Hello,
CLI back-end uses GIMPLE representation (to be more precise, a subset of
GIMPLE, the code undergoes a CLI-specific GIMPLE lowering at the end of
middle-end passes) and just emits bytecode in a CLI-specific assembler
generation pass.
Because of that, we (I mean CLI back-end project) wouldn't even have to
redefine our CFG, we already use CFG for GIMPLE.
I think it's interesting for us to check whether the existing RTL
reordering pass may be reused with little or no modification and, if
not, to see if it can be made it more IL independent.
Cheers,
Roberto
Jan Hubicka wrote:
Hi,
I know little about CLI, but assuming that your backend is nonstandard
enought so it seems to make sense to replace the RTL bits I guess it
would make sense to make the bb-reorder run on GIMPLE level too, while
keeping bb-reorder on RTL level for common compilation path. This
is example of pass that has very little dependency on the particular IL
so our CFG manipualtion abstraction can be probably extended rather
easilly to make it pracically IL independent.
The reason why it is run late is that the RTL backend modify CFG enough
to make this important. CLI might have the same property. What you
might want to consider is to simply port our CFG code to CLI IL
representation, whatever it is and share the pass.
The tracer pass, very similar to bb-rorder in nature, has been ported to
work on gimple, but the implementation is not in mainline yet. You
might want to take a look at changes neccesary as bb-reorder should be
about the same (minus the SSA updating since you probably want to
bb-reroder after leaving SSA form)
Honza
Hello,
While working on our CLI port, I realized that we were missing, among
others, the block reordering pass. This is because we emit CLI code
before the RTL passes are reached.
Looking at the backend optimizations, it is clear that some modify the
CFG. But my understanding is that loop optimizations and unrolling are
also being moved to GIMPLE. I do not know about others.
Could it be that sometime all the optimizations that modify the CFG are
run on GIMPLE?
Is there any plan/interest in having a block layout pass running at
GIMPLE level?
Cheers,
--
Erven.
