mirror of https://github.com/YosysHQ/abc.git
1030 lines
27 KiB
C++
1030 lines
27 KiB
C++
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/**CFile****************************************************************
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FileName [utilPrefix.cpp]
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SystemName [ABC: Logic synthesis and verification system.]
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PackageName [Generating prefix adders.]
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Synopsis [Generating prefix adders.]
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Author [Martin Povišer]
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Affiliation [<povik@cutebit.org>]
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Date [Ver. 1.0. Started -August 5, 2025.]
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Revision [$Id: utilPrefix.cpp,v 1.00 2025/08/05 00:00:00 Exp $]
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***********************************************************************/
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/*
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The implementation is inspired by S. Roy, M. Choudhury, R. Puri, D. Pan,
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"Polynomial time algorithm for area and power efficient adder synthesis
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in high-performance designs", Proc. ASP-DAC 2025.
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https://www.cerc.utexas.edu/utda/publications/C166.pdf
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*/
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#include <algorithm>
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#include <list>
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#include <iostream>
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#include <set>
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#include <assert.h>
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#include <limits>
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#include <vector>
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#include <map>
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#include <cstdio>
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class Graph;
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class Node {
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public:
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Node(int bitpos, int level=0)
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: level(level), msb(bitpos), lsb(bitpos), pi(true)
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{
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}
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Node(Node *fanin1, Node *fanin2)
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: fanin1(fanin1), fanin2(fanin2)
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{
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assert(fanin1 && fanin2);
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assert(fanin1->lsb == fanin2->msb + 1);
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level = std::max(fanin1->level, fanin2->level) + 1;
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msb = fanin1->msb;
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lsb = fanin2->lsb;
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ref_fanins();
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}
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~Node()
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{
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assert(fanouts.empty());
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deref_fanins();
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}
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Node(const Node&) = delete;
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Node& operator=(const Node&) = delete;
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Node(Node&& other) noexcept {
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fanin1 = other.fanin1;
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fanin2 = other.fanin2;
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level = other.level;
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msb = other.msb;
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lsb = other.lsb;
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other.clear_fanins();
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ref_fanins();
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}
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Node& operator=(Node&& other) noexcept {
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pi = other.pi;
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deref_fanins();
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fanin1 = other.fanin1;
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fanin2 = other.fanin2;
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level = other.level;
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msb = other.msb;
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lsb = other.lsb;
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other.clear_fanins();
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ref_fanins();
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return *this;
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}
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void update_levels() {
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if (!pi)
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level = std::max(fanin1->level, fanin2->level) + 1;
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}
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void update_cap(Graph &graph, bool force=false);
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void clear_fanins() {
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deref_fanins();
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fanin1 = nullptr;
