Add test for ait framework

unit/Makefile

@@ -7,6 +7,7 @@ SRC = unit_tests.cpp \
 
 # Test source files
 SRC += unit_tests.cpp \
+       analyses/ai/ai.cpp \
        analyses/ai/ai_simplify_lhs.cpp \
        analyses/call_graph.cpp \
        analyses/constant_propagator.cpp \

unit/analyses/ai/ai.cpp

@@ -0,0 +1,297 @@
+/*******************************************************************\
+
+ Module: Unit tests for ait
+
+ Author: Diffblue Ltd.
+
+\*******************************************************************/
+
+/// \file
+/// Unit tests for ait
+
+#include <testing-utils/catch.hpp>
+
+#include <analyses/ai.h>
+
+#include <ansi-c/ansi_c_language.h>
+
+#include <goto-programs/goto_convert_functions.h>
+
+#include <langapi/mode.h>
+
+#include <util/arith_tools.h>
+#include <util/config.h>
+#include <util/c_types.h>
+#include <util/optional.h>
+
+/// A very simple analysis that counts executed instructions along a particular
+/// path, taking the max at merge points and saturating at 100 instructions.
+/// It should indicate that instructions not within a loop have a certain path
+/// length, and those reachable from a loop have a path length of 100
+/// (i.e. potentially infinity)
+class instruction_counter_domaint : public ai_domain_baset
+{
+public:
+
+  optionalt<unsigned> path_length;
+
+  void transform(locationt, locationt, ai_baset &, const namespacet &) override
+  {
+    if(*path_length < 100)
+      ++*path_length;
+  }
+
+  void make_bottom() override
+  {
+    path_length = {};
+  }
+  void make_top() override
+  {
+    UNREACHABLE;
+  }
+  void make_entry() override
+  {
+    path_length = 0;
+  }
+  bool is_bottom() const override
+  {
+    return !path_length.has_value();
+  }
+  bool is_top() const override
+  {
+    UNREACHABLE;
+    return true;
+  }
+
+  bool merge(const instruction_counter_domaint &b, locationt from, locationt to)
+  {
+    if(b.is_bottom())
+      return false;
+
+    if(!path_length.has_value())
+      path_length = 0;
+
+    unsigned old_count = *path_length;
+    // Max path length to get here:
+    *path_length =
+      std::max(*path_length, *b.path_length);
+    return *path_length != old_count;
+  }
+};
+
+class instruction_counter_analysist : public ait<instruction_counter_domaint>
+{
+public:
+
+  static bool is_y_assignment(const goto_programt::instructiont &i)
+  {
+    if(!i.is_assign())
+      return false;
+    const code_assignt &assign = to_code_assign(i.code);
+    return
+      assign.lhs().id() == ID_symbol &&
+      id2string(to_symbol_expr(assign.lhs()).get_identifier()).find('y') !=
+      std::string::npos;
+  }
+
+  static bool is_y_assignment_location(locationt l)
+  {
+    // At assignments to variables with a 'y' in their name, keep the domain.
+    // Otherwise let ait decide whether to keep it.
+    return is_y_assignment(*l);
+  }
+};
+
+static code_function_callt make_void_call(const symbol_exprt &function)
+{
+  code_function_callt ret;
+  ret.function() = function;
+  return ret;
+}
+
+SCENARIO(
+  "ait general testing", "[core][analyses][ai][general]")
+{
+  // Make a program like:
+
+  // __CPROVER_start() { f(); }
+  //
+  // f() {
+  //   int x = 10;
+  //   int y = 20;
+  //   h();
+  //   while(x != 0) {
+  //     x -= 1;
+  //     y -= 1;
+  //     g();
+  //   }
+  //   g(); // To ensure that this later call doesn't overwrite the earlier
+  //        // calls from within the loop (i.e. the top of 'g' is respected
+  //        // as a merge point)
+  // }
+  //
+  // Called from within loop, so should have a long possible path
+  // g() { int gy = 0; }
+  //
+  // Only called before loop, so should have a short path
+  // h() { int hy = 0; }
+
+  register_language(new_ansi_c_language);
+  config.ansi_c.set_LP64();
+
+  goto_modelt goto_model;
+
+  // g:
+
+  symbolt gy;
+  gy.name = "gy";
+  gy.mode = ID_C;
+  gy.type = signed_int_type();
+
+  symbolt g;
+  g.name = "g";
+  g.mode = ID_C;
+  g.type = code_typet({}, void_typet());
+  g.value = code_assignt(gy.symbol_expr(), from_integer(0, signed_int_type()));
+
+  // h:
+
+  symbolt hy;
+  hy.name = "hy";
+  hy.mode = ID_C;
+  hy.type = signed_int_type();
