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This commit is contained in:
Mathieu Lacage
2010-04-08 13:25:00 +02:00
parent 992a77cb0a
commit b32ce16c67
1 changed files with 22 additions and 32 deletions
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54
src/simulator/high-precision-128.cc
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@@ -163,30 +163,23 @@ HighPrecision::SlowMul (HighPrecision const &o)
* of the operands to produce a signed 128 bits result.
*/
cairo_int128_t
HighPrecision::Mul128(cairo_int128_t a, cairo_int128_t b )
HighPrecision::Mul128(cairo_int128_t sa, cairo_int128_t sb )
{
//Implement the 128 bits multiplication
cairo_int128_t result;
cairo_uint128_t hiPart,loPart,midPart;
bool resultNegative = false, signA = false,signB = false;
bool negResult, negA, negB;
//take the sign of the operands
signA = _cairo_int128_negative (a);
signB = _cairo_int128_negative (b);
//the result is negative only if one of the operand is negative
if ((signA == true && signB == false) ||(signA == false && signB == true))
{
resultNegative = true;
}
//now take the absolute part to make sure that the resulting operands are positive
if (signA == true)
{
a = _cairo_int128_negate (a);
}
if (signB == true)
{
b = _cairo_int128_negate (b);
}
negA = _cairo_int128_negative (sa);
negB = _cairo_int128_negative (sb);
// the result is negative only if one of the operand is negative
negResult = (negA && !negB) || (!negA && negB);
// now take the absolute part to make sure that the resulting operands are positive
cairo_uint128_t a, b;
a = _cairo_int128_to_uint128 (sa);
b = _cairo_int128_to_uint128 (sb);
a = negA ? _cairo_uint128_negate (a):a;
b = negB ? _cairo_uint128_negate (b):b;
cairo_uint128_t result;
cairo_uint128_t hiPart,loPart,midPart;
//Multiplying (a.h 2^64 + a.l) x (b.h 2^64 + b.l) =
// 2^128 a.h b.h + 2^64*(a.h b.l+b.h a.l) + a.l b.l
@@ -195,7 +188,7 @@ HighPrecision::Mul128(cairo_int128_t a, cairo_int128_t b )
loPart = _cairo_uint64x64_128_mul (a.lo, b.lo);
//compute the middle part 2^64*(a.h b.l+b.h a.l)
midPart = _cairo_uint128_add(_cairo_uint64x64_128_mul(a.lo, b.hi),
_cairo_uint64x64_128_mul(a.hi, b.lo)) ;
_cairo_uint64x64_128_mul(a.hi, b.lo)) ;
//truncate the low part
result.lo = _cairo_uint64_add(loPart.hi,midPart.lo);
//compute the high part 2^128 a.h b.h
@@ -204,15 +197,12 @@ HighPrecision::Mul128(cairo_int128_t a, cairo_int128_t b )
result.hi = _cairo_uint64_add(hiPart.lo,midPart.hi);
//if the high part is not zero, put a warning
if (hiPart.hi !=0)
{
NS_FATAL_ERROR("High precision 128 bits multiplication error: multiplication overflow.");
}
//add the sign to the result
if (resultNegative)
{
result = _cairo_int128_negate (result);
}
return result;
{
NS_FATAL_ERROR("High precision 128 bits multiplication error: multiplication overflow.");
}
// add the sign to the result
result = negResult ? _cairo_uint128_negate (result):result;
return _cairo_uint128_to_int128 (result);
}
bool