[Bug tree-optimization/93435] [8/9/10 Regression] Hang with -O2 on innocuous looking code with GCC 8.3

[jamborm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93435

--- Comment #8 from Martin Jambor <jamborm at gcc dot gnu.org> ---
The issue actually started with my r8-344-2bba75411e1 and it is
basically a perfect SRA bomb, it makes SRA sub-access propagation
accross assignments create gazillions of accesses and then
replacements, because they facilitate forward propagation (and as ccp3
dumps shows, they do).

I already have a patch that simply limits the number of replacements
to a param, defaulting to 128, which makes the testcase compilation
finish in about 9 seconds on my machine.  However, SRA analysis still
takes 7 seconds of that, so I'm looking at capping the propagation
earlier.  That takes more book-keeping, so at least for backports, I'd
like to use the simpler approach on released branches.