yosys/passes/pmgen/xilinx_dsp_cascade.pmg

pattern xilinx_dsp_cascade

udata <std::function<SigSpec(const SigSpec&)>> unextend
udata <vector<std::tuple<Cell*,int,int,int>>> chain longest_chain
state <Cell*> next
state <SigSpec> clock
state <int> AREG BREG

// subpattern
state <SigSpec> argQ argD
state <bool> ffcepol ffrstpol
state <int> ffoffset
udata <SigSpec> dffD dffQ
udata <SigBit> dffclock
udata <Cell*> dff dffcemux dffrstmux
udata <bool> dffcepol dffrstpol

code
#define MAX_DSP_CASCADE 20
endcode

match first
	select first->type.in(\DSP48E1)
	select port(first, \OPMODE, Const(0, 7)).extract(4,3) == Const::from_string("000")
	select nusers(port(first, \PCOUT, SigSpec())) <= 1
endmatch

code
	longest_chain.clear();
	chain.emplace_back(first, -1, -1, -1);
	subpattern(tail);
finally
	chain.pop_back();
	log_assert(chain.empty());
	if (GetSize(longest_chain) > 1) {
		Cell *dsp = std::get<0>(longest_chain.front());

		Cell *dsp_pcin;
		int P, AREG, BREG;
		for (int i = 1; i < GetSize(longest_chain); i++) {
			std::tie(dsp_pcin,P,AREG,BREG) = longest_chain[i];

			dsp_pcin->setPort(ID(C), Const(0, 48));

			if (i % MAX_DSP_CASCADE > 0) {
				if (P >= 0) {
					Wire *cascade = module->addWire(NEW_ID, 48);
					dsp_pcin->setPort(ID(PCIN), cascade);
					dsp->setPort(ID(PCOUT), cascade);
					add_siguser(cascade, dsp_pcin);
					add_siguser(cascade, dsp);

					SigSpec opmode = port(dsp_pcin, \OPMODE, Const(0, 7));
					if (P == 17)
						opmode[6] = State::S1;
					else if (P == 0)
						opmode[6] = State::S0;
					else log_abort();

					opmode[5] = State::S0;
					opmode[4] = State::S1;
					dsp_pcin->setPort(\OPMODE, opmode);

					log_debug("PCOUT -> PCIN cascade for %s -> %s\n", log_id(dsp), log_id(dsp_pcin));
				}
				if (AREG >= 0) {
					Wire *cascade = module->addWire(NEW_ID, 30);
					dsp_pcin->setPort(ID(ACIN), cascade);
					dsp->setPort(ID(ACOUT), cascade);
					dsp_pcin->setPort(ID(A), Const(0, 30));
					add_siguser(cascade, dsp_pcin);
					add_siguser(cascade, dsp);

					dsp->setParam(ID(ACASCREG), AREG);
					dsp_pcin->setParam(ID(A_INPUT), Const("CASCADE"));

					log_debug("ACOUT -> ACIN cascade for %s -> %s\n", log_id(dsp), log_id(dsp_pcin));
				}
				if (BREG >= 0) {
					Wire *cascade = module->addWire(NEW_ID, 18);
					dsp_pcin->setPort(ID(BCIN), cascade);
					dsp->setPort(ID(BCOUT), cascade);
					dsp_pcin->setPort(ID(B), Const(0, 18));
					add_siguser(cascade, dsp_pcin);
					add_siguser(cascade, dsp);

					dsp->setParam(ID(BCASCREG), BREG);
					dsp_pcin->setParam(ID(B_INPUT), Const("CASCADE"));

					log_debug("BCOUT -> BCIN cascade for %s -> %s\n", log_id(dsp), log_id(dsp_pcin));
				}
			}
			else {
				log_debug("  Blocking %s -> %s cascade (exceeds max: %d)\n", log_id(dsp), log_id(dsp_pcin), MAX_DSP_CASCADE);
			}

