--- /dev/null
+/*
+ * yosys -- Yosys Open SYnthesis Suite
+ *
+ * Copyright (C) 2018 whitequark <whitequark@whitequark.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "kernel/yosys.h"
+#include "kernel/sigtools.h"
+#include "kernel/modtools.h"
+
+USING_YOSYS_NAMESPACE
+PRIVATE_NAMESPACE_BEGIN
+
+static bool evaluate_lut(SigMap &sigmap, RTLIL::Cell *lut, dict<SigBit, bool> inputs)
+{
+ SigSpec lut_input = sigmap(lut->getPort("\\A"));
+ int lut_width = lut->getParam("\\WIDTH").as_int();
+ Const lut_table = lut->getParam("\\LUT");
+ int lut_index = 0;
+
+ for (int i = 0; i < lut_width; i++)
+ {
+ SigBit input = sigmap(lut_input[i]);
+ if (inputs.count(input))
+ {
+ lut_index |= inputs[input] << i;
+ }
+ else
+ {
+ lut_index |= SigSpec(lut_input[i]).as_bool() << i;
+ }
+ }
+
+ return lut_table.extract(lut_index).as_int();
+}
+
+static void run_lut_opts(Module *module)
+{
+ ModIndex index(module);
+ SigMap sigmap(module);
+
+ log("Discovering LUTs.\n");
+
+ pool<RTLIL::Cell*> luts;
+ dict<RTLIL::Cell*, int> luts_arity;
+ for (auto cell : module->selected_cells())
+ {
+ if (cell->type == "$lut")
+ {
+ int lut_width = cell->getParam("\\WIDTH").as_int();
+ SigSpec lut_input = cell->getPort("\\A");
+ int lut_arity = 0;
+
+ for (auto &bit : lut_input)
+ {
+ if (bit.wire)
+ lut_arity++;
+ }
+
+ log("Found $lut cell %s.%s with WIDTH=%d implementing %d-LUT.\n", log_id(module), log_id(cell), lut_width, lut_arity);
+ luts.insert(cell);
+ luts_arity[cell] = lut_arity;
+ }
+ }
+
+ log("\n");
+ log("Combining LUTs.\n");
+
+ pool<RTLIL::Cell*> worklist = luts;
+ while (worklist.size())
+ {
+ auto lutA = worklist.pop();
+ SigSpec lutA_input = sigmap(lutA->getPort("\\A"));
+ SigSpec lutA_output = sigmap(lutA->getPort("\\Y")[0]);
+ int lutA_width = lutA->getParam("\\WIDTH").as_int();
+ int lutA_arity = luts_arity[lutA];
+
+ auto lutA_output_ports = index.query_ports(lutA->getPort("\\Y"));
+ if (lutA_output_ports.size() != 2)
+ continue;
+
+ for (auto port : lutA_output_ports)
+ {
+ if (port.cell == lutA)
+ continue;
+
+ if (luts.count(port.cell))
+ {
+ auto lutB = port.cell;
+ SigSpec lutB_input = sigmap(lutB->getPort("\\A"));
+ SigSpec lutB_output = sigmap(lutB->getPort("\\Y")[0]);
+ int lutB_width = lutB->getParam("\\WIDTH").as_int();
+ int lutB_arity = luts_arity[lutB];
+
+ log("Found %s.%s (cell A) feeding %s.%s (cell B).\n", log_id(module), log_id(lutA), log_id(module), log_id(lutB));
+
+ pool<SigBit> lutA_inputs;
+ pool<SigBit> lutB_inputs;
+ for (auto &bit : lutA_input)
+ {
+ if (bit.wire)
+ lutA_inputs.insert(sigmap(bit));
+ }
+ for (auto &bit : lutB_input)
+ {
+ if(bit.wire)
+ lutB_inputs.insert(sigmap(bit));
+ }
+
+ pool<SigBit> common_inputs;
+ for (auto &bit : lutA_inputs)
+ {
+ if (lutB_inputs.count(bit))
+ common_inputs.insert(bit);
+ }
+
+ int lutM_arity = lutA_arity + lutB_arity - 1 - common_inputs.size();
+ log(" Cell A is a %d-LUT. Cell B is a %d-LUT. Cells share %zu input(s) and can be merged into one %d-LUT.\n", lutA_arity, lutB_arity, common_inputs.size(), lutM_arity);
+
+ int combine = -1;
+ if (combine == -1)
+ {
+ if (lutM_arity > lutA_width)
+ {
+ log(" Not combining LUTs into cell A (combined LUT too wide).\n");
+ }
+ else if (lutB->get_bool_attribute("\\lut_keep"))
+ {
+ log(" Not combining LUTs into cell A (cell B has attribute \\lut_keep).\n");
