Do you know EmBlocks? http://www.emblocks.org
This is a free C/C++ IDE based on Code Blocks.
This IDE supports a lot of STM32, NXP-ARM and EFM32 and also PIC18/PIC32/dsPIC Controllers.
There is a Project Wizzard for each Controller Family.
At the moment the EFM32 Controllers can only be programmed with an J-Link (because EFM32 only supports SWD, so a lot of JTAG programmers doesn't work).
There is a discussion and tip Forum about this IDE with EFM32 on the Energy Micro Forum:
Debugg is based on GDB, so maybe there will be more supported adapters in future.