58 lines
2 KiB
C++
58 lines
2 KiB
C++
/*
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Copyright (c) 2016 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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#include "kernel/instantiate.h"
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#include "library/locals.h"
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#include "library/compiler/procedure.h"
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#include "library/compiler/compiler_step_visitor.h"
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namespace lean {
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class elim_unused_lets_fn : public compiler_step_visitor {
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virtual expr visit_lambda(expr const & e) override {
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type_context::tmp_locals locals(m_ctx);
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expr t = e;
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while (is_lambda(t)) {
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expr d = instantiate_rev(binding_domain(t), locals.size(), locals.data());
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locals.push_local(binding_name(t), d, binding_info(t));
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t = binding_body(t);
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}
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t = instantiate_rev(t, locals.size(), locals.data());
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t = visit(t);
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return copy_tag(e, locals.mk_lambda(t));
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}
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virtual expr visit_let(expr const & e) override {
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type_context::tmp_locals locals(m_ctx);
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collected_locals used_locals;
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expr t = e;
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while (is_let(t)) {
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expr d = instantiate_rev(let_type(t), locals.size(), locals.data());
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expr v = visit(instantiate_rev(let_value(t), locals.size(), locals.data()));
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collect_locals(d, used_locals);
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collect_locals(v, used_locals);
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locals.push_let(let_name(t), d, v);
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t = let_body(t);
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}
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t = instantiate_rev(t, locals.size(), locals.data());
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t = visit(t);
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collect_locals(t, used_locals);
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buffer<expr> new_locals;
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for (expr const & l : locals.as_buffer()) {
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if (used_locals.contains(l))
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new_locals.push_back(l);
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}
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return copy_tag(e, m_ctx.mk_lambda(new_locals, t));
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}
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public:
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elim_unused_lets_fn(environment const & env):compiler_step_visitor(env) {}
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};
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void elim_unused_lets(environment const & env, buffer<procedure> & procs) {
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elim_unused_lets_fn fn(env);
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for (auto & proc : procs)
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proc.m_code = fn(proc.m_code);
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}
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}
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