On Tue, 22 Nov 2005, Steven Bosscher wrote:
On Tuesday 22 November 2005 17:20, Diego Novillo wrote:
The initial impression I get is that LLVM involves starting from scratch.
I thought it would basically "only" replace the GIMPLE parts of the
compiler. That is,
FE --> GENERIC --> LLVM --> RTL --> asm
(trees) (trees)
In the longer-term, you could maybe cut out the RTL part for targets for
which LLVM has its own backend. This is not less evolutionary or
revolutionary than tree-ssa was IMHO.
Yes, agreed. For my work at Apple, we will probably end up using the LLVM
backends. For the bigger GCC picture, making use of the RTL backends is
essential.
With our limited resources, we cannot really afford to go off on a
multi-year tangent nurturing and growing a new technology just to add a
new feature.
It depends on who is going to invest these resources. Would you want
to tell Apple they can't do this even though they can? ;-)
:)
But what are the
timelines? What resources are needed?
Interesting questions. Both projects obviously will take significant
effort. But IIUC Chris has bits of the LLVM stuff already going, so
he has the head-start (like tree-SSA did when LLVM was introduced to
the GCC community, ironically? ;-) so maybe Chris can have a working
prototype implementation within, what, months? The GVM plan could
take years to get to that point...
That is the plan.
So my dummy prediction would be that the LLVM path would result in a
reasonable product more quickly than the GVM plan -- iff RTL stays.
Yes, totally agreed.
-Chris
--
http://nondot.org/sabre/
http://llvm.org/
