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Switch to actual mnenomics, temporarily(?) shrink table.

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This commit is contained in:
Thomas Harte 2024-02-17 15:41:57 -05:00
parent 4c53414cc3
commit 9a74ab6a8e
2 changed files with 27 additions and 21 deletions
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40
InstructionSets/ARM/Decoder.hpp
View File

@ -16,25 +16,25 @@
namespace InstructionSet::ARM {
template <Model model>
constexpr std::array<Operation, 256> operation_table() {
std::array<Operation, 256> result{};
for(int c = 0; c < 256; c++) {
const uint32_t opcode = c << 20;
using OperationTable = std::array<Operation, 128>;
template <Model model>
constexpr OperationTable<model> operation_table() {
OperationTable<model> result{};
for(std::size_t c = 0; c < result.size(); c++) {
const auto opcode = static_cast<uint32_t>(c << 21);
// Cf. the ARM2 datasheet, p45. Tests below match its ordering
// other than that 'undefined' is the fallthrough case.
if(((opcode >> 26) & 0b11) == 0b00) {
result[c] = Operation((c >> 21) & 0xf);
continue;
}
if(((opcode >> 25) & 0b111) == 0b101) {
result[c] =
((opcode >> 24) & 1) ? Operation::BranchWithLink : Operation::Branch;
continue;
}
if(((opcode >> 22) & 0b111'111) == 0b000'000) {
result[c] =
((opcode >> 21) & 1) ? Operation::MultiplyWithAccumulate : Operation::Multiply;
((opcode >> 21) & 1) ? Operation::MLA : Operation::MUL;
continue;
}
@ -48,8 +48,14 @@ constexpr std::array<Operation, 256> operation_table() {
continue;
}
if(((opcode >> 24) & 0b1111) == 0b1111) {
result[c] = Operation::SoftwareInterrupt;
if(((opcode >> 25) & 0b111) == 0b101) {
result[c] =
((opcode >> 24) & 1) ? Operation::BL : Operation::B;
continue;
}
if(((opcode >> 25) & 0b111) == 0b110) {
result[c] = Operation::CoprocessorDataTransfer;
continue;
}
@ -58,8 +64,8 @@ constexpr std::array<Operation, 256> operation_table() {
continue;
}
if(((opcode >> 25) & 0b111) == 0b110) {
result[c] = Operation::CoprocessorDataTransfer;
if(((opcode >> 24) & 0b1111) == 0b1111) {
result[c] = Operation::SoftwareInterrupt;
continue;
}
@ -70,8 +76,8 @@ constexpr std::array<Operation, 256> operation_table() {
template <Model model>
constexpr Operation operation(uint32_t opcode) {
constexpr std::array<Operation, 256> operations = operation_table<model>();
return operations[(opcode >> 20) & 0xff];
constexpr OperationTable<model> operations = operation_table<model>();
return operations[(opcode >> 21) & 0x7f];
}
}

8
InstructionSets/ARM/Operation.hpp
View File

@ -16,11 +16,11 @@ enum class Operation {
TST, TEQ, CMP, CMN,
ORR, MOV, BIC, MVN,
Branch, BranchWithLink,
Multiply, MultiplyWithAccumulate,
B, BL,
MUL, MLA,
SingleDataTransfer,
BlockDataTransfer,
SingleDataTransfer, // TODO: LDR or STR?
BlockDataTransfer, // TODO: LDM or STM?
SoftwareInterrupt,
CoprocessorDataOperationOrRegisterTransfer,