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dfflibmap: move expression code into libparse

This commit is contained in:
Lofty 2024-11-07 00:51:23 +00:00
parent 08ed2c765e
commit 4f40187759
3 changed files with 255 additions and 253 deletions
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315
passes/techmap/dfflibmap.cc
View File

@ -26,248 +26,6 @@
USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN
struct string_helper {
std::string s, expr;
string_helper(std::string s) : s{s}, expr{s} {}
bool empty() {
return s.empty();
}
char peek() {
return s[0];
}
char next() {
char c = s[0];
s = s.substr(1, s.size());
return c;
}
std::string pin() {
auto length = s.find_first_of("\t()'!^*& +|");
auto pin = s.substr(0, length);
s = s.substr(length, s.size());
return pin;
}
std::string full_expr() {
return expr;
}
};
enum expression_kind {
AND,
OR,
NOT,
XOR,
// the standard specifies constants, but they're probably rare in practice.
PIN,
EMPTY
};
struct expression_tree {
expression_kind kind;
std::string name;
std::vector<expression_tree> children;
expression_tree() : kind(expression_kind::EMPTY) {}
void get_pin_names(pool<std::string>& names) {
if (kind == expression_kind::PIN) {
names.insert(name);
} else {
for (auto& child : children)
child.get_pin_names(names);
}
}
bool eval(dict<std::string, bool>& values) {
bool result = false;
switch (kind) {
case expression_kind::AND:
result = true;
for (auto& child : children)
result &= child.eval(values);
return result;
case expression_kind::OR:
result = false;
for (auto& child : children)
result |= child.eval(values);
return result;
case expression_kind::NOT:
log_assert(children.size() == 1);
return !children[0].eval(values);
case expression_kind::XOR:
result = false;
for (auto& child : children)
result ^= child.eval(values);
return result;
case expression_kind::PIN:
return values.at(name);
case expression_kind::EMPTY:
log_assert(false);
}
return false;
}
std::string enable_pin(const std::string& ff_output, std::string &data_name, bool &data_not_inverted, bool &enable_not_inverted) {
auto pin_name_pool = pool<std::string>{};
get_pin_names(pin_name_pool);
if (pin_name_pool.size() != 3)
return "";
if (!pin_name_pool.count(ff_output))
return "";
pin_name_pool.erase(ff_output);
auto pins = std::vector<std::string>(pin_name_pool.begin(), pin_name_pool.end());
int lut = 0;
for (int n = 0; n < 8; n++) {
auto values = dict<std::string, bool>{};
values.insert(std::make_pair(pins[0], (n & 1) == 1));
values.insert(std::make_pair(pins[1], (n & 2) == 2));
values.insert(std::make_pair(ff_output, (n & 4) == 4));
if (eval(values))
lut |= 1 << n;
}
// the ff output Q is in a known bit location, so we now just have to compare the LUT mask to known values to find the enable pin and polarity.
if (lut == 0xD8) {
data_not_inverted = true;
data_name = pins[1];
enable_not_inverted = true;
return pins[0];
}
if (lut == 0xB8) {
data_not_inverted = true;
data_name = pins[0];
enable_not_inverted = true;
return pins[1];
}
if (lut == 0xE4) {
data_not_inverted = true;
data_name = pins[1];
enable_not_inverted = false;
return pins[0];
}
if (lut == 0xE2) {
data_not_inverted = true;
data_name = pins[0];
enable_not_inverted = false;
return pins[1];
}
// this does not match an enable flop.
