[Python-Dev] A new JIT compiler for a faster CPython?

Ned Deily nad at acm.org
Wed Jul 18 10:55:13 CEST 2012

In article 
<20120718075314.Horde.ty5wC7uWis5QBk9Krz1hyUA at webmail.df.eu>,
 martin at v.loewis.de wrote:
> I don't think it is. It is still slow and memory hungry. The fact that
> the version that Apple ships with Xcode still miscompiles Python 3.3
> tells me that it is still buggy.

Whether LLVM is suitable for a JIT is an interesting question but it's 
not LLVM per se that is the problem with compiling 3.3.  Apple ships two 
C compiler chains with Xcode 4 for OS X 10.7, both of them are based on 
LLVM.  It's the Apple transitional gcc-4.2 frontend with an old LLVM 
backend that is problematic (and not to be confused with the "pure" 
gcc-4.2 shipped with Xcode 3).  That compiler was the default compiler 
for early releases of Xcode 4 and for building OS X 10.7.  It has been 
frozen for a long time because Apple's efforts have been going into 
transitioning the OS X world to the new compiler: a clang frontend with 
a more current LLVM backend.  The latest releases of Xcode 4 now use 
clang-llvm as the default and that's what we now use as a default for 
building Python 3.3 with Xcode 4.  That transition will be complete with 
the imminent release of OS X 10.8 Mountain Lion when the whole OS is 
built with clang-llvm. The iOS world is already there.

 Ned Deily,
 nad at acm.org

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