190 lines
7 KiB
C++
190 lines
7 KiB
C++
/*
|
|
Copyright (c) 2016 Microsoft Corporation. All rights reserved.
|
|
Released under Apache 2.0 license as described in the file LICENSE.
|
|
|
|
Author: Leonardo de Moura
|
|
*/
|
|
#include "kernel/instantiate.h"
|
|
#include "kernel/abstract.h"
|
|
#include "kernel/for_each_fn.h"
|
|
#include "kernel/inductive/inductive.h"
|
|
#include "library/normalize.h"
|
|
#include "library/util.h"
|
|
#include "library/vm/vm.h"
|
|
#include "library/compiler/util.h"
|
|
#include "library/compiler/erase_irrelevant.h"
|
|
#include "library/compiler/compiler_step_visitor.h"
|
|
|
|
namespace lean {
|
|
class lambda_lifting_fn : public compiler_step_visitor {
|
|
buffer<pair<name, expr>> m_new_procs;
|
|
name m_prefix;
|
|
unsigned m_idx;
|
|
|
|
expr declare_aux_def(expr const & value) {
|
|
/* Try to avoid unnecessary aux decl by
|
|
1- Apply eta-reduction
|
|
2- Check if the result is of the form (f ...) where f is
|
|
a) VM builtin functions OR
|
|
b) A function without builtin support (i.e., it is not a constructor, cases_on or projection) */
|
|
expr new_value = try_eta(value);
|
|
expr const & fn = get_app_fn(new_value);
|
|
if (is_constant(fn)) {
|
|
name const & n = const_name(fn);
|
|
if (is_vm_builtin_function(n) ||
|
|
(!inductive::is_intro_rule(env(), n) && !is_cases_on_recursor(env(), n) && !is_projection(env(), n)))
|
|
return new_value;
|
|
}
|
|
name aux_name = mk_fresh_name(env(), m_prefix, "_lambda", m_idx);
|
|
m_new_procs.emplace_back(aux_name, value);
|
|
return mk_constant(aux_name);
|
|
}
|
|
|
|
typedef rb_map<unsigned, local_decl, unsigned_rev_cmp> idx2decls;
|
|
|
|
void collect_locals(expr const & e, idx2decls & r) {
|
|
local_context const & lctx = ctx().lctx();
|
|
for_each(e, [&](expr const & e, unsigned) {
|
|
if (is_local_decl_ref(e)) {
|
|
local_decl d = *lctx.get_local_decl(e);
|
|
r.insert(d.get_idx(), d);
|
|
}
|
|
return true;
|
|
});
|
|
}
|
|
|
|
expr visit_lambda_core(expr const & e) {
|
|
type_context::tmp_locals locals(m_ctx);
|
|
expr t = e;
|
|
while (is_lambda(t)) {
|
|
lean_assert(is_neutral_expr(binding_domain(t)));
|
|
locals.push_local(binding_name(t), binding_domain(t), binding_info(t));
|
|
t = binding_body(t);
|
|
}
|
|
t = instantiate_rev(t, locals.size(), locals.data());
|
|
t = visit(t);
|
|
return locals.mk_lambda(t);
|
|
}
|
|
|
|
expr abstract_locals(expr e, buffer<expr> & locals) {
|
|
idx2decls map;
|
|
collect_locals(e, map);
|
|
if (map.empty()) {
|
|
return e;
|
|
} else {
|
|
while (!map.empty()) {
|
|
/* remove local_decl with biggest idx */
|
|
local_decl d = map.erase_min();
|
|
expr l = d.mk_ref();
|
|
if (auto v = d.get_value()) {
|
|
collect_locals(*v, map);
|
|
e = instantiate(abstract_local(e, l), *v);
|
|
} else {
|
|
locals.push_back(l);
|
|
e = abstract_local(e, l);
|
|
e = mk_lambda(d.get_name(), d.get_type(), e);
|
|
}
|
|
}
|
|
return e;
|
|
}
|
|
}
|
|
|
|
virtual expr visit_lambda(expr const & e) override {
|
|
expr new_e = visit_lambda_core(e);
|
|
buffer<expr> locals;
|
|
new_e = abstract_locals(new_e, locals);
|
|
expr c = declare_aux_def(new_e);
|
|
return mk_rev_app(c, locals);
|
|
}
|
|
|
|
virtual expr visit_let(expr const & e) override {
