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1617 lines
50 KiB
C++
1617 lines
50 KiB
C++
/*
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* yosys -- Yosys Open SYnthesis Suite
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*
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* Copyright (C) 2018 whitequark <whitequark@whitequark.org>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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*/
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// [[CITE]] FlowMap algorithm
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// Jason Cong; Yuzheng Ding, "An Optimal Technology Mapping Algorithm for Delay Optimization in Lookup-Table Based FPGA Designs,"
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// Computer-Aided Design of Integrated Circuits and Systems, IEEE Transactions on, Vol. 13, pp. 1-12, Jan. 1994.
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// doi: 10.1109/43.273754
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// [[CITE]] FlowMap-r algorithm
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// Jason Cong; Yuzheng Ding, "On Area/Depth Tradeoff in LUT-Based FPGA Technology Mapping,"
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// Very Large Scale Integration Systems, IEEE Transactions on, Vol. 2, June 1994.
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// doi: 10.1109/92.28574
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// Required reading material:
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//
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// Min-cut max-flow theorem:
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// https://www.coursera.org/lecture/algorithms-part2/maxflow-mincut-theorem-beb9G
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// FlowMap paper:
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// http://cadlab.cs.ucla.edu/~cong/papers/iccad92.pdf (short version)
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// https://limsk.ece.gatech.edu/book/papers/flowmap.pdf (long version)
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// FlowMap-r paper:
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// http://cadlab.cs.ucla.edu/~cong/papers/dac93.pdf (short version)
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// https://sci-hub.tw/10.1109/92.285741 (long version)
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// Notes on correspondence between paper and implementation:
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//
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// 1. In the FlowMap paper, the nodes are logic elements (analogous to Yosys cells) and edges are wires. However, in our implementation,
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// we use an inverted approach: the nodes are Yosys wire bits, and the edges are derived from (but aren't represented by) Yosys cells.
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// This may seem counterintuitive. Three observations may help understanding this. First, for a cell with a 1-bit Y output that is
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// the sole driver of its output net (which is the typical case), these representations are equivalent, because there is an exact
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// correspondence between cells and output wires. Second, in the paper, primary inputs (analogous to Yosys cell or module ports) are
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// nodes, and in Yosys, inputs are wires; our approach allows a direct mapping from both primary inputs and 1-output logic elements to
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// flow graph nodes. Third, Yosys cells may have multiple outputs or multi-bit outputs, and by using Yosys wire bits as flow graph nodes,
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// such cells are supported without any additional effort; any Yosys cell with n output wire bits ends up being split into n flow graph
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// nodes.
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//
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// 2. The FlowMap paper introduces three networks: Nt, Nt', and Nt''. The network Nt is directly represented by a subgraph of RTLIL graph,
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// which is parsed into an equivalent but easier to traverse representation in FlowmapWorker. The network Nt' is built explicitly
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// from a subgraph of Nt, and uses a similar representation in FlowGraph. The network Nt'' is implicit in FlowGraph, which is possible
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// because of the following observation: each Nt' node corresponds to an Nt'' edge of capacity 1, and each Nt' edge corresponds to
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// an Nt'' edge of capacity ∞. Therefore, we only need to explicitly record flow for Nt' edges and through Nt' nodes.
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//
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// 3. The FlowMap paper ambiguously states: "Moreover, we can find such a cut (X′′, X̅′′) by performing a depth first search starting at
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// the source s, and including in X′′ all the nodes which are reachable from s." This actually refers to a specific kind of search,
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// min-cut computation. Min-cut computation involves computing the set of nodes reachable from s by an undirected path with no full
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// (i.e. zero capacity) forward edges or empty (i.e. no flow) backward edges. In addition, the depth first search is required to compute
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// a max-volume max-flow min-cut specifically, because a max-flow min-cut is not, in general, unique.
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// Notes on implementation:
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//
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// 1. To compute depth optimal packing, an intermediate representation is used, where each cell with n output bits is split into n graph
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// nodes. Each such graph node is represented directly with the wire bit (RTLIL::SigBit instance) that corresponds to the output bit
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// it is created from. Fan-in and fan-out are represented explicitly by edge lists derived from the RTLIL graph. This IR never changes
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// after it has been computed.
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//
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// In terms of data, this IR is comprised of `inputs`, `outputs`, `nodes`, `edges_fw` and `edges_bw` fields.
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//
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// We call this IR "gate IR".
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//
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// 2. To compute area optimal packing, another intermediate representation is used, which consists of some K-feasible cone for every node
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// that exists in the gate IR. Immediately after depth optimal packing with FlowMap, each such cone occupies the lowest possible depth,
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// but this is not true in general, and transformations of this IR may change the cones, although each transformation has to keep each
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// cone K-feasible. In this IR, LUT fan-in and fan-out are represented explicitly by edge lists; if a K-feasible cone chosen for node A
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// includes nodes B and C, there are edges between all predecessors of A, B and C in the gate IR and node A in this IR. Moreover, in
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// this IR, cones may be *realized* or *derealized*. Only realized cones will end up mapped to actual LUTs in the output of this pass.
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//
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// Intuitively, this IR contains (some, ideally but not necessarily optimal) LUT representation for each input cell. By starting at outputs
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// and traversing the graph of this IR backwards, each K-feasible cone is converted to an actual LUT at the end of the pass. This is
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// the same as iterating through each realized LUT.
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//
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// The following are the invariants of this IR:
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// a) Each gate IR node corresponds to a K-feasible cut.
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// b) Each realized LUT is reachable through backward edges from some output.
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// c) The LUT fan-in is exactly the fan-in of its constituent gates minus the fan-out of its constituent gates.
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// The invariants are kept even for derealized LUTs, since the whole point of this IR is ease of packing, unpacking, and repacking LUTs.
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//
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// In terms of data, this IR is comprised of `lut_nodes` (the set of all realized LUTs), `lut_gates` (the map from a LUT to its
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// constituent gates), `lut_edges_fw` and `lut_edges_bw` fields. The `inputs` and `outputs` fields are shared with the gate IR.
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//
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// We call this IR "LUT IR".
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#include "kernel/yosys.h"
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#include "kernel/sigtools.h"
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#include "kernel/modtools.h"
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#include "kernel/consteval.h"
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USING_YOSYS_NAMESPACE
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PRIVATE_NAMESPACE_BEGIN
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struct GraphStyle
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{
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string label;
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string color, fillcolor;
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GraphStyle(string label = "", string color = "black", string fillcolor = "") :
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label(label), color(color), fillcolor(fillcolor) {}
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};
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static string dot_escape(string value)
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{
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std::string escaped;
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for (char c : value) {
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if (c == '\n')
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{
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escaped += "\\n";
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continue;
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}
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if (c == '\\' || c == '"')
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escaped += "\\";
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escaped += c;
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}
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return escaped;
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}
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static void dump_dot_graph(string filename,
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pool<RTLIL::SigBit> nodes, dict<RTLIL::SigBit, pool<RTLIL::SigBit>> edges,
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pool<RTLIL::SigBit> inputs, pool<RTLIL::SigBit> outputs,
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std::function<GraphStyle(RTLIL::SigBit)> node_style =
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[](RTLIL::SigBit) { return GraphStyle{}; },
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std::function<GraphStyle(RTLIL::SigBit, RTLIL::SigBit)> edge_style =
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[](RTLIL::SigBit, RTLIL::SigBit) { return GraphStyle{}; },
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string name = "")
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{
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FILE *f = fopen(filename.c_str(), "w");
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fprintf(f, "digraph \"%s\" {\n", name.c_str());
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fprintf(f, " rankdir=\"TB\";\n");
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dict<RTLIL::SigBit, int> ids;
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for (auto node : nodes)
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{
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ids[node] = ids.size();
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string shape = "ellipse";
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if (inputs[node])
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shape = "box";
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if (outputs[node])
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shape = "octagon";
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auto prop = node_style(node);
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string style = "";
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if (!prop.fillcolor.empty())
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style = "filled";
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fprintf(f, " n%d [ shape=%s, fontname=\"Monospace\", label=\"%s\", color=\"%s\", fillcolor=\"%s\", style=\"%s\" ];\n",
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ids[node], shape.c_str(), dot_escape(prop.label.c_str()).c_str(), prop.color.c_str(), prop.fillcolor.c_str(), style.c_str());
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}
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fprintf(f, " { rank=\"source\"; ");
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for (auto input : inputs)
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if (nodes[input])
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fprintf(f, "n%d; ", ids[input]);
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fprintf(f, "}\n");
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fprintf(f, " { rank=\"sink\"; ");
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for (auto output : outputs)
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if (nodes[output])
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fprintf(f, "n%d; ", ids[output]);
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fprintf(f, "}\n");
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for (auto edge : edges)
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{
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auto source = edge.first;
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for (auto sink : edge.second) {
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if (nodes[source] && nodes[sink])
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{
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auto prop = edge_style(source, sink);
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fprintf(f, " n%d -> n%d [ label=\"%s\", color=\"%s\", fillcolor=\"%s\" ];\n",
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ids[source], ids[sink], dot_escape(prop.label.c_str()).c_str(), prop.color.c_str(), prop.fillcolor.c_str());
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}
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}
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}
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fprintf(f, "}\n");
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fclose(f);
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}
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struct FlowGraph
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{
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const RTLIL::SigBit source;
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RTLIL::SigBit sink;
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pool<RTLIL::SigBit> nodes = {source};
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dict<RTLIL::SigBit, pool<RTLIL::SigBit>> edges_fw, edges_bw;
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const int MAX_NODE_FLOW = 1;
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dict<RTLIL::SigBit, int> node_flow;
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dict<pair<RTLIL::SigBit, RTLIL::SigBit>, int> edge_flow;
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dict<RTLIL::SigBit, pool<RTLIL::SigBit>> collapsed;
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void dump_dot_graph(string filename)
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{
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auto node_style = [&](RTLIL::SigBit node) {
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string label = (node == source) ? "(source)" : log_signal(node);
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for (auto collapsed_node : collapsed[node])
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label += stringf(" %s", log_signal(collapsed_node));
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int flow = node_flow[node];
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if (node != source && node != sink)
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label += stringf("\n%d/%d", flow, MAX_NODE_FLOW);
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else
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label += stringf("\n%d/∞", flow);
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return GraphStyle{label, flow < MAX_NODE_FLOW ? "green" : "black"};
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};
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auto edge_style = [&](RTLIL::SigBit source, RTLIL::SigBit sink) {
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int flow = edge_flow[{source, sink}];
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return GraphStyle{stringf("%d/∞", flow), flow > 0 ? "blue" : "black"};
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};
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::dump_dot_graph(filename, nodes, edges_fw, {source}, {sink}, node_style, edge_style);
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}
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// Here, we are working on the Nt'' network, but our representation is the Nt' network.
