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Reformulate NOT in terms of EOR, and clean up elsewhere.

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This commit is contained in:
Thomas Harte 2022-10-18 12:17:55 -04:00
parent 5560a0ed39
commit b31b4a5d10
1 changed files with 11 additions and 42 deletions
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53
InstructionSets/M68k/Implementation/PerformImplementation.hpp
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@ -11,6 +11,7 @@
#include "../ExceptionVectors.hpp"
#include <algorithm>
#include <cassert>
#include <cmath>
@ -810,7 +811,6 @@ template <
LINK and UNLINK help with stack frames, allowing a certain
amount of stack space to be allocated or deallocated.
*/
case Operation::LINKw:
flow_controller.link(instruction, uint32_t(int16_t(dest.w)));
break;
@ -820,10 +820,8 @@ template <
break;
/*
TAS: sets zero and negative depending on the current value of the destination,
and sets the high bit, using a specialised atomic bus cycle.
TAS: requiring a specialised bus cycle, just kick this out to the flow controller.
*/
case Operation::TAS:
flow_controller.tas(instruction, src.l);
break;
@ -844,27 +842,9 @@ template <
case Operation::EORw: Primitive::bitwise<Operation::EORw>(src.w, dest.w, status); break;
case Operation::EORl: Primitive::bitwise<Operation::EORl>(src.l, dest.l, status); break;
// NOTs: take the logical inverse, affecting the negative and zero flags.
case Operation::NOTb:
src.b ^= 0xff;
status.zero_result = src.b;
status.negative_flag = status.zero_result & 0x80;
status.overflow_flag = status.carry_flag = 0;
break;
case Operation::NOTw:
src.w ^= 0xffff;
status.zero_result = src.w;
status.negative_flag = status.zero_result & 0x8000;
status.overflow_flag = status.carry_flag = 0;
break;
case Operation::NOTl:
src.l ^= 0xffffffff;
status.zero_result = src.l;
status.negative_flag = status.zero_result & 0x80000000;
status.overflow_flag = status.carry_flag = 0;
break;
case Operation::NOTb: Primitive::bitwise<Operation::EORb>(uint8_t(~0), src.b, status); break;
case Operation::NOTw: Primitive::bitwise<Operation::EORw>(uint16_t(~0), src.w, status); break;
case Operation::NOTl: Primitive::bitwise<Operation::EORl>(uint32_t(~0), src.l, status); break;
/*
SBCD subtracts the lowest byte of the source from that of the destination using
@ -892,12 +872,10 @@ template <
case Operation::SWAP: {
uint16_t *const words = reinterpret_cast<uint16_t *>(&src.l);
const auto temporary = words[0];
words[0] = words[1];
words[1] = temporary;
std::swap(words[0], words[1]);
status.zero_result = src.l;
status.negative_flag = temporary & 0x8000;
status.negative_flag = src.l & Primitive::top_bit<uint32_t>();
status.overflow_flag = status.carry_flag = 0;
} break;
@ -1019,24 +997,15 @@ template <
break;
/*
RTE and RTR share an implementation.
RTE, RTR and RTS defer to the flow controller.
*/
case Operation::RTR:
flow_controller.rtr();
break;
case Operation::RTE:
flow_controller.rte();
break;
case Operation::RTS:
flow_controller.rts();
break;
case Operation::RTR: flow_controller.rtr(); break;
case Operation::RTE: flow_controller.rte(); break;
case Operation::RTS: flow_controller.rts(); break;
/*
TSTs: compare to zero.
*/
case Operation::TSTb: Primitive::test(src.b, status); break;
case Operation::TSTw: Primitive::test(src.w, status); break;
case Operation::TSTl: Primitive::test(src.l, status); break;