LSWVST compiles to Assembly Language. This is traditionally known as JIT-compiling. We claim that LSWVST is faster than C. Why we can do such a claim ? Here we will uncover a few secrets why LSWVST can perform faster than C.
Traditionally Smalltalk has one Object-Memory which is garbage-collected. This introduces overhead and complicates things in multihreading programs. LSWVST introduces multiple Object-Spaces, in which garbage collection can be controlled by the programmer. Every thread has its own Standard-Object-Memory avoiding synchronisation problems.
Traditionally in Smalltalk every object is boxed. An object is a pointer which has a reference to the class. This is necessary to dynamically lookup the method during resolving a message-send. This makes programs which operate on huge data-collections of the same type rather inefficient.
LSWVST introduces a new object-type - IsoCollections. Iso-Collections stores type information of its elements only once.
Traditionally Smalltalk translates message-sends in a method-lookup in a cache. Tricky implementations uses a polmorphic-inline cache which means patching the translated Assembly-code with the address of the last method-address. This introduces two problems:
The resulting code is self-modifying and cannot be put in to a ROM. The resulting code must synchronize the self-modification in multithreaded programs - which is rather inefficient.
LSWVST message-send implementation is same as fast as the Virtual-Table mechanismn in C++.
LSWVST allows method annotation to further optimize compilation to native code, we call this technique adaptive native compilation.
Traditionally objects are allocated from ObjectMemory and cannot live on the stack. LSWVST introduces ObjectSpaces on the local stack:
messageWithStackObjectSpace
| 16r10000 a b c |
a := Array newFromLocalStack: 100.
self performOnLocalStack: self localStack.
if the message exits all the objects in the local stack become invalid.
the programmer must take care that no references to these objects exits after the method exits.