On Wed, Apr 17, 2019 at 09:37:54AM +0100, Jonathan Wakely wrote: > On Wed, 17 Apr 2019 at 03:20, Xi Ruoyao wrote: > > > > On 2019-04-17 02:09 +0000, Jason Mancini wrote: > > > > Using gcc 6.3, my C++ source file compiles in 1m2s with -O0. With snapshot > > > > 20190414 (compiled with --disable-checking > > > > and -O2 and make install-strip), it takes 31 minutes to compile the same > > > > file with -O0. Have I overlooked disabling some > > > > snapshot self-checking code? Are there known configuration mistakes that > > > > could result in this sort of performance > > > > degradation? Thanks! It will take a while to go back and try other gcc 6, > > > > 7, 8, and 9 snapshots to collect points of reference. > > > > Both are pretty heavy on memory, gcc6 uses 3.7G and gcc9 uses 5.4G for this > > > > file. There's a lot of templatized headers. > > > > > > Latest data points: > > > gcc-6.3/6.4 take about 43 seconds > > > gcc-7.2 takes 30 minutes > > > gcc-8.2 takes 27 minutes > > > gcc-9.0 takes 31 minutes (snapshot 20190414) > > > clang 6.0.1/7.01 take about 31 seconds > > > > > > This is frustrating, as I'm going to have to capitulate to using clang here > > > for a very large user base. We've been a gcc > > > shop for decades. > > > > We'll never know why unless you can give a testcase to reproduce this issue. > > Even better would be a bug report. Yes... With -ftime-report info, to start with. Segher
