Array bounds checks
Thu Oct 26 10:52:00 GMT 2000
Per> Some compilers generate code twice:
Per> [ ... ]
Per> I don't particularly care for this idea ...
Another approach is to modify the bounds:
__upper = min (upper, array.length)
for (int i = 0; i < __upper; i++)
... no bounds checking ...
for (; i < upper; i++)
... bounds checking ...
This gives better performance. I guess you don't even need a second
loop, just a copy of the body with bounds checking enabled.
Per> But as for the questions why the compiler cannot optimize away
Per> the bounds check in your example, I don't know. I thought there
Per> was code in gcc to do some range analysis and bounds check
My impression is that the value range code only handles constants, not
things like `array.length'. I recommend asking on the gcc list to get
the real answer though.
More information about the Java