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Switch to intended compact version of Instruction.
This commit is contained in:
Thomas Harte
parent
6dc9973754
commit
673ffc50da
@ -830,6 +830,7 @@ std::pair<int, typename Decoder<model>::InstructionT> Decoder<model>::decode(con
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if(expects_sib && (source_ == Source::Indirect | destination_ == Source::Indirect)) {
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phase_ = Phase::ScaleIndexBase;
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// TODO: test for IndirectNoBase.
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} else {
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phase_ = (displacement_size_ != DataSize::None || operand_size_ != DataSize::None) ? Phase::DisplacementOrOperand : Phase::ReadyToPost;
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}
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@ -434,6 +434,23 @@ enum class Source: uint8_t {
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IndirectNoBase = Indirect - 1,
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};
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constexpr Source default_data_segment([[maybe_unused]] Operation operation) {
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// TODO: is this really necessary, or can ::DS always be default?
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// i.e. can the stack operations actually take a segment override?
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// If not then the actual implementations just won't ask about a segment.
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// constexpr std::set<Operation> stack_ops = {
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//
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// };
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//
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// if(
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// operation == Operation::PUSH ||
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// operation == Operation::PUSHF ||
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// operation == Operation::POP) {
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// return Source::SS;
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// }
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return Source::DS;
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}
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enum class Repetition: uint8_t {
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None, RepE, RepNE
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};
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@ -497,6 +514,10 @@ class ScaleIndexBase {
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);
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}
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operator uint8_t() const {
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return sib_;
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}
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private:
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// Data is stored directly as an 80386 SIB byte.
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uint8_t sib_ = 0;
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@ -571,109 +592,147 @@ class DataPointer {
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template<bool is_32bit> class Instruction {
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public:
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Operation operation = Operation::Invalid;
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const Operation operation = Operation::Invalid;
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bool operator ==(const Instruction &rhs) const {
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return
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repetition_size_ == rhs.repetition_size_ &&
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sources_ == rhs.sources_ &&
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displacement_ == rhs.displacement_ &&
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operand_ == rhs.operand_ &&
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sib_ == rhs.sib_ &&
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length_ == rhs.length_;
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bool operator ==(const Instruction<is_32bit> &rhs) const {
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if( operation != rhs.operation ||
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mem_exts_source_ != rhs.mem_exts_source_ ||
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source_data_dest_sib_ != rhs.source_data_dest_sib_) {
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return false;
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}
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// Have already established above that this and RHS have the
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// same extensions, if any.
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const int extension_count = has_length_extension() + has_displacement() + has_operand();
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for(int c = 0; c < extension_count; c++) {
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if(extensions_[c] != rhs.extensions_[c]) return false;
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}
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return true;
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}
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using DisplacementT = typename std::conditional<is_32bit, int32_t, int16_t>::type;
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using ImmediateT = typename std::conditional<is_32bit, uint32_t, uint16_t>::type;
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using AddressT = ImmediateT;
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/* Note to self — current thinking is:
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First 32bits:
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5 bits source;
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5 bits dest;
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5 bits partial SIB, combined with three low bits of source or dest if indirect;
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8 bits operation;
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4 bits original instruction size;
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2 bits data size;
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1 bit memory size;
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2 bits extension flags.
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Extensions (16 or 32 bit, depending on templated size):
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1) reptition + segment override + lock + original instruction size (= 10 bits);
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2) displacement;
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3) immediate operand.
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Presence or absence of extensions is dictated by:
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* instruction size = 0 => the repetition, etc extension (including the real extension size); and
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* the extension flags for displacement and/or immediate.
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Therefore an instruction's footprint is:
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* 4–8 bytes (16-bit processors);
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* 4–12 bytes (32-bit processors).
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I'll then implement a collection suited to packing these things based on their
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packing_size(), and later iterating them.
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To verify: the 8086 allows unlimited-length instructions (which I'll probably handle by
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generating length-15 NOPs and not resetting parser state), the 80386 limits them to
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15 bytes, but what do the processors in between do?
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*/
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private:
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// b0, b1: a Repetition;
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// b2+: operation size.
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uint8_t repetition_size_ = 0;
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// Packing and encoding of fields is admittedly somewhat convoluted; what this
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// achieves is that instructions will be sized:
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//
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// four bytes + up to three extension words
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// (two bytes for 16-bit instructions, four for 32)
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//
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// Two of the extension words are used to retain an operand and displacement
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// if the instruction has those. The other can store sizes greater than 15
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// bytes (for earlier processors), plus any repetition, segment override or
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// repetition prefixes.