			dsp = dsp_pcin;
		}

		did_something = true;
		accept;
	}
endcode

// ------------------------------------------------------------------

subpattern tail
arg first
arg next

match nextP
	select nextP->type.in(\DSP48E1)
	select !param(nextP, \CREG, State::S1).as_bool()
	select port(nextP, \OPMODE, Const(0, 7)).extract(4,3) == Const::from_string("011")
	select nusers(port(nextP, \C, SigSpec())) > 1
	select nusers(port(nextP, \PCIN, SigSpec())) == 0
	index <SigBit> port(nextP, \C)[0] === port(std::get<0>(chain.back()), \P)[0]
	semioptional
endmatch

match nextP_shift17
	if !nextP
	select nextP_shift17->type.in(\DSP48E1)
	select !param(nextP_shift17, \CREG, State::S1).as_bool()
	select port(nextP_shift17, \OPMODE, Const(0, 7)).extract(4,3) == Const::from_string("011")
	select nusers(port(nextP_shift17, \C, SigSpec())) > 1
	select nusers(port(nextP_shift17, \PCIN, SigSpec())) == 0
	index <SigBit> port(nextP_shift17, \C)[0] === port(std::get<0>(chain.back()), \P)[17]
	semioptional
endmatch

code next
	next = nextP;
	if (!nextP)
		next = nextP_shift17;
	if (next) {
		unextend = [](const SigSpec &sig) {
			int i;
			for (i = GetSize(sig)-1; i > 0; i--)
				if (sig[i] != sig[i-1])
					break;
			// Do not remove non-const sign bit
			if (sig[i].wire)
				++i;
			return sig.extract(0, i);
		};
	}
endcode

code argQ clock AREG
	AREG = 0;
	if (next) {
		Cell *prev = std::get<0>(chain.back());
		if (param(prev, \AREG, 2).as_int() > 0 &&
				param(next, \AREG, 2).as_int() > 0 &&
				param(next, \A_INPUT, Const("DIRECT")).decode_string() == "DIRECT" &&
				port(next, \ACIN, SigSpec()).is_fully_zero() &&
				nusers(port(prev, \ACOUT, SigSpec())) <= 1) {
			argQ = unextend(port(next, \A));
			clock = port(prev, \CLK);
			subpattern(in_dffe);
			if (dff) {
				if (!dffrstmux && port(prev, \RSTA, State::S0) != State::S0)
					goto reject_AREG;
				if (dffrstmux && port(dffrstmux, \S) != port(prev, \RSTA, State::S0))
					goto reject_AREG;
				if (!dffcemux && port(prev, \CEA2, State::S0) != State::S0)
					goto reject_AREG;
				if (dffcemux && port(dffcemux, \S) != port(prev, \CEA2, State::S0))
					goto reject_AREG;
				if (dffD == unextend(port(prev, \A)))
					AREG = 1;
reject_AREG:			;
			}
		}
	}
endcode

code argQ clock BREG
	BREG = 0;
	if (next) {
		Cell *prev = std::get<0>(chain.back());
		if (param(prev, \BREG, 2).as_int() > 0 &&
				param(next, \BREG, 2).as_int() > 0 &&
				param(next, \B_INPUT, Const("DIRECT")).decode_string() == "DIRECT" &&
				port(next, \BCIN, SigSpec()).is_fully_zero() &&
				nusers(port(prev, \BCOUT, SigSpec())) <= 1) {
			argQ = unextend(port(next, \B));
			clock = port(prev, \CLK);
			subpattern(in_dffe);
			if (dff) {
				if (!dffrstmux && port(prev, \RSTB, State::S0) != State::S0)
					goto reject_BREG;
				if (dffrstmux && port(dffrstmux, \S) != port(prev, \RSTB, State::S0))
					goto reject_BREG;
				if (!dffcemux && port(prev, \CEB2, State::S0) != State::S0)
					goto reject_BREG;
				if (dffcemux && port(dffcemux, \S) != port(prev, \CEB2, State::S0))
					goto reject_BREG;
				if (dffD == unextend(port(prev, \B)))
					BREG = 1;
reject_BREG:			;
			}
		}
	}
endcode

code
	if (next) {
		chain.emplace_back(next, nextP_shift17 ? 17 : nextP ? 0 : -1, AREG, BREG);

