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ladybird/Userland/Libraries/LibJIT/Assembler.h
Andreas Kling bbde64e0b6 LibJIT: Emit 8-bit PUSH imm when possible
2023-10-28 18:20:07 +02:00

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/*
* Copyright (c) 2023, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Platform.h>
#include <AK/Vector.h>
#if ARCH(X86_64)
namespace JIT {
struct Assembler {
Assembler(Vector<u8>& output)
: m_output(output)
{
}
Vector<u8>& m_output;
enum class Reg {
RAX = 0,
RCX = 1,
RDX = 2,
RBX = 3,
RSP = 4,
RBP = 5,
RSI = 6,
RDI = 7,
R8 = 8,
R9 = 9,
R10 = 10,
R11 = 11,
R12 = 12,
R13 = 13,
R14 = 14,
R15 = 15,
};
struct Operand {
enum class Type {
Reg,
Imm,
Mem64BaseAndOffset,
};
Type type {};
Reg reg {};
u64 offset_or_immediate { 0 };
static Operand Register(Reg reg)
{
Operand operand;
operand.type = Type::Reg;
operand.reg = reg;
return operand;
}
static Operand Imm(u64 imm)
{
Operand operand;
operand.type = Type::Imm;
operand.offset_or_immediate = imm;
return operand;
}
static Operand Mem64BaseAndOffset(Reg base, u64 offset)
{
Operand operand;
operand.type = Type::Mem64BaseAndOffset;
operand.reg = base;
operand.offset_or_immediate = offset;
return operand;
}
bool fits_in_u8() const
{
VERIFY(type == Type::Imm);
return offset_or_immediate <= NumericLimits<u8>::max();
}
bool fits_in_u32() const
{
VERIFY(type == Type::Imm);
return offset_or_immediate <= NumericLimits<u32>::max();
}
bool fits_in_i8() const
{
VERIFY(type == Type::Imm);
return (offset_or_immediate <= NumericLimits<i8>::max()) || (((~offset_or_immediate) & NumericLimits<i8>::min()) == 0);
}
bool fits_in_i32() const
{
VERIFY(type == Type::Imm);
return (offset_or_immediate <= NumericLimits<i32>::max()) || (((~offset_or_immediate) & NumericLimits<i32>::min()) == 0);
}
};
static constexpr u8 encode_reg(Reg reg)
{
return to_underlying(reg) & 0x7;
}
void shift_right(Operand dst, Operand count)
{
VERIFY(dst.type == Operand::Type::Reg);
VERIFY(count.type == Operand::Type::Imm);
VERIFY(count.fits_in_u8());
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0xc1);
emit8(0xe8 | encode_reg(dst.reg));
emit8(count.offset_or_immediate);
}
enum class Patchable {
Yes,
No,
};
void mov(Operand dst, Operand src, Patchable patchable = Patchable::No)
{
if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Reg) {
if (src.reg == dst.reg)
return;
emit8(0x48
| ((to_underlying(src.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x89);
emit8(0xc0 | (encode_reg(src.reg) << 3) | encode_reg(dst.reg));
return;
}
if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Imm) {
if (patchable == Patchable::No) {
if (src.offset_or_immediate == 0) {
// xor dst, dst
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? (1 << 0 | 1 << 2) : 0));
emit8(0x31);
emit8(0xc0 | (encode_reg(dst.reg) << 3) | encode_reg(dst.reg));
return;
}
if (src.fits_in_u32()) {
if (dst.reg > Reg::RDI)
emit8(0x41);
emit8(0xb8 | encode_reg(dst.reg));
emit32(src.offset_or_immediate);
return;
}
}
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0xb8 | encode_reg(dst.reg));
emit64(src.offset_or_immediate);
return;
}
if (dst.type == Operand::Type::Mem64BaseAndOffset && src.type == Operand::Type::Reg) {
emit8(0x48
| ((to_underlying(src.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x89);
if (dst.offset_or_immediate <= 127) {
