CentaurTechnologies ran benchmarks against ICC with the CPUID set to the default and then with it set to the name of an Intel chip with equivalent CPU flags.

Intel's response was roughly "We don't trust CPU flags, so we have kernels for each specific Intel chip, and a generic kernel for non-Intel chips"

Luckily, from Agner's CPU blog linked above:

"[Update 2019:] The newest versions of Gnu and Clang C++ compilers are now optimizing better than the Intel compiler in my tests."

Good reason to avoid Intel compiler even more.

Newest ICC is an LLVM frontend anyway. Maybe some special sauce, maybe not.

The link in the post above is a reasonable intro: https://www.agner.org/optimize/blog/read.php?i=49

Thank you!