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// The difference between these is that where in Nt' we have a subgraph:
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//
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// v1 -> v2 -> v3
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//
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// in Nt'' we have a corresponding subgraph:
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//
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// v'1b -∞-> v'2t -f-> v'2b -∞-> v'3t
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//
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// To address this, we split each node v into two nodes, v't and v'b. This representation is virtual,
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// in the sense that nodes v't and v'b are overlaid on top of the original node v, and only exist
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// in paths and worklists.
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struct NodePrime
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{
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RTLIL::SigBit node;
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bool is_bottom;
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NodePrime(RTLIL::SigBit node, bool is_bottom) :
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node(node), is_bottom(is_bottom) {}
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bool operator==(const NodePrime &other) const
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{
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return node == other.node && is_bottom == other.is_bottom;
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}
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bool operator!=(const NodePrime &other) const
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{
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return !(*this == other);
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}
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[[nodiscard]] Hasher hash_into(Hasher h) const
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{
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std::pair<RTLIL::SigBit, int> p = {node, is_bottom};
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h.eat(p);
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return h;
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}
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static NodePrime top(RTLIL::SigBit node)
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{
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return NodePrime(node, /*is_bottom=*/false);
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}
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static NodePrime bottom(RTLIL::SigBit node)
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{
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return NodePrime(node, /*is_bottom=*/true);
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}
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NodePrime as_top() const
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{
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log_assert(is_bottom);
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return top(node);
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}
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NodePrime as_bottom() const
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{
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log_assert(!is_bottom);
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return bottom(node);
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}
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};
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bool find_augmenting_path(bool commit)
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{
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NodePrime source_prime = {source, true};
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NodePrime sink_prime = {sink, false};
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vector<NodePrime> path = {source_prime};
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pool<NodePrime> visited = {};
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bool found;
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do {
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found = false;
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auto node_prime = path.back();
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visited.insert(node_prime);
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if (!node_prime.is_bottom) // vt
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{
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if (!visited[node_prime.as_bottom()] && node_flow[node_prime.node] < MAX_NODE_FLOW)
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{
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path.push_back(node_prime.as_bottom());
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found = true;
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}
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else
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{
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for (auto node_pred : edges_bw[node_prime.node])
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{
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if (!visited[NodePrime::bottom(node_pred)] && edge_flow[{node_pred, node_prime.node}] > 0)
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{
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path.push_back(NodePrime::bottom(node_pred));
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found = true;
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break;
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}
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}
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}
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}
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else // vb
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{
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if (!visited[node_prime.as_top()] && node_flow[node_prime.node] > 0)
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{
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path.push_back(node_prime.as_top());
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found = true;
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}
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else
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{
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for (auto node_succ : edges_fw[node_prime.node])
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{
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if (!visited[NodePrime::top(node_succ)] /* && edge_flow[...] < ∞ */)
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{
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path.push_back(NodePrime::top(node_succ));
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found = true;
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break;
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}
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}
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}
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}
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if (!found && path.size() > 1)
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{
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path.pop_back();
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found = true;
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}
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} while(path.back() != sink_prime && found);
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if (commit && path.back() == sink_prime)
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{
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auto prev_prime = path.front();
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for (auto node_prime : path)
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{
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if (node_prime == source_prime)
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continue;
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log_assert(prev_prime.is_bottom ^ node_prime.is_bottom);
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if (prev_prime.node == node_prime.node)
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{
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auto node = node_prime.node;
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if (!prev_prime.is_bottom && node_prime.is_bottom)
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{
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log_assert(node_flow[node] == 0);
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node_flow[node]++;
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}
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else
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{
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log_assert(node_flow[node] != 0);
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node_flow[node]--;
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}
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}
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else
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{
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if (prev_prime.is_bottom && !node_prime.is_bottom)
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{
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log_assert(true /* edge_flow[...] < ∞ */);
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edge_flow[{prev_prime.node, node_prime.node}]++;
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}
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else
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{
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log_assert((edge_flow[{node_prime.node, prev_prime.node}] > 0));
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edge_flow[{node_prime.node, prev_prime.node}]--;
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}
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}
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prev_prime = node_prime;
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}
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node_flow[source]++;
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node_flow[sink]++;
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}
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return path.back() == sink_prime;
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}
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int maximum_flow(int order)
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{
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int flow = 0;
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while (flow < order && find_augmenting_path(/*commit=*/true))
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flow++;
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return flow + find_augmenting_path(/*commit=*/false);
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}
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pair<pool<RTLIL::SigBit>, pool<RTLIL::SigBit>> edge_cut()
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{
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pool<RTLIL::SigBit> x = {source}, xi; // X and X̅ in the paper
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NodePrime source_prime = {source, true};
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pool<NodePrime> visited;
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vector<NodePrime> worklist = {source_prime};
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while (!worklist.empty())
|
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{
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auto node_prime = worklist.back();
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worklist.pop_back();
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if (visited[node_prime])
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continue;
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visited.insert(node_prime);
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if (!node_prime.is_bottom)
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x.insert(node_prime.node);
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// Mincut is constructed by traversing a graph in an undirected way along forward edges that aren't full, or backward edges
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// that aren't empty.
