Using the Silvermont profile, I ran in to an issue building qtgui where it was failing saying the processor did not support AES and even though I had CPUFlags set in my make.conf they were being ignored to use the profile.

Research in to the issue showed that AES is supported on all Silvermont/Airmont processors except Bay Trail-D and Bay Trail-M.

Further research shows that this may come up on other SubArch's as well.

For example, AES is on in the SubArch's for Broadwell, Haswell, Ivy Bridge, Sandy Bridge, and Westmere, however the following has been discovered.

• Westmere based processors, specifically:
  • Clarkdale processors (except Core i3, Pentium and Celeron).
  • Arrandale processors (except Celeron, Pentium, Core i3, Core i5-4XXM).

• Sandy Bridge processors:
  • Desktop: all except Pentium, Celeron, Core i3.^[5][6]
  • Mobile: all Core i7 and Core i5. Several vendors have shipped BIOS configurations with the extension disabled;^[7] a BIOS update is required to enable them.^[8]
• Ivy Bridge processors.
  • All i5, i7, Xeon and i3-2115C^[9]^ only.
• Haswell processors (all except i3-4000m,^[10] Pentium and Celeron).
• Broadwell processors (all except Pentium and Celeron).

Source : https://en.wikipedia.org/wiki/AES_instruction_set