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fanin2 = nullptr;
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}
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int level;
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int level_cap = std::numeric_limits<int>::max();
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std::set<Node *> fanouts;
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int msb, lsb;
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bool pi = false;
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Node *fanin1 = nullptr, *fanin2 = nullptr;
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int node_id;
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int nfanouts() {
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return fanouts.size();
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}
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void deref_fanins() {
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if (fanin1)
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fanin1->fanouts.erase(this);
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if (fanin2)
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fanin2->fanouts.erase(this);
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}
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void ref_fanins() {
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if (fanin1)
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fanin1->fanouts.insert(this);
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if (fanin2)
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fanin2->fanouts.insert(this);
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}
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};
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class Column {
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public:
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Column(int position)
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{
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nodes.emplace_back(position);
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}
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~Column()
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{
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while (!nodes.empty())
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nodes.pop_back();
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}
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Column(const Column&) = delete;
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Column& operator=(const Column&) = delete;
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std::list<Node> nodes;
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int level_constraint;
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void link(Node *fanin2)
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{
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Node *fanin1 = &nodes.back();
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nodes.emplace_back(Node(fanin1, fanin2));
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}
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void link(Column &other)
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{
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Node *fanin1 = &nodes.back();
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Node *fanin2 = &other.nodes.back();
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nodes.emplace_back(Node(fanin1, fanin2));
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}
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bool has_level(int number)
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{
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for (auto &node : nodes)
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if (node.level == number)
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return true;
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return false;
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}
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int no_nodes()
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{
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return (int) nodes.size();
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}
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int level_target = std::numeric_limits<int>::max();
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};
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struct Graph {
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int bitwidth_;
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int fanout_constraint = std::numeric_limits<int>::max();
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Column **columns;
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~Graph()
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{
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for (int i = bitwidth_ - 1; i >= 0; i--)
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delete columns[i];
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delete[] columns;
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}
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void initialize(int ninputs)
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{
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bitwidth_ = ninputs;
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columns = new Column*[ninputs];
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for (int i = 0; i < ninputs; i++) {
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columns[i] = new Column(i);
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}
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}
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void set_max_fanout(int fanout)
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{
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fanout_constraint = fanout;
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}
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void set_max_depth(int depth)
