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From: "yyc1992 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/95775] New: Command line argument for target_clones?
Date: Sat, 20 Jun 2020 00:53:21 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95775

            Bug ID: 95775
           Summary: Command line argument for target_clones?
           Product: gcc
           Version: 10.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yyc1992 at gmail dot com
  Target Milestone: ---

Would it make sense to add a command line argument that is roughly equivale=
nt
to to adding `target_clones` to all functions?

In terms of usefulness, I believe it will be a very cheap way for many
libraries to turn on the support with minimal code change. It certainly won=
't
be as optimized as best possible but neither is target_clones attribute its=
elf
compared to hand wrote different implementations using compiler
intrinsics/assembly...

In terms of implementation, I believe most of the issues I've hit when addi=
ng
such attribute to functions has been fixed so I have little issue using it =
now.
It'll also be a new feature so it shouldn't really break any existing code.

And for further improvement, the compiler should have fair knowledge of what
instruction can be/has been used and can omit some of the cloning in order =
to
reduce code size. I don't think this needs to be included in the first vers=
ion
though...

And IIUC this is something that icc does automatically? (If that can serve =
as a
argument for this feature...)=