data_not_inverted = false;
data_name = "";
enable_not_inverted = false;
return "";
}
};
// https://matklad.github.io/2020/04/13/simple-but-powerful-pratt-parsing.html
expression_tree parse_expression(string_helper &s, int min_prio = 0) {
if (s.empty())
return expression_tree{};
char c = s.peek();
auto lhs = expression_tree{};
while (isspace(c)) {
if (s.empty())
return lhs;
s.next();
c = s.peek();
}
if (isalpha(c)) { // pin
lhs.kind = expression_kind::PIN;
lhs.name = s.pin();
} else if (c == '(') { // parens
s.next();
lhs = parse_expression(s);
if (s.peek() != ')') {
log_warning("expected ')' instead of '%c' while parsing Liberty expression '%s'\n", s.peek(), s.full_expr().c_str());
return lhs;
}
s.next();
} else if (c == '!') { // prefix NOT
s.next();
lhs.kind = expression_kind::NOT;
lhs.children.push_back(parse_expression(s, 7));
} else {
log_warning("unrecognised character '%c' while parsing Liberty expression '%s'\n", c, s.full_expr().c_str());
return lhs;
}
do {
if (s.empty())
break;
c = s.peek();
while (isspace(c)) {
if (s.empty())
return lhs;
s.next();
c = s.peek();
}
if (c == '\'') { // postfix NOT
if (min_prio > 7)
break;
s.next();
auto n = expression_tree{};
n.kind = expression_kind::NOT;
n.children.push_back(lhs);
lhs = std::move(n);
continue;
} else if (c == '^') { // infix XOR
if (min_prio > 5)
break;
s.next();
auto rhs = parse_expression(s, 6);
auto n = expression_tree{};
n.kind = expression_kind::XOR;
n.children.push_back(lhs);
n.children.push_back(rhs);
lhs = std::move(n);
continue;
} else if (c == '&' || c == '*') { // infix AND
// technically space should be considered infix AND. it seems rare in practice.
if (min_prio > 3)
break;
s.next();
auto rhs = parse_expression(s, 4);
auto n = expression_tree{};
n.kind = expression_kind::AND;
n.children.push_back(lhs);
n.children.push_back(rhs);
lhs = std::move(n);
continue;
} else if (c == '+' || c == '|') { // infix OR
if (min_prio > 1)
break;
s.next();
auto rhs = parse_expression(s, 2);
auto n = expression_tree{};
n.kind = expression_kind::OR;
n.children.push_back(lhs);
n.children.push_back(rhs);
lhs = std::move(n);
continue;
}
} while (false);
return lhs;
}
struct cell_mapping {
IdString cell_name;
std::map<std::string, char> ports;
@ -325,10 +83,13 @@ static void logmap_all()
static bool parse_next_state(const LibertyAst *cell, const LibertyAst *attr, std::string &data_name, bool &data_not_inverted, std::string &enable_name, bool &enable_not_inverted)
{
static pool<std::string> warned_cells{};
if (cell == nullptr || attr == nullptr || attr->value.empty())
return false;
std::string expr = attr->value;
auto expr = attr->value;
auto cell_name = cell->args[0];
for (size_t pos = expr.find_first_of("\" \t"); pos != std::string::npos; pos = expr.find_first_of("\" \t"))
expr.erase(pos, 1);
@ -350,11 +111,14 @@ static bool parse_next_state(const LibertyAst *cell, const LibertyAst *attr, std
return true;
// the next_state variable isn't just a pin name; perhaps this is an enable?
auto helper = string_helper(expr);
auto tree = parse_expression(helper);
auto helper = LibertyExpression::Lexer(expr);
auto tree = LibertyExpression::parse(helper);
if (tree.kind == expression_kind::EMPTY) {
log_warning("Invalid expression '%s' in next_state attribute of cell '%s' - skipping.\n", expr.c_str(), cell->args[0].c_str());
if (tree.kind == LibertyExpression::Kind::EMPTY) {
if (!warned_cells.count(cell_name)) {
log_warning("Invalid expression '%s' in next_state attribute of cell '%s' - skipping.\n", expr.c_str(), cell_name.c_str());
warned_cells.insert(cell_name);
}
return false;
}
@ -370,17 +134,60 @@ static bool parse_next_state(const LibertyAst *cell, const LibertyAst *attr, std
// This test is redundant with the one in enable_pin, but we're in a
// position that gives better diagnostics here.