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// b0–b5: source;
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// b6–b11: destination;
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// b12–b14: segment override;
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// b15: lock.
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uint16_t sources_ = 0;
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// b7: address size;
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// b6: has displacement;
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// b5: has operand;
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// [b4, b0]: source.
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const uint8_t mem_exts_source_ = 0xff;
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// Unpackable fields.
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DisplacementT displacement_ = 0;
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ImmediateT operand_ = 0; // ... or used to store a segment for far operations.
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bool has_displacement() const {
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return mem_exts_source_ & (1 << 6);
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}
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bool has_operand() const {
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return mem_exts_source_ & (1 << 5);
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}
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// Fields yet to be properly incorporated...
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ScaleIndexBase sib_;
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AddressSize address_size_ = AddressSize::b16;
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int length_ = 0;
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// [b15, b14]: data size;
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// [b13, b10]: source length (0 => has length extension);
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// [b9, b5]: top five of SIB;
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// [b4, b0]: dest.
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const uint16_t source_data_dest_sib_ = 0xffff;
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bool has_length_extension() const {
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return !((source_data_dest_sib_ >> 10) & 15);
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}
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// {length extension}, {operand}, {displacement}.
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// If length extension is present then:
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//
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// [b15, b6]: source length;
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// [b5, b4]: repetition;
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// [b3, b1]: segment override;
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// b0: lock.
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ImmediateT extensions_[3];
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public:
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/// @returns The number of bytes used for meaningful content within this class. A receiver must use at least @c sizeof(Instruction) bytes
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/// to store an @c Instruction but is permitted to reuse the trailing sizeof(Instruction) - packing_size() for any purpose it likes. Teleologically,
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/// this allows a denser packing of instructions into containers.
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size_t packing_size() const { return sizeof(*this); /* TODO */ }
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size_t packing_size() const {
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return
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offsetof(Instruction<is_32bit>, extensions) +
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(has_displacement() + has_operand() + has_length_extension()) * sizeof(ImmediateT);
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}
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DataPointer source() const { return DataPointer(Source(sources_ & 0x3f), sib_); }
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DataPointer destination() const { return DataPointer(Source((sources_ >> 6) & 0x3f), sib_); }
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bool lock() const { return sources_ & 0x8000; }
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private:
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// A lookup table to help with stripping parts of the SIB that have been
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// hidden within the source/destination fields.
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static constexpr uint8_t sib_masks[] = {
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0x1f, 0x1f, 0x1f, 0x18
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};
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public:
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DataPointer source() const {
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return DataPointer(
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Source(mem_exts_source_ & sib_masks[(mem_exts_source_ >> 3) & 3]),
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((source_data_dest_sib_ >> 2) & 0xf8) | (mem_exts_source_ & 0x07)
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);
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}
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DataPointer destination() const {
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return DataPointer(
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Source(source_data_dest_sib_ & sib_masks[(source_data_dest_sib_ >> 3) & 3]),
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((source_data_dest_sib_ >> 2) & 0xf8) | (source_data_dest_sib_ & 0x07)
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);
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}
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bool lock() const {
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return has_length_extension() && extensions_[0]&1;
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}
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AddressSize address_size() const {
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return AddressSize(address_size_);
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return AddressSize(mem_exts_source_ >> 7);
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}
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Source data_segment() const {
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const auto segment_override = Source(
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if(!has_length_extension()) return default_data_segment(operation);
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return Source(
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int(Source::ES) +
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((sources_ >> 12) & 7)
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((extensions_[0] >> 1) & 7)
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);
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if(segment_override != Source::None) return segment_override;
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// TODO: default source should be SS for anything touching the stack.
