On Sat, Dec 07, 2013 at 12:40:35AM +0100, bearophile wrote:
[...]
> Regarding Java performance matters, from my experience another
> significant source of optimization in the JavaVM that is often
> overlooked is that the JavaVM is able to partially unroll even loops
> with a statically-unknown number of cycles. Currently I think
> GCC/DMD/LDC2 are not able or willing to do this.
[...]
Really? I've seen gcc/gdc unroll loops with unknown number of
iterations, esp. when you're using -O3. It just unrolls into something
like:
loop_start:
if (!loopCondition) goto end;
loopBody();
if (!loopCondition) goto end;
loopBody();
if (!loopCondition) goto end;
loopBody();
if (!loopCondition) goto end;
loopBody();
goto loop_start;
end: ...
I'm pretty sure I've seen gcc/gdc do this before.
T
--
Windows 95 was a joke, and Windows 98 was the punchline.
