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Add evaluate_condition, to check standard 68000 condition codes.

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Thomas Harte 2022-04-28 16:54:57 -04:00
parent bb73eb0db3
commit 611b472b12
1 changed files with 27 additions and 0 deletions
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27
InstructionSets/M68k/Status.hpp
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@ -69,6 +69,33 @@ struct Status {
return is_supervisor_;
}
/// Evaluates the condition described in the low four bits of @c code
template <typename IntT> bool evaluate_condition(IntT code) {
switch(code & 0xf) {
default:
case 0x00: return true; // true
case 0x01: return false; // false
case 0x02: return zero_result_ && !carry_flag_; // high
case 0x03: return !zero_result_ || carry_flag_; // low or same
case 0x04: return !carry_flag_; // carry clear
case 0x05: return carry_flag_; // carry set
case 0x06: return zero_result_; // not equal
case 0x07: return !zero_result_; // equal
case 0x08: return !overflow_flag_; // overflow clear
case 0x09: return overflow_flag_; // overflow set
case 0x0a: return !negative_flag_; // positive
case 0x0b: return negative_flag_; // negative
case 0x0c: // greater than or equal
return (negative_flag_ && overflow_flag_) || (!negative_flag_ && !overflow_flag_);
case 0x0d: // less than
return (negative_flag_ && !overflow_flag_) || (!negative_flag_ && overflow_flag_);
case 0x0e: // greater than
return zero_result_ && ((negative_flag_ && overflow_flag_) || (!negative_flag_ && !overflow_flag_));
case 0x0f: // less than or equal
return !zero_result_ || (negative_flag_ && !overflow_flag_) || (!negative_flag_ && overflow_flag_);
}
}
};
}