ExpressionVariable.cpp

// -*- mode: C++ -*-
//
// Copyright (c) 2007, 2008, 2010, 2011, 2013, 2014 The University of Utah
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//
// This file is part of `csmith', a random generator of C programs.
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#include "ExpressionVariable.h"
#include <cassert>

#include "CGContext.h"
#include "CGOptions.h"
#include "Function.h"
#include "VariableSelector.h"
#include "Fact.h"
#include "FactPointTo.h"
#include "FactMgr.h"
#include "Bookkeeper.h"
#include "Error.h"
#include "DepthSpec.h"
#include "ArrayVariable.h"

#include "random.h"


///////////////////////////////////////////////////////////////////////////////

/*
 *
 */
ExpressionVariable *
ExpressionVariable::make_random(CGContext &cg_context, const Type* type, const CVQualifiers* qfer, bool as_param, bool as_return)
{
	DEPTH_GUARD_BY_TYPE_RETURN(dtExpressionVariable, NULL);
	Function *curr_func = cg_context.get_current_func(); 
	FactMgr* fm = get_fact_mgr_for_func(curr_func);
	vector<const Variable*> dummy; 

	// save current effects, in case we need to reset 
	Effect eff_accum = cg_context.get_accum_effect();
	Effect eff_stmt = cg_context.get_effect_stm();
  
	ExpressionVariable *ev = 0;
	do {
		const Variable* var = 0; 
		// try to use one of must_read_vars in CGContext 
		var = VariableSelector::select_must_use_var(Effect::READ, cg_context, type, qfer);  
		if (var == NULL) {
			var = VariableSelector::select(Effect::READ, cg_context, type, qfer, dummy, eFlexible);
		}
		ERROR_GUARD(NULL);
		if (!var) 
			continue;
		if (!type->is_float() && var->type->is_float())
			continue;
		// forbid a parameter to take the address of an argument
		// this is to simplify the path shortcutting delta
		if (as_param && var->is_argument() && var->type->is_dereferenced_from(type)) {
			continue;
		}
		if (!CGOptions::addr_taken_of_locals()
			&& var->type->is_dereferenced_from(type)
			&& (var->is_argument() || var->is_local())) {
			continue;
		}

		// forbid a escaping pointer to take the address of an argument or a local variable
		int indirection = var->type->get_indirect_level() - type->get_indirect_level();
		if (as_return && CGOptions::no_return_dead_ptr() &&
			FactPointTo::is_pointing_to_locals(var, cg_context.get_current_block(), indirection, fm->global_facts)) {
			continue;
		}
		int valid = FactPointTo::opportunistic_validate(var, type, fm->global_facts);
		if (valid) {
			ExpressionVariable tmp(*var, type);
			if (tmp.visit_facts(fm->global_facts, cg_context)) { 
				ev = tmp.get_indirect_level() == 0 ? new ExpressionVariable(*var) : new ExpressionVariable(*var, type); 
				cg_context.curr_blk = cg_context.get_current_block();
				break;
			}  
			else {
				cg_context.reset_effect_accum(eff_accum);
				cg_context.reset_effect_stm(eff_stmt);
			}
		}
		dummy.push_back(var);
	} while (true);

	// statistics
	int deref_level = ev->get_indirect_level();
	if (deref_level > 0) {
		incr_counter(Bookkeeper::read_dereference_cnts, deref_level); 
	}
	if (deref_level < 0) {
		Bookkeeper::record_address_taken(ev->get_var());
	}   
	Bookkeeper::record_volatile_access(ev->get_var(), deref_level, false);
	return ev;
}

/*
 *
 */
ExpressionVariable::ExpressionVariable(const Variable &v)
	: Expression(eVariable),
      var(v),
      type(v.type)
{ 
}

/*
 *
 */
ExpressionVariable::ExpressionVariable(const Variable &v, const Type* t)
	: Expression(eVariable),
	  var(v),
	  type(t)
{ 
}

/*
 *
 */
ExpressionVariable::ExpressionVariable(const ExpressionVariable &expr)
	: Expression(eVariable),
	  var(expr.var),
	  type(expr.type)
{
	// Nothing to do	
}

Expression *
ExpressionVariable::clone() const
{
	return new ExpressionVariable(*this);
}

/*
 *
 */
ExpressionVariable::~ExpressionVariable(void)
{
	// Nothing to do.
}

///////////////////////////////////////////////////////////////////////////////

/*
 *
 */
const Type &
ExpressionVariable::get_type(void) const
{
	return *(type);
}

/*
 *
 */
int
ExpressionVariable::get_indirect_level(void) const
{
	return var.type->get_indirect_level() - type->get_indirect_level();
}

/*
 *
 */
CVQualifiers 
ExpressionVariable::get_qualifiers(void) const
{
	int indirect = get_indirect_level();
	return var.qfer.indirect_qualifiers(indirect);
}

/*
 *
 */
void
ExpressionVariable::Output(std::ostream &out) const
{
	output_cast(out);
	Reducer* reducer = CGOptions::get_reducer();
	if (reducer && reducer->output_expr(this, out)) {
		return;
	}
	int i;
    int indirect_level = get_indirect_level(); 
    if (indirect_level > 0) {
        out << "(";
		for (i=0; i<indirect_level; i++) {
			out << "*";
		}
	}
	else if (indirect_level < 0) {
		assert(indirect_level == -1);
		out << "&";
    }
	var.Output(out);
    if (indirect_level > 0) {
        out << ")";
    }
}

std::vector<const ExpressionVariable*> 
ExpressionVariable::get_dereferenced_ptrs(void) const
{
	// return a empty vector by default
	std::vector<const ExpressionVariable*> refs;
	if (get_indirect_level() > 0) {
		refs.push_back(this);
	}
	return refs;
}

void 
ExpressionVariable::get_referenced_ptrs(std::vector<const Variable*>& ptrs) const
{ 
	if (var.is_pointer()) {
		ptrs.push_back(&var);
	}
}

bool 
ExpressionVariable::visit_facts(vector<const Fact*>& inputs, CGContext& cg_context) const
{ 
	int deref_level = get_indirect_level();
	const Variable* v = get_var();   
	if (deref_level > 0) { 
		if (!FactPointTo::is_valid_ptr(v, inputs)) {
			return false;
		}
		// Yang: do we need to consider the deref_level?
		bool valid = cg_context.check_read_var(v, inputs) && cg_context.read_pointed(this, inputs) && 
			cg_context.check_deref_volatile(v, deref_level);
		return valid;
	}
	// we filter out bitfield
	if (deref_level < 0) {
		if (v->isBitfield_) 
			return false; 
		// it's actually valid to take address of a null/dead pointer  
		return true;
	}
	else {
		return cg_context.check_read_var(v, inputs);
	} 
}

/*
 *
 */
bool
ExpressionVariable::compatible(const Expression *exp) const
{
	assert(exp);

	//if (!(exp->term_type == eVariable))
		//return false;

	return exp->compatible(&var);
}

/*
 *
 */
bool
ExpressionVariable::compatible(const Variable *v) const
{
	assert(v);

	return this->var.compatible(v);
}

///////////////////////////////////////////////////////////////////////////////

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// End of file.