Due to product release timing, EWARM 7.80.2 does not include device information for EFR32xG12 (EFR32MG12, EFR32BG12, EFR32FG12) and EFR32xG13 (EFR32MG13, EFR32BG13, EFR32FG13).
A device definition file for EWARM is available. Download IAR-EFR32xG12x-part-support-5.1.0.zip from the Silicon Labs website and copy the definition file to an appropriate location. Please use.

Here's how to get IAR-EFR32xG12x-part-support-5.1.0.zip.

1. Log into the Silicon Labs support site (https://siliconlabs.force.com/home/home.jsp).
2. Click the Software Release tab
3. Click Software Release: IAR Embedded Workbench for ARM, v7.80.2
4. Click IAR-EFR32xG12x-part-support-5.1.0.zip under Associated Content
5. click download zip

 
The file as of 2018/1/17 can be downloaded from the following. Please obtain the latest version from the Silicon Labs website.

IAR-EFR32-Mighty-5.1.0__1.zip

EFR32MG (for Mighty Gecko)

IAR-EFR32-Blue-5.1.0__1.zip

EFR32BG (for Blue Gecko)

IAR-EFR32-Flex-5.1.0__1.zip

EFR32FG (for Flex Gecko)