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More comments, cleanup

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This commit is contained in:
Eddie Hung 2019-10-04 13:31:44 -07:00
parent 7de9c33931
commit 6d68972619
2 changed files with 109 additions and 42 deletions
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43
passes/pmgen/xilinx_dsp_CREG.pmg
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@ -77,7 +77,7 @@ 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 a subpattern discussed below)
// reset functionality, using the in_dffe subpattern)
code argQ ffC ffCcemux ffCrstmux ffCcepol ffCrstpol sigC clock
argQ = sigC;
subpattern(in_dffe);
@ -103,22 +103,41 @@ endcode
// #######################
// Subpattern for matching against input registers, based on knowledge of the
// 'Q' input.
// 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
subpattern in_dffe
arg argD argQ clock
code
dff = nullptr;
for (auto c : argQ.chunks()) {
for (const auto &c : argQ.chunks()) {
// Abandon matches when 'Q' is a constant
if (!c.wire)
reject;
// Abandon matches when 'Q' has the keep attribute set
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;
// 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;
}
endcode
// (1) Starting from a $dff cell that (partially or fully) drives the given
// 'Q' argument
match ff
select ff->type.in($dff)
// DSP48E1 does not support clock inversion
@ -131,14 +150,12 @@ match ff
filter GetSize(port(ff, \Q)) >= offset + GetSize(argQ)
filter port(ff, \Q).extract(offset, GetSize(argQ)) == argQ
filter clock == SigBit() || port(ff, \CLK) == clock
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);
@ -150,9 +167,11 @@ code argQ argD
// 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)
@ -184,6 +203,10 @@ code argD
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)