow, &QuotientLow,
@ -1169,14 +1168,14 @@ Fast486FpuArithmeticOperation(PFAST486_STATE State,
/* FDIV */ /* FDIV */
case 6: case 6:
{ {
Fast486FpuDivide(State, DestOperand, SourceOperand, DestOperand); Fast486FpuDivide(State, SourceOperand, DestOperand, DestOperand);
break; break;
} }
/* FDIVR */ /* FDIVR */
case 7: case 7:
{ {
Fast486FpuDivide(State, SourceOperand, DestOperand, DestOperand); Fast486FpuDivide(State, DestOperand, SourceOperand, DestOperand);
break; break;
} }
} }