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Move common negative and zero logic into Status.

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This commit is contained in:
Thomas Harte 2022-10-18 14:51:51 -04:00
parent b31b4a5d10
commit d09473b66f
2 changed files with 36 additions and 39 deletions
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63
InstructionSets/M68k/Implementation/PerformImplementation.hpp
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@ -70,7 +70,7 @@ static void add_sub(IntT source, IntT &destination, Status &status) {
}
status.extend_flag =
status.carry_flag = is_add ? result < destination : result > destination;
status.negative_flag = Status::FlagT(result & top_bit<IntT>());
status.set_negative(result);
status.overflow_flag = overflow<is_add>(source, destination, result);
destination = result;
}
@ -97,7 +97,7 @@ inline void sbcd(uint8_t rhs, uint8_t lhs, uint8_t &destination, Status &status)
/* Set all remaining flags essentially as if this were normal subtraction. */
status.zero_result |= destination;
status.negative_flag = result & 0x80;
status.set_negative(destination);
status.overflow_flag = unadjusted_result & ~result & 0x80;
}
@ -124,17 +124,15 @@ void bitwise(IntT source, IntT &destination, Status &status) {
}
status.overflow_flag = status.carry_flag = 0;
status.zero_result = destination;
status.negative_flag = destination & top_bit<IntT>();
status.set_neg_zero(destination);
}
/// Compare of @c source to @c destination, setting zero, carry, negative and overflow flags.
template <typename IntT>
void compare(IntT source, IntT destination, Status &status) {
const IntT result = destination - source;
status.zero_result = result;
status.carry_flag = result > destination;
status.negative_flag = result & top_bit<IntT>();
status.set_neg_zero(result);
status.overflow_flag = Primitive::overflow<false>(source, destination, result);
}
@ -216,8 +214,7 @@ void multiply(uint16_t source, uint32_t &destination, Status &status, FlowContro
destination = u_extend16(source) * u_extend16(uint16_t(destination));
}
status.carry_flag = status.overflow_flag = 0;
status.zero_result = destination;
status.negative_flag = status.zero_result & top_bit<uint32_t>();
status.set_neg_zero(destination);
if constexpr (is_mulu) {
flow_controller.did_mulu(source);
@ -264,15 +261,14 @@ void divide(uint16_t source, uint32_t &destination, Status &status, FlowControll
status.overflow_flag = 0;
status.zero_result = Status::FlagT(quotient);
status.negative_flag = status.zero_result & 0x8000;
status.set_negative(uint16_t(quotient));
did_divide<is_divu, false>(dividend, divisor, flow_controller);
}
/// Move @c source to @c destination, updating @c status.
template <typename IntT> void move(IntT source, IntT &destination, Status &status) {
destination = source;
status.zero_result = Status::FlagT(source);
status.negative_flag = status.zero_result & top_bit<IntT>();
status.set_neg_zero(destination);
status.overflow_flag = status.carry_flag = 0;
}
@ -286,7 +282,7 @@ template <bool is_extend, typename IntT> void negative(IntT &source, Status &sta
status.zero_result = result;
}
status.extend_flag = status.carry_flag = result; // i.e. any value other than 0 will result in carry.
status.negative_flag = result & top_bit<IntT>();
status.set_negative(result);
status.overflow_flag = Primitive::overflow<false>(source, IntT(0), result);
source = result;
@ -295,8 +291,7 @@ template <bool is_extend, typename IntT> void negative(IntT &source, Status &sta
/// Perform TST.[b/l/w] with @c source, updating @c status.
template <typename IntT> void test(IntT source, Status &status) {
status.carry_flag = status.overflow_flag = 0;
status.zero_result = Status::FlagT(source);
status.negative_flag = status.zero_result & top_bit<IntT>();
status.set_neg_zero(source);
}
/// Decodes the proper shift distance from @c source, notifying the @c flow_controller.
@ -311,12 +306,6 @@ template <typename IntT> constexpr int bit_size() {
return sizeof(IntT) * 8;
}
/// Set the zero and negative flags on @c status according to @c result.
template <typename IntT> void set_neg_zero(IntT result, Status &status) {
status.zero_result = Status::FlagT(result);
status.negative_flag = result & top_bit<IntT>();
}
/// Perform an arithmetic or logical shift, i.e. any of LSL, LSR, ASL or ASR.
template <Operation operation, typename IntT, typename FlowController> void shift(uint32_t source, IntT &destination, Status &status, FlowController &flow_controller) {
static_assert(
