208 lines
6.4 KiB
C++
208 lines
6.4 KiB
C++
/*
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Copyright (c) 2013 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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*/
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#pragma once
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#include <tuple>
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#include "util/buffer.h"
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#include "util/interrupt.h"
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#include "kernel/expr.h"
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#include "kernel/expr_maps.h"
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#include "kernel/update_expr.h"
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namespace lean {
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/**
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\brief Default replace_fn postprocessor functional object. It is a
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do-nothing object.
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*/
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class default_replace_postprocessor {
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public:
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void operator()(expr const &, expr const &) {}
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};
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/**
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\brief Functional for applying <tt>F</tt> to the subexpressions of a given expression.
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The signature of \c F is
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expr const &, unsigned -> expr
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F is invoked for each subexpression \c s of the input expression e.
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In a call <tt>F(s, n)</tt>, n is the scope level, i.e., the number of
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bindings operators that enclosing \c s.
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P is a "post-processing" functional object that is applied to each
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pair (old, new)
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*/
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template<typename F, typename P = default_replace_postprocessor>
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class replace_fn {
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static_assert(std::is_same<typename std::result_of<F(expr const &, unsigned)>::type, expr>::value,
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"replace_fn: return type of F is not expr");
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// the return type of P()(e1, e2) should be void
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static_assert(std::is_same<typename std::result_of<decltype(std::declval<P>())(expr const &, expr const &)>::type,
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void>::value,
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"The return type of P()(e1, e2) is not void");
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struct frame {
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expr m_expr;
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unsigned m_offset;
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bool m_shared;
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unsigned m_index;
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frame(expr const & e, unsigned o, bool s):m_expr(e), m_offset(o), m_shared(s), m_index(0) {}
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};
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typedef buffer<frame> frame_stack;
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typedef buffer<expr> result_stack;
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expr_cell_offset_map<expr> m_cache;
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F m_f;
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P m_post;
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frame_stack m_fs;
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result_stack m_rs;
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static bool is_atomic(expr const & e) {
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switch (e.kind()) {
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case expr_kind::Constant: case expr_kind::Type: case expr_kind::Value:
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case expr_kind::Var: case expr_kind::MetaVar:
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return true;
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default:
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return false;
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}
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}
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void save_result(expr const & e, expr const & r, unsigned offset, bool shared) {
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if (shared)
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m_cache.insert(std::make_pair(expr_cell_offset(e.raw(), offset), r));
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m_post(e, r);
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m_rs.push_back(r);
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}
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/**
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\brief Visit \c e at the given offset. Return true iff the result is on the
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result stack \c m_rs. Return false iff a new frame was pushed on the stack \c m_fs.
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The idea is that after the frame is processed, the result will be on the result stack.
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*/
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bool visit(expr const & e, unsigned offset) {
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bool shared = false;
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if (is_shared(e)) {
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expr_cell_offset p(e.raw(), offset);
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auto it = m_cache.find(p);
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if (it != m_cache.end()) {
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m_rs.push_back(it->second);
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return true;
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}
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shared = true;
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}
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expr r = m_f(e, offset);
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if (is_atomic(r) || !is_eqp(e, r)) {
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save_result(e, r, offset, shared);
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return true;
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} else {
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m_fs.emplace_back(e, offset, shared);
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return false;
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}
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}
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/**
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\brief Return true iff <tt>f.m_index == idx</tt>.
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When the result is true, <tt>f.m_index</tt> is incremented.
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*/
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bool check_index(frame & f, unsigned idx) {
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if (f.m_index == idx) {
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f.m_index++;
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return true;
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} else {
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return false;
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}
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}
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expr const & rs(int i) {
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lean_assert(i < 0);
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return m_rs[m_rs.size() + i];
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}
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void pop_rs(unsigned num) {
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m_rs.shrink(m_rs.size() - num);
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}
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public:
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replace_fn(F const & f, P const & p = P()):
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m_f(f),
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m_post(p) {
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}
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expr operator()(expr const & e) {
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expr r;
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visit(e, 0);
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while (!m_fs.empty()) {
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begin_loop:
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check_interrupted();
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frame & f = m_fs.back();
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expr const & e = f.m_expr;
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unsigned offset = f.m_offset;
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switch (e.kind()) {
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case expr_kind::Constant: case expr_kind::Type: case expr_kind::Value: case expr_kind::Var: case expr_kind::MetaVar:
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lean_unreachable(); // LCOV_EXCL_LINE
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case expr_kind::App: {
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unsigned num = num_args(e);
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while (f.m_index < num) {
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expr const & c = arg(e, f.m_index);
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f.m_index++;
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if (!visit(c, offset))
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goto begin_loop;
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}
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r = update_app(e, num, m_rs.end() - num_args(e));
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pop_rs(num);
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break;
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}
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case expr_kind::Pi: case expr_kind::Lambda:
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if (check_index(f, 0) && !visit(abst_domain(e), offset))
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goto begin_loop;
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if (check_index(f, 1) && !visit(abst_body(e), offset + 1))
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goto begin_loop;
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r = update_abstraction(e, rs(-2), rs(-1));
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pop_rs(2);
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break;
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case expr_kind::Let:
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if (check_index(f, 0) && let_type(e) && !visit(*let_type(e), offset))
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goto begin_loop;
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if (check_index(f, 1) && !visit(let_value(e), offset))
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goto begin_loop;
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if (check_index(f, 2) && !visit(let_body(e), offset + 1))
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goto begin_loop;
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if (let_type(e)) {
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r = update_let(e, some_expr(rs(-3)), rs(-2), rs(-1));
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pop_rs(3);
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} else {
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r = update_let(e, none_expr(), rs(-2), rs(-1));
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pop_rs(2);
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}
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break;
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}
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save_result(e, r, offset, f.m_shared);
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m_fs.pop_back();
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}
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lean_assert(m_rs.size() == 1);
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r = m_rs.back();
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m_rs.pop_back();
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return r;
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}
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void clear() {
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m_cache.clear();
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m_fs.clear();
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m_rs.clear();
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}
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};
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template<typename F>
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expr replace(expr const & e, F f) {
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return replace_fn<F>(f)(e);
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}
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template<typename F, typename P>
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expr replace(expr const & e, F f, P p) {
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return replace_fn<F, P>(f, p)(e);
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}
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}
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