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return Source::DS;
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}
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Repetition repetition() const { return Repetition(repetition_size_ & 3); }
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DataSize operation_size() const { return DataSize(repetition_size_ >> 2); }
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Repetition repetition() const {
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if(!has_length_extension()) return Repetition::None;
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return Repetition((extensions_[0] >> 4) & 3);
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}
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DataSize operation_size() const {
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return DataSize(source_data_dest_sib_ >> 14);
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}
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uint16_t segment() const { return uint16_t(operand_); }
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DisplacementT offset() const { return displacement_; }
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int length() const {
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const int short_length = (source_data_dest_sib_ >> 10) & 15;
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if(short_length) return short_length;
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return extensions_[0] >> 6;
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}
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DisplacementT displacement() const { return displacement_; }
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ImmediateT operand() const { return operand_; }
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ImmediateT operand() const {
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const ImmediateT ops[] = {0, extensions_[has_length_extension()]};
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return ops[has_operand()];
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}
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DisplacementT displacement() const {
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return DisplacementT(offset());
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}
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int length() const { return length_; }
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uint16_t segment() const {
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return uint16_t(operand());
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}
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ImmediateT offset() const {
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const ImmediateT offsets[] = {0, extensions_[has_length_extension() + has_operand()]};
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return offsets[has_displacement()];
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}
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Instruction() noexcept {}
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Instruction(
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@ -685,27 +744,46 @@ template<bool is_32bit> class Instruction {
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AddressSize address_size,
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Source segment_override,
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Repetition repetition,
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DataSize operation_size,
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DataSize data_size,
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DisplacementT displacement,
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ImmediateT operand,
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int length) noexcept :
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operation(operation),
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repetition_size_(uint8_t((int(operation_size) << 2) | int(repetition))),
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sources_(uint16_t(
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mem_exts_source_(uint8_t(
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(int(address_size) << 7) |
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(displacement ? 0x40 : 0x00) |
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(operand ? 0x20 : 0x00) |
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int(source) |
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(int(destination) << 6) |
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((int(segment_override) & 7) << 12) |
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(int(lock) << 15)
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(source == Source::Indirect ? (uint8_t(sib) & 7) : 0)
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)),
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displacement_(displacement),
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operand_(operand),
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sib_(sib),
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address_size_(address_size),
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length_(length) {}
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source_data_dest_sib_(uint16_t(
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(int(data_size) << 14) |
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((
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(lock || (segment_override != Source::None) || (length > 15) || (repetition != Repetition::None))
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) ? 0 : (length << 10)) |
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((uint8_t(sib) & 0xf8) << 2) |
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int(destination) |
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(destination == Source::Indirect ? (uint8_t(sib) & 7) : 0)
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)) {
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int extension = 0;
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if(has_length_extension()) {
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if(segment_override == Source::None) segment_override = default_data_segment(operation);
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extensions_[extension] = ImmediateT(
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(length << 6) | (int(repetition) << 4) | ((int(segment_override) & 7) << 1) | int(lock)
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);
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++extension;
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}
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if(has_operand()) {
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extensions_[extension] = operand;
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++extension;
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}
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extensions_[extension] = ImmediateT(displacement);
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}
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};
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// TODO: repack.
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//static_assert(sizeof(Instruction) <= 8);
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static_assert(sizeof(Instruction<true>) <= 16);
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static_assert(sizeof(Instruction<false>) <= 10);
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}
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}
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@ -18,14 +18,6 @@ using namespace InstructionSet::x86;
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@implementation x86DataPointerTests
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//- (InstructionSet::x86::Instruction<false>)instruction16WithSourceDataPointer:(DataPointer)pointer {
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// return x86::Instruction<false>{
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// InstructionSet::x86::Operation::AAA,
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// S
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// };
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//}
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- (void)test16bitSize1 {
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const DataPointer indirectPointer(
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Source::eAX, Source::eDI, 0
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@ -539,4 +539,22 @@ std::vector<typename InstructionSet::x86::Decoder<model>::InstructionT> decode(c
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test(instructions[63], Operation::JPCX, 0, 0xd4 - 0x9d);
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}
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- (void)testSourceSIB1 {
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const auto instructions = decode<Model::i80386>({
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0x62, 0x90, 0x90, 0xdf, 0xcd, 0xf9
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}, true);
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XCTAssertEqual(instructions.size(), 1);
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test(instructions[0], DataSize::DWord, Operation::BOUND, ScaleIndexBase(Source::eAX), Source::eDX, 0, -0x6322070);
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}
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- (void)testSourceSIB2 {
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const auto instructions = decode<Model::i80386>({
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0x81, 0x47, 0xbe, 0xa9, 0x3a, 0x68, 0x9f
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}, true);
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XCTAssertEqual(instructions.size(), 1);
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test(instructions[0], DataSize::DWord, Operation::ADD, Source::Immediate, ScaleIndexBase(Source::eDI), 0x9f683aa9, -0x42);
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}
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@end
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