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LibJS/JIT: Add fast path for the ResolveThisBinding codegen

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We now generate a fast path for cached `this` values. The first time
`this` is resolved within a function, we call out to C++, but then
all subsequent accesses will hit the cache in Register::this_value().
This commit is contained in:
Andreas Kling 2023-10-21 16:08:57 +02:00
parent 7097169967
commit e4c4fb09f9
1 changed files with 24 additions and 1 deletions
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25
Userland/Libraries/LibJS/JIT/Compiler.cpp
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@ -536,14 +536,37 @@ void Compiler::compile_to_numeric(Bytecode::Op::ToNumeric const&)
static Value cxx_resolve_this_binding(VM& vm)
{
return TRY_OR_SET_EXCEPTION(vm.resolve_this_binding());
auto this_value = TRY_OR_SET_EXCEPTION(vm.resolve_this_binding());
vm.bytecode_interpreter().reg(Bytecode::Register::this_value()) = this_value;
return this_value;
}
void Compiler::compile_resolve_this_binding(Bytecode::Op::ResolveThisBinding const&)
{
// OPTIMIZATION: We cache the `this` value in a special VM register.
// So first we check if the cache is non-empty, and if so,
// we can avoid calling out to C++ at all. :^)
load_vm_register(GPR0, Bytecode::Register::this_value());
m_assembler.mov(
Assembler::Operand::Register(GPR1),
Assembler::Operand::Imm64(Value().encoded()));
auto slow_case = m_assembler.make_label();
m_assembler.jump_if_equal(
Assembler::Operand::Register(GPR0),
Assembler::Operand::Register(GPR1),
slow_case);
// Fast case: We have a cached `this` value!
store_vm_register(Bytecode::Register::accumulator(), GPR0);
auto end = m_assembler.jump();
slow_case.link(m_assembler);
m_assembler.native_call((void*)cxx_resolve_this_binding);
store_vm_register(Bytecode::Register::accumulator(), RET);
check_exception();
end.link(m_assembler);
}
static Value cxx_put_by_id(VM& vm, Value base, Bytecode::IdentifierTableIndex property, Value value, Bytecode::Op::PropertyKind kind)