Integer widening operators: some preliminary statistics.

[Ruslan Shevchenko]

>

 Results for open JDK:

all bit ands    :       6853
widening operator (semantics)   :       1098
widening operator (syntax)      :       1959

 (i.e. near 1/6 or 1/7 of all bit-ands)

all catchs      :       8404
all ifs :       28494
all integer literals    :       124355
big integer literals(undescores)        :       4066
byte literal    :       1454
catch in finally        :       103
elvis   :       877
instanceof switch       :       318
loop with remove        :       62
multi catch     :       411
object switch   :       1363
rethrow clause  :       3264
string in switch        :       445



> Good day, Bruce.
>
> Some data about integer widening operator:
> http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000906.html
>
> 3 checks was implemented:
>  1. model check for expression like  ($x && 0xff) or (0xff &  $x) where $x
> must have a type byte (original request). This check named as "widening
> operator (semantics)"
>
> 2. syntax check for expression like  ($x && 0xff) or (0xff &  $x) where $x
> can have any type. This check named as "widening operator (syntax)"
>
>  Example of second but not first:
> <pre>
>   public static short reverseBytes(short s) {
>     return (short) (((s & 0xff) << 8) | ((s & 0xff00) >> 8));
>   }
> </pre>
> <pre>
>        byte[] nounce = new byte[24];
>         for (int i=0;i<8;i++)
>         {
>             nounce[i]=(byte)(ts&0xff);
>             ts=ts>>8;
>             nounce[8+i]=(byte)(sk&0xff);
>             sk=sk>>8;
>         }
> </pre>
>
> 3. count of all expressions with bitwise and. (names as all bit ands)
>
> Than, results for jetty was:
>
> all bit ands    :       121
> widening operator (semantics)   :       10
> widening operator (syntax)      :       20
>
> // some other counts, to compare with:
> rethrow clause  :       34
> string in switch        :       19
>
> hibernate does not use bitwise and at all.
> gwt-users have 2 entries of syntax pattern (actually this is reverseBytes
> function).
>
> Result for jdk I will publish tomorrow, when ones will be ready.
>
> It was preliminary data (one from 3 packages use 'bitwise and') more
> statistics and some analysis will be available throught few days (with
> data about for-s and ERP in dataset).
>
>  Best Regards !
>
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