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Tidy up primarily as per PatickvL's comments.

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... though pulling the flag values out of an enum and into a namespace is entirely my own contribution, to keep them in their own namespace but having them overtly be ints.
This commit is contained in:
Thomas Harte 2022-05-12 16:23:07 -04:00
parent 6d43576db7
commit a6e4d23c29
1 changed files with 29 additions and 22 deletions
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51
InstructionSets/M68k/Status.hpp
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@ -14,44 +14,51 @@
namespace InstructionSet { namespace InstructionSet {
namespace M68k { namespace M68k {
namespace ConditionCode {
static constexpr uint16_t Carry = 1 << 0;
static constexpr uint16_t Overflow = 1 << 1;
static constexpr uint16_t Zero = 1 << 2;
static constexpr uint16_t Negative = 1 << 3;
static constexpr uint16_t Extend = 1 << 4;
static constexpr uint16_t Supervisor = 1 << 13;
static constexpr uint16_t Trace = 1 << 15;
static constexpr uint16_t InterruptPriorityMask = 0b111 << 8;
}
struct Status { struct Status {
/// Generally holds an unevaluated flag for potential later lazy evaluation; it'll be zero for one outcome,
/// non-zero for the other, but no guarantees are made about the potential range of non-zero values.
using FlagT = uint_fast32_t; using FlagT = uint_fast32_t;
enum ConditionCode: uint16_t {
Carry = (1 << 0),
Overflow = (1 << 1),
Zero = (1 << 2),
Negative = (1 << 3),
Extend = (1 << 4),
Supervisor = (1 << 13),
Trace = (1 << 15),
InterruptPriorityMask = (0b111 << 8),
};
/* b15 */ /* b15 */
FlagT trace_flag = 0; // The trace flag is set if this value is non-zero. FlagT trace_flag = 0; // The trace flag is set if and only if this value is non-zero.
/* b13 */ /* b13 */
int is_supervisor = 0; // 1 => processor is in supervisor mode; 0 => it isn't. int is_supervisor = 0; // 1 => processor is in supervisor mode; 0 => it isn't.
// All other values have undefined meaning.
/* b7–b9 */ /* b7–b9 */
int interrupt_level = 0; // The direct integer value of the current interrupt level. int interrupt_level = 0; // The direct integer value of the current interrupt level.
// Values of 8 or greater have undefined meaning.
/* b0–b4 */ /* b0–b4 */
FlagT zero_result = 0; // The zero flag is set if this value is zero. FlagT zero_result = 0; // The zero flag is set if and only if this value is zero.
FlagT carry_flag = 0; // The carry flag is set if this value is non-zero. FlagT carry_flag = 0; // The carry flag is set if and only if this value is non-zero.
FlagT extend_flag = 0; // The extend flag is set if this value is non-zero. FlagT extend_flag = 0; // The extend flag is set if and only if this value is non-zero.
FlagT overflow_flag = 0; // The overflow flag is set if this value is non-zero. FlagT overflow_flag = 0; // The overflow flag is set if and only if this value is non-zero.
FlagT negative_flag = 0; // The negative flag is set if this value is non-zero. FlagT negative_flag = 0; // The negative flag is set if and only this value is non-zero.
/// Gets the current condition codes. /// Gets the current condition codes.
constexpr uint16_t ccr() const { constexpr uint16_t ccr() const {
return return
(carry_flag ? ConditionCode::Carry : 0) | (carry_flag ? ConditionCode::Carry : 0) |
(overflow_flag ? ConditionCode::Overflow : 0) | (overflow_flag ? ConditionCode::Overflow : 0) |
(zero_result ? 0 : ConditionCode::Zero) | (!zero_result ? ConditionCode::Zero : 0) |
(negative_flag ? ConditionCode::Negative : 0) | (negative_flag ? ConditionCode::Negative : 0) |
(extend_flag ? ConditionCode::Extend : 0); (extend_flag ? ConditionCode::Extend : 0);
} }
@ -71,7 +78,7 @@ struct Status {
ccr() | ccr() |
(interrupt_level << 8) | (interrupt_level << 8) |
(trace_flag ? ConditionCode::Trace : 0) | (trace_flag ? ConditionCode::Trace : 0) |
(is_supervisor << 13) (is_supervisor ? ConditionCode::Supervisor : 0)
); );
} }
@ -82,7 +89,7 @@ struct Status {
interrupt_level = (status >> 8) & 7; interrupt_level = (status >> 8) & 7;
trace_flag = status & ConditionCode::Trace; trace_flag = status & ConditionCode::Trace;
is_supervisor = (status >> 13) & 1; is_supervisor = (status & ConditionCode::Supervisor) ? 1 : 0;
return is_supervisor; return is_supervisor;
} }