Polymorphic inline caches (PICs) provide a new way to reduce the overhead of polymorphic message sends by extending inline caches to include more than one cached lookup result per call site. For a set of typical object-oriented SELF programs, PICs achieve a median speedup of 11%. As an important side effect, PICs collect type information by recording all of the receiver types actually used at a given call site. The compiler can exploit this type information to generate better code when recompiling a method. An experimental version of such a system achieves a median speedup of 27% for our set of SELF programs, reducing the number of non-inlined message sends by a factor of two. Implementations of dynamically-typed object-oriented languages have been limited by the paucity of type information available to the compiler. The abundance of the type information provided by PICs suggests a new compilation approach for these languages, adaptive compilation. Such compilers may succeed in generating very efficient code for the time-critical parts of a program without incurring distracting compilation pauses.
['Urs Hölzle', 'Craig Chambers', 'David Ungar']
Optimizing Dynamically-Typed Object-Oriented Languages With Polymorphic Inline Caches