On Sat, Mar 21, 2015 at 01:47:10AM -0600, Jeff Law wrote:
> On 03/16/2015 01:27 PM, Jakub Jelinek wrote:
> >
> >What effect does the patch have on compile time on say x86_64 or ppc64?
> I bootstrapped x86_64 trunk then timed compiling 640 .i/.ii files with -O2.
> That was repeated 10 times (to get a sense of variability). Each run took a
> little over 40 minutes with variability of less than a second (slowest run
> compared to fastest run).
>
> I then also gathered data for a smaller set of runs for -O2 -funroll-loops
> (given the consistency between runs, 10 iterations seemed like major
> overkill). Again variability was less than a second.
>
> I then applied the patch and repeated the -O2 and -O2 -funroll-loops test.
> The patched compiler was within a second of the unpatched compiler for both
> the -O2 and -O2 -funroll-loops tests. Given the difference was within the
> noise level of those tests, my conclusion is the new code makes no
> measurable difference in compile time performance for x86_64.
>
> Similar tests are in progress on powerpc64-linux-gnu.
Thanks for the testing. I think we want the patch in now.
Jakub
