yosys/passes/pmgen/xilinx_dsp.pmg

pattern xilinx_dsp

state <SigBit> clock
state <SigSpec> P_used

match dsp
	select dsp->type.in(\DSP48E1)
endmatch

match ffA
	select ffA->type.in($dff, $dffe)
	// DSP48E1 does not support clock inversion
	select param(ffA, \CLK_POLARITY).as_bool()
	filter !port(dsp, \A).remove_const().empty()
	filter includes(port(ffA, \Q).to_sigbit_set(), port(dsp, \A).remove_const().to_sigbit_set())
	optional
endmatch

code clock
	if (ffA)
		clock = port(ffA, \CLK).as_bit();
endcode

match ffB
	select ffB->type.in($dff, $dffe)
	// DSP48E1 does not support clock inversion
	select param(ffB, \CLK_POLARITY).as_bool()
	filter !port(dsp, \B).remove_const().empty()
	filter includes(port(ffB, \Q).to_sigbit_set(), port(dsp, \B).remove_const().to_sigbit_set())
	optional
endmatch

code clock
	if (ffB) {
		SigBit c = port(ffB, \CLK).as_bit();

		if (clock != SigBit() && c != clock)
			reject;

		clock = c;
	}
endcode

// Extract the bits of P that actually have a consumer
// (as opposed to being a sign extension)
code P_used
	SigSpec P = port(dsp, \P);
	int i;
	for (i = GetSize(P); i > 0; i--)
		if (nusers(P[i-1]) > 1)
			break;
	P_used = P.extract(0, i).remove_const();
endcode

match ffP
	if !P_used.empty()
	select ffP->type.in($dff, $dffe)
	select nusers(port(ffP, \D)) == 2
	// DSP48E1 does not support clock inversion
	select param(ffP, \CLK_POLARITY).as_bool()
	filter param(ffP, \WIDTH).as_int() >= GetSize(P_used)
	filter includes(port(ffP, \D).to_sigbit_set(), P_used.to_sigbit_set())
	optional
endmatch

// $mux cell left behind by dff2dffe
//   would prefer not to run 'opt_expr -mux_undef'
//   since that would lose information helpful for
//   efficient wide-mux inference
match muxP
	if !P_used.empty() && !ffP
	select muxP->type.in($mux)
	select nusers(port(muxP, \B)) == 2
	select port(muxP, \A).is_fully_undef()
	filter param(muxP, \WIDTH).as_int() >= GetSize(P_used)
	filter includes(port(muxP, \B).to_sigbit_set(), P_used.to_sigbit_set())
	optional
endmatch

match ffY
	if muxP
	select ffY->type.in($dff, $dffe)
	select nusers(port(ffY, \D)) == 2
	// DSP48E1 does not support clock inversion
	select param(ffY, \CLK_POLARITY).as_bool()
	filter param(ffY, \WIDTH).as_int() >= GetSize(P_used)
	filter includes(port(ffY, \D).to_sigbit_set(), port(muxP, \Y).to_sigbit_set())
endmatch

code ffP clock
	if (ffY)
		ffP = ffY;

	if (ffP) {
		SigBit c = port(ffP, \CLK).as_bit();

		if (clock != SigBit() && c != clock)
			reject;

		clock = c;
	}
endcode