Support for the CPU code names in -march is a simple but really useful change:

   -march=nehalem, westmere, sandybridge, ivybridge, haswell,
   bonnell, broadwell, silvermont

Also this:

   -mtune=intel can now be used to generate code running well
   on the most current Intel processors, which are Haswell
   and Silvermont for GCC 4.9.