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Take a swing at PC-as-input.

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This commit is contained in:
Thomas Harte 2024-02-28 09:33:05 -05:00
parent b676153d21
commit d6bf1808f9
2 changed files with 57 additions and 33 deletions
InstructionSets/ARM
Registers.hpp
OSBindings/Mac/Clock SignalTests
ARMDecoderTests.mm

21
InstructionSets/ARM/Registers.hpp

@ -59,24 +59,14 @@ struct Registers {
overflow_flag_ = value;
}
/// @returns The program counter address only, optionally with a post-increment.
template <bool increment>
uint32_t pc() {
const uint32_t result = pc_;
if constexpr (increment) {
pc_ = (pc_ + 4) & ConditionCode::Address;
}
return result;
}
void begin_irq() { interrupt_flags_ |= ConditionCode::IRQDisable; }
void begin_fiq() { interrupt_flags_ |= ConditionCode::FIQDisable; }
/// @returns The full PC + status bits.
uint32_t get() const {
uint32_t status(uint32_t offset) const {
return
uint32_t(mode_) |
pc_ |
((active[15] + offset) & ConditionCode::Address) |
(negative_flag_ & ConditionCode::Negative) |
(zero_result_ ? 0 : ConditionCode::Zero) |
(carry_flag_ ? ConditionCode::Carry : 0) |
@ -84,6 +74,10 @@ struct Registers {
interrupt_flags_;
}
uint32_t pc(uint32_t offset) const {
return (active[15] + offset) & ConditionCode::Address;
}
bool test(Condition condition) {
const auto ne = [&]() -> bool {
return zero_result_;
@ -129,8 +123,9 @@ struct Registers {
}
}
uint32_t active[16]; // TODO: register swaps with mode.
private:
uint32_t pc_ = 0;
Mode mode_ = Mode::Supervisor;
uint32_t zero_result_ = 0;

69
OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm

@ -106,7 +106,7 @@ void shift(ShiftType type, uint32_t &source, uint32_t amount, uint32_t *carry) {
struct Scheduler {
bool should_schedule(Condition condition) {
return status.test(condition);
return registers_.test(condition);
}
template <Flags f> void perform(DataProcessing fields) {
@ -146,10 +146,23 @@ struct Scheduler {
// or Rm.
constexpr DataProcessingFlags flags(f);
auto &destination = registers_[fields.destination()];
const uint32_t operand1 = registers_[fields.operand1()];
const bool shift_by_register = !flags.operand2_is_immediate() && fields.shift_count_is_register();
auto &destination = registers_.active[fields.destination()];
// When R15 appears in either of the Rn or Rs positions it will give the value
// of the PC alone, with the PSR bits replaced by zeroes. ...
//
// If the shift amount is specified in the instruction, the PC will be 8 bytes ahead.
// If a register is used to specify the shift amount, the PC will be ... 12 bytes ahead
// when used as Rn or Rm.
const uint32_t operand1 =
(fields.operand1() == 15) ?
registers_.pc(shift_by_register ? 12 : 8) :
registers_.active[fields.operand1()];
uint32_t operand2;
uint32_t rotate_carry = status.c();
uint32_t rotate_carry = registers_.c();
// Populate carry from the shift only if it'll be used.
constexpr bool shift_sets_carry = is_logical(flags.operation()) && flags.set_condition_codes();
@ -163,12 +176,30 @@ struct Scheduler {
} else {
uint32_t shift_amount;
if(fields.shift_count_is_register()) {
shift_amount = registers_[fields.shift_register()];
// When R15 appears in either of the Rn or Rs positions it will give the value
// of the PC alone, with the PSR bits replaced by zeroes. ...
//
// If a register is used to specify the shift amount, the
// PC will be 8 bytes ahead when used as Rs.
shift_amount =
fields.shift_register() == 15 ?
registers_.pc(8) :
registers_.active[fields.shift_register()];
} else {
shift_amount = fields.shift_amount();
}
operand2 = registers_[fields.operand2()];
// When R15 appears in the Rm position it will give the value of the PC together
// with the PSR flags to the barrel shifter. ...
//
// If the shift amount is specified in the instruction, the PC will be 8 bytes ahead.
// If a register is used to specify the shift amount, the PC will be ... 12 bytes ahead
// when used as Rn or Rm.
if(fields.operand2() == 15) {
operand2 = registers_.status(shift_by_register ? 12 : 8);
} else {
operand2 = registers_.active[fields.operand2()];
}
shift<shift_sets_carry>(fields.shift_type(), operand2, shift_amount, &rotate_carry);
}
@ -193,12 +224,12 @@ struct Scheduler {
conditions = operand1 + operand2;
if constexpr (flags.operation() == DataProcessingOperation::ADC) {
conditions += status.c();
conditions += registers_.c();
}
if constexpr (flags.set_condition_codes()) {
status.set_c(Numeric::carried_out<true, 31>(operand1, operand2, conditions));
status.set_v(Numeric::overflow<true>(operand1, operand2, conditions));
registers_.set_c(Numeric::carried_out<true, 31>(operand1, operand2, conditions));
registers_.set_v(Numeric::overflow<true>(operand1, operand2, conditions));
}
if constexpr (!is_comparison(flags.operation())) {
@ -212,12 +243,12 @@ struct Scheduler {
conditions = operand1 - operand2;
if constexpr (flags.operation() == DataProcessingOperation::SBC) {
conditions -= status.c();
conditions -= registers_.c();
}
if constexpr (flags.set_condition_codes()) {
status.set_c(Numeric::carried_out<false, 31>(operand1, operand2, conditions));
status.set_v(Numeric::overflow<false>(operand1, operand2, conditions));
registers_.set_c(Numeric::carried_out<false, 31>(operand1, operand2, conditions));
registers_.set_v(Numeric::overflow<false>(operand1, operand2, conditions));
}
if constexpr (!is_comparison(flags.operation())) {
@ -230,12 +261,12 @@ struct Scheduler {
conditions = operand2 - operand1;
if constexpr (flags.operation() == DataProcessingOperation::RSC) {
conditions -= status.c();
conditions -= registers_.c();
}
if constexpr (flags.set_condition_codes()) {
status.set_c(Numeric::carried_out<false, 31>(operand2, operand1, conditions));
status.set_v(Numeric::overflow<false>(operand2, operand1, conditions));
registers_.set_c(Numeric::carried_out<false, 31>(operand2, operand1, conditions));
registers_.set_v(Numeric::overflow<false>(operand2, operand1, conditions));
}
destination = conditions;
@ -244,12 +275,12 @@ struct Scheduler {
// Set N and Z in a unified way.
if constexpr (flags.set_condition_codes()) {
status.set_nz(conditions);
registers_.set_nz(conditions);
}
// Set C from the barrel shifter if applicable.
if constexpr (shift_sets_carry) {
status.set_c(rotate_carry);
registers_.set_c(rotate_carry);
}
// TODO: If register 15 was in use as a destination, write back and clean up.
@ -270,9 +301,7 @@ struct Scheduler {
void unknown(uint32_t) {}
private:
Registers status;
uint32_t registers_[16]; // TODO: register swaps with mode.
Registers registers_;
};
}