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LibJIT: Add jump_if_zero() and jump_if_not_zero() to Assembler
These can use test reg,reg on x86 which gives us a shorter encoding.
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1 changed files with 50 additions and 0 deletions
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@ -281,8 +281,53 @@ struct Assembler {
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}
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}
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void test(Operand lhs, Operand rhs)
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{
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if (lhs.type == Operand::Type::Reg && rhs.type == Operand::Type::Reg) {
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emit8(0x48
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| ((to_underlying(rhs.reg) >= 8) ? 1 << 2 : 0)
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| ((to_underlying(lhs.reg) >= 8) ? 1 << 0 : 0));
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emit8(0x85);
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emit8(0xc0 | (encode_reg(rhs.reg) << 3) | encode_reg(lhs.reg));
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} else if (lhs.type == Operand::Type::Reg && rhs.type == Operand::Type::Imm32) {
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emit8(0x48 | ((to_underlying(lhs.reg) >= 8) ? 1 << 0 : 0));
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emit8(0xf7);
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emit8(0xc0 | encode_reg(lhs.reg));
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emit32(rhs.offset_or_immediate);
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} else {
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VERIFY_NOT_REACHED();
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}
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}
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void jump_if_zero(Operand reg, Label& label)
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{
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test(reg, reg);
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// jz label (RIP-relative 32-bit offset)
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emit8(0x0f);
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emit8(0x84);
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emit32(0xdeadbeef);
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label.add_jump(m_output.size());
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}
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void jump_if_not_zero(Operand reg, Label& label)
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{
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test(reg, reg);
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// jnz label (RIP-relative 32-bit offset)
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emit8(0x0f);
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emit8(0x85);
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emit32(0xdeadbeef);
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label.add_jump(m_output.size());
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}
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void jump_if_equal(Operand lhs, Operand rhs, Label& label)
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{
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if (rhs.type == Operand::Type::Imm32 && rhs.offset_or_immediate == 0) {
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jump_if_zero(lhs, label);
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return;
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}
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cmp(lhs, rhs);
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// je label (RIP-relative 32-bit offset)
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@ -294,6 +339,11 @@ struct Assembler {
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void jump_if_not_equal(Operand lhs, Operand rhs, Label& label)
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{
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if (rhs.type == Operand::Type::Imm32 && rhs.offset_or_immediate == 0) {
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jump_if_not_zero(lhs, label);
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return;
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}
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cmp(lhs, rhs);
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// jne label (RIP-relative 32-bit offset)
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