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From: "vries at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/105018] New: [nvptx] Need better alias support
Date: Tue, 22 Mar 2022 14:29:01 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105018

            Bug ID: 105018
           Summary: [nvptx] Need better alias support
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

We currently have alias support enabled by malias, which relies on the ptx
.alias directive.

There is a number of limitations, listed in the commit adding malias:
...
Only function aliases are supported.

Weak aliases are not supported.  That is, if I disable the check in
nvptx_asm_output_def_from_decls that disallows this, a weak alias is emitted
and parsed by the driver.  But the test gcc.dg/globalalias.c starts failing,
with the behaviour matching the comment about "weird behavior of AIX's .set
pseudo-op": a weak alias may resolve to different functions in different
files.

Aliases to weak symbols are not supported (see gcc.dg/localalias.c).  This =
is
currently not prohibited by the compiler, but with the driver link we run
into: "error: Function test with .weak scope cannot be aliased".

Aliases to aliases are not supported (see libgomp.c-c++-common/pr96390.c).
This is currently not prohibited by the compiler, but with the driver link =
we
run into:  "Internal error: alias to unknown symbol" .

Unreferenced aliases are not emitted (these can occur f.i. when inlining a
call to an alias).  This avoids driver link error "Internal error: reference
to deleted section".
...

We'd like an implementation that doesn't have (all of) these limitations.=