emit8(0x40 | (encode_reg(src.reg) << 3) | encode_reg(dst.reg));
emit8(dst.offset_or_immediate);
} else {
emit8(0x80 | (encode_reg(src.reg) << 3) | encode_reg(dst.reg));
emit32(dst.offset_or_immediate);
}
return;
}
if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Mem64BaseAndOffset) {
emit8(0x48
| ((to_underlying(dst.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(src.reg) >= 8) ? 1 << 0 : 0));
emit8(0x8b);
if (src.offset_or_immediate <= 127) {
emit8(0x40 | (encode_reg(dst.reg) << 3) | encode_reg(src.reg));
emit8(src.offset_or_immediate);
} else {
emit8(0x80 | (encode_reg(dst.reg) << 3) | encode_reg(src.reg));
emit32(src.offset_or_immediate);
}
return;
}
VERIFY_NOT_REACHED();
}
void emit8(u8 value)
{
m_output.append(value);
}
void emit32(u32 value)
{
m_output.append((value >> 0) & 0xff);
m_output.append((value >> 8) & 0xff);
m_output.append((value >> 16) & 0xff);
m_output.append((value >> 24) & 0xff);
}
void emit64(u64 value)
{
m_output.append((value >> 0) & 0xff);
m_output.append((value >> 8) & 0xff);
m_output.append((value >> 16) & 0xff);
m_output.append((value >> 24) & 0xff);
m_output.append((value >> 32) & 0xff);
m_output.append((value >> 40) & 0xff);
m_output.append((value >> 48) & 0xff);
m_output.append((value >> 56) & 0xff);
}
struct Label {
size_t offset_of_label_in_instruction_stream { 0 };
Vector<size_t> jump_slot_offsets_in_instruction_stream;
void add_jump(size_t offset)
{
jump_slot_offsets_in_instruction_stream.append(offset);
}
void link(Assembler& assembler)
{
link_to(assembler, assembler.m_output.size());
}
void link_to(Assembler& assembler, size_t link_offset)
{
offset_of_label_in_instruction_stream = link_offset;
for (auto offset_in_instruction_stream : jump_slot_offsets_in_instruction_stream) {
auto offset = offset_of_label_in_instruction_stream - 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 Label {
.offset_of_label_in_instruction_stream = m_output.size(),
.jump_slot_offsets_in_instruction_stream = {},
};
}
[[nodiscard]] Label jump()
{
// jmp target (RIP-relative 32-bit offset)
emit8(0xe9);
emit32(0xdeadbeef);
auto label = make_label();
label.add_jump(m_output.size());
return label;
}
void jump(Label& label)
{
// jmp target (RIP-relative 32-bit offset)
emit8(0xe9);
emit32(0xdeadbeef);
label.add_jump(m_output.size());
}
void jump(Operand op)
{
if (op.type == Operand::Type::Reg) {
if (to_underlying(op.reg) >= 8)
emit8(0x41);
emit8(0xff);
emit8(0xe0 | encode_reg(op.reg));
} else {
VERIFY_NOT_REACHED();
}
}
void verify_not_reached()
{
// ud2
emit8(0x0f);
emit8(0x0b);
}
void cmp(Operand lhs, Operand rhs)
{
if (lhs.type == Operand::Type::Reg && rhs.type == Operand::Type::Reg) {
emit8(0x48
| ((to_underlying(rhs.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(lhs.reg) >= 8) ? 1 << 0 : 0));
emit8(0x39);
emit8(0xc0 | (encode_reg(rhs.reg) << 3) | encode_reg(lhs.reg));
} else if (lhs.type == Operand::Type::Reg && rhs.type == Operand::Type::Imm && rhs.fits_in_i8()) {
emit8(0x48 | ((to_underlying(lhs.reg) >= 8) ? 1 << 0 : 0));
emit8(0x83);
emit8(0xf8 | encode_reg(lhs.reg));
emit8(rhs.offset_or_immediate);
} else if (lhs.type == Operand::Type::Reg && rhs.type == Operand::Type::Imm && rhs.fits_in_i32()) {
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();
}
}
void test(Operand lhs, Operand rhs)
{
