Changes in response to initial comments

Author: Sonny Martin

src/util/simplify_expr_int.cpp

@@ -41,6 +41,10 @@ bool simplify_exprt::simplify_bswap(bswap_exprt &expr)
 
     // put back together, but backwards
     mp_integer new_value=0;
+
+    //May I suggest to move this out of the loop and instead check that at least as many elements are contained in bytes?
+      // this invariant protects against someone modifying the loop
+        // expression - a bit pointless for it to be outside the loop.
     for(std::size_t bit = 0; bit < width; bit += bits_per_byte)
     {
       INVARIANT(
@@ -858,27 +862,22 @@ bool simplify_exprt::simplify_bitwise(exprt &expr)
 bool simplify_exprt::simplify_extractbit(exprt &expr)
 {
   PRECONDITION(expr.id() == ID_extractbit);
-  auto &extractbit_expr = to_extractbit_expr(expr);
+  const auto &extractbit_expr = to_extractbit_expr(expr);
 
   const typet &src_type = extractbit_expr.src().type();
 
   if(!is_bitvector_type(src_type))
     return true;
 
-  std::size_t src_bit_width = to_bitvector_type(src_type).get_width();
+  const std::size_t src_bit_width = to_bitvector_type(src_type).get_width();
 
-  if(extractbit_expr.index().id() != ID_constant)
-  {
-    return true;
-  }
-
-  auto index_converted_to_int =
+  const auto index_converted_to_int =
     numeric_cast<mp_integer>(extractbit_expr.index());
   if(!index_converted_to_int.has_value())
   {
     return true;
   }
-  mp_integer index_as_int = index_converted_to_int.has_value();
+  const mp_integer index_as_int = index_converted_to_int.value();
   if(!extractbit_expr.src().is_constant())
     return true;
 
@@ -888,12 +887,15 @@ bool simplify_exprt::simplify_extractbit(exprt &expr)
   const irep_idt &src_value =
     to_constant_expr(extractbit_expr.src()).get_value();
 
-  if(src_value.size() != src_bit_width)
+
+  std::string src_value_as_string=id2string(src_value);
+
+  if(src_value_as_string.size() != src_bit_width)
     return true;
 
-  bool bit =
-    (id2string(src_value)
-       [src_bit_width - numeric_cast_v<std::size_t>(index_as_int) - 1] == '1');
+  const bool bit =
+    (src_value_as_string
+       [src_bit_width - numeric_cast_v<std::size_t>(index_as_int) - 1]=='1');
 
   expr.make_bool(bit);