Compilers used to build packages must honor the applicable compiler flags set in the system rpm configuration. Honoring means that the contents of that variable is used as the basis of the flags actually used by the compiler during the package build.

  Overriding these flags for performance optimizations (for instance, -O3 instead of -O2) is generally discouraged. If you can present benchmarks that show a significant speedup for this particular code, this could be revisited on a case-by-case basis. Adding to and overriding or filtering parts of these flags is permitted if there's a good reason to do so; the rationale for doing so must be documented in the specfile.

  There are certain, security related flags that are commonly allowed. These flags may degrade performance slightly but the increased security can be worthwhile for some programs.