Re: [dataflow][PATCH] Compute dominance information in ce2 pass.

[Andrey Belevantsev <abel at ispras dot ru>]

Seongbae Park (ëìë, ææå) wrote:
> I think we probably want to add
> df-based routines that do equivalent to
> propagate_one_insn() so that people can compute
> live sets at arbitrary points in the instruction stream
> (without directly using df infrastructure).
> I'll try to do that sometime.
I'd take this opportunity to ask.  Yes, we'd want to use it in the 
scheduler in the end.  What do we actually need is:

1. Registers that are set/used/clobbered by an insn.  Now we get this
from the dependence analysis.

2. Update these register sets for new insns.

3. Liveness sets at any points on a code motion path.  Now we compute 
this by ourselves using the above sets.

4. Update liveness sets along certain paths, which we know, and don't 
touch them on the other paths.

The reason we need all this is to find registers that are available for 
renaming, i.e. could be destination registers for an insn at a given 
point.  We'd also want a quick update of those, as the sets get 
invalidated after each code motion.

AFAIK I can do 1 and 2 with df infrastructure via df_rescan_insn.  How 
can we do 3 and 4?

Andrey