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Dump notes on intended Instruction layout, add memory size flag.

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This commit is contained in:
Thomas Harte 2022-02-21 15:48:58 -05:00
parent 159e869fe6
commit b968a662d3
3 changed files with 37 additions and 1 deletions
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1
InstructionSets/x86/Decoder.cpp
View File

@ -696,6 +696,7 @@ std::pair<int, typename Decoder<model>::InstructionT> Decoder<model>::decode(con
destination_,
sib_,
lock_,
memory_size_,
segment_override_,
repetition_,
Size(operation_size_),

2
InstructionSets/x86/Decoder.hpp
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@ -154,6 +154,7 @@ template <Model model> class Decoder {
// Prefix capture fields.
Repetition repetition_ = Repetition::None;
bool lock_ = false;
bool memory_size_ = false;
Source segment_override_ = Source::None;
/// Resets size capture and all fields with default values.
@ -162,6 +163,7 @@ template <Model model> class Decoder {
displacement_size_ = operand_size_ = 0;
displacement_ = operand_ = 0;
lock_ = false;
memory_size_ = false;
segment_override_ = Source::None;
repetition_ = Repetition::None;
phase_ = Phase::Instruction;

35
InstructionSets/x86/Instruction.hpp
View File

@ -432,6 +432,35 @@ template<bool is_32bit> class Instruction {
using DisplacementT = typename std::conditional<is_32bit, int32_t, int16_t>::type;
using ImmediateT = typename std::conditional<is_32bit, uint32_t, uint16_t>::type;
/* Note to self — current thinking is:
First 32bits:
5 bits source;
5 bits dest;
5 bits partial SIB, combined with three low bits of source or dest if indirect;
8 bits operation;
4 bits original instruction size;
2 bits data size;
3 bits extension flags.
Extensions (16 or 32 bit, depending on templated size):
1) reptition + segment override + lock + memory size toggle (= 7 bits);
2) displacement;
3) immediate operand.
Presence or absence of extensions is dictated by the extention flags.
Therefore an instruction's footprint is:
* 4–8 bytes (16-bit processors);
* 4–12 bytes (32-bit processors).
I'll then implement a collection suited to packing these things based on their
packing_size(), and later iterating them.
To verify: do the 8086 and 80286 limit instructions to 15 bytes as later members
of the family do? If not then consider original instruction size = 0 to imply an
extension of one word prior to the other extensions.
*/
private:
// b0, b1: a Repetition;
// b2+: operation size.
@ -449,6 +478,7 @@ template<bool is_32bit> class Instruction {
// Fields yet to be properly incorporated...
ScaleIndexBase sib_;
bool memory_size_ = false;
public:
/// @returns The number of bytes used for meaningful content within this class. A receiver must use at least @c sizeof(Instruction) bytes
@ -459,6 +489,7 @@ template<bool is_32bit> class Instruction {
SourceSIB source() const { return SourceSIB(Source(sources_ & 0x3f), sib_); }
SourceSIB destination() const { return SourceSIB(Source((sources_ >> 6) & 0x3f), sib_); }
bool lock() const { return sources_ & 0x8000; }
bool memory_size() const { return memory_size_; }
Source segment_override() const { return Source((sources_ >> 12) & 7); }
Repetition repetition() const { return Repetition(repetition_size_ & 3); }
@ -478,6 +509,7 @@ template<bool is_32bit> class Instruction {
Source destination,
ScaleIndexBase sib,
bool lock,
bool memory_size,
Source segment_override,
Repetition repetition,
Size operation_size,
@ -493,7 +525,8 @@ template<bool is_32bit> class Instruction {
)),
displacement_(displacement),
operand_(operand),
sib_(sib) {}
sib_(sib),
memory_size_(memory_size) {}
};
// TODO: repack.