if (lhs.type == Operand::Type::Reg && rhs.type == Operand::Type::Reg) {
emit8(0x48
| ((to_underlying(rhs.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(lhs.reg) >= 8) ? 1 << 0 : 0));
emit8(0x85);
emit8(0xc0 | (encode_reg(rhs.reg) << 3) | encode_reg(lhs.reg));
} else if (lhs.type == Operand::Type::Reg && rhs.type == Operand::Type::Imm) {
VERIFY(rhs.fits_in_i32());
emit8(0x48 | ((to_underlying(lhs.reg) >= 8) ? 1 << 0 : 0));
emit8(0xf7);
emit8(0xc0 | encode_reg(lhs.reg));
emit32(rhs.offset_or_immediate);
} else {
VERIFY_NOT_REACHED();
}
}
void jump_if_zero(Operand reg, Label& label)
{
test(reg, reg);
// jz label (RIP-relative 32-bit offset)
emit8(0x0f);
emit8(0x84);
emit32(0xdeadbeef);
label.add_jump(m_output.size());
}
void jump_if_not_zero(Operand reg, Label& label)
{
test(reg, reg);
// jnz label (RIP-relative 32-bit offset)
emit8(0x0f);
emit8(0x85);
emit32(0xdeadbeef);
label.add_jump(m_output.size());
}
void jump_if_equal(Operand lhs, Operand rhs, Label& label)
{
if (rhs.type == Operand::Type::Imm && rhs.offset_or_immediate == 0) {
jump_if_zero(lhs, label);
return;
}
cmp(lhs, rhs);
// je label (RIP-relative 32-bit offset)
emit8(0x0f);
emit8(0x84);
emit32(0xdeadbeef);
label.add_jump(m_output.size());
}
void jump_if_not_equal(Operand lhs, Operand rhs, Label& label)
{
if (rhs.type == Operand::Type::Imm && rhs.offset_or_immediate == 0) {
jump_if_not_zero(lhs, label);
return;
}
cmp(lhs, rhs);
// jne label (RIP-relative 32-bit offset)
emit8(0x0f);
emit8(0x85);
emit32(0xdeadbeef);
label.add_jump(m_output.size());
}
void jump_if_less_than(Operand lhs, Operand rhs, Label& label)
{
cmp(lhs, rhs);
// jl label (RIP-relative 32-bit offset)
emit8(0x0f);
emit8(0x8c);
emit32(0xdeadbeef);
label.add_jump(m_output.size());
}
void sign_extend_32_to_64_bits(Reg reg)
{
// movsxd (reg as 64-bit), (reg as 32-bit)
emit8(0x48 | ((to_underlying(reg) >= 8) ? 1 << 0 : 0));
emit8(0x63);
emit8(0xc0 | (encode_reg(reg) << 3) | encode_reg(reg));
}
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(src.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x21);
emit8(0xc0 | (encode_reg(src.reg) << 3) | encode_reg(dst.reg));
} else if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Imm && src.fits_in_i8()) {
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x83);
emit8(0xe0 | encode_reg(dst.reg));
emit8(src.offset_or_immediate);
} else if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Imm && src.fits_in_i32()) {
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 bitwise_or(Operand dst, Operand src)
{
// or dst,src
if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Reg) {
emit8(0x48
| ((to_underlying(src.reg) >= 8) ? 1 << 2 : 0)
| ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x09);
emit8(0xc0 | (encode_reg(src.reg) << 3) | encode_reg(dst.reg));
} else if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Imm && src.fits_in_i8()) {
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x83);
emit8(0xc8 | encode_reg(dst.reg));
emit8(src.offset_or_immediate);
} else if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Imm && src.fits_in_i32()) {
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x81);
emit8(0xc8 | encode_reg(dst.reg));
emit32(src.offset_or_immediate);
} else {
VERIFY_NOT_REACHED();
}
}
void enter()
{
push_callee_saved_registers();
push(Operand::Register(Reg::RBP));
