C++/C#: Refactor some integer constant code

Make `bitsToBytesAndBits` omit the leftover bits if zero.

cpp/ql/src/semmle/code/cpp/ir/internal/IntegerConstant.qll

@@ -192,3 +192,36 @@ predicate isGT(IntValue a, IntValue b) { hasValue(a) and hasValue(b) and a > b }
  */
 bindingset[a, b]
 predicate isGE(IntValue a, IntValue b) { hasValue(a) and hasValue(b) and a >= b }
+
+/**
+ * Converts the bit count in `bits` to a byte count and a bit count in the form
+ * "bytes:bits". If `bits` represents an integer number of bytes, the ":bits" section is omitted.
+ * If `bits` does not have a known value, the result is "?".
+ */
+bindingset[bits]
+string bitsToBytesAndBits(IntValue bits) {
+  exists(int bytes, int leftoverBits |
+    hasValue(bits) and
+    bytes = bits / 8 and
+    leftoverBits = bits % 8 and
+    if leftoverBits = 0 then
+      result = bytes.toString()
+    else
+      result = bytes + ":" + leftoverBits
+  ) or
+  not hasValue(bits) and result = "?"
+}
+
+/**
+ * Gets a printable string for a bit offset with possibly unknown value.
+ */
+bindingset[bitOffset]
+string getBitOffsetString(IntValue bitOffset) {
+  if hasValue(bitOffset) then
+    if bitOffset >= 0 then
+      result = "+" + bitsToBytesAndBits(bitOffset)
+    else
+      result = "-" + bitsToBytesAndBits(neg(bitOffset))
+  else
+    result = "+?"
+}

cpp/ql/src/semmle/code/cpp/ir/internal/IntegerInterval.qll

@@ -30,5 +30,5 @@ Overlap getOverlap(IntValue defStart, IntValue defEnd, IntValue useStart, IntVal
 bindingset[start, end]
 string getIntervalString(IntValue start, IntValue end) {
   // We represent an interval has half-open, so print it as "[start..end)".
-  result = "[" + intValueToString(start) + ".." + intValueToString(end) + ")"
+  result = "[" + bitsToBytesAndBits(start) + ".." + bitsToBytesAndBits(end) + ")"
 }