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.
Jeff
