The attached Fortran file takes unusually long to compile with full optimization on the latest GCC trunk builds. I tried a lot of the optimization flags, and found that -fstrict-aliasing seems to trigger the long compile-time.
Without this flag the compile-time is perfectly reasonable, as you can see from the following numbers (using trunk revision 131325 on i686-pc-linux-gnu, Pentium M 1,7Ghz and 1GB memory): -O0: 0.9s -O1: 4.5s -O2 -fno-strict-aliasing: 8.0s -O3 -fno-strict-aliasing: 10.4s But once I use -fstrict-aliasing, compile-time explodes: -O1 -fstrict-aliasing: 1m10s -O2: 2m16s -O3: 1m43s (-fstrict-aliasing is included in -O2 and -O3, but not in -O1) I don't know why -O3 is faster than -O2 here (which seems funny), but anyway all three numbers are way too large in my opinion. I mean: compile-time rises by a factor of roughly 15, just due to this one flag! I don't even know what the flag is supposed to do for this code. Maybe someone can explain this to me? I didn't examine memory consumption very carefully, but this also seems unusually high, as a similar file failed to compile on an old machine (with only 256MB) due to lack of memory(!). Am I right to assume that something goes wrong here somehow, or can someone tell me why I should expect this kind of behaviour for this code? -- Summary: compile-time problem with -fstrict-aliasing Product: gcc Version: 4.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: jaydub66 at gmail dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34683