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if (!node_prime.is_bottom) // top
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{
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if (node_flow[node_prime.node] < MAX_NODE_FLOW)
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worklist.push_back(node_prime.as_bottom());
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for (auto node_pred : edges_bw[node_prime.node])
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if (edge_flow[{node_pred, node_prime.node}] > 0)
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worklist.push_back(NodePrime::bottom(node_pred));
|
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}
|
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else // bottom
|
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{
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if (node_flow[node_prime.node] > 0)
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worklist.push_back(node_prime.as_top());
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for (auto node_succ : edges_fw[node_prime.node])
|
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if (true /* edge_flow[...] < ∞ */)
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worklist.push_back(NodePrime::top(node_succ));
|
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}
|
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}
|
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|
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for (auto node : nodes)
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||
if (!x[node])
|
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xi.insert(node);
|
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|
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for (auto collapsed_node : collapsed[sink])
|
||
xi.insert(collapsed_node);
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|
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log_assert(x[source] && !xi[source]);
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log_assert(!x[sink] && xi[sink]);
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return {x, xi};
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}
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};
|
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|
||
struct FlowmapWorker
|
||
{
|
||
int order;
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||
int r_alpha, r_beta, r_gamma;
|
||
bool debug, debug_relax;
|
||
|
||
RTLIL::Module *module;
|
||
SigMap sigmap;
|
||
ModIndex index;
|
||
|
||
dict<RTLIL::SigBit, ModIndex::PortInfo> node_origins;
|
||
|
||
// Gate IR
|
||
pool<RTLIL::SigBit> nodes, inputs, outputs;
|
||
dict<RTLIL::SigBit, pool<RTLIL::SigBit>> edges_fw, edges_bw;
|
||
dict<RTLIL::SigBit, int> labels;
|
||
|
||
// LUT IR
|
||
pool<RTLIL::SigBit> lut_nodes;
|
||
dict<RTLIL::SigBit, pool<RTLIL::SigBit>> lut_gates;
|
||
dict<RTLIL::SigBit, pool<RTLIL::SigBit>> lut_edges_fw, lut_edges_bw;
|
||
dict<RTLIL::SigBit, int> lut_depths, lut_altitudes, lut_slacks;
|
||
|
||
int gate_count = 0, lut_count = 0, packed_count = 0;
|
||
int gate_area = 0, lut_area = 0;
|
||
|
||
enum class GraphMode {
|
||
Label,
|
||
Cut,
|
||
Slack,
|
||
};
|
||
|
||
void dump_dot_graph(string filename, GraphMode mode,
|
||
pool<RTLIL::SigBit> subgraph_nodes = {}, dict<RTLIL::SigBit, pool<RTLIL::SigBit>> subgraph_edges = {},
|
||
dict<RTLIL::SigBit, pool<RTLIL::SigBit>> collapsed = {},
|
||
pair<pool<RTLIL::SigBit>, pool<RTLIL::SigBit>> cut = {})
|
||
{
|
||
if (subgraph_nodes.empty())
|
||
subgraph_nodes = nodes;
|
||
if (subgraph_edges.empty())
|
||
subgraph_edges = edges_fw;
|
||
|
||
auto node_style = [&](RTLIL::SigBit node) {
|
||
string label = log_signal(node);
|
||
for (auto collapsed_node : collapsed[node])
|
||
if (collapsed_node != node)
|
||
label += stringf(" %s", log_signal(collapsed_node));
|
||
switch (mode)
|
||
{
|
||
case GraphMode::Label:
|
||
if (labels[node] == -1)
|
||
{
|
||
label += "\nl=?";
|
||
return GraphStyle{label};
|
||
}
|
||
else
|
||
{
|
||
label += stringf("\nl=%d", labels[node]);
|
||
string fillcolor = stringf("/set311/%d", 1 + labels[node] % 11);
|
||
return GraphStyle{label, "", fillcolor};
|
||
}
|
||
|
||
case GraphMode::Cut:
|
||
if (cut.first[node])
|
||
return GraphStyle{label, "blue"};
|
||
if (cut.second[node])
|
||
return GraphStyle{label, "red"};
|
||
return GraphStyle{label};
|
||
|
||
case GraphMode::Slack:
|
||
label += stringf("\nd=%d a=%d\ns=%d", lut_depths[node], lut_altitudes[node], lut_slacks[node]);
|
||
return GraphStyle{label, lut_slacks[node] == 0 ? "red" : "black"};
|
||
}
|
||
return GraphStyle{label};
|
||
};
|
||
auto edge_style = [&](RTLIL::SigBit, RTLIL::SigBit) {
|
||
return GraphStyle{};
|
||
};
|
||
::dump_dot_graph(filename, subgraph_nodes, subgraph_edges, inputs, outputs, node_style, edge_style, module->name.str());
|
||
}
|
||
|
||
void dump_dot_lut_graph(string filename, GraphMode mode)
|
||
{
|
||
pool<RTLIL::SigBit> lut_and_input_nodes;
|
||
lut_and_input_nodes.insert(lut_nodes.begin(), lut_nodes.end());
|
||
lut_and_input_nodes.insert(inputs.begin(), inputs.end());
|
||
dump_dot_graph(filename, mode, lut_and_input_nodes, lut_edges_fw, lut_gates);
|
||
}
|
||
|
||
pool<RTLIL::SigBit> find_subgraph(RTLIL::SigBit sink)
|
||
{
|
||
pool<RTLIL::SigBit> subgraph;
|
||
pool<RTLIL::SigBit> worklist = {sink};
|
||
while (!worklist.empty())
|
||
{
|
||
auto node = worklist.pop();
|
||
subgraph.insert(node);
|
||
for (auto source : edges_bw[node])
|
||
{
|
||
if (!subgraph[source])
|
||
worklist.insert(source);
|
||
}
|
||
}
|
||
return subgraph;
|
||
}
|
||
|
||
FlowGraph build_flow_graph(RTLIL::SigBit sink, int p)
|
||
{
|
||
FlowGraph flow_graph;
|
||
flow_graph.sink = sink;
|
||
|
||
pool<RTLIL::SigBit> worklist = {sink}, visited;
|
||
while (!worklist.empty())
|
||
{
|
||
auto node = worklist.pop();
|
||
visited.insert(node);
|
||
|
||
auto collapsed_node = labels[node] == p ? sink : node;
|
||
if (node != collapsed_node)
|
||
flow_graph.collapsed[collapsed_node].insert(node);
|
||
flow_graph.nodes.insert(collapsed_node);
|
||
|
||
for (auto node_pred : edges_bw[node])
|
||
{
|
||
auto collapsed_node_pred = labels[node_pred] == p ? sink : node_pred;
|
||
if (node_pred != collapsed_node_pred)
|
||
flow_graph.collapsed[collapsed_node_pred].insert(node_pred);
|
||
if (collapsed_node != collapsed_node_pred)
|
||
{
|
||
flow_graph.edges_bw[collapsed_node].insert(collapsed_node_pred);
|
||
flow_graph.edges_fw[collapsed_node_pred].insert(collapsed_node);
|
||
}
|
||
if (inputs[node_pred])
|
||
{
|
||
flow_graph.edges_bw[collapsed_node_pred].insert(flow_graph.source);
|
||
flow_graph.edges_fw[flow_graph.source].insert(collapsed_node_pred);
|
||
}
|
||
|
||
if (!visited[node_pred])
|
||
worklist.insert(node_pred);
|
||
}
|
||
}
|
||
return flow_graph;
|
||
}
|
||
|
||
void discover_nodes(pool<IdString> cell_types)
|
||
{
|
||
for (auto cell : module->selected_cells())
|
||
{
|
||
if (!cell_types[cell->type])
|
||
continue;
|
||
|
||
if (!cell->known())
|
||
log_error("Cell %s (%s.%s) is unknown.\n", cell->type.c_str(), log_id(module), log_id(cell));
|
||
|
||
pool<RTLIL::SigBit> fanout;
|
||
for (auto conn : cell->connections())
|
||
{
|
||
if (!cell->output(conn.first)) continue;
|
||
int offset = -1;