@ -404,7 +393,7 @@ template <Operation operation, typename IntT, typename FlowController> void shif
}
}
set_neg_zero(destination, status);
status.set_neg_zero(destination);
}
/// Perform a rotate without extend, i.e. any of RO[L/R].[b/w/l].
@ -444,7 +433,7 @@ template <Operation operation, typename IntT, typename FlowController> void rota
}
}
set_neg_zero(destination, status);
status.set_neg_zero(destination);
status.overflow_flag = 0;
}
@ -510,7 +499,7 @@ template <Operation operation, typename IntT, typename FlowController> void rox(
}
}
set_neg_zero(destination, status);
status.set_neg_zero(destination);
status.overflow_flag = 0;
}
@ -545,7 +534,7 @@ template <
// Set all flags essentially as if this were normal addition.
status.zero_result |= result & 0xff;
status.extend_flag = status.carry_flag = uint_fast32_t(result & ~0xff);
status.negative_flag = result & 0x80;
status.set_negative(uint8_t(result));
status.overflow_flag = ~unadjusted_result & result & 0x80;
// Store the result.
@ -718,15 +707,13 @@ template <
case Operation::EXTbtow:
src.w = uint16_t(int8_t(src.b));
status.overflow_flag = status.carry_flag = 0;
status.zero_result = src.w;
status.negative_flag = status.zero_result & 0x8000;
status.set_neg_zero(src.w);
break;
case Operation::EXTwtol:
src.l = u_extend16(src.w);
status.overflow_flag = status.carry_flag = 0;
status.zero_result = src.l;
status.negative_flag = status.zero_result & 0x80000000;
status.set_neg_zero(src.l);
break;
case Operation::ANDItoSR: Primitive::apply_sr_ccr<Operation::ANDItoSR>(src.w, status, flow_controller); break;
@ -873,9 +860,7 @@ template <
case Operation::SWAP: {
uint16_t *const words = reinterpret_cast<uint16_t *>(&src.l);
std::swap(words[0], words[1]);
status.zero_result = src.l;
status.negative_flag = src.l & Primitive::top_bit<uint32_t>();
status.set_neg_zero(src.l);
status.overflow_flag = status.carry_flag = 0;
} break;
@ -886,42 +871,42 @@ template <
status.extend_flag = status.carry_flag = src.w & Primitive::top_bit<uint16_t>();
status.overflow_flag = (src.w ^ (src.w << 1)) & Primitive::top_bit<uint16_t>();
src.w <<= 1;
Primitive::set_neg_zero(src.w, status);
status.set_neg_zero(src.w);
break;
case Operation::LSLm:
status.extend_flag = status.carry_flag = src.w & Primitive::top_bit<uint16_t>();
status.overflow_flag = 0;
src.w <<= 1;
Primitive::set_neg_zero(src.w, status);
status.set_neg_zero(src.w);
break;
case Operation::ASRm:
status.extend_flag = status.carry_flag = src.w & 1;
status.overflow_flag = 0;
src.w = (src.w & Primitive::top_bit<uint16_t>()) | (src.w >> 1);
Primitive::set_neg_zero(src.w, status);
status.set_neg_zero(src.w);
break;
case Operation::LSRm:
status.extend_flag = status.carry_flag = src.w & 1;
status.overflow_flag = 0;
src.w >>= 1;
Primitive::set_neg_zero(src.w, status);
status.set_neg_zero(src.w);
break;
case Operation::ROLm:
src.w = uint16_t((src.w << 1) | (src.w >> 15));
status.carry_flag = src.w & 0x0001;
status.overflow_flag = 0;
Primitive::set_neg_zero(src.w, status);
status.set_neg_zero(src.w);
break;
case Operation::RORm:
src.w = uint16_t((src.w >> 1) | (src.w << 15));
status.carry_flag = src.w & Primitive::top_bit<uint16_t>();
status.overflow_flag = 0;
Primitive::set_neg_zero(src.w, status);
status.set_neg_zero(src.w);
break;
case Operation::ROXLm:
@ -929,7 +914,7 @@ template <
src.w = uint16_t((src.w << 1) | (status.extend_flag ? 0x0001 : 0x0000));
status.extend_flag = status.carry_flag;
status.overflow_flag = 0;
Primitive::set_neg_zero(src.w, status);
status.set_neg_zero(src.w);
break;
case Operation::ROXRm:
@ -937,7 +922,7 @@ template <
src.w = uint16_t((src.w >> 1) | (status.extend_flag ? 0x8000 : 0x0000));
status.extend_flag = status.carry_flag;
status.overflow_flag = 0;
Primitive::set_neg_zero(src.w, status);
status.set_neg_zero(src.w);
break;
case Operation::ASLb: Primitive::shift<Operation::ASLb>(src.l, dest.b, status, flow_controller); break;

12
InstructionSets/M68k/Status.hpp
View File

@ -54,6 +54,18 @@ struct Status {
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 and only this value is non-zero.
/// Sets the negative flag per @c value
template <typename IntT> void set_negative(IntT value) {
constexpr auto top_bit = IntT(1 << ((sizeof(IntT) * 8) - 1));
negative_flag = value & top_bit;
}
/// Sets both the negative and zero flags according to @c value.
template <typename IntT> void set_neg_zero(IntT value) {
zero_result = value;
set_negative(value);
}
/// Gets the current condition codes.
constexpr uint16_t ccr() const {
return