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{
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for (int i = 0; i < bitwidth(); i++) {
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columns[i]->level_target = depth;
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}
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}
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int bitwidth()
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{
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return bitwidth_;
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}
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Column &operator[](int i)
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{
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return *(columns[i]);
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}
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int min_level()
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{
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int level = std::numeric_limits<int>::max();;
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for (int i = 0; i < bitwidth(); i++)
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level = std::min(level, columns[i]->nodes.front().level);
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return level;
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}
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int max_level()
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{
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int level = std::numeric_limits<int>::min();
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for (int i = 0; i < bitwidth(); i++) {
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level = std::max(level, columns[i]->nodes.back().level);
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}
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return level;
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}
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int size()
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{
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int size = 0;
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for (int i = 0; i < bitwidth(); i++)
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size += columns[i]->nodes.size() - 1;
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return size;
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}
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int max_fanout()
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{
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int max_fanout = 0;
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for (int i = 0; i < bitwidth(); i++) {
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for (auto &node : columns[i]->nodes) {
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max_fanout = std::max(max_fanout, node.nfanouts()); // + (node.lsb == 0));
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}
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}
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return max_fanout;
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}
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bool validate()
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{
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for (int i = 0; i < bitwidth(); i++) {
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if (columns[i]->nodes.back().lsb != 0)
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return false;
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}
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return true;
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}
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void print()
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{
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for (int j = 0; j < bitwidth(); j++)
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for (auto &node : (*this)[j].nodes)
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node.update_levels();
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int min_level1 = min_level();
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int max_level1 = max_level();
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std::cout << "\n" << "size=" << size() \
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<< " max_fanout=" << max_fanout() << " depth=" << max_level1 - min_level1 \
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<< " " << (validate() ? "(validates)" : "") << "\n";
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for (int i = max_level1 + 1; i >= min_level1; i--) {
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std::cout << " ";
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for (int j = bitwidth() - 1; j >= 0; j--) {
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if (i == (*this)[j].nodes.front().level) {
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std::cout << j % 10;
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} else if (i >= (*this)[j].nodes.front().level && i <= (*this)[j].nodes.back().level) {
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if ((*this)[j].has_level(i))
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std::cout << "#";
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else
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std::cout << ".";
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} else if (i - 1 == (*this)[j].level_target) {
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std::cout << "-";
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} else {
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std::cout << " ";
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}
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}
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std::cout << "\n";
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}
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}
