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LibJS/JIT: Compile the EnterUnwindContext and LeaveUnwindContext ops

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These push a "valid" unwind context on the stack and check_exception()
now knows how to jump to the (catch) handler if present.

(finally) finalizers will require some more work, but with this change,
we now have basic support for try...catch. :^)
This commit is contained in:
Andreas Kling 2023-10-17 18:37:04 +02:00
parent 9d35016284
commit 9dd5be0186
2 changed files with 63 additions and 2 deletions
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63
Userland/Libraries/LibJS/JIT/Compiler.cpp
View file

@ -214,6 +214,47 @@ void Compiler::check_exception()
// handle_exception:
handle_exception.link(m_assembler);
// if (unwind_context.handler) {
// accumulator = exception;
// exception = Value();
// goto handler;
// }
auto no_handler = m_assembler.make_label();
m_assembler.mov(
Assembler::Operand::Register(GPR0),
Assembler::Operand::Mem64BaseAndOffset(UNWIND_CONTEXT_BASE, 8));
m_assembler.jump_if_equal(
Assembler::Operand::Register(GPR0),
Assembler::Operand::Imm32(0),
no_handler);
load_vm_register(GPR1, Bytecode::Register::exception());
store_vm_register(Bytecode::Register::accumulator(), GPR1);
m_assembler.mov(
Assembler::Operand::Register(GPR1),
Assembler::Operand::Imm64(Value().encoded()));
store_vm_register(Bytecode::Register::exception(), GPR1);
m_assembler.jump(Assembler::Operand::Register(GPR0));
// no_handler:
no_handler.link(m_assembler);
// if (unwind_context.finalizer) goto finalizer;
auto no_finalizer = m_assembler.make_label();
m_assembler.mov(
Assembler::Operand::Register(GPR0),
Assembler::Operand::Mem64BaseAndOffset(UNWIND_CONTEXT_BASE, 16));
m_assembler.jump_if_equal(
Assembler::Operand::Register(GPR0),
Assembler::Operand::Imm32(0),
no_finalizer);
m_assembler.jump(Assembler::Operand::Register(GPR0));
// no_finalizer:
// NOTE: No catch and no finally!? Crash.
no_finalizer.link(m_assembler);
m_assembler.verify_not_reached();
// no_exception:
no_exception.link(m_assembler);
}
@ -230,7 +271,7 @@ void Compiler::push_unwind_context(bool valid, Optional<Bytecode::Label> const&
// push finalizer (patched later)
m_assembler.mov(
Assembler::Operand::Register(GPR0),
Assembler::Operand::Imm64(0xdeadbeef));
Assembler::Operand::Imm64(0));
if (finalizer.has_value())
const_cast<Bytecode::BasicBlock&>(finalizer.value().block()).absolute_references_to_here.append(m_assembler.m_output.size() - 8);
m_assembler.push(Assembler::Operand::Register(GPR0));
@ -238,7 +279,7 @@ void Compiler::push_unwind_context(bool valid, Optional<Bytecode::Label> const&
// push handler (patched later)
m_assembler.mov(
Assembler::Operand::Register(GPR0),
Assembler::Operand::Imm64(0xdeadbeef));
Assembler::Operand::Imm64(0));
if (handler.has_value())
const_cast<Bytecode::BasicBlock&>(handler.value().block()).absolute_references_to_here.append(m_assembler.m_output.size() - 8);
m_assembler.push(Assembler::Operand::Register(GPR0));
@ -261,6 +302,18 @@ void Compiler::pop_unwind_context()
m_assembler.add(Assembler::Operand::Register(UNWIND_CONTEXT_BASE), Assembler::Operand::Imm8(32));
}
void Compiler::compile_enter_unwind_context(Bytecode::Op::EnterUnwindContext const& op)
{
push_unwind_context(true, op.handler_target(), op.finalizer_target());
m_assembler.jump(const_cast<Bytecode::BasicBlock&>(op.entry_point().block()));
}
void Compiler::compile_leave_unwind_context(Bytecode::Op::LeaveUnwindContext const&)
{
pop_unwind_context();
}
OwnPtr<NativeExecutable> Compiler::compile(Bytecode::Executable const& bytecode_executable)
{
if (getenv("LIBJS_NO_JIT"))
@ -313,6 +366,12 @@ OwnPtr<NativeExecutable> Compiler::compile(Bytecode::Executable const& bytecode_
case Bytecode::Instruction::Type::Increment:
compiler.compile_increment(static_cast<Bytecode::Op::Increment const&>(op));
break;
case Bytecode::Instruction::Type::EnterUnwindContext:
compiler.compile_enter_unwind_context(static_cast<Bytecode::Op::EnterUnwindContext const&>(op));
break;
case Bytecode::Instruction::Type::LeaveUnwindContext:
compiler.compile_leave_unwind_context(static_cast<Bytecode::Op::LeaveUnwindContext const&>(op));
break;
default:
dbgln("JIT compilation failed: {}", bytecode_executable.name);
dbgln("Unsupported bytecode op: {}", op.to_deprecated_string(bytecode_executable));

2
Userland/Libraries/LibJS/JIT/Compiler.h
View file

@ -38,6 +38,8 @@ private:
void compile_jump_conditional(Bytecode::Op::JumpConditional const&);
void compile_less_than(Bytecode::Op::LessThan const&);
void compile_increment(Bytecode::Op::Increment const&);
void compile_enter_unwind_context(Bytecode::Op::EnterUnwindContext const&);
void compile_leave_unwind_context(Bytecode::Op::LeaveUnwindContext const&);
void store_vm_register(Bytecode::Register, Assembler::Reg);
void load_vm_register(Assembler::Reg, Bytecode::Register);