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LibJIT: Add jump_if_zero() and jump_if_not_zero() to Assembler

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These can use test reg,reg on x86 which gives us a shorter encoding.
This commit is contained in:
Andreas Kling 2023-10-26 15:35:25 +02:00
parent fb483f1950
commit 6f0baea594
1 changed files with 50 additions and 0 deletions
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50
Userland/Libraries/LibJIT/Assembler.h
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@ -281,8 +281,53 @@ struct Assembler {
}
}
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::Imm32) {
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::Imm32 && rhs.offset_or_immediate == 0) {
jump_if_zero(lhs, label);
return;
}
cmp(lhs, rhs);
// je label (RIP-relative 32-bit offset)
@ -294,6 +339,11 @@ struct Assembler {
void jump_if_not_equal(Operand lhs, Operand rhs, Label& label)
{
if (rhs.type == Operand::Type::Imm32 && rhs.offset_or_immediate == 0) {
jump_if_not_zero(lhs, label);
return;
}
cmp(lhs, rhs);
// jne label (RIP-relative 32-bit offset)