https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87663
--- Comment #5 from Lukas Mosimann <lumosimann at gmail dot com> --- I was able to track down the error. The problem is caused due to `set_underlying_type` in cfamily/c_common.c. I tried to disable that function by simply returning on entry - and compilation times for cc1plus are completely restored in all examples in this issue. This of course breaks other code, but for the case of demonstration this is enough. The first example with Version C used to compile in N=23: 181s, N=24: 493s, N=25: 1348s. We would expect this to be a fibonacchi sequence - and this are the new compile times for the same source: N=23: 5s, N=24: 8s, N=25: 13s. Tests of Consider the example in the last comment. There the problem arises because the variant list gets huge as this function adds type variants for the int-typedef over and over. When looking for the right variant later, we need to iterate over potentially all this variants. Now I need your help: I don't know the code base for gcc that well. Why do we need this functionality, and how could we solve this issue? I could imagine that this can also impact real code - but it's hard to say because the quick-fix above only works in simple codes. I would love to continue working on this, but I need some hints how I could do this (or that it cannot be done without major rework).
