RFR: 8145096: Undefined behaviour in HotSpot

[Kim Barrett]

On Dec 17, 2015, at 8:37 AM, Andrew Haley <aph at redhat.com> wrote:
> 
> OK.  I think this change addresses all of your points.
> 
> http://cr.openjdk.java.net/~aph/8145096-3
> 
> The complex (and incorrect)
> 
>   ((jlong)CONST64(1) << (jlong)(BitsPerJavaLong - con)) - CONST64(1);
> 
> is merely a difficult way to write
> 
>   jlong((~ UCONST64(0)) >> con)
> 
> Andrew.

Nice.

There's another that looks like that here:
src/share/vm/opto/mulnode.cpp
 577       jlong t1_support = java_subtract(((jlong)1 << (1 + log2_long(t1->_hi))), (jlong)1);

Everything else looks good.