A64/decoder: Use a lookup table instead of doing a linear scan
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0c51313479
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8db4d65587
1 changed files with 26 additions and 6 deletions
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@ -24,14 +24,23 @@ template <typename Visitor>
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using Matcher = Decoder::Matcher<Visitor, u32>;
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template <typename Visitor>
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std::vector<Matcher<Visitor>> GetDecodeTable() {
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std::vector<Matcher<Visitor>> table = {
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using DecodeTable = std::array<std::vector<Matcher<Visitor>>, 0x1000>;
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namespace detail {
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inline size_t ToFastLookupIndex(u32 instruction) {
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return ((instruction >> 10) & 0x00F) | ((instruction >> 18) & 0xFF0);
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}
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} // namespace detail
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template <typename Visitor>
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DecodeTable<Visitor> GetDecodeTable() {
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std::vector<Matcher<Visitor>> list = {
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#define INST(fn, name, bitstring) Decoder::detail::detail<Matcher<Visitor>>::GetMatcher(&Visitor::fn, name, bitstring),
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#include "a64.inc"
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#undef INST
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};
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std::stable_sort(table.begin(), table.end(), [](const auto& matcher1, const auto& matcher2) {
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std::stable_sort(list.begin(), list.end(), [](const auto& matcher1, const auto& matcher2) {
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// If a matcher has more bits in its mask it is more specific, so it should come first.
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return Common::BitCount(matcher1.GetMask()) > Common::BitCount(matcher2.GetMask());
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});
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@ -43,10 +52,20 @@ std::vector<Matcher<Visitor>> GetDecodeTable() {
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"Unallocated SIMD modified immediate",
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};
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std::stable_partition(table.begin(), table.end(), [&](const auto& matcher) {
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std::stable_partition(list.begin(), list.end(), [&](const auto& matcher) {
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return comes_first.count(matcher.GetName()) > 0;
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});
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DecodeTable<Visitor> table{};
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for (size_t i = 0; i < table.size(); ++i) {
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for (auto matcher : list) {
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const auto expect = detail::ToFastLookupIndex(matcher.GetExpected());
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const auto mask = detail::ToFastLookupIndex(matcher.GetMask());
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if ((i & mask) == expect) {
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table[i].push_back(matcher);
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}
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}
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}
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return table;
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}
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@ -56,8 +75,9 @@ std::optional<std::reference_wrapper<const Matcher<Visitor>>> Decode(u32 instruc
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const auto matches_instruction = [instruction](const auto& matcher) { return matcher.Matches(instruction); };
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auto iter = std::find_if(table.begin(), table.end(), matches_instruction);
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return iter != table.end() ? std::optional<std::reference_wrapper<const Matcher<Visitor>>>(*iter) : std::nullopt;
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const auto& subtable = table[detail::ToFastLookupIndex(instruction)];
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auto iter = std::find_if(subtable.begin(), subtable.end(), matches_instruction);
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return iter != subtable.end() ? std::optional<std::reference_wrapper<const Matcher<Visitor>>>(*iter) : std::nullopt;
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}
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} // namespace Dynarmic::A64
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