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Date: Mon, 12 Nov 2012 05:04:00 -0000
From: Jason Merrill <jason@redhat.com>
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To: Sriraman Tallam <tmsriram@google.com>
CC: David Li <davidxl@google.com>, "H.J. Lu" <hjl.tools@gmail.com>,        gcc-patches List <gcc-patches@gcc.gnu.org>, Jan Hubicka <jh@suse.cz>,        Diego Novillo <dnovillo@google.com>
Subject: Re: User directed Function Multiversioning via Function Overloading (issue5752064)
References: <CAAs8HmxHF38ktt6syjWp-MpjiX+6NcXh7_8Xn6iKnAiF2vRymQ@mail.gmail.com> <CAAs8HmyKPG_LxxxP2ngkGTFAKUPXQDJsbbsrOB_oAP0ViyER3g@mail.gmail.com> <506F27AF.3070805@redhat.com> <CAAs8HmxEod=EJNyUjrD0-WaP0-cB5o_AN9oc2O2ryu--MRQf4w@mail.gmail.com> <CAAs8Hmyy9S+Ucg6rTDU3xGMg8JEaa0r3rNjbxhbjuk9H8Sb6wg@mail.gmail.com> <50816D63.3020908@google.com> <CAAs8HmzZUnGq9G3KQ-wesKOHVWJBHn1n0zyFhEOPxo+i0PBrww@mail.gmail.com> <CAAs8HmxXfBdsLOrhEnd=syUXfbo5gKa-QkdWQG=4bUeWOPrSfQ@mail.gmail.com> <20121026155447.GA4348@atrey.karlin.mff.cuni.cz> <CAAs8Hmw0KBhKp_3qe0gzVi1jw=LVg6GD1cv-++=Kh3OjThwB+A@mail.gmail.com> <50902624.3020705@redhat.com> <CAAs8Hmw09giv-5_v0irhByTjTJV=kD58rCAD2SAz7M8zrwjBOA@mail.gmail.com> <50912F66.3030707@redhat.com> <CAAs8Hmz4CNzyJHAPoRkEe5gtL3YXSqoNHGMeZdm0uJujFHkMhQ@mail.gmail.com> <CAAs8Hmz7aDcN+2YGfH8ixrgUt+A=PuTt8ZzPhUVeQTgSWGP-Ww@mail.gmail.com> <50993222.3010609@redhat.com> <CAAs8Hmw-WXwbgUvwmegd680i0rT8CG2M=XYRa1V5ejMqbRd1Bw@mail.gmail.com>
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On 11/09/2012 08:33 PM, Sriraman Tallam wrote:
> +	  /* Skip calling decls_match for versioned functions.  */
> +          if (DECL_FUNCTION_VERSIONED (fn)
> +	      && DECL_FUNCTION_VERSIONED (TREE_PURPOSE (match)))
> +	    continue;
> +	  if (!decls_match (fn, TREE_PURPOSE (match)))
> +            break;

This seems like it would allow multiple versioned functions from 
different namespaces; I want to allow mismatches only if they are 
versions of the same function.  I was thinking

          for (match = TREE_CHAIN (matches); match; match = TREE_CHAIN 
(match))
   	    if (!decls_match (fn, TREE_PURPOSE (match))
                 && !targetm.target_option.function_versions (fn, 
TREE_PURPOSE (match)))
	      break;

> +      error_at (input_location, "Call/Pointer to multiversioned function"
> +                " without a default cannot be dispatched");

Let's just say "use of multiversioned  function without a default".

Jason