[LLVMdev] complex branching generation

Bill Wendling isanbard at gmail.com
Wed Oct 1 14:28:19 PDT 2008

On Wed, Oct 1, 2008 at 2:14 PM, Dale Johannesen <dalej at apple.com> wrote:
> On Oct 1, 2008, at 1:44 PMPDT, Bill Wendling wrote:
>> -Os runs these passes more than -O2: -domfrontier -lcssa -loop-unroll
> Are you sure?  That looks wrong; I don't think -Os should be doing
> loop unrolling.  (Perhaps it should be on at -O2, as well.  gcc's loop
> unrolling is not turned on by -Oanything, you have to use the switch
> explicitly, and that's how it's documented.  But I think that's
> because its loop unrolling heuristics aren't all that good, and I
> don't think we should feel constrained to follow this if ours shows a
> win at -O2.)
Strike that. Reverse it. It's -O2 that does those, not -Os. Sorry for
the confusion. :-)


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