[Bug target/104957] New: [nvptx] Use .alias directive (available starting ptx isa version 6.3)

[vries at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104957

            Bug ID: 104957
           Summary: [nvptx] Use .alias directive (available starting ptx
                    isa version 6.3)
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

[ There is a number of nvptx PRs open about alias support.  The focus of this
PR is $subject, rather than supporting some specific source construct. ]

So, we have an .alias directive in ptx, can we use it for something?

Ideally, we'd use the .alias directive for all our needs, but it's too limited
for that.

OTOH, currently we just error out on any .alias usage in the source code, so we
could try to add an implementation that only errors out for things it doesn't
support.