This is SWARM - SoftWare ARM.

The initial stage in this process is implement a plain software model
of the basic ARM.  There are, of course, already software models of
the ARM available, so why do another one?  Well, this one will need to
allow the instruction set to be modified at run time, and provide not
just an execution environment, but also a way of monitoring things
like cache hits.

To this end a hierarchical model of an ARM CPU has been implemented in
C++.  It currently supports:

+ Arm 6 based core.  Currently able to handle data processing
instructions, word/byte load and stores, load/store multiple,
branches, 32 bit multiplication, and SWIs.
+ Support for plugging in different caches - be they unified or
separate I & D caches.  Currently only a direct mapped cache is
implemented.
+ Compile for SWARM using ARM targeted gcc.