if (!pin_names.count(ff_output)) {
log_warning("Inference failed on expression '%s' in next_state attribute of cell '%s' because it does not contain ff output '%s' - skipping.\n", expr.c_str(), cell->args[0].c_str(), ff_output.c_str());
if (!warned_cells.count(cell_name)) {
log_warning("Inference failed on expression '%s' in next_state attribute of cell '%s' because it does not contain ff output '%s' - skipping.\n", expr.c_str(), cell_name.c_str(), ff_output.c_str());
warned_cells.insert(cell_name);
}
return false;
}
enable_name = tree.enable_pin(ff_output, data_name, data_not_inverted, enable_not_inverted);
if (enable_name.empty()) {
log_warning("Inference failed on expression '%s' in next_state attribute of cell '%s' because it does not evaluate to an enable flop - skipping.\n", expr.c_str(), cell->args[0].c_str());
return false;
data_not_inverted = true;
data_name = "";
enable_not_inverted = true;
enable_name = "";
if (pin_names.size() == 3 && pin_names.count(ff_output)) {
pin_names.erase(ff_output);
auto pins = std::vector<std::string>(pin_names.begin(), pin_names.end());
int lut = 0;
for (int n = 0; n < 8; n++) {
auto values = dict<std::string, bool>{};
values.insert(std::make_pair(pins[0], (n & 1) == 1));
values.insert(std::make_pair(pins[1], (n & 2) == 2));
values.insert(std::make_pair(ff_output, (n & 4) == 4));
if (tree.eval(values))
lut |= 1 << n;
}
// the ff output Q is in a known bit location, so we now just have to compare the LUT mask to known values to find the enable pin and polarity.
if (lut == 0xD8) {
data_name = pins[1];
enable_name = pins[0];
return true;
}
if (lut == 0xB8) {
data_name = pins[0];
enable_name = pins[1];
return true;
}
enable_not_inverted = false;
if (lut == 0xE4) {
data_name = pins[1];
enable_name = pins[0];
return true;
}
if (lut == 0xE2) {
data_name = pins[0];
enable_name = pins[1];
return true;
}
// this does not match an enable flop.
}
return true;
if (!warned_cells.count(cell_name)) {
log_warning("Inference failed on expression '%s' in next_state attribute of cell '%s' because it does not evaluate to an enable flop - skipping.\n", expr.c_str(), cell_name.c_str());
warned_cells.insert(cell_name);
}
return false;
}
static bool parse_pin(const LibertyAst *cell, const LibertyAst *attr, std::string &pin_name, bool &pin_pol)
@ -556,6 +363,8 @@ static void find_cell_sr(const LibertyAst *ast, IdString cell_type, bool clkpol,
bool best_cell_noninv = false;
double best_cell_area = 0;
log_assert(!enapol && "set/reset cell with enable is unimplemented due to lack of cells for testing");
if (ast->id != "library")
log_error("Format error in liberty file.\n");

146
passes/techmap/libparse.cc
View File

@ -80,6 +80,152 @@ void LibertyAst::dump(FILE *f, sieve &blacklist, sieve &whitelist, std::string i
fprintf(f, " ;\n");
}
#ifndef FILTERLIB
// https://matklad.github.io/2020/04/13/simple-but-powerful-pratt-parsing.html
LibertyExpression LibertyExpression::parse(Lexer &s, int min_prio) {
if (s.empty())
return LibertyExpression{};
char c = s.peek();
auto lhs = LibertyExpression{};
while (isspace(c)) {
if (s.empty())
return lhs;
s.next();
c = s.peek();
}
if (isalpha(c)) { // pin
lhs.kind = Kind::PIN;
lhs.name = s.pin();
} else if (c == '(') { // parens
s.next();
lhs = parse(s);
if (s.peek() != ')') {
log_warning("expected ')' instead of '%c' while parsing Liberty expression '%s'\n", s.peek(), s.full_expr().c_str());
return lhs;
}
s.next();
} else if (c == '!') { // prefix NOT
s.next();
lhs.kind = Kind::NOT;
lhs.children.push_back(parse(s, 7));
} else {
log_warning("unrecognised character '%c' while parsing Liberty expression '%s'\n", c, s.full_expr().c_str());
return lhs;
}
while (true) {
if (s.empty())
break;
c = s.peek();
while (isspace(c)) {
if (s.empty())
return lhs;
s.next();
c = s.peek();
}
if (c == '\'') { // postfix NOT
if (min_prio > 7)
break;
s.next();
auto n = LibertyExpression{};
n.kind = Kind::NOT;
n.children.push_back(lhs);
lhs = std::move(n);
continue;
} else if (c == '^') { // infix XOR
if (min_prio > 5)
break;
s.next();
auto rhs = parse(s, 6);
auto n = LibertyExpression{};
n.kind = Kind::XOR;
n.children.push_back(lhs);
n.children.push_back(rhs);
lhs = std::move(n);
continue;
} else if (c == '&' || c == '*') { // infix AND
// technically space should be considered infix AND. it seems rare in practice.
