[Bug tree-optimization/125944] New: 3/4 different copyprops

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125944

            Bug ID: 125944
           Summary: 3/4 different copyprops
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: compile-time-hog, internal-improvement
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

>From IRC:
<richi> we have ccp, copyprop and sccopy (and forwprop to some extent), there's
quite some redundancy.  Not to mention DOM.  And FRE in non-iterating mode.

ccp (tree-ssa-ccp.cc)
copy_prop (tree-ssa-copy.cc)
sccopy (gimple-ssa-sccopy.cc)

Now ccp does some bitbased proping. This was useful/needed before ranger (and
prange).  How useful is it after prange?
copy_prop is the traditional SSA copy prop pass.
While sc-copy is the strongly connected copy-prop pass.

We should figure out if copy_prop can be removed or replaced with sccopy.

Second does ccp bit get some stuff that ranger misses now? If so let's improve
ranger/vrp. Can the first ccp be replaced with sccopy and one that exports
"global" ranges? Or do that handling in forwprop (which has its own copy prop
too).