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Edge towards single data transfer.

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This commit is contained in:
Thomas Harte 2024-02-29 10:02:57 -05:00
parent 0de8240238
commit 0b287c55d5
1 changed files with 86 additions and 28 deletions
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114
OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm
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@ -22,6 +22,44 @@ struct Scheduler {
return registers_.test(condition);
}
template <bool allow_register, bool set_carry, typename FieldsT>
uint32_t decode_shift(FieldsT fields, uint32_t &rotate_carry, uint32_t pc_offset) {
uint32_t shift_amount;
if constexpr (allow_register) {
if(fields.shift_count_is_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();
}
} else {
shift_amount = fields.shift_amount();
}
// "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."
uint32_t operand2;
if(fields.operand2() == 15) {
operand2 = registers_.pc_status(pc_offset);
} else {
operand2 = registers_.active[fields.operand2()];
}
shift<set_carry>(fields.shift_type(), operand2, shift_amount, rotate_carry);
return operand2;
}
template <Flags f> void perform(DataProcessing fields) {
constexpr DataProcessingFlags flags(f);
const bool shift_by_register = !flags.operand2_is_immediate() && fields.shift_count_is_register();
@ -54,33 +92,7 @@ struct Scheduler {
shift<ShiftType::RotateRight, shift_sets_carry>(operand2, fields.rotate(), rotate_carry);
}
} else {
uint32_t shift_amount;
if(fields.shift_count_is_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();
}
// "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_.pc_status(shift_by_register ? 12 : 8);
} else {
operand2 = registers_.active[fields.operand2()];
}
shift<shift_sets_carry>(fields.shift_type(), operand2, shift_amount, rotate_carry);
operand2 = decode_shift<true, shift_sets_carry>(fields, rotate_carry, shift_by_register ? 12 : 8);
}
// Perform the data processing operation.
@ -223,7 +235,53 @@ struct Scheduler {
registers_.set_pc(registers_.pc(8) + branch.offset());
}
template <Flags> void perform(SingleDataTransfer) {}
template <Flags f> void perform(SingleDataTransfer transfer) {
constexpr SingleDataTransferFlags flags(f);
// Calculate offset.
uint32_t offset;
if constexpr (flags.offset_is_immediate()) {
offset = transfer.immediate();
} else {
// The 8 shift control bits are described in 6.2.3, but
// the register specified shift amounts are not available
// in this instruction class.
uint32_t carry = registers_.c();
offset = decode_shift<false, false>(transfer, carry, 8);
}
// Obtain base address.
uint32_t address =
transfer.base() == 15 ?
registers_.pc(8) :
registers_.active[transfer.base()];
// Determine what the address will be after offsetting.
uint32_t offsetted_address = address;
if constexpr (flags.add_offset()) {
offsetted_address += offset;
} else {
offsetted_address -= offset;
}
// If preindexing, apply now.
if constexpr (flags.pre_index()) {
address = offsetted_address;
}
// TODO: attempt access, possibly abort.
// Cf. transfer_byte()
// If either postindexing or else with writeback, update base.
if constexpr (!flags.pre_index() || flags.write_back_address()) {
// TODO: check for R15.
if(transfer.base() == 15) {
registers_.set_pc(offsetted_address);
} else {
registers_.active[transfer.base()] = offsetted_address;
}
}
}
template <Flags> void perform(BlockDataTransfer) {}
void software_interrupt() {