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};
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void Node::update_cap(Graph &graph, bool force) {
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int cap = std::numeric_limits<int>::max();
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if (lsb == 0) {
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cap = std::min(cap, graph.columns[msb]->level_target);
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}
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for (auto fanout : fanouts) {
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cap = std::min(cap, fanout->level_cap - 1);
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}
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if (cap != level_cap || force) {
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level_cap = cap;
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if (fanin1)
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fanin1->update_cap(graph);
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if (fanin2)
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fanin2->update_cap(graph);
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}
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}
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int ceil_log2(int x)
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{
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if (x <= 0)
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return 0;
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x -= 1;
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for (int i = 0;; i++, x >>= 1)
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if (!x)
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return i;
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}
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void search(Node &node, Graph &graph, std::vector<Node *> &candidate,
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std::vector<Node *> &best, int level_cap, int lsb, int ttl, bool first=false)
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{
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if (node.lsb == lsb) {
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/*
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printf("- ");
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for (auto &node : candidate) {
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printf("[%d:%d] ", node->msb, node->lsb);
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}
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printf("\n");
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*/
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if (best.empty() || (candidate.size() <= best.size())) {
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best = candidate;
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}
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} else if ((best.empty() || candidate.size() <= best.size() - 1) && ttl >= 1) {
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auto &nodes = graph.columns[node.lsb - 1]->nodes;
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for (auto it = nodes.rbegin(); it != nodes.rend(); ++it) {
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auto &next_node = *it;
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if ((first || next_node.level > node.level) && next_node.level <= level_cap - 1
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&& next_node.nfanouts() < graph.fanout_constraint && next_node.lsb >= lsb) {
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candidate.push_back(&next_node);
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search(next_node, graph, candidate, best, level_cap, lsb,
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std::min(ttl, level_cap - next_node.level - 1));
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candidate.pop_back();
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}
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}
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}
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}
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void greedy(Graph &graph, bool algo2=false, bool print=false)
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{
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for (int i = graph.bitwidth() - 1; i >= 0; i--)
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graph[i].nodes.back().update_cap(graph);
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for (int i = graph.bitwidth() - 1; i >= 0; i--) {
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Column &column = graph[i];
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for (auto base = std::prev(std::end(column.nodes)); base != std::begin(column.nodes);) {
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auto head = base;
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// find consecutive nodes `base` to `head` within the column which we can replace;
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int prior_area = 1;
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while (!std::prev(base)->pi && std::prev(base)->nfanouts() == 1 \
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&& (!algo2 || !std::prev(std::prev(base))->pi)) {
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base--;
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prior_area++;
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}
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if (prior_area >= 2) {
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std::vector<Node *> candidate, best;
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auto next_head = std::prev(base);
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for (auto it = base; it != std::next(head); it++)
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it->deref_fanins();
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search(*next_head, graph, candidate, best, head->level_cap,
