The CPU architecture tuning target of "ia" is now a handy way for always targeting the very latest Intel CPU tuning optimizations by the GCC compiler. At the moment, "-mtune=ia" is the equivalent of using "-mtune=slm" for the latest Intel Atom "Silvermont" and "-mtune=core-avx-i" for the latest Intel "Haswell" CPU support.
The IA target will simply be updated as new Intel CPUs are supported to always reflect the most current Intel processors that are supported by the compiler. It's handy for those using static build scripts and wanting to always target the latest CPU architecture extensions when testing, but the change doesn't provide anything fundamentally new for Intel x86 performance on GCC.
The change to support "-mtune=ia" was made to the GCC compiler on Friday with this commit.