Put conditions for headers depending on the architecture

[mrodozov]

MkFit as it is builds only on Intel architectures, yet at CMS we also have non production ARM and PowerPC builds. To bring MkFit also into this non prod builds I introduced some hacks here:
cms-sw/cmsdist#5174
which does two things:

1. Substitutes immintrin.h with whats available on that arch/machine
2. Change some calls not available on non Intel archs with whatever I though was appropriate (although I'm not sure if it is)

For the headers substitutes we proposed similar changes in other repos (see this example AIDASoft/DD4hep#496) which looks something like :

#if defined(__powerpc64__) 
#include <ppc_header.h>

etc i.e. using preprocessor directives to include whats needed.
Can we have something like this in the files including immintrin.h ?
And proper substitutes for the mmintel_stuff calls, since I'm not sure they are appropriate now.

Thank you,
Mircho

[slava77]

most of the updates in cms-sw/cmsdist#5174 are apparently related to the intel intrinsics.
There is a USE_INTRINSICS flag accessible for the makefile in command line (or environment). It seems like the problem is that not all of the intrinsics are covered by this flag.
I think that initially for the ppc and aarch we can just not use the intrinsics; although something better is always welcome.

[smuzaffar]

we are now trying out a simple patch to build mkfit for non-x86_64 archs. Patch is available here https://github.com/cms-sw/cmsdist/pull/5179/files#diff-b996bc38d41188ee072f517d8691432e .
Basically we

• build with -sdt=c++1z
• use allign_alloc (available in c++11) instead of _mm_malloc
• use free instead of _mm_free
• use __buildin_prefetch instead of _mm_prefetch

These changes allowed us to build it for ARM and Power PC.