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Resolve for work factored out.

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This commit is contained in:
Thomas Harte 2023-10-25 22:21:23 -04:00
parent 29a921f764
commit de230fb6be
1 changed files with 22 additions and 48 deletions
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70
InstructionSets/M68k/Implementation/PerformImplementation.hpp
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@ -9,6 +9,7 @@
#ifndef InstructionSets_M68k_PerformImplementation_h
#define InstructionSets_M68k_PerformImplementation_h
#include "../../../Numeric/Carry.hpp"
#include "../ExceptionVectors.hpp"
#include <algorithm>
@ -25,28 +26,6 @@ inline int32_t s_extend16(uint16_t x) { return int32_t(int16_t(x)); }
namespace Primitive {
/// @returns An int of type @c IntT with only the most-significant bit set.
template <typename IntT> constexpr IntT top_bit() {
static_assert(!std::numeric_limits<IntT>::is_signed);
constexpr IntT max = std::numeric_limits<IntT>::max();
return max - (max >> 1);
}
/// @returns An int with the top bit indicating whether overflow occurred when @c source and @c destination
/// were either added (if @c is_add is true) or subtracted (if @c is_add is false) and the result was @c result.
/// All other bits will be clear.
template <bool is_add, typename IntT>
static Status::FlagT overflow(IntT source, IntT destination, IntT result) {
const IntT output_changed = result ^ destination;
const IntT input_differed = source ^ destination;
if constexpr (is_add) {
return top_bit<IntT>() & output_changed & ~input_differed;
} else {
return top_bit<IntT>() & output_changed & input_differed;
}
}
/// Performs an add or subtract (as per @c is_add) between @c source and @c destination,
/// updating @c status. @c is_extend indicates whether this is an extend operation (e.g. ADDX)
/// or a plain one (e.g. ADD).
@ -81,7 +60,7 @@ static void add_sub(IntT source, IntT &destination, Status &status) {
status.zero_result = Status::FlagT(result);
}
status.set_negative(result);
status.overflow_flag = overflow<is_add>(source, destination, result);
status.overflow_flag = Numeric::overflow<is_add>(destination, source, result);
destination = result;
}
@ -143,7 +122,7 @@ void compare(IntT source, IntT destination, Status &status) {
const IntT result = destination - source;
status.carry_flag = result > destination;
status.set_neg_zero(result);
status.overflow_flag = Primitive::overflow<false>(source, destination, result);
status.overflow_flag = Numeric::overflow<false>(destination, source, result);
}
/// @returns the name of the bit to be used as a mask for BCLR, BCHG, BSET or BTST for
@ -293,7 +272,7 @@ template <bool is_extend, typename IntT> void negative(IntT &source, Status &sta
}
status.extend_flag = status.carry_flag = result; // i.e. any value other than 0 will result in carry.
status.set_negative(result);
status.overflow_flag = Primitive::overflow<false>(source, IntT(0), result);
status.overflow_flag = Numeric::overflow<false>(IntT(0), source, result);
source = result;
}
@ -311,11 +290,6 @@ template <typename IntT, typename FlowController> int shift_count(uint8_t source
return count;
}
/// @returns The number of bits in @c IntT.
template <typename IntT> constexpr int bit_size() {
return sizeof(IntT) * 8;
}
/// 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(
@ -325,7 +299,7 @@ template <Operation operation, typename IntT, typename FlowController> void shif
operation == Operation::LSRb || operation == Operation::LSRw || operation == Operation::LSRl
);
constexpr auto size = bit_size<IntT>();
constexpr auto size = Numeric::bit_size<IntT>();
const auto shift = shift_count<IntT>(uint8_t(source), flow_controller);
if(!shift) {
@ -355,7 +329,7 @@ template <Operation operation, typename IntT, typename FlowController> void shif
if(shift > size) {
status.carry_flag = status.extend_flag = 0;
} else {
status.carry_flag = status.extend_flag = (destination << (shift - 1)) & top_bit<IntT>();
status.carry_flag = status.extend_flag = (destination << (shift - 1)) & Numeric::top_bit<IntT>();
}
if(type == Type::LSL) {
@ -370,7 +344,7 @@ template <Operation operation, typename IntT, typename FlowController> void shif
// For a shift of n places, overflow will be set if the top n+1 bits were not
// all the same value.
const auto affected_bits = IntT(
~((top_bit<IntT>() >> shift) - 1)
~((Numeric::top_bit<IntT>() >> shift) - 1)
); // e.g. shift = 1 => ~((0x80 >> 1) - 1) = ~(0x40 - 1) = ~0x3f = 0xc0, i.e. if shift is
// 1 then the top two bits are relevant to whether there was overflow. If they have the
// same value, i.e. are both 0 or are both 1, then there wasn't. Otherwise there was.
