Our embedded design employs one STM32F0 and one STM8L microcontroller. What would be a good IDE/MDK for these two MCUs? I was leaning toward armKeil but they don't support STM8, while Cosmic SW supports the STM8 but not the STM32.

[Tesla DeLorean]

Not sure you've got something that does both well. Keil can build other code (ie start compilers, linker) via user command options from a primary project.

Probably other source management / static analysis tools or editors that could do an effective job. Perhaps Visual Studio would allow multi-target projects, or at least form a common editor function.

IAR looks to support both, not sure the level of integration across multiple targets.

[Philipp Krause]

I can see the advantage of not having to learn to different IDEs, and of implementation-defined behaviour being similar for both compilers.

So Keil is out. AFAIK, Cosmic supports ARM. AFAIK, Raisonance also supports both ARM and STM8, but these days (and already since a few years), Raisonance is not considered a good choice for STM8 unless you value code size above everything else (see e.g. the comparison of STM8 C compilers at http://www.colecovision.eu/stm8/compilers.shtml).

Since IAR supports both, it could be an option.

I would use free tools for both, i.e. SDCC for STM8, GCC or LLVM for STM32. There are free IDEs, that support all those compilers, e.g. Code::Blocks.