|
||
for (auto bit : conn.second)
|
||
{
|
||
offset++;
|
||
if (!bit.wire) continue;
|
||
auto mapped_bit = sigmap(bit);
|
||
if (nodes[mapped_bit])
|
||
log_error("Multiple drivers found for wire %s.\n", log_signal(mapped_bit));
|
||
nodes.insert(mapped_bit);
|
||
node_origins[mapped_bit] = ModIndex::PortInfo(cell, conn.first, offset);
|
||
fanout.insert(mapped_bit);
|
||
}
|
||
}
|
||
|
||
int fanin = 0;
|
||
for (auto conn : cell->connections())
|
||
{
|
||
if (!cell->input(conn.first)) continue;
|
||
for (auto bit : sigmap(conn.second))
|
||
{
|
||
if (!bit.wire) continue;
|
||
for (auto fanout_bit : fanout)
|
||
{
|
||
edges_fw[bit].insert(fanout_bit);
|
||
edges_bw[fanout_bit].insert(bit);
|
||
}
|
||
fanin++;
|
||
}
|
||
}
|
||
|
||
if (fanin > order)
|
||
log_error("Cell %s (%s.%s) with fan-in %d cannot be mapped to a %d-LUT.\n",
|
||
cell->type.c_str(), log_id(module), log_id(cell), fanin, order);
|
||
|
||
gate_count++;
|
||
gate_area += 1 << fanin;
|
||
}
|
||
|
||
for (auto edge : edges_fw)
|
||
{
|
||
if (!nodes[edge.first])
|
||
{
|
||
inputs.insert(edge.first);
|
||
nodes.insert(edge.first);
|
||
}
|
||
}
|
||
|
||
for (auto node : nodes)
|
||
{
|
||
auto node_info = index.query(node);
|
||
if (node_info->is_output && !inputs[node])
|
||
outputs.insert(node);
|
||
for (auto port : node_info->ports)
|
||
if (!cell_types[port.cell->type] && !inputs[node])
|
||
outputs.insert(node);
|
||
}
|
||
|
||
if (debug)
|
||
{
|
||
dump_dot_graph("flowmap-initial.dot", GraphMode::Label);
|
||
log("Dumped initial graph to `flowmap-initial.dot`.\n");
|
||
}
|
||
}
|
||
|
||
void label_nodes()
|
||
{
|
||
for (auto node : nodes)
|
||
labels[node] = -1;
|
||
for (auto input : inputs)
|
||
{
|
||
if (input.wire->attributes.count(ID($flowmap_level)))
|
||
labels[input] = input.wire->attributes[ID($flowmap_level)].as_int();
|
||
else
|
||
labels[input] = 0;
|
||
}
|
||
|
||
pool<RTLIL::SigBit> worklist = nodes;
|
||
int debug_num = 0;
|
||
while (!worklist.empty())
|
||
{
|
||
auto sink = worklist.pop();
|
||
if (labels[sink] != -1)
|
||
continue;
|
||
|
||
bool inputs_have_labels = true;
|
||
for (auto sink_input : edges_bw[sink])
|
||
{
|
||
if (labels[sink_input] == -1)
|
||
{
|
||
inputs_have_labels = false;
|
||
break;
|
||
}
|
||
}
|
||
if (!inputs_have_labels)
|
||
continue;
|
||
|
||
if (debug)
|
||
{
|
||
debug_num++;
|
||
log("Examining subgraph %d rooted in %s.\n", debug_num, log_signal(sink));
|
||
}
|
||
|
||
pool<RTLIL::SigBit> subgraph = find_subgraph(sink);
|
||
|
||
int p = 1;
|
||
for (auto subgraph_node : subgraph)
|
||
p = max(p, labels[subgraph_node]);
|
||
|
||
FlowGraph flow_graph = build_flow_graph(sink, p);
|
||
int flow = flow_graph.maximum_flow(order);
|
||
pool<RTLIL::SigBit> x, xi;
|
||
if (flow <= order)
|
||
{
|
||
labels[sink] = p;
|
||
auto cut = flow_graph.edge_cut();
|
||
x = cut.first;
|
||
xi = cut.second;
|
||
}
|
||
else
|
||
{
|
||
labels[sink] = p + 1;
|
||
x = subgraph;
|
||
x.erase(sink);
|
||
xi.insert(sink);
|
||
}
|
||
lut_gates[sink] = xi;
|
||
|
||
pool<RTLIL::SigBit> k;
|
||
for (auto xi_node : xi)
|
||
{
|
||
for (auto xi_node_pred : edges_bw[xi_node])
|
||
if (x[xi_node_pred])
|
||
k.insert(xi_node_pred);
|
||
}
|
||
log_assert((int)k.size() <= order);
|
||
lut_edges_bw[sink] = k;
|
||
for (auto k_node : k)
|
||
lut_edges_fw[k_node].insert(sink);
|
||
|
||
if (debug)
|
||
{
|
||
log(" Maximum flow: %d. Assigned label %d.\n", flow, labels[sink]);
|
||
dump_dot_graph(stringf("flowmap-%d-sub.dot", debug_num), GraphMode::Cut, subgraph, {}, {}, {x, xi});
|
||
log(" Dumped subgraph to `flowmap-%d-sub.dot`.\n", debug_num);
|
||
flow_graph.dump_dot_graph(stringf("flowmap-%d-flow.dot", debug_num));
|
||
log(" Dumped flow graph to `flowmap-%d-flow.dot`.\n", debug_num);
|
||
log(" LUT inputs:");
|
||
for (auto k_node : k)
|
||
log(" %s", log_signal(k_node));
|
||
log(".\n");
|
||
log(" LUT packed gates:");
|
||
for (auto xi_node : xi)
|
||
log(" %s", log_signal(xi_node));
|
||
log(".\n");
|
||
}
|
||
|
||
for (auto sink_succ : edges_fw[sink])
|
||
worklist.insert(sink_succ);
|
||
}
|
||
|
||
if (debug)
|
||
{
|
||
dump_dot_graph("flowmap-labeled.dot", GraphMode::Label);
|
||
log("Dumped labeled graph to `flowmap-labeled.dot`.\n");
|
||
}
|
||
}
|
||
|
||
int map_luts()
|
||
{
|
||
pool<RTLIL::SigBit> worklist = outputs;
|
||
while (!worklist.empty())
|
||
{
|
||
auto lut_node = worklist.pop();
|
||
lut_nodes.insert(lut_node);
|
||
for (auto input_node : lut_edges_bw[lut_node])
|
||
if (!lut_nodes[input_node] && !inputs[input_node])
|
||
worklist.insert(input_node);
|
||
}
|
||
|
||
int depth = 0;
|
||
for (auto label : labels)
|
||
depth = max(depth, label.second);
|
||
log("Mapped to %d LUTs with maximum depth %d.\n", GetSize(lut_nodes), depth);
|
||
|
||
if (debug)
|
||
{
|
||
dump_dot_lut_graph("flowmap-mapped.dot", GraphMode::Label);
|
||
log("Dumped mapped graph to `flowmap-mapped.dot`.\n");
|
||
}
|
||
|
||
return depth;
|
||
}
|
||
|
||
void realize_derealize_lut(RTLIL::SigBit lut, pool<RTLIL::SigBit> *changed = nullptr)
|
||
{
|
||
pool<RTLIL::SigBit> worklist = {lut};
|
||
while (!worklist.empty())
|
||
{
|
||
auto lut = worklist.pop();
|
||
if (inputs[lut])
|
||
continue;
|
||
|
||
bool realized_successors = false;
|
||
for (auto lut_succ : lut_edges_fw[lut])
|
||
if (lut_nodes[lut_succ])
|
||
realized_successors = true;
|
||
|
||
if (realized_successors && !lut_nodes[lut])
|
||
lut_nodes.insert(lut);
|
||
else if (!realized_successors && lut_nodes[lut])
|
||
lut_nodes.erase(lut);
|
||
else
|
||
continue;
|
||
|
||
for (auto lut_pred : lut_edges_bw[lut])
|
||
worklist.insert(lut_pred);
|
||
|
||
if (changed)
|
||
changed->insert(lut);
|
||
}
|
||
}
|
||
|
||
void add_lut_edge(RTLIL::SigBit pred, RTLIL::SigBit succ, pool<RTLIL::SigBit> *changed = nullptr)
|
||
{
|
||
log_assert(!lut_edges_fw[pred][succ] && !lut_edges_bw[succ][pred]);
|
||
log_assert((int)lut_edges_bw[succ].size() < order);
|
||
|
||
lut_edges_fw[pred].insert(succ);
|
||
lut_edges_bw[succ].insert(pred);
|
||
realize_derealize_lut(pred, changed);
|
||
|
||
if (changed)
|
||
{
|
||
changed->insert(pred);
|
||
changed->insert(succ);
|
||
}
|
||
}
|
||
|
||
void remove_lut_edge(RTLIL::SigBit pred, RTLIL::SigBit succ, pool<RTLIL::SigBit> *changed = nullptr)
|
||
{
|
||
log_assert(lut_edges_fw[pred][succ] && lut_edges_bw[succ][pred]);
|
||
|
||
lut_edges_fw[pred].erase(succ);
|
||
lut_edges_bw[succ].erase(pred);
|
||
realize_derealize_lut(pred, changed);
|
||
|
||
if (changed)
|
||
{
|
||
if (lut_nodes[pred])
|
||
changed->insert(pred);
|
||
changed->insert(succ);
|
||
}
|
||
}
|
||
|
||
pair<pool<RTLIL::SigBit>, pool<RTLIL::SigBit>> cut_lut_at_gate(RTLIL::SigBit lut, RTLIL::SigBit lut_gate)
|
||
{
|
||
pool<RTLIL::SigBit> gate_inputs = lut_edges_bw[lut];
|
||
pool<RTLIL::SigBit> other_inputs;
|
||
pool<RTLIL::SigBit> worklist = {lut};
|
||
while (!worklist.empty())
|
||
{
|
||
auto node = worklist.pop();
|
||
for (auto node_pred : edges_bw[node])
|
||
{
|
||
if (node_pred == lut_gate)
|
||
continue;
|
||
if (lut_gates[lut][node_pred])
|
||
worklist.insert(node_pred);
|
||
else
|
||
{
|
||
gate_inputs.erase(node_pred);
|
||
other_inputs.insert(node_pred);
|
||
}
|
||
}
|
||
}
|
||
return {gate_inputs, other_inputs};
|
||
}
|
||
|
||
void compute_lut_distances(dict<RTLIL::SigBit, int> &lut_distances, bool forward,