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head->lsb, std::numeric_limits<int>::max(), true);
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for (auto it = base; it != std::next(head); it++)
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it->ref_fanins();
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std::vector<Node*> old_fanins;
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if (best.size() < static_cast<size_t>(prior_area) && !best.empty()) {
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if (print) {
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printf("(%d) replacing ", i);
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for (auto it = base; it != std::next(head); it++)
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printf("[%d:%d] ", it->fanin2->msb, it->fanin2->lsb);
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printf("with ");
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for (auto node : best)
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|
|
printf("[%d:%d] ", node->msb, node->lsb);
|
||
|
|
printf("\n");
|
||
|
|
}
|
||
|
|
|
||
|
|
// clear the head so that it derefs its fanin1
|
||
|
|
old_fanins.push_back(head->fanin2);
|
||
|
|
head->clear_fanins();
|
||
|
|
|
||
|
|
// remove all but the head; head will be replaced
|
||
|
|
// in place so that its pointer is preserved (it has
|
||
|
|
// fanouts)
|
||
|
|
auto to_remove = std::prev(head);
|
||
|
|
while (to_remove != next_head) {
|
||
|
|
auto next = std::prev(to_remove);
|
||
|
|
old_fanins.push_back(to_remove->fanin2);
|
||
|
|
column.nodes.erase(to_remove);
|
||
|
|
to_remove = next;
|
||
|
|
}
|
||
|
|
|
||
|
|
// insert replacement nodes
|
||
|
|
auto fanin1 = next_head;
|
||
|
|
for (auto fanin2 : best) {
|
||
|
|
if (fanin2->lsb == head->lsb) {
|
||
|
|
*head = Node(&*fanin1, fanin2);
|
||
|
|
} else {
|
||
|
|
fanin1 = column.nodes.insert(std::next(fanin1), Node(&*fanin1, fanin2));
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
for (auto it = head; it != next_head; it--)
|
||
|
|
it->update_cap(graph);
|
||
|
|
for (auto old_fanin : old_fanins)
|
||
|
|
old_fanin->update_cap(graph);
|
||
|
|
for (auto new_fanin : best)
|
||
|
|
new_fanin->update_cap(graph);
|
||
|
|
next_head->update_cap(graph, true);
|
||
|
|
|
||
|
|
base = next_head;
|
||
|
|
} else {
|
||
|
|
base--;
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
base--;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
for (int j = 0; j < graph.bitwidth(); j++)
|
||
|
|
for (auto &node : graph[j].nodes)
|
||
|
|
node.update_levels();
|
||
|
|
}
|
||
|
|
|
||
|
|
void seed(Graph &graph)
|
||
|
|
{
|
||
|
|
for (int l = 1; l <= ceil_log2(graph.bitwidth()); l++) {
|
||
|
|
for (int i = (graph.bitwidth() / 2) * 2 - 1;
|
||
|
|
i >= ((l == 1) ? 3 : ((1 << l) + (1 << (l - 1)) + 1)); i -= 2) {
|
||
|
|
graph[i].link(graph[i - (1 << (l - 1))]);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
for (int i = 1; i < (graph.bitwidth() / 2) * 2; i += 2) {
|
||
|
|
if (i == 1) {
|
||
|
|
graph[i].link(graph[0]);
|
||
|
|
} else {
|
||
|
|
int base = 1 << (ceil_log2(i) - 1);
|
||
|
|
graph[i].link(graph[((i - base) % (base / 2)) + (base / 2)]);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// `search2` saves the first candidate of minimal size (compared to `search` which saves the last)
|
||
|
|
void search2(Node &node, Graph &graph, std::vector<Node *> &candidate,
|
||
|
|
std::vector<Node *> &best, int level_cap, int lsb, int ttl, bool first=false)
|
||
|
|
{
|
||
|
|
if (node.lsb == lsb) {
|
||
|
|
/*
|
||
|
|
printf("- ");
|
||
|
|
for (auto &node : candidate) {
|
||
|
|
printf("[%d:%d] ", node->msb, node->lsb);
|
||
|
|
}
|
||
|
|
printf("\n");
|
||
|
|
*/
|
||
|
|
if (best.empty() || (candidate.size() < best.size())) {
|
||
|
|
best = candidate;
|
||
|
|
}
|
||
|
|
} else if ((best.empty() || candidate.size() < best.size() - 1) && ttl >= 1) {
|
||
|
|
auto &nodes = graph.columns[node.lsb - 1]->nodes;
|
||
|
|
for (auto it = nodes.rbegin(); it != nodes.rend(); ++it) {
|
||
|
|
auto &next_node = *it;
|
||
|
|
if ((first || next_node.level > node.level) && next_node.level <= level_cap - 1
|
||
|
|
&& next_node.nfanouts() < graph.fanout_constraint && next_node.lsb >= lsb) {
|
||
|
|
candidate.push_back(&next_node);
|
||
|
|
search2(next_node, graph, candidate, best, level_cap, lsb,
|
||
|
|
std::min(ttl, level_cap - next_node.level - 1));
|
||
|
|
candidate.pop_back();
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
void algo3(Graph &graph)
|
||
|
|
{
|
||
|
|
for (int i = ((graph.bitwidth() - 1) / 2) * 2; i >= 2; i -= 2) {
|
||
|
|
Column &column = graph[i];
|
||
|
|
std::vector<Node *> candidate, best;
|
||
|
|
search2(column.nodes.back(), graph, candidate, best, column.level_target,
|
||
|
|
0, std::numeric_limits<int>::max(), true);
|
||
|
|
// if you hit the assert perhaps the fanout constraint was too low
|
||
|
|
assert(!best.empty());
|
||
|
|
for (auto fanin2 : best) {
|
||
|
|
column.nodes.push_back(Node(&column.nodes.back(), fanin2));
|
||
|
|
}
|
||
|
|
column.nodes.back().update_cap(graph);
|
||
|
|
}
|
||
|
|
|
||
|
|
for (int i = 0; i < graph.bitwidth(); i++)
|
||
|
|
for (auto &node : graph[i].nodes)
|
||
|
|
node.update_cap(graph);
|
||
|
|
}
|
||
|
|
|
||
|
|
void algo4(Graph &graph)
|
||
|
|
{
|
||
|
|
for (int i = ((graph.bitwidth() - 1) / 2) * 2; i >= 2; i -= 2) {
|
||
|
|
Column &column = graph[i];
|
||
|
|
|
||
|
|
if (column.nodes.size() >= 3) {
|
||
|
|
Node &node1 = graph[i - 1].nodes.back();
|
||
|
|
std::vector<Node *> old_fanins;
|
||
|
|
|
||
|
|
// Try transformation 1
|
||
|
|
if (node1.nfanouts() < graph.fanout_constraint
|
||
|
|
&& node1.level < column.nodes.back().level_cap) {
|
||
|
|
auto head = std::prev(std::end(column.nodes));
|
||
|
|
|
||
|
|
old_fanins.push_back(head->fanin2);
|
||
|
|
head->clear_fanins();
|
||
|
|
|
||
|
|
// Remove nodes before their fanins
|
||
|
|
auto to_remove = std::prev(head);
|
||
|
|
while (to_remove != std::begin(column.nodes)) {
|
||
|
|
auto next = std::prev(to_remove);
|
||
|
|
old_fanins.push_back(to_remove->fanin2);
|
||
|
|
column.nodes.erase(to_remove);
|
||
|
|
to_remove = next;
|
