Really slow compilation with large maps

[fbarbari]

Hello, I am experiencing a really slow compilation time with OneAPI 2024 on a single file which initializes some constant unordered_maps.

The source code is quite large (~4500 lines), so I just put it on Compiler Explorer.

The full command is this:

icpx -O1 -std=c++17 -fPIC -fno-fast-math -fsanitize=address,undefined -Wall -Wextra -pedantic -Wsign-conversion -Wfloat-conversion -Wfloat-equal -Wno-unknown-pragmas -Werror example.cpp -o example.x

Here are some compilation times measured with time.

OneAPI 2024.2.0.495:

real	16m51.163s
user	16m49.798s
sys	0m0.890s

OneAPI 2025.0.4.20:

real	15m40.380s
user	15m39.558s
sys	0m0.509s

clang++ 19.1.7:

real	0m39.850s
user	0m39.226s
sys	0m0.576s

I didn't measure the compilation time for g++ 14.2 but it surely is less than the time limit on Compiler Explorer as you can see here.

If it may be of any help, I also tried disabling optimizations and sanitizers and gathered these times:

Flags	Time [s]
<other flags> -O0	~12
<other flags> -O1	~47
<other flags> -O0 -fsanitize=address,undefined	~8