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. -- Xi Ruoyao <xry111@xxxxxxxxxxxxxxxx> School of Aerospace Science and Technology, Xidian University
