new rewriter

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/ast/rewriter/hoist_rewriter.cpp

@@ -0,0 +1,178 @@
+/*++
+Copyright (c) 2019 Microsoft Corporation
+
+Module Name:
+
+    hoist_rewriter.cpp
+
+Abstract:
+
+    Hoist predicates over disjunctions
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2019-2-4
+
+Notes:
+
+--*/
+
+
+#include "ast/rewriter/hoist_rewriter.h"
+#include "ast/ast_util.h"
+#include "ast/rewriter/expr_safe_replace.h"
+#include "ast/ast_pp.h"
+
+
+hoist_rewriter::hoist_rewriter(ast_manager & m, params_ref const & p):
+    m_manager(m), m_args(m) { 
+    updt_params(p); 
+}
+
+br_status hoist_rewriter::mk_or(unsigned num_args, expr * const * args, expr_ref & result) {
+    if (num_args < 2) {
+        return BR_FAILED;
+    }
+    for (unsigned i = 0; i < num_args; ++i) {
+        if (!is_and(args[i])) {
+            return BR_FAILED;
+        }
+    }
+
+    bool turn = false;
+    m_preds1.reset(); 
+    m_preds2.reset();
+    m_uf1.reset(); 
+    m_uf2.reset();
+    m_expr2var.reset();
+    m_var2expr.reset();
+    basic_union_find* uf[2] = { &m_uf1, &m_uf2 };
+    obj_hashtable<expr>* preds[2] = { &m_preds1, &m_preds2 };
+    VERIFY(is_and(args[0]));
+    expr* e1, *e2;
+    for (expr* e : m_args) {
+        if (m().is_eq(e, e1, e2)) {            
+            (*uf)[turn].merge(mk_var(e1), mk_var(e2));
+        }
+        else {
+            (*preds)[turn].insert(e);
+        }
+    }
+    unsigned round = 0;
+    for (unsigned j = 1; j < num_args; ++j) {
+        ++round;
+        m_es.reset();
+        m_mark.reset();
+
+        bool last = turn;
+        turn = !turn;
+        (*preds)[turn].reset();
+        reset(m_uf0);
+        unsigned v1 = 0, v2 = 0;
+        VERIFY(is_and(args[j]));
+        for (expr* e : m_args) {
+            if (m().is_eq(e, e1, e2)) {
+                m_es.push_back(e1);                
+                m_uf0.merge(mk_var(e1), mk_var(e2));
+            }    
+            else if ((*preds)[last].contains(e)) {
+                (*preds)[turn].insert(e);
+            }
+        }
+        if ((*preds)[turn].empty() && m_es.empty()) {
+            return BR_FAILED;
+        }
+
+        m_eqs.reset();
+        for (expr* e : m_es) {
+            if (m_mark.is_marked(e)) {
+                continue;
+            }
+            unsigned u = mk_var(e);
+            unsigned v = u;
+            m_roots.reset();
+            do {
+                m_mark.mark(e);
+                unsigned r = (*uf)[last].find(v);
+                if (m_roots.find(r, e2)) {
+                    m_eqs.push_back(std::make_pair(e, e2));
+                }
+                else {
+                    m_roots.insert(r, e);
+                }
+                v = m_uf0.next(v);
+                e = mk_expr(v);
+            }
+            while (u != v);
+        }
+        reset((*uf)[turn]);
+        for (auto const& p : m_eqs) {
+            (*uf)[turn].merge(mk_var(p.first), mk_var(p.second));
+        }
+    }
+    // p & eqs & (or fmls)
+    expr_ref_vector fmls(m()), ors(m());
+    expr_safe_replace subst(m());
+    for (expr * p : (*preds)[turn]) {
+        subst.insert(p, m().mk_true());
+        fmls.push_back(p);
+    }
+    for (auto const& p : m_eqs) {
+        subst.insert(p.first, p.second);
+        fmls.push_back(m().mk_eq(p.first, p.second));
+    }
+
+    for (unsigned i = 0; i < num_args; ++i) {
+        expr_ref tmp(m());
+        subst(args[i], tmp);
+        ors.push_back(tmp);
+    }
+    fmls.push_back(m().mk_or(ors.size(), ors.c_ptr()));
+    result = m().mk_and(fmls.size(), fmls.c_ptr());
+    return BR_DONE;
+}
+
+unsigned hoist_rewriter::mk_var(expr* e) {
+    unsigned v = 0;
+    if (m_expr2var.find(e, v)) {
+        return v;
+    }
+    v = m_uf1.mk_var();
+    v = m_uf2.mk_var();
+    SASSERT(v == m_var2expr.size());
+    m_expr2var.insert(e, v);
+    m_var2expr.push_back(e);
+    return v;
+}
+
+br_status hoist_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * const * args, expr_ref & result) {
+    switch (f->get_decl_kind()) {
+    case OP_OR:
+        return mk_or(num_args, args, result);
+    default:
+        return BR_FAILED;
+    }
+}
+
+bool hoist_rewriter::is_and(expr * e) {
+    m_args.reset();
+    if (m().is_and(e)) {
+        m_args.append(to_app(e)->get_num_args(), to_app(e)->get_args());
+        return true;
+    }
+    if (m().is_not(e, e) && m().is_or(e)) {
+        for (expr* arg : *to_app(e)) {
+            m_args.push_back(::mk_not(m(), arg));
+        }
+        return true;
+    }
+    return false;
+}
+
+
+void hoist_rewriter::reset(basic_union_find& uf) {
+    uf.reset();
+    for (expr* e : m_var2expr) {
+        uf.mk_var();
+    }
+}