[Bug bootstrap/125598] [16/17 regression] Comparing stages 2 and 3 with -with-build-config=bootstrap-O3

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125598

--- Comment #9 from 伊泽平 <yizeyi18 at mail dot nankai.edu.cn> ---
(In reply to Sam James from comment #8)

> With empty BUILD_CONFIG, it's likely PR126526. I don't know if OP's issue is
> the same or not though.

Seems the same; my agent also says a lot about var tracking caused difference
here, which I am not familiar with.

To be helpful, it also hints me that the mechanism ENABLE_GC_CHECKING take
effect is that ENABLE_GC_CHECKING affects init_ggc_heuristics()(from
gcc/ggc-common.cc:1127) then somewhat heap size changed then some template
initialize-associated variable address changed for different GC behavior;
finally this addr diff yields different debug section.