From f6d94e87209103a6076bcef71235ac804ad32e86 Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Thu, 22 Jan 2015 14:03:18 +0100
Subject: [PATCH] Added equiv_induct
---
passes/equiv/Makefile.inc | 1 +
passes/equiv/equiv_induct.cc | 181 +++++++++++++++++++++++++++++++++++
2 files changed, 182 insertions(+)
create mode 100644 passes/equiv/equiv_induct.cc
diff --git a/passes/equiv/Makefile.inc b/passes/equiv/Makefile.inc
index 16abcd96c..385170c9a 100644
--- a/passes/equiv/Makefile.inc
+++ b/passes/equiv/Makefile.inc
@@ -2,4 +2,5 @@
OBJS += passes/equiv/equiv_make.o
OBJS += passes/equiv/equiv_simple.o
OBJS += passes/equiv/equiv_status.o
+OBJS += passes/equiv/equiv_induct.o
diff --git a/passes/equiv/equiv_induct.cc b/passes/equiv/equiv_induct.cc
new file mode 100644
index 000000000..ccf4f957f
--- /dev/null
+++ b/passes/equiv/equiv_induct.cc
@@ -0,0 +1,181 @@
+/*
+ * yosys -- Yosys Open SYnthesis Suite
+ *
+ * Copyright (C) 2012 Clifford Wolf <clifford@clifford.at>
+ *
+ * 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/satgen.h"
+#include "kernel/sigtools.h"
+
+USING_YOSYS_NAMESPACE
+PRIVATE_NAMESPACE_BEGIN
+
+struct EquivInductWorker
+{
+ Module *module;
+ SigMap sigmap;
+
+ vector<Cell*> cells;
+ pool<Cell*> workset;
+
+ ezDefaultSAT ez;
+ SatGen satgen;
+
+ int max_seq;
+ int success_counter;
+
+ dict<int, int> ez_step_is_consistent;
+ pool<Cell*> cell_warn_cache;
+
+ EquivInductWorker(Module *module, const pool<Cell*> &unproven_equiv_cells, int max_seq) : module(module), sigmap(module),
+ cells(module->selected_cells()), workset(unproven_equiv_cells), satgen(&ez, &sigmap), max_seq(max_seq), success_counter(0)
+ {
+ }
+
+ void create_timestep(int step)
+ {
+ vector<int> ez_equal_terms;
+ for (auto cell : cells) {
+ if (!satgen.importCell(cell, step) && !cell_warn_cache.count(cell)) {
+ log_warning("No SAT model available for cell %s (%s).\n", log_id(cell), log_id(cell->type));
+ cell_warn_cache.insert(cell);
+ }
+ if (cell->type == "$equiv") {
+ SigBit bit_a = sigmap(cell->getPort("\\A")).to_single_sigbit();
+ SigBit bit_b = sigmap(cell->getPort("\\B")).to_single_sigbit();
+ if (bit_a != bit_b) {
+ int ez_a = satgen.importSigBit(bit_a, step);
+ int ez_b = satgen.importSigBit(bit_b, step);
+ ez_equal_terms.push_back(ez.IFF(ez_a, ez_b));
+ }
+ }
+ }
+
+ log_assert(!ez_step_is_consistent.count(step));
+ ez_step_is_consistent[step] = ez.expression(ez.OpAnd, ez_equal_terms);
+ }
+
+ void run()
+ {
+ log("Found %d unproven $equiv cells in module %s:\n", GetSize(workset), log_id(module));
+
+ create_timestep(1);
+ for (int step = 1; step <= max_seq; step++)
+ {
+ ez.assume(ez_step_is_consistent[step]);
+
+ log(" Proving existence of base case for step %d. (%d clauses over %d variables)\n", step, ez.numCnfClauses(), ez.numCnfVariables());
+ if (!ez.solve()) {
+ log(" Proof for base case failed. Circuit inherently diverges!\n");
+ break;
+ }
+
+ create_timestep(step+1);
+ int new_step_not_consistent = ez.NOT(ez_step_is_consistent[step+1]);
+ ez.bind(new_step_not_consistent);
+
+ log(" Proving induction step %d. (%d clauses over %d variables)\n", step, ez.numCnfClauses(), ez.numCnfVariables());
+ if (!ez.solve(new_step_not_consistent)) {
+ log(" Proof for induction step holds. Entire workset of %d cells proven!\n", GetSize(workset));
+ for (auto cell : workset)
+ cell->setPort("\\B", cell->getPort("\\A"));
+ success_counter += GetSize(workset);
+ return;
+ }
+
+ log(" Proof for induction step failed. %s\n", step != max_seq ? "Extending to next time step." : "Trying to prove individual $equiv from workset.");
+ }
+
+ for (auto cell : workset)
+ {
+ SigBit bit_a = sigmap(cell->getPort("\\A")).to_single_sigbit();
+ SigBit bit_b = sigmap(cell->getPort("\\B")).to_single_sigbit();
+
+ int ez_a = satgen.importSigBit(bit_a, max_seq+1);
+ int ez_b = satgen.importSigBit(bit_b, max_seq+1);
+
+ log(" Trying to prove $equiv for %s:", log_signal(sigmap(cell->getPort("\\Y"))));
+ if (!ez.solve(ez.XOR(ez_a, ez_b))) {
+ log(" success!\n");
+ cell->setPort("\\B", cell->getPort("\\A"));
+ success_counter++;
+ } else {
+ log(" failed.\n");
+ }
+ }
+ }
+};
+
+struct EquivInductPass : public Pass {
+ EquivInductPass() : Pass("equiv_induct", "proving $equiv cells using temporal induction") { }
+ virtual void help()
+ {
+ // |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+ log("\n");
+ log(" equiv_induct [options] [selection]\n");
+ log("\n");
+ log("Uses a version of temporal induction to prove $equiv cells.\n");
+ log("\n");
+ log("Only selected $equiv cells are proven and only selected cells are used to\n");
+ log("perform the proof.\n");
+ log("\n");
+ log(" -seq <N>\n");
+ log(" the max. number of time steps to be considered (default = 4)\n");
+ log("\n");
+ }
+ virtual void execute(std::vector<std::string> args, Design *design)
+ {
+ int success_counter = 0;
+ int max_seq = 4;
+
+ log_header("Executing EQUIV_INDUCT pass.\n");
+
+ size_t argidx;
+ for (argidx = 1; argidx < args.size(); argidx++) {
+ if (args[argidx] == "-seq" && argidx+1 < args.size()) {
+ max_seq = atoi(args[++argidx].c_str());
+ continue;
+ }
+ break;
+ }
+ extra_args(args, argidx, design);
+
+ for (auto module : design->selected_modules())
+ {
+ pool<Cell*> unproven_equiv_cells;
+
+ for (auto cell : module->selected_cells())
+ if (cell->type == "$equiv") {
+ if (cell->getPort("\\A") != cell->getPort("\\B"))
+ unproven_equiv_cells.insert(cell);
+ }
+
+ if (unproven_equiv_cells.empty()) {
+ log("No selected unproven $equiv cells found in %s.\n", log_id(module));
+ continue;
+ }
+
+ EquivInductWorker worker(module, unproven_equiv_cells, max_seq);
+ worker.run();
+ success_counter += worker.success_counter;
+ }
+
+ log("Proved %d previously unproven $equiv cells.\n", success_counter);
+ }
+} EquivInductPass;
+
+PRIVATE_NAMESPACE_END