This is the mail archive of the
java@gcc.gnu.org
mailing list for the Java project.
Re: eliminating null pointer checks on mmu-less machines
- From: Jeff Sturm <jsturm at one-point dot com>
- To: Tom Tromey <tromey at redhat dot com>
- Cc: Adam Megacz <adam at megacz dot com>, <java at gcc dot gnu dot org>
- Date: Sat, 13 Sep 2003 17:59:05 -0400 (EDT)
- Subject: Re: eliminating null pointer checks on mmu-less machines
On 13 Sep 2003, Tom Tromey wrote:
> How good a job does the optimizer do at eliminating redundant checks?
The RTL optimizers do pretty well recognizing redundant scalar checks, but
lose on COMPONENT_REF. This is already fixed on tree-ssa.
Gcj still needs to somehow tell the optimizers about methods that never
return null (_Jv_AllocObject etc.) before the null check elimination will
be very effective.
> If it doesn't do so well, then I wonder whether the VRP pass (which,
> as far as I know, still hasn't gone in) would help.
VRP ought to help with bounds checking, but null checks are currently
handled in a separate pass.
Jeff