|
||
pool<RTLIL::SigBit> initial = {}, pool<RTLIL::SigBit> *changed = nullptr)
|
||
{
|
||
pool<RTLIL::SigBit> terminals = forward ? inputs : outputs;
|
||
auto &lut_edges_next = forward ? lut_edges_fw : lut_edges_bw;
|
||
auto &lut_edges_prev = forward ? lut_edges_bw : lut_edges_fw;
|
||
|
||
if (initial.empty())
|
||
initial = terminals;
|
||
for (auto node : initial)
|
||
lut_distances.erase(node);
|
||
|
||
pool<RTLIL::SigBit> worklist = initial;
|
||
while (!worklist.empty())
|
||
{
|
||
auto lut = worklist.pop();
|
||
int lut_distance = 0;
|
||
if (forward && inputs[lut])
|
||
lut_distance = labels[lut]; // to support (* $flowmap_level=n *)
|
||
for (auto lut_prev : lut_edges_prev[lut])
|
||
if ((lut_nodes[lut_prev] || inputs[lut_prev]) && lut_distances.count(lut_prev))
|
||
lut_distance = max(lut_distance, lut_distances[lut_prev] + 1);
|
||
if (!lut_distances.count(lut) || lut_distances[lut] != lut_distance)
|
||
{
|
||
lut_distances[lut] = lut_distance;
|
||
if (changed != nullptr && !inputs[lut])
|
||
changed->insert(lut);
|
||
for (auto lut_next : lut_edges_next[lut])
|
||
if (lut_nodes[lut_next] || inputs[lut_next])
|
||
worklist.insert(lut_next);
|
||
}
|
||
}
|
||
}
|
||
|
||
void check_lut_distances(const dict<RTLIL::SigBit, int> &lut_distances, bool forward)
|
||
{
|
||
dict<RTLIL::SigBit, int> gold_lut_distances;
|
||
compute_lut_distances(gold_lut_distances, forward);
|
||
for (auto lut_distance : lut_distances)
|
||
if (lut_nodes[lut_distance.first])
|
||
log_assert(lut_distance.second == gold_lut_distances[lut_distance.first]);
|
||
}
|
||
|
||
// LUT depth is the length of the longest path from any input in LUT fan-in to LUT.
|
||
// LUT altitude (for lack of a better term) is the length of the longest path from LUT to any output in LUT fan-out.
|
||
void update_lut_depths_altitudes(pool<RTLIL::SigBit> worklist = {}, pool<RTLIL::SigBit> *changed = nullptr)
|
||
{
|
||
compute_lut_distances(lut_depths, /*forward=*/true, worklist, changed);
|
||
compute_lut_distances(lut_altitudes, /*forward=*/false, worklist, changed);
|
||
if (debug_relax && !worklist.empty()) {
|
||
check_lut_distances(lut_depths, /*forward=*/true);
|
||
check_lut_distances(lut_altitudes, /*forward=*/false);
|
||
}
|
||
}
|
||
|
||
// LUT critical output set is the set of outputs whose depth will increase (equivalently, slack will decrease) if the depth of
|
||
// the LUT increases. (This is referred to as RPOv for LUTv in the paper.)
|
||
void compute_lut_critical_outputs(dict<RTLIL::SigBit, pool<RTLIL::SigBit>> &lut_critical_outputs,
|
||
pool<RTLIL::SigBit> worklist = {})
|
||
{
|
||
if (worklist.empty())
|
||
worklist = lut_nodes;
|
||
|
||
while (!worklist.empty())
|
||
{
|
||
bool updated_some = false;
|
||
for (auto lut : worklist)
|
||
{
|
||
if (outputs[lut])
|
||
lut_critical_outputs[lut] = {lut};
|
||
else
|
||
{
|
||
bool all_succ_computed = true;
|
||
lut_critical_outputs[lut] = {};
|
||
for (auto lut_succ : lut_edges_fw[lut])
|
||
{
|
||
if (lut_nodes[lut_succ] && lut_depths[lut_succ] == lut_depths[lut] + 1)
|
||
{
|
||
if (lut_critical_outputs.count(lut_succ))
|
||
lut_critical_outputs[lut].insert(lut_critical_outputs[lut_succ].begin(), lut_critical_outputs[lut_succ].end());
|
||
else
|
||
{
|
||
all_succ_computed = false;
|
||
break;
|
||
}
|
||
}
|
||
}
|
||
if (!all_succ_computed)
|
||
{
|
||
lut_critical_outputs.erase(lut);
|
||
continue;
|
||
}
|
||
}
|
||
worklist.erase(lut);
|
||
updated_some = true;
|
||
}
|
||
log_assert(updated_some);
|
||
}
|
||
}
|
||
|
||
// Invalidating LUT critical output sets is tricky, because increasing the depth of a LUT may take other, adjacent LUTs off the critical
|
||
// path to the output. Conservatively, if we increase depth of some LUT, every LUT in its input cone needs to have its critical output
|
||
// set invalidated, too.
|
||
pool<RTLIL::SigBit> invalidate_lut_critical_outputs(dict<RTLIL::SigBit, pool<RTLIL::SigBit>> &lut_critical_outputs,
|
||
pool<RTLIL::SigBit> worklist)
|
||
{
|
||
pool<RTLIL::SigBit> changed;
|
||
while (!worklist.empty())
|
||
{
|
||
auto lut = worklist.pop();
|
||
changed.insert(lut);
|
||
lut_critical_outputs.erase(lut);
|
||
for (auto lut_pred : lut_edges_bw[lut])
|
||
{
|
||
if (lut_nodes[lut_pred] && !changed[lut_pred])
|
||
{
|
||
changed.insert(lut_pred);
|
||
worklist.insert(lut_pred);
|
||
}
|
||
}
|
||
}
|
||
return changed;
|
||
}
|
||
|
||
void check_lut_critical_outputs(const dict<RTLIL::SigBit, pool<RTLIL::SigBit>> &lut_critical_outputs)
|
||
{
|
||
dict<RTLIL::SigBit, pool<RTLIL::SigBit>> gold_lut_critical_outputs;
|
||
compute_lut_critical_outputs(gold_lut_critical_outputs);
|
||
for (auto lut_critical_output : lut_critical_outputs)
|
||
if (lut_nodes[lut_critical_output.first])
|
||
log_assert(lut_critical_output.second == gold_lut_critical_outputs[lut_critical_output.first]);
|
||
}
|
||
|
||
void update_lut_critical_outputs(dict<RTLIL::SigBit, pool<RTLIL::SigBit>> &lut_critical_outputs,
|
||
pool<RTLIL::SigBit> worklist = {})
|
||
{
|
||
if (!worklist.empty())
|
||
{
|
||
pool<RTLIL::SigBit> invalidated = invalidate_lut_critical_outputs(lut_critical_outputs, worklist);
|
||
compute_lut_critical_outputs(lut_critical_outputs, invalidated);
|
||
check_lut_critical_outputs(lut_critical_outputs);
|
||
}
|
||
else
|
||
compute_lut_critical_outputs(lut_critical_outputs);
|
||
}
|
||
|
||
void update_breaking_node_potentials(dict<RTLIL::SigBit, dict<RTLIL::SigBit, int>> &potentials,
|
||
const dict<RTLIL::SigBit, pool<RTLIL::SigBit>> &lut_critical_outputs)
|
||
{
|
||
for (auto lut : lut_nodes)
|
||
{
|
||
if (potentials.count(lut))
|
||
continue;
|
||
if (lut_gates[lut].size() == 1 || lut_slacks[lut] == 0)
|
||
continue;
|
||
|
||
if (debug_relax)
|
||
log(" Computing potentials for LUT %s.\n", log_signal(lut));
|
||
|
||
for (auto lut_gate : lut_gates[lut])
|
||
{
|
||
if (lut == lut_gate)
|
||
continue;
|
||
|
||
if (debug_relax)
|
||
log(" Considering breaking node %s.\n", log_signal(lut_gate));
|
||
|
||
int r_ex, r_im, r_slk;
|
||
|
||
auto cut_inputs = cut_lut_at_gate(lut, lut_gate);
|
||
pool<RTLIL::SigBit> gate_inputs = cut_inputs.first, other_inputs = cut_inputs.second;
|
||
if (gate_inputs.empty() && (int)other_inputs.size() >= order)
|
||
{
|
||
if (debug_relax)
|
||
log(" Breaking would result in a (k+1)-LUT.\n");
|
||
continue;
|
||
}
|
||
|
||
pool<RTLIL::SigBit> elim_fanin_luts;
|
||
for (auto gate_input : gate_inputs)
|
||
{
|
||
if (lut_edges_fw[gate_input].size() == 1)
|
||
{
|
||
log_assert(lut_edges_fw[gate_input][lut]);
|
||
elim_fanin_luts.insert(gate_input);
|
||
}
|
||
}
|
||
if (debug_relax)
|
||
{
|
||
if (!lut_nodes[lut_gate])
|
||
log(" Breaking requires a new LUT.\n");
|
||
if (!gate_inputs.empty())
|
||
{
|
||
log(" Breaking eliminates LUT inputs");
|
||
for (auto gate_input : gate_inputs)
|
||
log(" %s", log_signal(gate_input));
|
||
log(".\n");
|
||
}
|
||
if (!elim_fanin_luts.empty())
|
||
{
|
||
log(" Breaking eliminates fan-in LUTs");
|
||
for (auto elim_fanin_lut : elim_fanin_luts)
|
||
log(" %s", log_signal(elim_fanin_lut));
|
||
log(".\n");
|
||
}
|
||
}
|
||
r_ex = (lut_nodes[lut_gate] ? 0 : -1) + elim_fanin_luts.size();
|
||
|
||
pool<pair<RTLIL::SigBit, RTLIL::SigBit>> maybe_mergeable_luts;
|
||
|
||
// Try to merge LUTv with one of its successors.
