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synth_xilinx: Use opt_dff.

Browse source 
The main part is converting xilinx_dsp to recognize the new FF types
created in opt_dff instead of trying to recognize the patterns on its
own.

The fsm call has been moved upwards because the passes cannot deal with
$dffe/$sdff*, and other optimizations don't help it much anyway.
This commit is contained in:
Marcelina Kościelnicka 2020-07-22 12:27:15 +02:00
parent 4a05cad7f8
commit 8501342fc5
7 changed files with 219 additions and 887 deletions
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122
passes/pmgen/xilinx_dsp_CREG.pmg
View file

@ -26,17 +26,14 @@ pattern xilinx_dsp_packC
udata <std::function<SigSpec(const SigSpec&)>> unextend
state <SigBit> clock
state <SigSpec> sigC sigP
state <bool> ffCcepol ffCrstpol
state <Cell*> ffC ffCcemux ffCrstmux
state <Cell*> ffC
// Variables used for subpatterns
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
udata <Cell*> dff
// (1) Starting from a DSP48* cell that (a) doesn't have a CREG already,
// and (b) uses the 'C' port
@ -80,20 +77,12 @@ endcode
// (2) Match the driver of the 'C' input to a possible $dff cell (CREG)
// (attached to at most two $mux cells that implement clock-enable or
// reset functionality, using the in_dffe subpattern)
code argQ ffC ffCcemux ffCrstmux ffCcepol ffCrstpol sigC clock
code argQ ffC sigC clock
argQ = sigC;
subpattern(in_dffe);
if (dff) {
ffC = dff;
clock = dffclock;
if (dffrstmux) {
ffCrstmux = dffrstmux;
ffCrstpol = dffrstpol;
}
if (dffcemux) {
ffCcemux = dffcemux;
ffCcepol = dffcepol;
}
sigC = dffD;
}
endcode
@ -106,25 +95,14 @@ endcode
// #######################
// Subpattern for matching against input registers, based on knowledge of the
// 'Q' input. Typically, identifying registers with clock-enable and reset
// capability would be a task would be handled by other Yosys passes such as
// dff2dffe, but since DSP inference happens much before this, these patterns
// have to be manually identified.
// At a high level:
// (1) Starting from a $dff cell that (partially or fully) drives the given
// 'Q' argument
// (2) Match for a $mux cell implementing synchronous reset semantics ---
// one that exclusively drives the 'D' input of the $dff, with one of its
// $mux inputs being fully zero
// (3) Match for a $mux cell implement clock enable semantics --- one that
// exclusively drives the 'D' input of the $dff (or the other input of
// the reset $mux) and where one of this $mux's inputs is connected to
// the 'Q' output of the $dff
// 'Q' input.
subpattern in_dffe
arg argD argQ clock
arg argQ clock
code
dff = nullptr;
if (argQ.empty())
reject;
for (const auto &c : argQ.chunks()) {
// Abandon matches when 'Q' is a constant
if (!c.wire)
@ -135,19 +113,21 @@ code
// Abandon matches when 'Q' has a non-zero init attribute set
// (not supported by DSP48E1)
Const init = c.wire->attributes.at(\init, Const());
for (auto b : init.extract(c.offset, c.width))
if (b != State::Sx && b != State::S0)
reject;
if (!init.empty())
for (auto b : init.extract(c.offset, c.width))
if (b != State::Sx && b != State::S0)
reject;
}
endcode
// (1) Starting from a $dff cell that (partially or fully) drives the given
// 'Q' argument
match ff
select ff->type.in($dff)
select ff->type.in($dff, $dffe, $sdff, $sdffe)
// DSP48E1 does not support clock inversion
select param(ff, \CLK_POLARITY).as_bool()
// Check that reset value, if present, is fully 0.
filter ff->type.in($dff, $dffe) || param(ff, \SRST_VALUE).is_fully_zero()
slice offset GetSize(port(ff, \D))
index <SigBit> port(ff, \Q)[offset] === argQ[0]
@ -156,80 +136,14 @@ match ff
filter port(ff, \Q).extract(offset, GetSize(argQ)) == argQ
filter clock == SigBit() || port(ff, \CLK) == clock
set ffoffset offset
endmatch
code argQ argD
code argQ
SigSpec Q = port(ff, \Q);
dff = ff;
dffclock = port(ff, \CLK);
dffD = argQ;
argD = port(ff, \D);
SigSpec D = 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
// (2) Match for a $mux cell implementing synchronous reset semantics ---
// exclusively drives the 'D' input of the $dff, with one of the $mux
// inputs being fully zero
match ffrstmux
if !argD.empty()
select ffrstmux->type.in($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
// (3) Match for a $mux cell implement clock enable semantics --- one that
// exclusively drives the 'D' input of the $dff (or the other input of
// the reset $mux) and where one of this $mux's inputs is connected to
// the 'Q' output of the $dff
match ffcemux
if !argD.empty()
select ffcemux->type.in($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;
dffD.replace(argQ, D);
endcode