Re: [PATCH] C++: target attribute - local decl

[Jason Merrill <jason@redhat.com>]

On 3/4/21 10:39 AM, Martin Liška wrote:
> On 3/4/21 4:03 PM, Jason Merrill wrote:
>> Do you really need to register all these pairs?  I was expecting that 
>> you'd just look through DECL_LOCAL_DECL_ALIAS and then register the 
>> pair you end up with.  Local decls shouldn't need a cgraph node.
> 
> Well, doing that:
> 
> 
> commit 662c486edafa467ec41091e84857d594eaf280a2
> Author: Martin Liska <mliska@suse.cz>
> Date:   Wed Mar 3 09:38:55 2021 +0100
> 
>      c++: support target attr for DECL_LOCAL_DECL_P fns
>      gcc/cp/ChangeLog:
>              PR c++/99108
>              * call.c (get_function_version_dispatcher): Understand
>              DECL_LOCAL_DECL_ALIAS.
>              * decl.c (record_function_versions): New.
>              (maybe_version_functions): Call record_function_versions
>              for both declarations and DECL_LOCAL_DECL_ALIAS aliases.
>      gcc/testsuite/ChangeLog:
>              PR c++/99108
>              * g++.target/i386/pr99108.C: New test.
> 
> diff --git a/gcc/cp/call.c b/gcc/cp/call.c
> index 123f06b1f2b..117f1755191 100644
> --- a/gcc/cp/call.c
> +++ b/gcc/cp/call.c
> @@ -8467,6 +8467,10 @@ get_function_version_dispatcher (tree fn)
>   {
>     tree dispatcher_decl = NULL;
> 
> +  if (DECL_LOCAL_DECL_P (fn)
> +      && DECL_LOCAL_DECL_ALIAS (fn) != NULL_TREE)
> +    fn = DECL_LOCAL_DECL_ALIAS (fn);
> +
>     gcc_assert (TREE_CODE (fn) == FUNCTION_DECL
>             && DECL_FUNCTION_VERSIONED (fn));
> 
> diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
> index 1742e286d9f..a092539bfa0 100644
> --- a/gcc/cp/decl.c
> +++ b/gcc/cp/decl.c
> @@ -1115,6 +1115,14 @@ decls_match (tree newdecl, tree olddecl, bool 
> record_versions /* = true */)
>   bool
>   maybe_version_functions (tree newdecl, tree olddecl, bool record)
>   {
> +  if (DECL_LOCAL_DECL_P (olddecl)
> +      && DECL_LOCAL_DECL_ALIAS (olddecl) != NULL_TREE)
> +    olddecl = DECL_LOCAL_DECL_ALIAS (olddecl);
> +
> +  if (DECL_LOCAL_DECL_P (newdecl)
> +      && DECL_LOCAL_DECL_ALIAS (newdecl) != NULL_TREE)
> +    newdecl = DECL_LOCAL_DECL_ALIAS (newdecl);
> +
>     if (!targetm.target_option.function_versions (newdecl, olddecl))
>       return false;
> 
> The compilation then fails:
> /home/marxin/Programming/gcc/gcc/testsuite/g++.target/i386/pr99108.C: In 
> member function ‘void A::foo(auto:2)’:
> /home/marxin/Programming/gcc/gcc/testsuite/g++.target/i386/pr99108.C:12:13: 
> error: call of overloaded ‘f()’ is ambiguous
>     12 |   int b = f();
>        |             ^
> /home/marxin/Programming/gcc/gcc/testsuite/g++.target/i386/pr99108.C:10:7: 
> note: candidate: ‘int f()’
>     10 |   int f(void) __attribute__((target("default")));
>        |       ^
> /home/marxin/Programming/gcc/gcc/testsuite/g++.target/i386/pr99108.C:11:7: 
> note: candidate: ‘int f()’
>     11 |   int f(void) __attribute__((target("arch=atom")));
>        |       ^
> 
> likely because DECL_FUNCTION_VERSIONED is missing for the local decls.

Sure, I guess you do need to set that flag for the local decls, but that 
should be all.

Jason