[Bug middle-end/19207] New: Suggestion for speeding up data flow analysis

["steven at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

This is a suggestion from item 108 of the "old PROBLEMS" file that
actually still makes a lot of sense, for a change:

----------------------------------------
Can speed up flow analysis by making a table saying
which register is set and which registers are used by each instruction
that only sets one register and only uses two.  This way avoid the
tree walk for such instructions (most instructions).
----------------------------------------

As it is now, we actually have this - sometimes.  The above is how we
compute liveness in df.c, and indeed it would be nice to unify these
parts of flow.c and df.c that are basically duplicating code. Liveness
is computed quite a few times in the RTL path, so speeding it up is a
Good Thing.

-- 
           Summary: Suggestion for speeding up data flow analysis
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: steven at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19207