|
||
RTLIL::SigBit last_lut_succ;
|
||
int fanout = 0;
|
||
for (auto lut_succ : lut_edges_fw[lut])
|
||
{
|
||
if (lut_nodes[lut_succ])
|
||
{
|
||
fanout++;
|
||
last_lut_succ = lut_succ;
|
||
}
|
||
}
|
||
if (fanout == 1)
|
||
maybe_mergeable_luts.insert({lut, last_lut_succ});
|
||
|
||
// Try to merge LUTv with one of its predecessors.
|
||
for (auto lut_pred : other_inputs)
|
||
{
|
||
int fanout = 0;
|
||
for (auto lut_pred_succ : lut_edges_fw[lut_pred])
|
||
if (lut_nodes[lut_pred_succ] || lut_pred_succ == lut_gate)
|
||
fanout++;
|
||
if (fanout == 1)
|
||
maybe_mergeable_luts.insert({lut_pred, lut});
|
||
}
|
||
|
||
// Try to merge LUTw with one of its predecessors.
|
||
for (auto lut_gate_pred : lut_edges_bw[lut_gate])
|
||
{
|
||
int fanout = 0;
|
||
for (auto lut_gate_pred_succ : lut_edges_fw[lut_gate_pred])
|
||
if (lut_nodes[lut_gate_pred_succ] || lut_gate_pred_succ == lut_gate)
|
||
fanout++;
|
||
if (fanout == 1)
|
||
maybe_mergeable_luts.insert({lut_gate_pred, lut_gate});
|
||
}
|
||
|
||
r_im = 0;
|
||
for (auto maybe_mergeable_pair : maybe_mergeable_luts)
|
||
{
|
||
log_assert(lut_edges_fw[maybe_mergeable_pair.first][maybe_mergeable_pair.second]);
|
||
pool<RTLIL::SigBit> unique_inputs;
|
||
for (auto fst_lut_pred : lut_edges_bw[maybe_mergeable_pair.first])
|
||
if (lut_nodes[fst_lut_pred])
|
||
unique_inputs.insert(fst_lut_pred);
|
||
for (auto snd_lut_pred : lut_edges_bw[maybe_mergeable_pair.second])
|
||
if (lut_nodes[snd_lut_pred])
|
||
unique_inputs.insert(snd_lut_pred);
|
||
unique_inputs.erase(maybe_mergeable_pair.first);
|
||
if ((int)unique_inputs.size() <= order)
|
||
{
|
||
if (debug_relax)
|
||
log(" Breaking may allow merging %s and %s.\n",
|
||
log_signal(maybe_mergeable_pair.first), log_signal(maybe_mergeable_pair.second));
|
||
r_im++;
|
||
}
|
||
}
|
||
|
||
int lut_gate_depth;
|
||
if (lut_nodes[lut_gate])
|
||
lut_gate_depth = lut_depths[lut_gate];
|
||
else
|
||
{
|
||
lut_gate_depth = 0;
|
||
for (auto lut_gate_pred : lut_edges_bw[lut_gate])
|
||
lut_gate_depth = max(lut_gate_depth, lut_depths[lut_gate_pred] + 1);
|
||
}
|
||
if (lut_depths[lut] >= lut_gate_depth + 1)
|
||
r_slk = 0;
|
||
else
|
||
{
|
||
int depth_delta = lut_gate_depth + 1 - lut_depths[lut];
|
||
if (depth_delta > lut_slacks[lut])
|
||
{
|
||
if (debug_relax)
|
||
log(" Breaking would increase depth by %d, which is more than available slack.\n", depth_delta);
|
||
continue;
|
||
}
|
||
|
||
if (debug_relax)
|
||
{
|
||
log(" Breaking increases depth of LUT by %d.\n", depth_delta);
|
||
if (lut_critical_outputs.at(lut).size())
|
||
{
|
||
log(" Breaking decreases slack of outputs");
|
||
for (auto lut_critical_output : lut_critical_outputs.at(lut))
|
||
{
|
||
log(" %s", log_signal(lut_critical_output));
|
||
log_assert(lut_slacks[lut_critical_output] > 0);
|
||
}
|
||
log(".\n");
|
||
}
|
||
}
|
||
r_slk = lut_critical_outputs.at(lut).size() * depth_delta;
|
||
}
|
||
|
||
int p = 100 * (r_alpha * r_ex + r_beta * r_im + r_gamma) / (r_slk + 1);
|
||
if (debug_relax)
|
||
log(" Potential for breaking node %s: %d (Rex=%d, Rim=%d, Rslk=%d).\n",
|
||
log_signal(lut_gate), p, r_ex, r_im, r_slk);
|
||
potentials[lut][lut_gate] = p;
|
||
}
|
||
}
|
||
}
|
||
|
||
bool relax_depth_for_bound(bool first, int depth_bound, dict<RTLIL::SigBit, pool<RTLIL::SigBit>> &lut_critical_outputs)
|
||
{
|
||
int initial_count = GetSize(lut_nodes);
|
||
|
||
for (auto node : lut_nodes)
|
||
{
|
||
lut_slacks[node] = depth_bound - (lut_depths[node] + lut_altitudes[node]);
|
||
log_assert(lut_slacks[node] >= 0);
|
||
}
|
||
if (debug)
|
||
{
|
||
dump_dot_lut_graph(stringf("flowmap-relax-%d-initial.dot", depth_bound), GraphMode::Slack);
|
||
log(" Dumped initial slack graph to `flowmap-relax-%d-initial.dot`.\n", depth_bound);
|
||
}
|
||
|
||
dict<RTLIL::SigBit, dict<RTLIL::SigBit, int>> potentials;
|
||
for (int break_num = 1; ; break_num++)
|
||
{
|
||
update_breaking_node_potentials(potentials, lut_critical_outputs);
|
||
|
||
if (potentials.empty())
|
||
{
|
||
log(" Relaxed to %d (+%d) LUTs.\n", GetSize(lut_nodes), GetSize(lut_nodes) - initial_count);
|
||
if (!first && break_num == 1)
|
||
{
|
||
log(" Design fully relaxed.\n");
|
||
return true;
|
||
}
|
||
else
|
||
{
|
||
log(" Slack exhausted.\n");
|
||
break;
|
||
}
|
||
}
|
||
|
||
RTLIL::SigBit breaking_lut, breaking_gate;
|
||
int best_potential = INT_MIN;
|
||
for (auto lut_gate_potentials : potentials)
|
||
{
|
||
for (auto gate_potential : lut_gate_potentials.second)
|
||
{
|
||
if (gate_potential.second > best_potential)
|
||
{
|
||
breaking_lut = lut_gate_potentials.first;
|
||
breaking_gate = gate_potential.first;
|
||
best_potential = gate_potential.second;
|
||
}
|
||
}
|
||
}
|
||
log(" Breaking LUT %s to %s LUT %s (potential %d).\n",
|
||
log_signal(breaking_lut), lut_nodes[breaking_gate] ? "reuse" : "extract", log_signal(breaking_gate), best_potential);
|
||
|
||
if (debug_relax)
|
||
log(" Removing breaking gate %s from LUT.\n", log_signal(breaking_gate));
|
||
lut_gates[breaking_lut].erase(breaking_gate);
|
||
|
||
auto cut_inputs = cut_lut_at_gate(breaking_lut, breaking_gate);
|
||
pool<RTLIL::SigBit> gate_inputs = cut_inputs.first, other_inputs = cut_inputs.second;
|
||
|
||
pool<RTLIL::SigBit> worklist = lut_gates[breaking_lut];
|
||
pool<RTLIL::SigBit> elim_gates = gate_inputs;
|
||
while (!worklist.empty())
|
||
{
|
||
auto lut_gate = worklist.pop();
|
||
bool all_gate_preds_elim = true;
|
||
for (auto lut_gate_pred : edges_bw[lut_gate])
|
||
if (!elim_gates[lut_gate_pred])
|
||
all_gate_preds_elim = false;
|
||
if (all_gate_preds_elim)
|
||
{
|
||
if (debug_relax)
|
||
log(" Removing gate %s from LUT.\n", log_signal(lut_gate));
|
||
lut_gates[breaking_lut].erase(lut_gate);
|
||
for (auto lut_gate_succ : edges_fw[lut_gate])
|
||
worklist.insert(lut_gate_succ);
|
||
}
|
||
}
|
||
log_assert(!lut_gates[breaking_lut].empty());
|
||
|
||
