[Python-Dev] Rattlesnake progress (original) (raw)

Michael Hudson mwh@python.net
19 Feb 2002 16:50:04 +0000

Daniel Berlin <dan@dberlin.org> writes:

On Tuesday, February 19, 2002, at 11:01 AM, Kevin Jacobs wrote:

> On Tue, 19 Feb 2002, Daniel Berlin wrote: >> On Tuesday, February 19, 2002, at 09:51 AM, Neil Schemenauer wrote: >> >>> Daniel Berlin wrote: >>>> When you get to optimizations, you want Advanced Compiler Design and >>>> Implementation by Muchnick. >>> >>> Right now I'm not planning to do any optimizations (except perhaps >>> limiting the number of registers used). >>> >> This is, of course, a tricky optimization to do. >> Limiting registers used involves splitting live ranges at the right >> places, etc. > > Why limit the number of registers at all? So long as they fit in L1 > cache > you are golden. Err, what makes you think this? The largest problem on architectures like x86 is the number of registers. You end up with about 4 usable registers. (hardware register renaming only helps eliminate instruction dependencies, before someone mentions it). Performance quickly drops when you start spilling registers to the stack.

I think you misunderstand what Rattlesnake is; AIUI it is (or will/intends to be) a register based VM for Python replacing the current stack based VM -- I think gcc still gets to decide which x86 registers to use...

Cheers, M.

-- ARTHUR: The ravenours bugblatter beast of Traal ... is it safe? FORD: Oh yes, it's perfectly safe ... it's just us who are in trouble. -- The Hitch-Hikers Guide to the Galaxy, Episode 6