mov(Operand::Register(Reg::RBP), Operand::Register(Reg::RSP));
}
void exit()
{
// leave
emit8(0xc9);
pop_callee_saved_registers();
// ret
emit8(0xc3);
}
void push_callee_saved_registers()
{
// FIXME: Don't push RBX twice :^)
push(Operand::Register(Reg::RBX));
push(Operand::Register(Reg::RBX));
push(Operand::Register(Reg::R12));
push(Operand::Register(Reg::R13));
push(Operand::Register(Reg::R14));
push(Operand::Register(Reg::R15));
}
void pop_callee_saved_registers()
{
pop(Operand::Register(Reg::R15));
pop(Operand::Register(Reg::R14));
pop(Operand::Register(Reg::R13));
pop(Operand::Register(Reg::R12));
// FIXME: Don't pop RBX twice :^)
pop(Operand::Register(Reg::RBX));
pop(Operand::Register(Reg::RBX));
}
void push(Operand op)
{
if (op.type == Operand::Type::Reg) {
if (to_underlying(op.reg) >= 8)
emit8(0x49);
emit8(0x50 | encode_reg(op.reg));
} else if (op.type == Operand::Type::Imm) {
if (op.fits_in_i8()) {
emit8(0x6a);
emit8(op.offset_or_immediate);
} else if (op.fits_in_i32()) {
emit8(0x68);
emit32(op.offset_or_immediate);
} else {
VERIFY_NOT_REACHED();
}
} else {
VERIFY_NOT_REACHED();
}
}
void pop(Operand op)
{
if (op.type == Operand::Type::Reg) {
if (to_underlying(op.reg) >= 8)
emit8(0x49);
emit8(0x58 | encode_reg(op.reg));
} else {
VERIFY_NOT_REACHED();
}
}
void add(Operand dst, Operand 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(0x01);
emit8(0xc0 | (encode_reg(dst.reg) << 3) | encode_reg(src.reg));
} else if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Imm && src.fits_in_i8()) {
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x83);
emit8(0xc0 | encode_reg(dst.reg));
emit8(src.offset_or_immediate);
} else if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Imm && src.fits_in_i32()) {
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x81);
emit8(0xc0 | encode_reg(dst.reg));
emit32(src.offset_or_immediate);
} else {
VERIFY_NOT_REACHED();
}
}
void sub(Operand dst, Operand 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(0x29);
emit8(0xc0 | (encode_reg(dst.reg) << 3) | encode_reg(src.reg));
} else if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Imm && src.fits_in_i8()) {
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x83);
emit8(0xe8 | encode_reg(dst.reg));
emit8(src.offset_or_immediate);
} else if (dst.type == Operand::Type::Reg && src.type == Operand::Type::Imm && src.fits_in_i32()) {
emit8(0x48 | ((to_underlying(dst.reg) >= 8) ? 1 << 0 : 0));
emit8(0x81);
emit8(0xe8 | encode_reg(dst.reg));
emit32(src.offset_or_immediate);
} else {
VERIFY_NOT_REACHED();
}
}
// NOTE: It's up to the caller of this function to preserve registers as needed.
void native_call(void* callee, Vector<Operand> const& stack_arguments = {})
{
// Preserve 16-byte stack alignment for non-even amount of stack-passed arguments
if ((stack_arguments.size() % 2) == 1)
push(Operand::Imm(0));
for (auto const& stack_argument : stack_arguments.in_reverse())
push(stack_argument);
// load callee into RAX
mov(Operand::Register(Reg::RAX), Operand::Imm(bit_cast<u64>(callee)));
// call RAX
emit8(0xff);
emit8(0xd0);
if (!stack_arguments.is_empty())
add(Operand::Register(Reg::RSP), Operand::Imm(align_up_to(stack_arguments.size(), 2) * sizeof(void*)));
}
void trap()
{
// int3
emit8(0xcc);
}
};
}
#endif
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