Is anyone else noticing a linux C++ compiler performance regression?

Using the c++ compiler from the 2020 tools distribution on linux I am noticing a very significant increase in compilation times for our robot code relative to what I get using the compiler from the 2019 tools.

Specifically, when I do a gradlew build using the 2020 compiler for our 2020 code the compileFrcUserProgramReleaseExecutableFrcUserProgramCpp task takes 6 minutes and 6 seconds (reported by gradle). The compileFrcUserProgramDebugExecutableFrcUserProgramCpp task takes 5 minutes and 55 seconds.

I copied the 2019 compiler over top of the 2020 compiler binary and reran the full build of the 2020 code (this is apples-to-apples as I a compiling the 2020 codebase with the 2019 compiler). compileFrcUserProgramDebugExecutableFrcUserProgramCpp took 3:57 and compileFrcUserProgramReleaseExecutableFrcUserProgramCpp takes 4:10.

The 2020 compiler is about 50% slower than the 2019 compiler which is a very significant hit on development times.

I don’t have direct experience with compiling on Windows. Our student who has the most experience with compiling using Windows told me that he had noticed no difference from what he was expecting.

The Rio compiler was upgraded from GCC 6.3 to GCC 7.3 for 2020. Gradle was also upgraded from 5.3 to 6.0, which may also be a contributing factor.

I don’t think the gradle version change is a factor as I was using the 2020 gradle in both cases. The only change was the compiler. Is it expected that the g++ 7.3 compiler is 50% slower than the g++ 6.3 compiler?
I did a bit of looking around for reports of g++ slow compilation last night and found some discussion of an ARM compiler in the gcc 8.x series that was released after having been itself compiled incorrectly leading to slowness relative to 7.x compiler, but I didn’t find anything about slowness in the 7.x series.
I’m going to investigate the performance of the compiler on Windows – maybe that will shed some light as to whether this is expected or anomalous.

Well, I did not do the experiment that I thought I did. I have no solid data demonstrating apples-to-apples comparison of the old and new compilers. Sorry for that claim. On the other hand, I don’t recall ever experiencing 6+ minute build times last year. So I’ll do more investigation and report anything of significance that I find.

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