pool<RTLIL::SigBit> directly_affected_nodes = {breaking_lut};
|
||
for (auto gate_input : gate_inputs)
|
||
{
|
||
if (debug_relax)
|
||
log(" Removing LUT edge %s -> %s.\n", log_signal(gate_input), log_signal(breaking_lut));
|
||
remove_lut_edge(gate_input, breaking_lut, &directly_affected_nodes);
|
||
}
|
||
if (debug_relax)
|
||
log(" Adding LUT edge %s -> %s.\n", log_signal(breaking_gate), log_signal(breaking_lut));
|
||
add_lut_edge(breaking_gate, breaking_lut, &directly_affected_nodes);
|
||
|
||
if (debug_relax)
|
||
log(" Updating slack and potentials.\n");
|
||
|
||
pool<RTLIL::SigBit> indirectly_affected_nodes = {};
|
||
update_lut_depths_altitudes(directly_affected_nodes, &indirectly_affected_nodes);
|
||
update_lut_critical_outputs(lut_critical_outputs, indirectly_affected_nodes);
|
||
for (auto node : indirectly_affected_nodes)
|
||
{
|
||
lut_slacks[node] = depth_bound - (lut_depths[node] + lut_altitudes[node]);
|
||
log_assert(lut_slacks[node] >= 0);
|
||
if (debug_relax)
|
||
log(" LUT %s now has depth %d and slack %d.\n", log_signal(node), lut_depths[node], lut_slacks[node]);
|
||
}
|
||
|
||
worklist = indirectly_affected_nodes;
|
||
pool<RTLIL::SigBit> visited;
|
||
while (!worklist.empty())
|
||
{
|
||
auto node = worklist.pop();
|
||
visited.insert(node);
|
||
potentials.erase(node);
|
||
// We are invalidating the entire output cone of the gate IR node, not just of the LUT IR node. This is done to also invalidate
|
||
// all LUTs that could contain one of the indirectly affected nodes as a *part* of them, as they may not be in the output cone
|
||
// of any of the LUT IR nodes, e.g. if we have a LUT IR node A and node B as predecessors of node C, where node B includes all
|
||
// gates from node A.
|
||
for (auto node_succ : edges_fw[node])
|
||
if (!visited[node_succ])
|
||
worklist.insert(node_succ);
|
||
}
|
||
|
||
if (debug)
|
||
{
|
||
dump_dot_lut_graph(stringf("flowmap-relax-%d-break-%d.dot", depth_bound, break_num), GraphMode::Slack);
|
||
log(" Dumped slack graph after break %d to `flowmap-relax-%d-break-%d.dot`.\n", break_num, depth_bound, break_num);
|
||
}
|
||
}
|
||
|
||
return false;
|
||
}
|
||
|
||
void optimize_area(int depth, int optarea)
|
||
{
|
||
dict<RTLIL::SigBit, pool<RTLIL::SigBit>> lut_critical_outputs;
|
||
update_lut_depths_altitudes();
|
||
update_lut_critical_outputs(lut_critical_outputs);
|
||
|
||
for (int depth_bound = depth; depth_bound <= depth + optarea; depth_bound++)
|
||
{
|
||
log("Relaxing with depth bound %d.\n", depth_bound);
|
||
bool fully_relaxed = relax_depth_for_bound(depth_bound == depth, depth_bound, lut_critical_outputs);
|
||
|
||
if (fully_relaxed)
|
||
break;
|
||
}
|
||
}
|
||
|
||
void pack_cells(int minlut)
|
||
{
|
||
ConstEval ce(module);
|
||
for (auto input_node : inputs)
|
||
ce.stop(input_node);
|
||
|
||
pool<RTLIL::SigBit> mapped_nodes;
|
||
for (auto node : lut_nodes)
|
||
{
|
||
if (node_origins.count(node))
|
||
{
|
||
auto origin = node_origins[node];
|
||
if (origin.cell->getPort(origin.port).size() == 1)
|
||
log("Packing %s.%s.%s (%s).\n",
|
||
log_id(module), log_id(origin.cell), origin.port.c_str(), log_signal(node));
|
||
else
|
||
log("Packing %s.%s.%s [%d] (%s).\n",
|
||
log_id(module), log_id(origin.cell), origin.port.c_str(), origin.offset, log_signal(node));
|
||
}
|
||
else
|
||
{
|
||
log("Packing %s.%s.\n", log_id(module), log_signal(node));
|
||
}
|
||
|
||
for (auto gate_node : lut_gates[node])
|
||
{
|
||
log_assert(node_origins.count(gate_node));
|
||
|
||
if (gate_node == node)
|
||
continue;
|
||
|
||
auto gate_origin = node_origins[gate_node];
|
||
if (gate_origin.cell->getPort(gate_origin.port).size() == 1)
|
||
log(" Packing %s.%s.%s (%s).\n",
|
||
log_id(module), log_id(gate_origin.cell), gate_origin.port.c_str(), log_signal(gate_node));
|
||
else
|
||
log(" Packing %s.%s.%s [%d] (%s).\n",
|
||
log_id(module), log_id(gate_origin.cell), gate_origin.port.c_str(), gate_origin.offset, log_signal(gate_node));
|
||
}
|
||
|
||
vector<RTLIL::SigBit> input_nodes(lut_edges_bw[node].begin(), lut_edges_bw[node].end());
|
||
RTLIL::Const lut_table(State::Sx, max(1 << input_nodes.size(), 1 << minlut));
|
||
unsigned const mask = 1 << input_nodes.size();
|
||
for (unsigned i = 0; i < mask; i++)
|
||
{
|
||
ce.push();
|
||
for (size_t n = 0; n < input_nodes.size(); n++)
|
||
ce.set(input_nodes[n], ((i >> n) & 1) ? State::S1 : State::S0);
|
||
|
||
RTLIL::SigSpec value = node, undef;
|
||
if (!ce.eval(value, undef))
|
||
{
|
||
string env;
|
||
for (auto input_node : input_nodes)
|
||
env += stringf(" %s = %s\n", log_signal(input_node), log_signal(ce.values_map(input_node)));
|
||
log_error("Cannot evaluate %s because %s is not defined.\nEvaluation environment:\n%s",
|
||
log_signal(node), log_signal(undef), env.c_str());
|
||
}
|
||
|
||
lut_table.bits()[i] = value.as_bool() ? State::S1 : State::S0;
|
||
ce.pop();
|
||
}
|
||
|
||
RTLIL::SigSpec lut_a, lut_y = node;
|
||
for (auto input_node : input_nodes)
|
||
lut_a.append(input_node);
|
||
if ((int)input_nodes.size() < minlut)
|
||
lut_a.append(RTLIL::Const(State::Sx, minlut - input_nodes.size()));
|
||
|
||
RTLIL::Cell *lut = module->addLut(NEW_ID, lut_a, lut_y, lut_table);
|
||
mapped_nodes.insert(node);
|
||
for (auto gate_node : lut_gates[node])
|
||
{
|
||
auto gate_origin = node_origins[gate_node];
|
||
lut->add_strpool_attribute(ID::src, gate_origin.cell->get_strpool_attribute(ID::src));
|
||
packed_count++;
|
||
}
|
||
lut_count++;
|
||
lut_area += lut_table.size();
|
||
|
||
if ((int)input_nodes.size() >= minlut)
|
||
log(" Packed into a %d-LUT %s.%s.\n", GetSize(input_nodes), log_id(module), log_id(lut));
|
||
else
|
||
log(" Packed into a %d-LUT %s.%s (implemented as %d-LUT).\n", GetSize(input_nodes), log_id(module), log_id(lut), minlut);
|
||
}
|
||
|
||
for (auto node : mapped_nodes)
|
||
{
|
||
auto origin = node_origins[node];
|
||