||
|
|
}
|
||
|
|
|
||
|
|
column.nodes.back() = Node(&column.nodes.front(), &node1);
|
||
|
|
column.nodes.back().update_cap(graph, true);
|
||
|
|
} else {
|
||
|
|
// Try transformation 2
|
||
|
|
Node &node2 = graph[i - 2].nodes.back();
|
||
|
|
|
||
|
|
if (node2.nfanouts() < graph.fanout_constraint
|
||
|
|
&& graph[i - 1].nodes.front().nfanouts() < graph.fanout_constraint
|
||
|
|
&& node2.level < column.nodes.back().level_cap) {
|
||
|
|
|
||
|
|
auto head = std::prev(std::end(column.nodes));
|
||
|
|
old_fanins.push_back(head->fanin2);
|
||
|
|
head->clear_fanins();
|
||
|
|
|
||
|
|
// Remove nodes before their fanins
|
||
|
|
auto to_remove = std::prev(head);
|
||
|
|
while (to_remove != std::begin(column.nodes)) {
|
||
|
|
auto next = std::prev(to_remove);
|
||
|
|
old_fanins.push_back(to_remove->fanin2);
|
||
|
|
column.nodes.erase(to_remove);
|
||
|
|
to_remove = next;
|
||
|
|
}
|
||
|
|
|
||
|
|
auto it = std::prev(std::end(column.nodes));
|
||
|
|
column.nodes.insert(it, Node(&column.nodes.front(), &graph[i - 1].nodes.front()));
|
||
|
|
column.nodes.back() = Node(&*std::prev(it), &graph[i - 2].nodes.back());
|
||
|
|
column.nodes.back().update_cap(graph, true);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
for (auto old_fanin : old_fanins)
|
||
|
|
old_fanin->update_cap(graph);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// initialize graph with Kogge-Stone
|
||
|
|
void kogge_stone(Graph &graph)
|
||
|
|
{
|
||
|
|
int width = graph.bitwidth();
|
||
|
|
|
||
|
|
for (int l = 0; l < ceil_log2(width); l++) {
|
||
|
|
int stride = 1 << l;
|
||
|
|
for (int i = width - 1; i >= stride; i--)
|
||
|
|
graph[i].link(graph[i - stride]);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// initialize graph with ripple carry
|
||
|
|
void ripple(Graph &graph)
|
||
|
|
{
|
||
|
|
int width = graph.bitwidth();
|
||
|
|
|
||
|
|
for (int i = 1; i < width; i++) {
|
||
|
|
graph[i].link(graph[i - 1]);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Generate complete prefix adder Verilog
|
||
|
|
void generate_prefix_adder_verilog(Graph& graph, int width, int mfo, int print_miter = 0)
|
||
|
|
{
|
||
|
|
char filename[100];
|
||
|
|
sprintf(filename, "prefix_adder_%d_%d.v", width, mfo);
|
||
|
|
FILE *fp = fopen(filename, "w");
|
||
|
|
if (!fp) {
|
||
|
|
std::cerr << "Error: Cannot create " << filename << std::endl;
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
int actual_mfo = graph.max_fanout();
|
||
|
|
int size = graph.size();
|
||
|
|
// bool valid = graph.validate(); // unused
|
||
|
|
|
||
|
|
fprintf(fp, "// Complete Prefix Adder: width=%d, mfo=%d, tree_size=%d\n", width, actual_mfo, size);
|
||
|
|
fprintf(fp, "// Generated by C++ version\n");
|
||
|
|
fprintf(fp, "module prefix_adder_%d (\n", width);
|
||
|
|
fprintf(fp, " input [%d:0] a,\n", width-1);
|
||
|
|
fprintf(fp, " input [%d:0] b,\n", width-1);
|
||
|
|
fprintf(fp, " output [%d:0] sum\n", width);
|
||
|
|
fprintf(fp, ");\n\n");
|
||
|
|
|
||
|
|
// Generate propagate and generate signals
|
||
|
|
fprintf(fp, " // Generate propagate (p) and generate (g) signals\n");
|
||
|
|
for (int i = 0; i < width; i++) {
|
||
|
|
fprintf(fp, " wire p%d = a[%d] ^ b[%d];\n", i, i, i);
|
||
|
|
fprintf(fp, " wire g%d = a[%d] & b[%d];\n", i, i, i);
|
||
|
|
}
|
||
|
|
fprintf(fp, "\n");
|
||
|
|
|
||
|
|
// Assign unique wire names to all nodes
|
||
|
|
// int wire_id = 0; // unused
|
||
|
|
std::map<Node*, std::string> node_to_p_wire;
|
||
|
|
std::map<Node*, std::string> node_to_g_wire;
|
||
|
|
|
||
|
|
// Assign wire names to input nodes
|
||
|
|
for (int i = 0; i < graph.bitwidth(); i++) {
|
||
|
|
Node* node = &graph[i].nodes.front();
|
||
|
|
char p_name[20], g_name[20];
|
||
|
|
sprintf(p_name, "p%d", i);
|
||
|
|
sprintf(g_name, "g%d", i);
|
||
|
|
node_to_p_wire[node] = p_name;
|
||
|
|
node_to_g_wire[node] = g_name;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Assign wire names to internal nodes
|
||
|
|
for (int i = 0; i < graph.bitwidth(); i++) {
|
||
|
|
for (auto &node : graph[i].nodes) {
|
||
|
|
if (!node.pi) {
|
||
|
|
char p_name[20], g_name[20];
|
||
|
|
sprintf(p_name, "p_%d_%d", node.msb, node.lsb);
|
||
|
|
sprintf(g_name, "g_%d_%d", node.msb, node.lsb);
|
||
|
|
node_to_p_wire[&node] = p_name;
|
||
|
|
node_to_g_wire[&node] = g_name;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Generate prefix tree internal nodes using compact prefix cells
|
||
|
|
fprintf(fp, " // Prefix tree computation using traditional prefix cells\n");
|
||
|
|
fprintf(fp, " // Each prefix cell computes:\n");
|
||
|
|
fprintf(fp, " // p_out = p_in1 & p_in2\n");
|
||
|
|
fprintf(fp, " // g_out = g_in1 | (p_in1 & g_in2)\n");
|
||
|
|
fprintf(fp, "\n");
|
||
|
|
|
||
|
|
for (int i = 0; i < graph.bitwidth(); i++) {
|
||
|
|
for (auto &node : graph[i].nodes) {
|
||
|
|
if (!node.pi) {
|
||
|
|
// Generate the propagate output
|
||
|
|
fprintf(fp, " wire %s = %s & %s;\n",
|
||
|
|
node_to_p_wire[&node].c_str(),
|
||
|
|
node_to_p_wire[node.fanin1].c_str(),
|
||
|
|
node_to_p_wire[node.fanin2].c_str());
|
||
|
|
|
||
|
|
// Generate the generate output
|
||
|
|
fprintf(fp, " wire %s = %s | (%s & %s); // [%d:%d] = [%d:%d] o [%d:%d]\n",
|
||
|
|
node_to_g_wire[&node].c_str(),
|
||
|
|
node_to_g_wire[node.fanin1].c_str(),
|
||
|
|
node_to_p_wire[node.fanin1].c_str(),
|
||
|
|
node_to_g_wire[node.fanin2].c_str(),
|
||
|
|
node.msb, node.lsb,
|
||
|
|
node.fanin1->msb, node.fanin1->lsb,
|
||
|
|
node.fanin2->msb, node.fanin2->lsb);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
fprintf(fp, "\n");
|
||
|
|
|
||
|
|
// Extract carry signals from prefix tree
|
||
|
|
fprintf(fp, " // Extract carry signals from prefix tree\n");
|
||
|
|
fprintf(fp, " wire cin = 1'b0; // No carry input\n");
|
||
|
|
for (int i = 0; i < graph.bitwidth(); i++) {
|
||
|
|
if (graph[i].nodes.back().lsb == 0) {
|
||
|
|
fprintf(fp, " wire c%d = %s; // Carry out of bit %d\n",
|
||
|
|
graph[i].nodes.back().msb,
|
||
|
|
node_to_g_wire[&graph[i].nodes.back()].c_str(),
|
||
|
|
graph[i].nodes.back().msb);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
fprintf(fp, "\n");
|
||
|
|
|
||
|
|
