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LibJS: Streamline InstructionStreamIterator

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Nuke all the per-instruction bounds checking when iterating instructions
by using raw pointers instead of indexing into a ReadonlyBytes.

The interpreter loop already checks that we're in-bounds anyway.
This commit is contained in:
Andreas Kling 2023-09-26 16:03:42 +02:00
parent 213b835b57
commit 031ec98803
1 changed files with 10 additions and 13 deletions
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23
Userland/Libraries/LibJS/Bytecode/Instruction.h
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@ -158,35 +158,32 @@ private:
class InstructionStreamIterator { class InstructionStreamIterator {
public: public:
InstructionStreamIterator(ReadonlyBytes bytes, Executable const* executable = nullptr) InstructionStreamIterator(ReadonlyBytes bytes, Executable const* executable = nullptr)
: m_bytes(bytes) : m_begin(bytes.data())
, m_end(bytes.data() + bytes.size())
, m_ptr(bytes.data())
, m_executable(executable) , m_executable(executable)
{ {
} }
size_t offset() const { return m_offset; } size_t offset() const { return m_ptr - m_begin; }
bool at_end() const { return m_offset >= m_bytes.size(); } bool at_end() const { return m_ptr >= m_end; }
void jump(size_t offset)
{
VERIFY(offset <= m_bytes.size());
m_offset = offset;
}
Instruction const& operator*() const { return dereference(); } Instruction const& operator*() const { return dereference(); }
ALWAYS_INLINE void operator++() ALWAYS_INLINE void operator++()
{ {
VERIFY(!at_end()); m_ptr += dereference().length();
m_offset += dereference().length();
} }
UnrealizedSourceRange source_range() const; UnrealizedSourceRange source_range() const;
RefPtr<SourceCode> source_code() const; RefPtr<SourceCode> source_code() const;
private: private:
Instruction const& dereference() const { return *reinterpret_cast<Instruction const*>(m_bytes.data() + offset()); } Instruction const& dereference() const { return *reinterpret_cast<Instruction const*>(m_ptr); }
ReadonlyBytes m_bytes; u8 const* m_begin { nullptr };
size_t m_offset { 0 }; u8 const* m_end { nullptr };
u8 const* m_ptr { nullptr };
Executable const* m_executable { nullptr }; Executable const* m_executable { nullptr };
}; };