What's the influence of compilers on binary kernel size?

[FAMILIAR-project]

Prior works have been done on gcc 6.4 for several versions of the kernel (4.13.3, 4.15, 4.20, 5.0, 5.4, 5.7, 5.8), over 20K+ configurations (or more) per version.
We have pretty good results for predicting binary kernel size.
A threat is that the gathered data has only been computed with gcc 6.4, because this compiler was the "one" for 4.13.3.
We can wonder to what extent a change in compiler version can change our results and prediction.
For instance, given the same configuration and the same kernel version 5.8, is the binary size the same with gcc 6.4 and gcc 10?
Formally, given the same (random) configuration (says c) and the same kernel version (says kv), is the binary kernel size the same using different compiler versions (says cc1 and cc2)?
We can think of a function like this:
ksize (c, kv, cc) = bz with c a configuration, kv a kernel version, cc a compiler, bz the binary size
Right now, we can envision to operate over: kv in {4.13.3, 4.15, 4.20, 5.0, 5.4, 5.7, 5.8}, cc in {gcc 6.4, gcc 8.0, gcc 10, clang}
Examples are:

• c=tinyconfig, kv=5.8, cc1=6.4, cc2=8.0
• c=defconfig, kv=5.8, cc1=6.4, cc2=8.0
• c (obtained with randconfig), kv=5.8, cc1=6.4, cc2=8.0
  For the sake of comparison among compilers, the configuration and the kernel version should be the same.
  The last case (randconfig) is the most interesting, since we can compare on a large set of data.
  In fact, we have already a bunch of configurations for which we know the binary size with gcc 6.4.
  So an obvious experiment is as follows:
• select a kernel version (says kv=5.8)
• select a new compiler version (cc2=gcc 10)
• take a configuration c_i of the database that has already been compiled with cc1=gcc 6.4 (bzi is known!)
• compile it
• repeat N times
  The outcome would be new binary sizes {bz'1, bz'2, ..., bz'N}.
  Then we can compare this set of measurements with {bz1, bz2, ..., bzN}.
  There are various ways of comparing distributions (eg Pearson).

Another, perhaps simpler, and similar experiment is as follows:

• consider tinyconfig/defconfig
• compute binary size for all kernel versions (4.13.3, 4.15, 4.20, 5.0, 5.4, 5.7, 5.8) and for all compiler versions
• compare!