+ }
+ else combine = 0;
+ }
+ if (combine == -1)
+ {
+ if (lutM_arity > lutB_width)
+ {
+ log(" Not combining LUTs into cell B (combined LUT too wide).\n");
+ }
+ else if (lutA->get_bool_attribute("\\lut_keep"))
+ {
+ log(" Not combining LUTs into cell B (cell A has attribute \\lut_keep).\n");
+ }
+ else combine = 1;
+ }
+
+ RTLIL::Cell *lutM, *lutR;
+ pool<SigBit> lutM_inputs, lutR_inputs;
+ if (combine == 0)
+ {
+ log(" Combining LUTs into cell A.\n");
+ lutM = lutA;
+ lutM_inputs = lutA_inputs;
+ lutR = lutB;
+ lutR_inputs = lutB_inputs;
+ }
+ else if (combine == 1)
+ {
+ log(" Combining LUTs into cell B.\n");
+ lutM = lutB;
+ lutM_inputs = lutB_inputs;
+ lutR = lutA;
+ lutR_inputs = lutA_inputs;
+ }
+ else
+ {
+ log(" Cannot combine LUTs.\n");
+ continue;
+ }
+
+ pool<SigBit> lutR_unique;
+ for (auto &bit : lutR_inputs)
+ {
+ if (!common_inputs.count(bit) && bit != lutA_output)
+ lutR_unique.insert(bit);
+ }
+
+ int lutM_width = lutM->getParam("\\WIDTH").as_int();
+ SigSpec lutM_input = sigmap(lutM->getPort("\\A"));
+ std::vector<SigBit> lutM_new_inputs;
+ for (int i = 0; i < lutM_width; i++)
+ {
+ if ((!lutM_input[i].wire || sigmap(lutM_input[i]) == lutA_output) && lutR_unique.size())
+ {
+ SigBit new_input = lutR_unique.pop();
+ log(" Connecting input %d as %s.\n", i, log_signal(new_input));
+ lutM_new_inputs.push_back(new_input);
+ }
+ else if (sigmap(lutM_input[i]) == lutA_output)
+ {
+ log(" Disconnecting input %d.\n", i);
+ lutM_new_inputs.push_back(SigBit());
+ }
+ else
+ {
+ log(" Leaving input %d as %s.\n", i, log_signal(lutM_input[i]));
+ lutM_new_inputs.push_back(lutM_input[i]);
+ }
+ }
+ log_assert(lutR_unique.size() == 0);
+
+ RTLIL::Const lutM_new_table(State::Sx, 1 << lutM_width);
+ for (int eval = 0; eval < 1 << lutM_width; eval++)
+ {
+ dict<SigBit, bool> eval_inputs;
+ for (size_t i = 0; i < lutM_new_inputs.size(); i++)
+ {
+ eval_inputs[lutM_new_inputs[i]] = (eval >> i) & 1;
+ }
+ eval_inputs[lutA_output] = evaluate_lut(sigmap, lutA, eval_inputs);
+ lutM_new_table[eval] = (RTLIL::State) evaluate_lut(sigmap, lutB, eval_inputs);
+ }
+
+ log(" Old truth table: %s.\n", lutM->getParam("\\LUT").as_string().c_str());
+ log(" New truth table: %s.\n", lutM_new_table.as_string().c_str());
+
+ lutM->setParam("\\LUT", lutM_new_table);
+ lutM->setPort("\\A", lutM_new_inputs);
+ lutM->setPort("\\Y", lutB_output);
+
+ luts_arity[lutM] = lutM_arity;
+ luts.erase(lutR);
+ luts_arity.erase(lutR);
+ lutR->module->remove(lutR);
+
+ worklist.insert(lutM);
+ worklist.erase(lutR);
+ }
+ }
+ }
+}
+
+struct OptLutPass : public Pass {
+ OptLutPass() : Pass("opt_lut", "optimize LUT cells") { }
+ void help() YS_OVERRIDE
+ {
+ log("\n");
+ log(" opt_lut [options] [selection]\n");
+ log("\n");
+ log("This pass combines cascaded $lut cells with unused inputs.\n");
+ log("\n");
+ }
+ void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
+ {
+ log_header(design, "Executing OPT_LUT pass (optimize LUTs).\n");
+
+ size_t argidx;
+ for (argidx = 1; argidx < args.size(); argidx++)
+ {
+ // if (args[argidx] == "-???") {
+ // continue;
+ // }
+ break;
+ }
+ extra_args(args, argidx, design);
+
+ for (auto module : design->selected_modules())
+ run_lut_opts(module);
+ }
+} OptLutPass;
+
+PRIVATE_NAMESPACE_END
projects / yosys.git / commitdiff