Consider removing pyqir_0_6_compatibility code

[qartik]

We explicitly require pyqir 0.8.2 at

pytket-qir/setup.py

Line 49 in 6b500b8

"pyqir == 0.8.2",

So the bit below and other pyqir_0_6_compatibility code is unneeded.

pytket-qir/pytket/qir/conversion/api.py

Lines 88 to 129 in 6b500b8

	if pyqir_0_6_compatibility:
	if len(circ.c_registers) > 1:
	raise ValueError(
	"""The qir optimised for pyqir 0.6 can only contain
	one classical register"""
	)
	initial_result = str(populated_module.module.ir()) # type: ignore
	initial_result = (
	initial_result.replace("entry_point", "EntryPoint")
	.replace("num_required_qubits", "requiredQubits")
	.replace("num_required_results", "requiredResults")
	)
	def keep_line(line: str) -> bool:
	return (
	("@__quantum__qis__read_result__body" not in line)
	and ("@set_one_bit_in_reg" not in line)
	and ("@reg2var" not in line)
	and ("@read_bit_from_reg" not in line)
	and ("@set_all_bits_in_reg" not in line)
	)
	result = "\n".join(filter(keep_line, initial_result.split("\n")))
	# replace the use of the removed register variable with i64 0
	result = result.replace("i64 %0", "i64 0")
	for _ in range(10):
	result = result.replace("\n\n\n\n", "\n\n")
	bitcode = pyqir.Module.from_ir(pyqir.Context(), result).bitcode # type: ignore
	if qir_format == QIRFormat.BINARY:
	return bitcode # type: ignore
	elif qir_format == QIRFormat.STRING:
	return result # type: ignore
	else:
	assert not "unsupported return type" # type: ignore
	else:

[qartik]

@cqc-melf any objections? I can go ahead and remove this dead code if you agree.

[cqc-melf]

We have added this in the past because we wanted to be compatible with older versions used on your side, if you don't need this it can be removed. Are you using now 0.8.x as well?

[qartik]

Yes, we are. There is no support for PyQIR below 0.8.2 in the backend compiler, AFAIK.

Just to confirm, @peter-campora do you think old versions are still in use and may require compatibility with pytket-qir?

Update (2023-08-15): We agreed that it can be removed.

[cqc-melf]

solved by #66