On 09/19/2011 09:52 AM, Andi Kleen wrote:
> I think it also improves branch target prediction - if you have a tight
> loop of a few opcodes the predictor can guess where you're headed (since
> there is a separate lookup key for each opcode), whereas with the
> original code, there's a single key which cannot be used to predict the
> branch target.
At least usually. I caught at least one version of gcc to CSE the jump
instruction into a common location in one of my interpreters
:-( But not all do it at least, and I hope gcc gets fixed.
You generally want CSE, yes? So you can't blame gcc for getting it
wrong sometimes.
--
error compiling committee.c: too many arguments to function
