Example with GCL: compile individual function to C, compile it with C to a .o (for example on my 32bit ARM it is a elf32-littlearm file) file and then load it:

    >(defun foo (a) (* a 42)) 

    FOO

    >(compile 'foo)

    Compiling /tmp/gazonk_24158_0.lsp.
    End of Pass 1.  
    End of Pass 2.  
    OPTIMIZE levels: Safety=0 (No runtime error checking), Space=0, Speed=3
    Finished compiling /tmp/gazonk_24158_0.lsp.
    Loading /tmp/gazonk_24158_0.o
    start address -T 0x888488 Finished loading /tmp/gazonk_24158_0.o
    #<compiled-function FOO>
    NIL
    NIL