if (min_prio > 3)
break;
s.next();
auto rhs = parse(s, 4);
auto n = LibertyExpression{};
n.kind = Kind::AND;
n.children.push_back(lhs);
n.children.push_back(rhs);
lhs = std::move(n);
continue;
} else if (c == '+' || c == '|') { // infix OR
if (min_prio > 1)
break;
s.next();
auto rhs = parse(s, 2);
auto n = LibertyExpression{};
n.kind = Kind::OR;
n.children.push_back(lhs);
n.children.push_back(rhs);
lhs = std::move(n);
continue;
}
break;
}
return lhs;
}
void LibertyExpression::get_pin_names(pool<std::string>& names) {
if (kind == Kind::PIN) {
names.insert(name);
} else {
for (auto& child : children)
child.get_pin_names(names);
}
}
bool LibertyExpression::eval(dict<std::string, bool>& values) {
bool result = false;
switch (kind) {
case Kind::AND:
result = true;
for (auto& child : children)
result &= child.eval(values);
return result;
case Kind::OR:
result = false;
for (auto& child : children)
result |= child.eval(values);
return result;
case Kind::NOT:
log_assert(children.size() == 1);
return !children[0].eval(values);
case Kind::XOR:
result = false;
for (auto& child : children)
result ^= child.eval(values);
return result;
case Kind::PIN:
return values.at(name);
case Kind::EMPTY:
log_assert(false);
}
return false;
}
#endif
int LibertyParser::lexer(std::string &str)
{
int c;

47
passes/techmap/libparse.h
View File

@ -20,6 +20,7 @@
#ifndef LIBPARSE_H
#define LIBPARSE_H
#include "kernel/yosys.h"
#include <stdio.h>
#include <string>
#include <vector>
@ -39,6 +40,52 @@ namespace Yosys
void dump(FILE *f, sieve &blacklist, sieve &whitelist, std::string indent = "", std::string path = "", bool path_ok = false) const;
};
struct LibertyExpression
{
struct Lexer {
std::string s, expr;
Lexer(std::string s) : s{s}, expr{s} {}
bool empty() { return s.empty();}
char peek() { return s[0]; }
std::string full_expr() { return expr; }
char next() {
char c = s[0];
s = s.substr(1, s.size());
return c;
}
std::string pin() {
auto length = s.find_first_of("\t()'!^*& +|");
auto pin = s.substr(0, length);
s = s.substr(length, s.size());
return pin;
}
};
enum Kind {
AND,
OR,
NOT,
XOR,
// the standard specifies constants, but they're probably rare in practice.
PIN,
EMPTY
};
Kind kind;
std::string name;
std::vector<LibertyExpression> children;
LibertyExpression() : kind(Kind::EMPTY) {}
static LibertyExpression parse(Lexer &s, int min_prio = 0);
void get_pin_names(pool<std::string>& names);
bool eval(dict<std::string, bool>& values);
};
class LibertyParser
{
private: