Add unsigned overflow checks to the system.

Now, all unsigned operations are checked to avoid overflow.

src/main/java/ca/mcscert/jtet/cvc3generator/HierarchicalGridCVC3Generator.java

@@ -28,6 +28,9 @@
  */
 package ca.mcscert.jtet.cvc3generator;
 
+import ca.mcscert.jtet.expression.BinaryOperation;
+import ca.mcscert.jtet.expression.CheckerGeneratorSpy;
+import ca.mcscert.jtet.expression.FixedPointVariableType;
 import ca.mcscert.jtet.expression.VariableCollection;
 import ca.mcscert.jtet.parsers.MatlabParser;
 import ca.mcscert.jtet.expression.BooleanVariableType;
@@ -129,8 +132,16 @@ final public class HierarchicalGridCVC3Generator implements HierarchicalGridChec
 
     @Override
     public void handleLeafCell(Cell cell) {
-        // First get the appropriate CVC3 code from matlab.
-        String newCellCode = MatlabParser.parseMatlabCode(m_variableDefinitions, cell.contents()).getCheckerOutput(m_CVC3Generator, BooleanVariableType.Type);
+        // First get the appropriate CVC3 code from matlab.  Capture generation for further processing.
+        CheckerGeneratorSpy spy = new CheckerGeneratorSpy(m_CVC3Generator);
+        String newCellCode = MatlabParser.parseMatlabCode(m_variableDefinitions, cell.contents()).getCheckerOutput(spy, BooleanVariableType.Type);
+
+        // Next, find all the fixed point expressions and handle them.
+        for(CheckerGeneratorSpy.SpiedBinaryOp op : spy.getBinaryOps()) {
+            if (op.usedType instanceof FixedPointVariableType) {
+                generateOverflowTCC(op);
+            }
+        }
 
         // Next form the disjoint queries and add to the list.
         for(String otherCellCode : m_currentCompleteQueries) {
@@ -142,6 +153,54 @@ final public class HierarchicalGridCVC3Generator implements HierarchicalGridChec
         m_currentCompleteQueries.add(newCellCode);
     }
 
+    private void generateOverflowTCC(CheckerGeneratorSpy.SpiedBinaryOp binaryOp) {
+        // Comparisons never overflow, so ignore them.
+        switch (binaryOp.op) {
+            case GreaterThen:
+            case GreaterThenEqual:
+            case LessThen:
+            case LessThenEqual:
+            case Equals:
+            case NotEquals:
+                return;
+        }
+        FixedPointVariableType type = (FixedPointVariableType) binaryOp.usedType;
+        if (!type.isSigned() && binaryOp.op == BinaryOperation.Division) {
+            return ; // Skip this generation.  Unsigned division requires no checks, since it never over/under flows.
+        }
+
+        m_output += "ECHO \"begin" + m_currentTCC + "\";\n";
+        m_output += "PUSH;\n";
+
+        String query = null;
+        //@todo: Handle signed integers.
+        switch (binaryOp.op) {
+            case Addition:
+                // Extend the addition and verify the extra bit remains unchanged.
+                query = "QUERY BVPLUS(" + (type.digits() + 1) + "," + binaryOp.lhsExp + "," + binaryOp.rhsExp + ")[" +
+                        (type.digits() + 1) + ":" + type.digits() + "] = 0bin0;";
+                break;
+            case Minus:
+                // Test rhs <= lhs, which guarantees this case as (lhs >= rhs => lhs - rhs > 0).
+                query = "QUERY BVLE(" + binaryOp.rhsExp + "," + binaryOp.lhsExp + ");";
+                break;
+            case Multiplication:
+                // Extend the addition and test extra bits remain zero, like addition.
+                query = "QUERY BVMULT(" + (type.digits() * 2) + "," + binaryOp.lhsExp + "," + binaryOp.rhsExp + ")[" +
+                        (type.digits() * 2 - 1) + ":" + type.digits() + "] = 0bin" + StringUtils.repeat('0', type.digits()) + ";";
+                break;
+            case Division:
+                // Unsigned never overflows, as the result never grows.  We skip any generation, so we should never come here.
+                throw new IllegalStateException("No check necessary for unsigned division!  Should never get here!");
+        }
+        m_queries.add(query);
+        m_output += query + "\n";
+
+        m_output += "POP;\n";
+        m_output += "ECHO \"end" + m_currentTCC + "\";\n";
+        m_currentTCC++; // For now, just screw up the TCC counting.
+    }
+
     @Override
     public String getFinalString() {
         if (m_currentlyRunning) {
@@ -161,7 +220,7 @@ final public class HierarchicalGridCVC3Generator implements HierarchicalGridChec
 