+
+  symbolt h;
+  h.name = "h";
+  h.mode = ID_C;
+  h.type = code_typet({}, void_typet());
+  h.value = code_assignt(hy.symbol_expr(), from_integer(0, signed_int_type()));
+
+  goto_model.symbol_table.add(g);
+  goto_model.symbol_table.add(gy);
+  goto_model.symbol_table.add(h);
+  goto_model.symbol_table.add(hy);
+
+  // f:
+
+  symbolt x;
+  x.name = "x";
+  x.mode = ID_C;
+  x.type = signed_int_type();
+
+  symbolt y;
+  y.name = "y";
+  y.mode = ID_C;
+  y.type = signed_int_type();
+
+  goto_model.symbol_table.add(x);
+  goto_model.symbol_table.add(y);
+
+  code_blockt f_body;
+
+  f_body.copy_to_operands(code_declt(x.symbol_expr()));
+  f_body.copy_to_operands(code_declt(y.symbol_expr()));
+
+  f_body.copy_to_operands(
+    code_assignt(x.symbol_expr(), from_integer(10, signed_int_type())));
+  f_body.copy_to_operands(
+    code_assignt(y.symbol_expr(), from_integer(20, signed_int_type())));
+
+  f_body.copy_to_operands(make_void_call(h.symbol_expr()));
+
+  code_whilet loop;
+
+  loop.cond() =
+    notequal_exprt(x.symbol_expr(), from_integer(0, signed_int_type()));
+
+  code_blockt loop_body;
+  loop_body.copy_to_operands(
+    code_assignt(
+      x.symbol_expr(),
+      minus_exprt(x.symbol_expr(), from_integer(1, signed_int_type()))));
+  loop_body.copy_to_operands(
+    code_assignt(
+      y.symbol_expr(),
+      minus_exprt(y.symbol_expr(), from_integer(1, signed_int_type()))));
+  loop_body.copy_to_operands(make_void_call(g.symbol_expr()));
+
+  loop.body() = loop_body;
+
+  f_body.move_to_operands(loop);
+
+  f_body.copy_to_operands(make_void_call(g.symbol_expr()));
+
+  symbolt f;
+  f.name = "f";
+  f.mode = ID_C;
+  f.type = code_typet({}, void_typet());
+  f.value = f_body;
+
+  goto_model.symbol_table.add(f);
+
+  // __CPROVER_start:
+
+  symbolt start;
+  start.name = goto_functionst::entry_point();
+  start.mode = ID_C;
+  start.type = code_typet({}, void_typet());
+  start.value = make_void_call(f.symbol_expr());
+
+  goto_model.symbol_table.add(start);
+
+  null_message_handlert nullout;
+  goto_convert(goto_model, nullout);
+
+  WHEN("The target program is analysed")
+  {
+    instruction_counter_analysist example_analysis;
+    example_analysis(goto_model);
+
+    THEN("No state should be bottom")
+    {
+      forall_goto_functions(f_it, goto_model.goto_functions)
+      {
+        forall_goto_program_instructions(i_it, f_it->second.body)
+        {
+          REQUIRE_FALSE(example_analysis[i_it].is_bottom());
+        }
+      }
+    }
+
+    THEN("The first y-assignment should have a short path; "
+         "the second should have a long one")
+    {
+      const auto &f_instructions =
+        goto_model.goto_functions.function_map.at("f").body.instructions;
+
+      std::vector<goto_programt::const_targett> y_assignments;
+      for(auto l = f_instructions.begin(); l != f_instructions.end(); ++l)
+        if(instruction_counter_analysist::is_y_assignment_location(l))
+          y_assignments.push_back(l);
+
+      REQUIRE(y_assignments.size() == 2);
+      REQUIRE_FALSE(example_analysis[y_assignments[0]].is_bottom());
+      REQUIRE(*(example_analysis[y_assignments[0]].path_length) < 100);
+      REQUIRE_FALSE(example_analysis[y_assignments[1]].is_bottom());
+      REQUIRE(*(example_analysis[y_assignments[1]].path_length) == 100);
+    }
+
+    THEN("The assignment in function 'g' should have a long path")
+    {
+      const auto &g_instructions =
+        goto_model.goto_functions.function_map.at("g").body.instructions;
+      REQUIRE(g_instructions.begin()->is_assign());
+      REQUIRE_FALSE(example_analysis[g_instructions.begin()].is_bottom());
+      REQUIRE(*example_analysis[g_instructions.begin()].path_length == 100);
+    }
+
+    THEN("The assignment in function 'h' should have a short path")
+    {
+      const auto &h_instructions =
+        goto_model.goto_functions.function_map.at("h").body.instructions;
+      REQUIRE(h_instructions.begin()->is_assign());
+      REQUIRE_FALSE(example_analysis[h_instructions.begin()].is_bottom());
+      REQUIRE(*example_analysis[h_instructions.begin()].path_length < 100);
+    }
+  }
+}