> On Feb 19, 2016, at 9:03 AM, John Rose <john.r.r...@oracle.com> wrote: > > On Feb 19, 2016, at 9:57 AM, Christian Thalinger > <christian.thalin...@oracle.com <mailto:christian.thalin...@oracle.com>> > wrote: >> >> Why don’t you change the values to: >> >> static final byte LATIN1 = 1; >> static final byte UTF16 = 2; > > > Not sure what you are asking, but here's my take on why 0,1 is the (slight) > winner. > The values 0,1 are the log2 of the array element sizes 1,2, so they can be > used with shift instructions. > With 1,2 they would have to be used with multiply instructions, or else > tweaked back to shift inputs. > Most loops will speculate on the scale factor, but those loops which must > work with a non-constant scale will be slightly cleaner with 0,1.
I see what you are saying: int len = val.length >> coder; // assume LATIN1=0/UTF16=1; But if coder is stable for both values the compiler can constant fold the if-statement for the shift value: int len = val.length >> (coder == LATIN1 ? 0 : 1); That should produce the same code and we would avoid: 143 * Constant-folding this field is handled internally in VM.