		SigSpec sigC = unextend(port(next, \C));

		// TODO: Cannot use 'reject' since semioptional
		if (nextP_shift17) {
			if (GetSize(sigC)+17 <= GetSize(port(std::get<0>(chain.back()), \P)) &&
					port(std::get<0>(chain.back()), \P).extract(17, GetSize(sigC)) != sigC)
				subpattern(tail);
		}
		else {
			if (GetSize(sigC) <= GetSize(port(std::get<0>(chain.back()), \P)) &&
					port(std::get<0>(chain.back()), \P).extract(0, GetSize(sigC)) != sigC)
				subpattern(tail);

		}
	} else {
		if (GetSize(chain) > GetSize(longest_chain))
			longest_chain = chain;
	}
finally
	if (next)
		chain.pop_back();
endcode

// #######################

subpattern in_dffe
arg argD argQ clock

code
	dff = nullptr;
	for (auto c : argQ.chunks()) {
		if (!c.wire)
			reject;
		if (c.wire->get_bool_attribute(\keep))
			reject;
		Const init = c.wire->attributes.at(\init, State::Sx);
		if (!init.is_fully_undef() && !init.is_fully_zero())
			reject;
	}
endcode

match ff
	select ff->type.in($dff)
	// DSP48E1 does not support clock inversion
	select param(ff, \CLK_POLARITY).as_bool()

	slice offset GetSize(port(ff, \D))
	index <SigBit> port(ff, \Q)[offset] === argQ[0]

	// Check that the rest of argQ is present
	filter GetSize(port(ff, \Q)) >= offset + GetSize(argQ)
	filter port(ff, \Q).extract(offset, GetSize(argQ)) == argQ

	set ffoffset offset
endmatch

code argQ argD
{
	if (clock != SigBit() && port(ff, \CLK) != clock)
		reject;

	SigSpec Q = port(ff, \Q);
	dff = ff;
	dffclock = port(ff, \CLK);
	dffD = argQ;
	argD = port(ff, \D);
	argQ = Q;
	dffD.replace(argQ, argD);
	// Only search for ffrstmux if dffD only
	//   has two (ff, ffrstmux) users
	if (nusers(dffD) > 2)
		argD = SigSpec();
}
endcode

match ffrstmux
	if !argD.empty()
	select ffrstmux->type.in($mux)
	index <SigSpec> port(ffrstmux, \Y) === argD

	choice <IdString> BA {\B, \A}
	// DSP48E1 only supports reset to zero
	select port(ffrstmux, BA).is_fully_zero()

	define <bool> pol (BA == \B)
	set ffrstpol pol
	semioptional
endmatch

code argD
	if (ffrstmux) {
		dffrstmux = ffrstmux;
		dffrstpol = ffrstpol;
		argD = port(ffrstmux, ffrstpol ? \A : \B);
		dffD.replace(port(ffrstmux, \Y), argD);

		// Only search for ffcemux if argQ has at
		//   least 3 users (ff, <upstream>, ffrstmux) and
		//   dffD only has two (ff, ffrstmux)
		if (!(nusers(argQ) >= 3 && nusers(dffD) == 2))
			argD = SigSpec();
	}
	else
		dffrstmux = nullptr;
endcode

match ffcemux
	if !argD.empty()
	select ffcemux->type.in($mux)
	index <SigSpec> port(ffcemux, \Y) === argD
	choice <IdString> AB {\A, \B}
	index <SigSpec> port(ffcemux, AB) === argQ
	define <bool> pol (AB == \A)
	set ffcepol pol
	semioptional
endmatch

code argD
	if (ffcemux) {
		dffcemux = ffcemux;
		dffcepol = ffcepol;
		argD = port(ffcemux, ffcepol ? \B : \A);
		dffD.replace(port(ffcemux, \Y), argD);
	}
	else
		dffcemux = nullptr;
endcode