@ -396,7 +370,7 @@ template <Operation operation, typename IntT, typename FlowController> void shif
const IntT sign_word =
type == Type::LSR ?
0 : (destination & top_bit<IntT>() ? IntT(~0) : 0);
0 : (destination & Numeric::top_bit<IntT>() ? IntT(~0) : 0);
if(shift >= size) {
destination = sign_word;
@ -417,7 +391,7 @@ template <Operation operation, typename IntT, typename FlowController> void rota
operation == Operation::RORb || operation == Operation::RORw || operation == Operation::RORl
);
constexpr auto size = bit_size<IntT>();
constexpr auto size = Numeric::bit_size<IntT>();
auto shift = shift_count<IntT>(uint8_t(source), flow_controller);
if(!shift) {
@ -442,7 +416,7 @@ template <Operation operation, typename IntT, typename FlowController> void rota
(destination << (size - shift))
);
}
status.carry_flag = Status::FlagT(destination & top_bit<IntT>());
status.carry_flag = Status::FlagT(destination & Numeric::top_bit<IntT>());
break;
}
}
@ -458,7 +432,7 @@ template <Operation operation, typename IntT, typename FlowController> void rox(
operation == Operation::ROXRb || operation == Operation::ROXRw || operation == Operation::ROXRl
);
constexpr auto size = bit_size<IntT>();
constexpr auto size = Numeric::bit_size<IntT>();
auto shift = shift_count<IntT>(uint8_t(source), flow_controller) % (size + 1);
if(!shift) {
@ -469,9 +443,9 @@ template <Operation operation, typename IntT, typename FlowController> void rox(
case Operation::ROXLb: case Operation::ROXLw: case Operation::ROXLl:
status.carry_flag = Status::FlagT((destination >> (size - shift)) & 1);
if(shift == bit_size<IntT>()) {
if(shift == Numeric::bit_size<IntT>()) {
destination = IntT(
(status.extend_flag ? top_bit<IntT>() : 0) |
(status.extend_flag ? Numeric::top_bit<IntT>() : 0) |
(destination >> 1)
);
} else if(shift == 1) {
@ -491,7 +465,7 @@ template <Operation operation, typename IntT, typename FlowController> void rox(
case Operation::ROXRb: case Operation::ROXRw: case Operation::ROXRl:
status.carry_flag = Status::FlagT(destination & (1 << (shift - 1)));
if(shift == bit_size<IntT>()) {
if(shift == Numeric::bit_size<IntT>()) {
destination = IntT(
(status.extend_flag ? 1 : 0) |
(destination << 1)
@ -499,12 +473,12 @@ template <Operation operation, typename IntT, typename FlowController> void rox(
} else if(shift == 1) {
destination = IntT(
(destination >> 1) |
(status.extend_flag ? top_bit<IntT>() : 0)
(status.extend_flag ? Numeric::top_bit<IntT>() : 0)
);
} else {
destination = IntT(
(destination >> shift) |
((status.extend_flag ? top_bit<IntT>() : 0) >> (shift - 1)) |
((status.extend_flag ? Numeric::top_bit<IntT>() : 0) >> (shift - 1)) |
(destination << (size + 1 - shift))
);
}
@ -882,14 +856,14 @@ template <
Shifts and rotates.
*/
case Operation::ASLm:
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>();
status.extend_flag = status.carry_flag = src.w & Numeric::top_bit<uint16_t>();
status.overflow_flag = (src.w ^ (src.w << 1)) & Numeric::top_bit<uint16_t>();
src.w <<= 1;
status.set_neg_zero(src.w);
break;
case Operation::LSLm:
status.extend_flag = status.carry_flag = src.w & Primitive::top_bit<uint16_t>();
status.extend_flag = status.carry_flag = src.w & Numeric::top_bit<uint16_t>();
status.overflow_flag = 0;
src.w <<= 1;
status.set_neg_zero(src.w);
@ -898,7 +872,7 @@ template <
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);
src.w = (src.w & Numeric::top_bit<uint16_t>()) | (src.w >> 1);
status.set_neg_zero(src.w);
break;
@ -918,13 +892,13 @@ template <
case Operation::RORm:
src.w = uint16_t((src.w >> 1) | (src.w << 15));
status.carry_flag = src.w & Primitive::top_bit<uint16_t>();
status.carry_flag = src.w & Numeric::top_bit<uint16_t>();
status.overflow_flag = 0;
status.set_neg_zero(src.w);
break;
case Operation::ROXLm:
status.carry_flag = src.w & Primitive::top_bit<uint16_t>();
status.carry_flag = src.w & Numeric::top_bit<uint16_t>();
src.w = uint16_t((src.w << 1) | (status.extend_flag ? 0x0001 : 0x0000));
status.extend_flag = status.carry_flag;
status.overflow_flag = 0;