     List<String> m_currentDisjointQueries = new ArrayList<String>();
     List<String> m_currentCompleteQueries = new ArrayList<String>();
-    
+
     boolean m_currentlyRunning = true;
     int m_currentTCC = 1;
 

src/test/java/ca/mcscert/jtet/cvc3generator/HierarchicalGridCVC3GeneratorTest.java

@@ -102,5 +102,60 @@ public class HierarchicalGridCVC3GeneratorTest {
         assertEquals(expected, out);
     }
 
+    // Exercise the cvc3 generator's overflow protection
+    @Test
+    public void testCVC3GeneratorOverflow() {
+        HierarchicalGrid grid = new HierarchicalGrid();
+        List<HierarchicalCell> topCells = grid.getSubHierarchy();
+
+        topCells.add(new HierarchicalCell("(x + y) > 0"));
+        topCells.add(new HierarchicalCell("(x * y) == 0"));
+        topCells.add(new HierarchicalCell("(x / y) > 0"));
+
+        List<HierarchicalCell> nextGrid = topCells.get(1).getSubHierarchy();
+        nextGrid.add(new HierarchicalCell("(x - y) > 0"));
+
+        String out = HierarchicalGridCheckerWalkerGenerator.GenerateCheckerFromGrid(grid, new HierarchicalGridCVC3Generator(variableParser.parseVariables("x:fixedt(0,8,0),y:fixedt(0,8,0)"), 1));
+
+        String expected = "ECHO \"begin1\";\n" +
+                "PUSH;\n" +
+                "QUERY BVPLUS(9,x,y)[9:8] = 0bin0;\n" +
+                "POP;\n" +
+                "ECHO \"end1\";\n" +
+                "ECHO \"begin2\";\n" +
+                "PUSH;\n" +
+                "QUERY BVMULT(16,x,y)[15:8] = 0bin00000000;\n" +
+                "POP;\n" +
+                "ECHO \"end2\";\n" +
+                "ECHO \"begin3\";\n" +
+                "PUSH;\n" +
+                "QUERY (NOT ( BVGT(BVPLUS(8,x,y),0bin00000000) AND (BVMULT(8,x,y) = 0bin00000000) ) AND\n" +
+                "NOT ( BVGT(BVPLUS(8,x,y),0bin00000000) AND BVGT(BVUDIV(x,y),0bin00000000) ) AND\n" +
+                "NOT ( (BVMULT(8,x,y) = 0bin00000000) AND BVGT(BVUDIV(x,y),0bin00000000) ));\n" +
+                "POP;\n" +
+                "ECHO \"end3\";\n" +
+                "ECHO \"begin4\";\n" +
+                "PUSH;\n" +
+                "QUERY (BVGT(BVPLUS(8,x,y),0bin00000000) OR (BVMULT(8,x,y) = 0bin00000000) OR BVGT(BVUDIV(x,y),0bin00000000));\n" +
+                "POP;\n" +
+                "ECHO \"end4\";\n" +
+                "ECHO \"begin5\";\n" +
+                "PUSH;\n" +
+                "QUERY BVLE(y,x);\n" +
+                "POP;\n" +
+                "ECHO \"end5\";\n" +
+                "ECHO \"begin6\";\n" +
+                "PUSH;\n" +
+                "QUERY ((BVMULT(8,x,y) = 0bin00000000)) => ();\n" +
+                "POP;\n" +
+                "ECHO \"end6\";\n" +
+                "ECHO \"begin7\";\n" +
+                "PUSH;\n" +
+                "QUERY ((BVMULT(8,x,y) = 0bin00000000)) => (BVGT(BVSUB(8,x,y),0bin00000000));\n" +
+                "POP;\n" +
+                "ECHO \"end7\";\n";
+        assertEquals(expected, out);
+    }
+
     VariableParser variableParser = new VariableParser();
 }