RTLIL::SigSpec driver = origin.cell->getPort(origin.port);
|
||
driver[origin.offset] = module->addWire(NEW_ID);
|
||
origin.cell->setPort(origin.port, driver);
|
||
}
|
||
}
|
||
|
||
FlowmapWorker(int order, int minlut, pool<IdString> cell_types, int r_alpha, int r_beta, int r_gamma,
|
||
bool relax, int optarea, bool debug, bool debug_relax,
|
||
RTLIL::Module *module) :
|
||
order(order), r_alpha(r_alpha), r_beta(r_beta), r_gamma(r_gamma), debug(debug), debug_relax(debug_relax),
|
||
module(module), sigmap(module), index(module)
|
||
{
|
||
log("Labeling cells.\n");
|
||
discover_nodes(cell_types);
|
||
label_nodes();
|
||
int depth = map_luts();
|
||
|
||
if (relax)
|
||
{
|
||
log("\n");
|
||
log("Optimizing area.\n");
|
||
optimize_area(depth, optarea);
|
||
}
|
||
|
||
log("\n");
|
||
log("Packing cells.\n");
|
||
pack_cells(minlut);
|
||
}
|
||
};
|
||
|
||
static void split(std::vector<std::string> &tokens, const std::string &text, char sep)
|
||
{
|
||
size_t start = 0, end = 0;
|
||
while ((end = text.find(sep, start)) != std::string::npos) {
|
||
tokens.push_back(text.substr(start, end - start));
|
||
start = end + 1;
|
||
}
|
||
tokens.push_back(text.substr(start));
|
||
}
|
||
|
||
struct FlowmapPass : public Pass {
|
||
FlowmapPass() : Pass("flowmap", "pack LUTs with FlowMap") { }
|
||
void help() override
|
||
{
|
||
// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
|
||
log("\n");
|
||
log(" flowmap [options] [selection]\n");
|
||
log("\n");
|
||
log("This pass uses the FlowMap technology mapping algorithm to pack logic gates\n");
|
||
log("into k-LUTs with optimal depth. It allows mapping any circuit elements that can\n");
|
||
log("be evaluated with the `eval` pass, including cells with multiple output ports\n");
|
||
log("and multi-bit input and output ports.\n");
|
||
log("\n");
|
||
log(" -maxlut k\n");
|
||
log(" perform technology mapping for a k-LUT architecture. if not specified,\n");
|
||
log(" defaults to 3.\n");
|
||
log("\n");
|
||
log(" -minlut n\n");
|
||
log(" only produce n-input or larger LUTs. if not specified, defaults to 1.\n");
|
||
log("\n");
|
||
log(" -cells <cell>[,<cell>,...]\n");
|
||
log(" map specified cells. if not specified, maps $_NOT_, $_AND_, $_OR_,\n");
|
||
log(" $_XOR_ and $_MUX_, which are the outputs of the `simplemap` pass.\n");
|
||
log("\n");
|
||
log(" -relax\n");
|
||
log(" perform depth relaxation and area minimization.\n");
|
||
log("\n");
|
||
log(" -r-alpha n, -r-beta n, -r-gamma n\n");
|
||
log(" parameters of depth relaxation heuristic potential function.\n");
|
||
log(" if not specified, alpha=8, beta=2, gamma=1.\n");
|
||
log("\n");
|
||
log(" -optarea n\n");
|
||
log(" optimize for area by trading off at most n logic levels for fewer LUTs.\n");
|
||
log(" n may be zero, to optimize for area without increasing depth.\n");
|
||
log(" implies -relax.\n");
|
||
log("\n");
|
||
log(" -debug\n");
|
||
log(" dump intermediate graphs.\n");
|
||
log("\n");
|
||
log(" -debug-relax\n");
|
||
log(" explain decisions performed during depth relaxation.\n");
|
||
log("\n");
|
||
}
|
||
void execute(std::vector<std::string> args, RTLIL::Design *design) override
|
||
{
|
||
int order = 3;
|
||
int minlut = 1;
|
||
vector<string> cells;
|
||
bool relax = false;
|
||
int r_alpha = 8, r_beta = 2, r_gamma = 1;
|
||
int optarea = 0;
|
||
bool debug = false, debug_relax = false;
|
||
|
||
size_t argidx;
|
||
for (argidx = 1; argidx < args.size(); argidx++)
|
||
{
|
||
if (args[argidx] == "-maxlut" && argidx + 1 < args.size())
|
||
{
|
||
order = atoi(args[++argidx].c_str());
|
||
continue;
|
||
}
|
||
if (args[argidx] == "-minlut" && argidx + 1 < args.size())
|
||
{
|
||
minlut = atoi(args[++argidx].c_str());
|
||
continue;
|
||
}
|
||
if (args[argidx] == "-cells" && argidx + 1 < args.size())
|
||
{
|
||
split(cells, args[++argidx], ',');
|
||
continue;
|
||
}
|
||
if (args[argidx] == "-relax")
|
||
{
|
||
relax = true;
|
||
continue;
|
||
}
|
||
if (args[argidx] == "-r-alpha" && argidx + 1 < args.size())
|
||
{
|
||
r_alpha = atoi(args[++argidx].c_str());
|
||
continue;
|
||
}
|
||
if (args[argidx] == "-r-beta" && argidx + 1 < args.size())
|
||
{
|
||
r_beta = atoi(args[++argidx].c_str());
|
||
continue;
|
||
}
|
||
if (args[argidx] == "-r-gamma" && argidx + 1 < args.size())
|
||
{
|
||
r_gamma = atoi(args[++argidx].c_str());
|
||
continue;
|
||
}
|
||
if (args[argidx] == "-optarea" && argidx + 1 < args.size())
|
||
{
|
||
relax = true;
|
||
optarea = atoi(args[++argidx].c_str());
|
||
continue;
|
||
}
|
||
if (args[argidx] == "-debug")
|
||
{
|
||
debug = true;
|
||
continue;
|
||
}
|
||
if (args[argidx] == "-debug-relax")
|
||
{
|
||
debug = debug_relax = true;
|
||
continue;
|
||
}
|
||
break;
|
||
}
|
||
extra_args(args, argidx, design);
|
||
|
||
pool<IdString> cell_types;
|
||
if (!cells.empty())
|
||
{
|
||
for (auto &cell : cells)
|
||
cell_types.insert(cell);
|
||
}
|
||
else
|
||
{
|
||
cell_types = {ID($_NOT_), ID($_AND_), ID($_OR_), ID($_XOR_), ID($_MUX_)};
|
||
}
|
||
|
||
const char *algo_r = relax ? "-r" : "";
|
||
log_header(design, "Executing FLOWMAP pass (pack LUTs with FlowMap%s).\n", algo_r);
|
||
|
||
int gate_count = 0, lut_count = 0, packed_count = 0;
|
||
int gate_area = 0, lut_area = 0;
|
||
for (auto module : design->selected_modules())
|
||
{
|
||
FlowmapWorker worker(order, minlut, cell_types, r_alpha, r_beta, r_gamma, relax, optarea, debug, debug_relax, module);
|
||
gate_count += worker.gate_count;
|
||
lut_count += worker.lut_count;
|
||
packed_count += worker.packed_count;
|
||
gate_area += worker.gate_area;
|
||
lut_area += worker.lut_area;
|
||
}
|
||
|
||
log("\n");
|
||
log("Packed %d cells (%d of them duplicated) into %d LUTs.\n", packed_count, packed_count - gate_count, lut_count);
|
||
log("Solution takes %.1f%% of original gate area.\n", lut_area * 100.0 / gate_area);
|
||
}
|
||
} FlowmapPass;
|
||
|
||
PRIVATE_NAMESPACE_END
|