Totally shameless self promotion but if we’re talking small compilers, this compiler for a functional language to C and this type inferencer may interest folks.

Tiny CC http://bellard.org/tcc/

But so far nothing I have seen beats Joy0

joy0  == 
[ [ [ joy0          body            joy0     ] 
    [ []                                     ] 
    [ pop           pop             pop      ] 
    [ cons          pop             cons     ] 
    [ opcase        pop             opcase   ] 
    [ body          pop             body     ] 
    [ i             pop             joy0     ] 
    [ step          pop [joy0] cons step     ] 
    [               [] cons         i        ] ] 
  opcase 
  i ] 
step

also see https://github.com/rswier/c4