|
|
type_context::tmp_locals locals(m_ctx);
|
|
expr t = e;
|
|
while (is_let(t)) {
|
|
lean_assert(is_neutral_expr(let_type(t)));
|
|
expr v = visit(instantiate_rev(let_value(t), locals.size(), locals.data()));
|
|
locals.push_let(let_name(t), let_type(t), v);
|
|
t = let_body(t);
|
|
}
|
|
t = instantiate_rev(t, locals.size(), locals.data());
|
|
t = visit(t);
|
|
return locals.mk_let(t);
|
|
}
|
|
|
|
expr visit_cases_on_minor(unsigned data_sz, expr e) {
|
|
type_context::tmp_locals locals(ctx());
|
|
for (unsigned i = 0; i < data_sz; i++) {
|
|
if (is_lambda(e)) {
|
|
expr l = locals.push_local_from_binding(e);
|
|
e = instantiate(binding_body(e), l);
|
|
} else {
|
|
expr l = locals.push_local("a", mk_neutral_expr());
|
|
e = mk_app(e, l);
|
|
}
|
|
}
|
|
e = visit(e);
|
|
return locals.mk_lambda(e);
|
|
}
|
|
|
|
/* We should preserve the lambda's in minor premises */
|
|
expr visit_cases_on_app(expr const & e) {
|
|
buffer<expr> args;
|
|
expr const & fn = get_app_args(e, args);
|
|
lean_assert(is_constant(fn));
|
|
name const & rec_name = const_name(fn);
|
|
name const & I_name = rec_name.get_prefix();
|
|
/* erase_irrelevant already removed parameters and indices from cases_on applications */
|
|
unsigned nminors = *inductive::get_num_minor_premises(env(), I_name);
|
|
unsigned nparams = *inductive::get_num_params(env(), I_name);
|
|
unsigned arity = nminors + 1 /* major premise */;
|
|
unsigned major_idx = 0;
|
|
unsigned first_minor_idx = 1;
|
|
/* This transformation assumes eta-expansion have already been applied.
|
|
So, we should have a sufficient number of arguments. */
|
|
lean_assert(args.size() >= arity);
|
|
buffer<name> cnames;
|
|
get_intro_rule_names(env(), I_name, cnames);
|
|
/* Process major premise */
|
|
args[major_idx] = visit(args[major_idx]);
|
|
/* Process extra arguments */
|
|
for (unsigned i = arity; i < args.size(); i++)
|
|
args[i] = visit(args[i]);
|
|
/* Process minor premises */
|
|
for (unsigned i = 0, j = first_minor_idx; i < cnames.size(); i++, j++) {
|
|
unsigned carity = get_constructor_arity(env(), cnames[i]);
|
|
lean_assert(carity >= nparams);
|
|
unsigned cdata_sz = carity - nparams;
|
|
args[j] = visit_cases_on_minor(cdata_sz, args[j]);
|
|
}
|
|
return mk_app(fn, args);
|
|
}
|
|
|
|
virtual expr visit_app(expr const & e) override {
|
|
expr const & fn = get_app_fn(e);
|
|
if (is_constant(fn) && is_cases_on_recursor(env(), const_name(fn))) {
|
|
return visit_cases_on_app(e);
|
|
} else {
|
|
return compiler_step_visitor::visit_app(beta_reduce(e));
|
|
}
|
|
}
|
|
|
|
public:
|
|
lambda_lifting_fn(environment const & env, name const & prefix):
|
|
compiler_step_visitor(env), m_prefix(prefix), m_idx(1) {
|
|
}
|
|
|
|
void operator()(buffer<pair<name, expr>> & procs) {
|
|
for (auto p : procs) {
|
|
expr val = p.second;
|
|
expr new_val = is_lambda(val) ? visit_lambda_core(val) : visit(val);
|
|
m_new_procs.emplace_back(p.first, new_val);
|
|
}
|
|
procs.clear();
|
|
procs.append(m_new_procs);
|
|
}
|
|
};
|
|
|
|
void lambda_lifting(environment const & env, name const & prefix, buffer<pair<name, expr>> & procs) {
|
|
return lambda_lifting_fn(env, prefix)(procs);
|
|
}
|
|
}
|