From 6d689726193db4d46f7618ff00707e4f30366ad5 Mon Sep 17 00:00:00 2001 From: Eddie Hung Date: Fri, 4 Oct 2019 13:31:44 -0700 Subject: More comments, cleanup --- passes/pmgen/xilinx_dsp.pmg | 106 +++++++++++++++++++++++++++++++------------- 1 file changed, 75 insertions(+), 31 deletions(-) (limited to 'passes/pmgen/xilinx_dsp.pmg') diff --git a/passes/pmgen/xilinx_dsp.pmg b/passes/pmgen/xilinx_dsp.pmg index 6b6151564..3523db3a4 100644 --- a/passes/pmgen/xilinx_dsp.pmg +++ b/passes/pmgen/xilinx_dsp.pmg @@ -425,22 +425,42 @@ 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()); + 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) // DSP48E1 does not support clock inversion @@ -453,14 +473,12 @@ 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); @@ -472,9 +490,11 @@ 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) @@ -506,6 +526,10 @@ 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) @@ -530,16 +554,32 @@ endcode // ####################### +// Subpattern for matching against output registers, based on knowledge of the +// 'D' input. +// At a high level: +// (1) Starting from an optional $mux cell that implements clock enable +// semantics --- one where the given 'D' argument (partially or fully) +// drives one of its two inputs +// (2) Starting from, or continuing onto, another optional $mux cell that +// implements synchronous reset semantics --- one where the given 'D' +// argument (or the clock enable $mux output) drives one of its two inputs +// and where the other input is fully zero +// (3) Match for a $dff cell (whose 'D' input is the 'D' argument, or the +// output of the previous clock enable or reset $mux cells) subpattern out_dffe arg argD argQ clock code dff = nullptr; for (auto c : argD.chunks()) + // Abandon matches when 'D' has the keep attribute set if (c.wire->get_bool_attribute(\keep)) reject; endcode +// (1) Starting from an optional $mux cell that implements clock enable +// semantics --- one where the given 'D' argument (partially or fully) +// drives one of its two inputs match ffcemux select ffcemux->type.in($mux) // ffcemux output must have two users: ffcemux and ff.D @@ -578,6 +618,10 @@ code argD argQ } endcode +// (2) Starting from, or continuing onto, another optional $mux cell that +// implements synchronous reset semantics --- one where the given 'D' +// argument (or the clock enable $mux output) drives one of its two inputs +// and where the other input is fully zero match ffrstmux select ffrstmux->type.in($mux) // ffrstmux output must have two users: ffrstmux and ff.D @@ -616,6 +660,8 @@ code argD argQ } endcode +// (3) Match for a $dff cell (whose 'D' input is the 'D' argument, or the +// output of the previous clock enable or reset $mux cells) match ff select ff->type.in($dff) // DSP48E1 does not support clock inversion @@ -632,32 +678,30 @@ match ff // Check that FF.Q is connected to CE-mux filter !ffcemux || port(ff, \Q).extract(offset, GetSize(argQ)) == argQ + filter clock == SigBit() || port(ff, \CLK) == clock + set ffoffset offset endmatch code argQ - if (ff) { - if (clock != SigBit() && port(ff, \CLK) != clock) - reject; - - SigSpec D = port(ff, \D); - SigSpec Q = port(ff, \Q); - if (!ffcemux) { - argQ = argD; - argQ.replace(D, Q); - } - - for (auto c : argQ.chunks()) { - Const init = c.wire->attributes.at(\init, State::Sx); - if (!init.is_fully_undef() && !init.is_fully_zero()) - reject; - } + SigSpec D = port(ff, \D); + SigSpec Q = port(ff, \Q); + if (!ffcemux) { + argQ = argD; + argQ.replace(D, Q); + } - dff = ff; - dffQ = argQ; - dffclock = port(ff, \CLK); + // Abandon matches when 'Q' has a non-zero init attribute set + // (not supported by DSP48E1) + for (auto c : argQ.chunks()) { + Const init = c.wire->attributes.at(\init, Const()); + if (!init.empty()) + for (auto b : init.extract(c.offset, c.width)) + if (b != State::Sx && b != State::S0) + reject; } - // No enable/reset mux possible without flop - else if (dffcemux || dffrstmux) - reject; + + dff = ff; + dffQ = argQ; + dffclock = port(ff, \CLK); endcode -- cgit v1.2.3