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fp: Change FPUnpacked to a normalized representation

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Having a known position for the highest set bit makes writing algorithms easier
This commit is contained in:
MerryMage 2018-07-25 17:39:14 +01:00
parent 680395a803
commit 7a673a8a43
10 changed files with 71 additions and 56 deletions
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12
src/common/fp/op/FPToFixed.cpp
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@ -40,12 +40,12 @@ u64 FPToFixed(size_t ibits, FPT op, size_t fbits, bool unsigned_, FPCR fpcr, Rou
return 0;
}
// value *= 2.0^fbits
value.exponent += static_cast<int>(fbits);
// value *= 2.0^fbits and reshift the decimal point back to bit zero.
int exponent = value.exponent + static_cast<int>(fbits) - normalized_point_position;
u64 int_result = sign ? Safe::Negate<u64>(value.mantissa) : static_cast<u64>(value.mantissa);
const ResidualError error = ResidualErrorOnRightShift(int_result, -value.exponent);
int_result = Safe::ArithmeticShiftLeft(int_result, value.exponent);
const ResidualError error = ResidualErrorOnRightShift(int_result, -exponent);
int_result = Safe::ArithmeticShiftLeft(int_result, exponent);
bool round_up = false;
switch (rounding) {
@ -74,7 +74,7 @@ u64 FPToFixed(size_t ibits, FPT op, size_t fbits, bool unsigned_, FPCR fpcr, Rou
// Detect Overflow
const int min_exponent_for_overflow = static_cast<int>(ibits) - static_cast<int>(Common::HighestSetBit(value.mantissa + (round_up ? 1 : 0))) - (unsigned_ ? 0 : 1);
if (value.exponent >= min_exponent_for_overflow) {
if (exponent >= min_exponent_for_overflow) {
// Positive overflow
if (unsigned_ || !sign) {
FPProcessException(FPExc::InvalidOp, fpcr, fpsr);
@ -83,7 +83,7 @@ u64 FPToFixed(size_t ibits, FPT op, size_t fbits, bool unsigned_, FPCR fpcr, Rou
// Negative overflow
const u64 min_value = Safe::Negate<u64>(static_cast<u64>(1) << (ibits - 1));
if (!(value.exponent == min_exponent_for_overflow && int_result == min_value)) {
if (!(exponent == min_exponent_for_overflow && int_result == min_value)) {
FPProcessException(FPExc::InvalidOp, fpcr, fpsr);
return static_cast<u64>(1) << (ibits - 1);
}