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LibJS/JIT: Fast path for boolean JS::Value in compile_to_boolean()

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This commit is contained in:
Andreas Kling 2023-10-15 18:23:16 +02:00
parent babdc0a25b
commit f9041c7b31
3 changed files with 142 additions and 6 deletions
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99
Userland/Libraries/LibJS/JIT/Assembler.h
View file

@ -37,6 +37,8 @@ struct Assembler {
struct Operand {
enum class Type {
Reg,
Imm8,
Imm32,
Imm64,
Mem64BaseAndOffset,
};
@ -54,6 +56,22 @@ struct Assembler {
return operand;
}
static Operand Imm8(u8 imm8)
{
Operand operand;
operand.type = Type::Imm8;
operand.offset_or_immediate = imm8;
return operand;
}
static Operand Imm32(u32 imm32)
{
Operand operand;
operand.type = Type::Imm32;
operand.offset_or_immediate = imm32;
return operand;
}
static Operand Imm64(u64 imm64)
{
Operand operand;
@ -77,6 +95,16 @@ struct Assembler {
return to_underlying(reg) & 0x7;
}
void shift_right(Operand dst, Operand count)
{
VERIFY(dst.type == Operand::Type::Reg);
VERIFY(count.type == Operand::Type::Imm8);
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0xc1);
emit8(0xe8 | encode_reg(dst.reg));
emit8(count.offset_or_immediate);
}
void mov(Operand dst, Operand src)
{
if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Reg) {
@ -176,6 +204,33 @@ struct Assembler {
emit8(0xc0 | (to_underlying(dst) << 3) | to_underlying(dst));
}
struct Label {
size_t offset_in_instruction_stream { 0 };
void link(Assembler& assembler)
{
auto offset = assembler.m_output.size() - offset_in_instruction_stream;
auto jump_slot = offset_in_instruction_stream - 4;
assembler.m_output[jump_slot + 0] = (offset >> 0) & 0xff;
assembler.m_output[jump_slot + 1] = (offset >> 8) & 0xff;
assembler.m_output[jump_slot + 2] = (offset >> 16) & 0xff;
assembler.m_output[jump_slot + 3] = (offset >> 24) & 0xff;
}
};
[[nodiscard]] Label make_label()
{
return { .offset_in_instruction_stream = m_output.size() };
}
[[nodiscard]] Label jump()
{
// jmp target (RIP-relative 32-bit offset)
emit8(0xe9);
emit32(0xdeadbeef);
return make_label();
}
void jump(Bytecode::BasicBlock& target)
{
// jmp target (RIP-relative 32-bit offset)
@ -203,6 +258,50 @@ struct Assembler {
jump(true_target);
}
void jump_if_not_equal(Operand lhs, Operand rhs, Label& label)
{
// cmp lhs, rhs
if (lhs.type == Operand::Type::Reg && rhs.type == Operand::Type::Reg) {
emit8(0x48
| ((to_underlying(lhs.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(rhs.reg) >= 8) ? 1 << 0 : 0));
emit8(0x39);
emit8(0xc0 | (encode_reg(lhs.reg) << 3) | encode_reg(rhs.reg));
} else if (lhs.type == Operand::Type::Reg && rhs.type == Operand::Type::Imm32) {
emit8(0x48 | ((to_underlying(lhs.reg) >= 8) ? 1 << 0 : 0));
emit8(0x81);
emit8(0xf8 | encode_reg(lhs.reg));
emit32(rhs.offset_or_immediate);
} else {
VERIFY_NOT_REACHED();
}
// jne label (RIP-relative 32-bit offset)
emit8(0x0f);
emit8(0x85);
emit32(0xdeadbeef);
label.offset_in_instruction_stream = m_output.size();
}
void bitwise_and(Operand dst, Operand src)
{
// and dst,src
if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Reg) {
emit8(0x48
| ((to_underlying(dst.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(src.reg) >= 8) ? 1 << 0 : 0));
emit8(0x21);
emit8(0xc0 | (encode_reg(dst.reg) << 3) | encode_reg(src.reg));
} else if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Imm32) {
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x81);
emit8(0xe0 | encode_reg(dst.reg));
emit32(src.offset_or_immediate);
} else {
VERIFY_NOT_REACHED();
}
}
void exit()
{
// ret

47
Userland/Libraries/LibJS/JIT/Compiler.cpp
View file

@ -82,22 +82,59 @@ static bool cxx_to_boolean(VM&, Value value)
return value.to_boolean();
}
void Compiler::compile_to_boolean(Assembler::Reg reg)
void Compiler::compile_to_boolean(Assembler::Reg dst, Assembler::Reg src)
{
// dst = src;
m_assembler.mov(
Assembler::Operand::Register(dst),
Assembler::Operand::Register(src));
// dst >>= 48;
m_assembler.shift_right(
Assembler::Operand::Register(dst),
Assembler::Operand::Imm8(48));
// if (dst != BOOLEAN_TAG) goto slow_case;
auto slow_case = m_assembler.make_label();
m_assembler.jump_if_not_equal(
Assembler::Operand::Register(dst),
Assembler::Operand::Imm32(BOOLEAN_TAG),
slow_case);
// Fast path for JS::Value booleans.
// dst = src;
m_assembler.mov(
Assembler::Operand::Register(dst),
Assembler::Operand::Register(src));
// dst &= 1;
m_assembler.bitwise_and(
Assembler::Operand::Register(dst),
Assembler::Operand::Imm32(1));
// goto end;
auto end = m_assembler.jump();
// slow_case: // call C++ helper
slow_case.link(m_assembler);
m_assembler.mov(
Assembler::Operand::Register(Assembler::Reg::Arg1),
Assembler::Operand::Register(reg));
Assembler::Operand::Register(src));
m_assembler.native_call((void*)cxx_to_boolean);
m_assembler.mov(
Assembler::Operand::Register(reg),
Assembler::Operand::Register(dst),
Assembler::Operand::Register(Assembler::Reg::Ret));
// end:
end.link(m_assembler);
}
void Compiler::compile_jump_conditional(Bytecode::Op::JumpConditional const& op)
{
load_vm_register(Assembler::Reg::GPR0, Bytecode::Register::accumulator());
load_vm_register(Assembler::Reg::GPR1, Bytecode::Register::accumulator());
compile_to_boolean(Assembler::Reg::GPR0);
compile_to_boolean(Assembler::Reg::GPR0, Assembler::Reg::GPR1);
m_assembler.jump_conditional(Assembler::Reg::GPR0,
const_cast<Bytecode::BasicBlock&>(op.true_target()->block()),

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

@ -34,7 +34,7 @@ private:
void store_vm_local(size_t, Assembler::Reg);
void load_vm_local(Assembler::Reg, size_t);
void compile_to_boolean(Assembler::Reg);
void compile_to_boolean(Assembler::Reg dst, Assembler::Reg src);
Vector<u8> m_output;
Assembler m_assembler { m_output };