MapleSim automatically chooses which compiler to use. If you are simulating your model with a variable solver then there is no user choice or switch.
For Windows, if a MSVC++ Compiler is properly configured on the machine, MapleSim will use it, even though MapleSim now ships with the LLVM Compiler, which isn't quite as robust. If you are using a fixed solver and would like to use the LLVM Compiler then you are able to uncheck the Compiler checkbox under Simulation Settings.
When you simulate a model, in the "Console Output" > "Preparing for Integration" section, you will see the following, which can tell you which compiler is being used:
MSVC++ installed: "SelectCompiler: Check for installed compiler successful"
MSVC++ not installed: "SelectCompiler: Check for installed compiler failed, using built-in"
It is possible, though, to force MapleSim to use the LLVM Compiler, even when the MSVC++ Compiler is installed, by using the inmem=false option. For instance, in the API:
p := proc( x :: float ) :: float: 2.3 * x: end proc: cp1 := Compiler:-Compile( p, inmem=true ); cp2 := Compiler:-Compile( p, inmem=false );
The first call to Compile(), as you will see, produces an IN_MEM argument, whereas the second produces LIB.
Note: The choice of compiler does not affect the C-code generation, only the compiling of the C-code.