// Generate final sum
|
||
|
|
fprintf(fp, " // Compute final sum\n");
|
||
|
|
fprintf(fp, " assign sum[0] = p0 ^ cin;\n");
|
||
|
|
for (int i = 1; i < width; i++) {
|
||
|
|
fprintf(fp, " assign sum[%d] = p%d ^ c%d;\n", i, i, i-1);
|
||
|
|
}
|
||
|
|
fprintf(fp, " assign sum[%d] = c%d; // Final carry out\n", width, width-1);
|
||
|
|
|
||
|
|
fprintf(fp, "\nendmodule\n");
|
||
|
|
|
||
|
|
// Generate miter module if requested
|
||
|
|
if (print_miter) {
|
||
|
|
fprintf(fp, "\n// Miter module for verification\n");
|
||
|
|
fprintf(fp, "module prefix_adder_%d_miter (\n", width);
|
||
|
|
fprintf(fp, " input [%d:0] a,\n", width-1);
|
||
|
|
fprintf(fp, " input [%d:0] b,\n", width-1);
|
||
|
|
fprintf(fp, " output miter_output\n");
|
||
|
|
fprintf(fp, ");\n\n");
|
||
|
|
|
||
|
|
fprintf(fp, " // Instantiate the prefix adder\n");
|
||
|
|
fprintf(fp, " wire [%d:0] sum_impl;\n", width);
|
||
|
|
fprintf(fp, " prefix_adder_%d adder_inst (\n", width);
|
||
|
|
fprintf(fp, " .a(a),\n");
|
||
|
|
fprintf(fp, " .b(b),\n");
|
||
|
|
fprintf(fp, " .sum(sum_impl)\n");
|
||
|
|
fprintf(fp, " );\n\n");
|
||
|
|
|
||
|
|
fprintf(fp, " // Golden reference using simple addition\n");
|
||
|
|
fprintf(fp, " wire [%d:0] sum_gold = a + b;\n\n", width);
|
||
|
|
|
||
|
|
fprintf(fp, " // Compare outputs - miter_output is 1 if they differ\n");
|
||
|
|
fprintf(fp, " assign miter_output = (sum_gold != sum_impl);\n\n");
|
||
|
|
|
||
|
|
fprintf(fp, "endmodule\n");
|
||
|
|
}
|
||
|
|
|
||
|
|
fclose(fp);
|
||
|
|
std::cerr << "Generated complete prefix adder: " << filename << std::endl;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Write variable-length encoded unsigned integer for binary AIGER
|
||
|
|
void write_aiger_encoded(FILE* fp, unsigned x) {
|
||
|
|
unsigned char ch;
|
||
|
|
while (x & ~0x7f) {
|
||
|
|
ch = (x & 0x7f) | 0x80;
|
||
|
|
fputc(ch, fp);
|
||
|
|
x >>= 7;
|
||
|
|
}
|
||
|
|
ch = x;
|
||
|
|
fputc(ch, fp);
|
||
|
|
}
|
||
|
|
|
||
|
|
// Create integer array representation of prefix adder AIG
|
||
|
|
// Returns array in same format as Mini_AigerReadInt, compatible with generate_prefix_adder_aiger_int
|
||
|
|
extern "C" int* adder_return_array(int width, int mfo, int* pnObjs, int* pnIns, int* pnLatches, int* pnOuts, int* pnAnds, int fDumpVer, int fDumpMiter, int fVerbose) {
|
||
|
|
// Build the prefix adder graph
|
||
|
|
Graph graph;
|
||
|
|
graph.initialize(width);
|
||
|
|
graph.set_max_depth(ceil_log2(width));
|
||
|
|
graph.set_max_fanout(mfo / 2);
|
||
|
|
|
||
|
|
// Build the prefix tree using the same algorithm sequence as main
|
||
|
|
seed(graph);
|
||
|
|
greedy(graph);
|
||
|
|
greedy(graph);
|
||
|
|
graph.set_max_fanout(mfo);
|
||
|
|
algo3(graph);
|
||
|
|
algo4(graph);
|
||
|
|
greedy(graph);
|
||
|
|
greedy(graph);
|
||
|
|
|
||
|
|
// generate prefix adder with miter
|
||
|
|
if ( fDumpVer )
|
||
|
|
generate_prefix_adder_verilog(graph, width, mfo, fDumpMiter);
|
||
|
|
|
||
|
|
// Count components
|
||
|
|
int num_inputs = 2 * width; // a[0..width-1], b[0..width-1]
|
||
|
|
int num_outputs = width + 1; // sum[0..width]
|
||
|
|
int num_latches = 0; // combinational circuit
|
||
|
|
|
||
|
|
// We'll count AND gates as we generate them
|
||
|
|
std::vector<std::pair<int, std::pair<int, int>>> and_gates;
|
||
|
|
|
||
|
|
// Variable allocation
|
||
|
|
int next_var = 2;
|
||
|
|
std::map<std::string, int> signal_map;
|
||
|
|
|
||
|
|
// Allocate input variables
|
||
|
|
for (int i = 0; i < width; i++) {
|
||
|
|
signal_map[std::string("a") + std::to_string(i)] = next_var;
|
||
|
|
next_var += 2;
|
||
|
|
}
|
||
|
|
for (int i = 0; i < width; i++) {
|
||
|
|
signal_map[std::string("b") + std::to_string(i)] = next_var;
|
||
|
|
next_var += 2;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Generate propagate and generate signals (same as in AIGER generation)
|
||
|
|
for (int i = 0; i < width; i++) {
|
||
|
|
// pi = ai XOR bi = (ai | bi) & !(ai & bi)
|
||
|
|
// First create ai & bi
|
||
|
|
int ai = signal_map[std::string("a") + std::to_string(i)];
|
||
|
|
int bi = signal_map[std::string("b") + std::to_string(i)];
|
||
|
|
|
||
|
|
signal_map[std::string("g") + std::to_string(i)] = next_var;
|
||
|
|
and_gates.push_back({next_var, {ai, bi}});
|
||
|
|
next_var += 2;
|
||
|
|
|
||
|
|
// Create ai | bi = !(!ai & !bi)
|
||
|
|
int not_ai_and_not_bi = next_var;
|
||
|
|
and_gates.push_back({not_ai_and_not_bi, {ai ^ 1, bi ^ 1}});
|
||
|
|
next_var += 2;
|
||
|
|
|
||
|
|
// pi = (ai | bi) & !(ai & bi)
|
||
|
|
signal_map[std::string("p") + std::to_string(i)] = next_var;
|
||
|
|
and_gates.push_back({next_var, {not_ai_and_not_bi ^ 1, signal_map[std::string("g") + std::to_string(i)] ^ 1}});
|
||
|
|
next_var += 2;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Generate prefix tree
|
||
|
|
std::map<std::pair<int, int>, std::pair<int, int>> computed_nodes;
|
||
|
|
|
||
|
|
for (int i = 0; i < width; i++) {
|
||
|
|
computed_nodes[{i, i}] = {
|
||
|
|
signal_map[std::string("p") + std::to_string(i)],
|
||
|
|
signal_map[std::string("g") + std::to_string(i)]
|
||
|
|
};
|
||
|
|
}
|
||
|
|
|
||
|
|
// Process each node in the graph
|
||
|
|
for (int i = 0; i < graph.bitwidth(); i++) {
|
||
|
|
for (auto &node : graph[i].nodes) {
|
||
|
|
if (node.pi)
|
||
|
|
continue;
|
||
|
|
|
||
|
|
int msb1 = node.fanin1->msb;
|
||
|
|
int lsb1 = node.fanin1->lsb;
|
||
|
|
int msb2 = node.fanin2->msb;
|
||
|
|
int lsb2 = node.fanin2->lsb;
|
||
|
|
|
||
|
|
int p1 = computed_nodes[{msb1, lsb1}].first;
|
||
|
|
int g1 = computed_nodes[{msb1, lsb1}].second;
|
||
|
|
int p2 = computed_nodes[{msb2, lsb2}].first;
|
||
|
|
int g2 = computed_nodes[{msb2, lsb2}].second;
|
||
|
|
|
||
|
|
// p_out = p1 & p2
|
||
|
|
int p_out = next_var;
|
||
|
|
and_gates.push_back({p_out, {p1, p2}});
|
||
|
|
next_var += 2;
|
||
|
|
|
||
|
|
// g_out = g1 | (p1 & g2)
|
||
|
|
int p1_and_g2 = next_var;
|
||
|
|
and_gates.push_back({p1_and_g2, {p1, g2}});
|
||
|
|
next_var += 2;
|
||
|
|
|
||
|
|
// g1 | (p1 & g2) = !(!g1 & !(p1 & g2))
|
||
|
|
int g_out = next_var;
|
||
|
|
and_gates.push_back({g_out, {g1 ^ 1, p1_and_g2 ^ 1}});
|
||
|
|
next_var += 2;
|
||
|
|
