RFR: 8150617: nth_bit and friends are broken

[Thomas Schatzl]

Hi,

On Thu, 2016-02-25 at 13:22 +0100, Stefan Karlsson wrote:
> Hi all,
> 
> Please review this patch to fix the nth_bit, right_n_bits, and 
> left_n_bits macros.
>   http://cr.openjdk.java.net/~stefank/8150617/webrev.00
> 
> The macros were broken when expressions with low-precedence operators
> were used. For example (in 64 bit JVMs):
>    nth_bit(true ? 32 : 64) returns 0x20 instead of 0x100000000
> nth_bit(1|2) returns 0x0 instead of 0x8
> 
> The fix is to add parentheses around all usages of the macro input 
> parameter. I also added some extra parentheses to further
> disambiguate 
> the expression for readers of the code.
> 
> I added STATIC_ASSERTS to show the problem, but I can remove them if 
> someone thinks they are unnecessary. Tested with JPRT.

  looks good.

Thomas