[pypy-svn] r65361 - pypy/branch/pyjitpl5-experiments/pypy/jit/metainterp/doc

[fijal at codespeak.net]

Author: fijal
Date: Fri May 22 21:18:45 2009
New Revision: 65361

Added:
   pypy/branch/pyjitpl5-experiments/pypy/jit/metainterp/doc/simple_virtualizables.txt   (contents, props changed)
Log:
start a document explaining simplified approach to virtualizables


Added: pypy/branch/pyjitpl5-experiments/pypy/jit/metainterp/doc/simple_virtualizables.txt
==============================================================================
--- (empty file)
+++ pypy/branch/pyjitpl5-experiments/pypy/jit/metainterp/doc/simple_virtualizables.txt	Fri May 22 21:18:45 2009
@@ -0,0 +1,24 @@
+Simplified virtualizables
+=========================
+
+As a first step for speeding up code, we plan to implement simplified version
+of virtualizables. Simplified in a sense that it won't support virtuals stored
+on virtualizables.
+
+For those unaware:
+
+* Virtuals are objects which are known not to escape from jit code, hence
+  they're not allocated at all and their fields are stored in registers and or
+  on the stack.
+
+* Virtualizables are objects that are known to escape (for example the frame
+  object), but they're stored anyway on the stack with a way to access and
+  modify from outside the jit code. So the jit knows where they're and have
+  a way to reconstruct them if necessary.
+
+The way to implement virtualizables would be as follows:
+
+* During translation, all field accesses to virtualizables are replace by
+  calls to helpers that read/write fields via the jit.
+
+XXX