g_out = g_out ^ 1;
|
||
|
|
|
||
|
|
int msb = node.msb;
|
||
|
|
int lsb = node.lsb;
|
||
|
|
computed_nodes[{msb, lsb}] = {p_out, g_out};
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Generate sum outputs
|
||
|
|
std::vector<int> output_signals;
|
||
|
|
|
||
|
|
// sum[0] = p0 ^ cin, where cin = 0
|
||
|
|
output_signals.push_back(signal_map[std::string("p0")]);
|
||
|
|
|
||
|
|
// sum[i] = pi ^ c[i-1] for i = 1 to width-1
|
||
|
|
for (int i = 1; i < width; i++) {
|
||
|
|
int pi = signal_map[std::string("p") + std::to_string(i)];
|
||
|
|
int gi_minus_1 = computed_nodes[{i-1, 0}].second;
|
||
|
|
|
||
|
|
// pi XOR gi_minus_1 = (pi | gi_minus_1) & !(pi & gi_minus_1)
|
||
|
|
int pi_and_gi = next_var;
|
||
|
|
and_gates.push_back({pi_and_gi, {pi, gi_minus_1}});
|
||
|
|
next_var += 2;
|
||
|
|
|
||
|
|
int not_pi_and_not_gi = next_var;
|
||
|
|
and_gates.push_back({not_pi_and_not_gi, {pi ^ 1, gi_minus_1 ^ 1}});
|
||
|
|
next_var += 2;
|
||
|
|
|
||
|
|
int sum_i = next_var;
|
||
|
|
and_gates.push_back({sum_i, {not_pi_and_not_gi ^ 1, pi_and_gi ^ 1}});
|
||
|
|
next_var += 2;
|
||
|
|
|
||
|
|
output_signals.push_back(sum_i);
|
||
|
|
}
|
||
|
|
|
||
|
|
// sum[width] = c[width-1] = g[width-1:0]
|
||
|
|
output_signals.push_back(computed_nodes[{width-1, 0}].second);
|
||
|
|
|
||
|
|
// Now create the integer array in miniaig format
|
||
|
|
int nObjs = 1 + num_inputs + 2*num_latches + num_outputs + and_gates.size();
|
||
|
|
int* pObjs = (int*)calloc(nObjs * 2, sizeof(int));
|
||
|
|
|
||
|
|
// Initialize all entries to NULL (0)
|
||
|
|
for (int i = 0; i < nObjs * 2; i++) {
|
||
|
|
pObjs[i] = 0; // MINI_AIG_NULL is typically 0
|
||
|
|
}
|
||
|
|
|
||
|
|
// Primary inputs don't need initialization beyond NULL
|
||
|
|
// Primary outputs
|
||
|
|
for (int i = 0; i < num_outputs; i++) {
|
||
|
|
pObjs[2*(nObjs-num_outputs-num_latches+i)+0] = output_signals[i];
|
||
|
|
pObjs[2*(nObjs-num_outputs-num_latches+i)+1] = 0; // NULL
|
||
|
|
}
|
||
|
|
|
||
|
|
// AND gates
|
||
|
|
for (size_t i = 0; i < and_gates.size(); i++) {
|
||
|
|
int node_lit = and_gates[i].first;
|
||
|
|
int lit0 = and_gates[i].second.first;
|
||
|
|
int lit1 = and_gates[i].second.second;
|
||
|
|
|
||
|
|
// Ensure lit0 < lit1
|
||
|
|
if (lit0 > lit1) {
|
||
|
|
std::swap(lit0, lit1);
|
||
|
|
}
|
||
|
|
|
||
|
|
int node_var = node_lit / 2;
|
||
|
|
int and_index = node_var - 1 - num_inputs - num_latches;
|
||
|
|
|
||
|
|
pObjs[2*(1+num_inputs+num_latches+and_index)+0] = lit0;
|
||
|
|
pObjs[2*(1+num_inputs+num_latches+and_index)+1] = lit1;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Set output parameters
|
||
|
|
*pnObjs = nObjs;
|
||
|
|
*pnIns = num_inputs;
|
||
|
|
*pnLatches = num_latches;
|
||
|
|
*pnOuts = num_outputs;
|
||
|
|
*pnAnds = and_gates.size();
|
||
|
|
|
||
|
|
return pObjs;
|
||
|
|
}
|
||
|
|
|
||
|
|
void generate_prefix_adder_aiger_int( char * pFileName, int * pObjs, int nObjs, int nIns, int nLatches, int nOuts, int nAnds )
|
||
|
|
{
|
||
|
|
FILE * pFile = fopen( pFileName, "wb" ); int i;
|
||
|
|
if ( pFile == NULL )
|
||
|
|
{
|
||
|
|
fprintf( stdout, "generate_prefix_adder_aiger_int(): Cannot open the output file \"%s\".\n", pFileName );
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
fprintf( pFile, "aig %d %d %d %d %d\n", nIns + nLatches + nAnds, nIns, nLatches, nOuts, nAnds );
|
||
|
|
for ( i = 0; i < nLatches; i++ )
|
||
|
|
fprintf( pFile, "%d\n", pObjs[2*(nObjs-nLatches+i)+0] );
|
||
|
|
for ( i = 0; i < nOuts; i++ )
|
||
|
|
fprintf( pFile, "%d\n", pObjs[2*(nObjs-nOuts-nLatches+i)+0] );
|
||
|
|
for ( i = 0; i < nAnds; i++ )
|
||
|
|
{
|
||
|
|
int uLit = 2*(1+nIns+nLatches+i);
|
||
|
|
int uLit0 = pObjs[uLit+0];
|
||
|
|
int uLit1 = pObjs[uLit+1];
|
||
|
|
write_aiger_encoded( pFile, uLit - uLit1 );
|
||
|
|
write_aiger_encoded( pFile, uLit1 - uLit0 );
|
||
|
|
}
|
||
|
|
fprintf( pFile, "c\n" );
|
||
|
|
fclose( pFile );
|
||
|
|
}
|
||
|
|
void generate_prefix_adder_aiger( int width, int mfo )
|
||
|
|
{
|
||
|
|
char pFileName[100];
|
||
|
|
sprintf( pFileName, "prefix_adder_%d_%d.aig", width, mfo );
|
||
|
|
int nObjs = 0, nIns = 0, nLatches = 0, nOuts = 0, nAnds = 0;
|
||
|
|
int * pObjs = adder_return_array( width, mfo, &nObjs, &nIns, &nLatches, &nOuts, &nAnds, 0, 0, 0 );
|
||
|
|
generate_prefix_adder_aiger_int( pFileName, pObjs, nObjs, nIns, nLatches, nOuts, nAnds );
|
||
|
|
printf( "Written prefix adder into AIGER file \"%s\".\n", pFileName );
|
||
|
|
free(pObjs);
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
int main(int argc, char const *argv[])
|
||
|
|
{
|
||
|
|
for (auto width : {8, 16, 32, 64, 96, 128}) {
|
||
|
|
for (auto mfo : {4, 6, 8, 10, 12, 16, 32}) {
|
||
|
|
Graph graph;
|
||
|
|
graph.initialize(width);
|
||
|
|
graph.set_max_depth(ceil_log2(width));
|
||
|
|
graph.set_max_fanout(mfo / 2);
|
||
|
|
seed(graph);
|
||
|
|
greedy(graph);
|
||
|
|
greedy(graph);
|
||
|
|
graph.set_max_fanout(mfo);
|
||
|
|
algo3(graph);
|
||
|
|
algo4(graph);
|
||
|
|
greedy(graph);
|
||
|
|
greedy(graph);
|
||
|
|
|
||
|
|
// Validate the graph
|
||
|
|
bool valid = graph.validate();
|
||
|
|
int actual_mfo = graph.max_fanout();
|
||
|
|
int size = graph.size();
|
||
|
|
int depth = graph.max_level() - graph.min_level();
|
||
|
|
|
||
|
|
std::cerr << "width=" << graph.bitwidth() << "\tmfo=" << actual_mfo << "\tsize=" << size;
|
||
|
|
|
||
|
|
// Add validation status and check constraints
|
||
|
|
if (!valid) {
|
||
|
|
std::cerr << "\t[INVALID: not all columns reach lsb=0]";
|
||
|
|
}
|
||
|
|
if (actual_mfo > mfo) {
|
||
|
|
std::cerr << "\t[ERROR: max_fanout " << actual_mfo << " exceeds constraint " << mfo << "]";
|
||
|
|
}
|
||
|
|
if (depth > ceil_log2(width)) {
|
||
|
|
std::cerr << "\t[WARNING: depth " << depth << " exceeds target " << ceil_log2(width) << "]";
|
||
|
|
}
|
||
|
|
std::cerr << "\n";
|
||
|
|
|
||
|
|
// Generate prefix adder with miter for verification
|
||
|
|
//generate_prefix_adder_verilog(graph, width, mfo, "cpp_miter", 1);
|
||
|
|
|
||
|
|
// Generate AIGER format
|
||
|
|
generate_prefix_adder_aiger(width, mfo);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
*/
|