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Ensure ScaleIndexBase can be used constexpr; add note-to-self on indexing table.

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This commit is contained in:
Thomas Harte 2022-02-20 19:22:28 -05:00
parent 63d8a88e2f
commit 546b4edbf1
2 changed files with 17 additions and 6 deletions
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11
InstructionSets/x86/Decoder.cpp
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@ -440,6 +440,17 @@ std::pair<int, InstructionSet::x86::Instruction> Decoder::decode(const uint8_t *
} break;
default: {
// TODO: switch to this table.
// constexpr ScaleIndexBase rm_table[8] = {
// ScaleIndexBase(0, Source::eBX, Source::eSI),
// ScaleIndexBase(0, Source::eBX, Source::eDI),
// ScaleIndexBase(0, Source::eBP, Source::eSI),
// ScaleIndexBase(0, Source::eBP, Source::eDI),
// ScaleIndexBase(0, Source::None, Source::eSI),
// ScaleIndexBase(0, Source::None, Source::eDI),
// ScaleIndexBase(0, Source::None, Source::eBP),
// ScaleIndexBase(0, Source::None, Source::eBX),
// };
constexpr Source rm_table[8] = {
Source::IndBXPlusSI, Source::IndBXPlusDI,
Source::IndBPPlusSI, Source::IndBPPlusDI,

12
InstructionSets/x86/Instruction.hpp
View File

@ -364,17 +364,17 @@ enum class Repetition: uint8_t {
/// even though it is a superset of that supported prior to the 80386.
class ScaleIndexBase {
public:
ScaleIndexBase() {}
ScaleIndexBase(uint8_t sib) : sib_(sib) {}
ScaleIndexBase(int scale, Source index, Source base) : sib_(uint8_t(scale << 6 | (int(index != Source::None ? index : Source::eSI) << 3) | int(base))) {}
constexpr ScaleIndexBase() noexcept {}
constexpr ScaleIndexBase(uint8_t sib) noexcept : sib_(sib) {}
constexpr ScaleIndexBase(int scale, Source index, Source base) noexcept : sib_(uint8_t(scale << 6 | (int(index != Source::None ? index : Source::eSI) << 3) | int(base))) {}
/// @returns the power of two by which to multiply @c index() before adding it to @c base().
int scale() const {
constexpr int scale() const {
return sib_ >> 6;
}
/// @returns the @c index for this address; this is guaranteed to be one of eAX, eBX, eCX, eDX, None, eBP, eSI or eDI.
Source index() const {
constexpr Source index() const {
constexpr Source sources[] = {
Source::eAX, Source::eCX, Source::eDX, Source::eBX, Source::None, Source::eBP, Source::eSI, Source::eDI,
};
@ -383,7 +383,7 @@ class ScaleIndexBase {
}
/// @returns the @c base for this address; this is guaranteed to be one of eAX, eBX, eCX, eDX, eSP, eBP, eSI or eDI.
Source base() const {
constexpr Source base() const {
return Source(sib_ & 0x7);
}