Re: [PATCH] c++: Add target hook for emit_support_tinfos [PR108883]

[Jason Merrill <jason@redhat.com>]

On 2/23/23 05:23, Jakub Jelinek wrote:
> Hi!
> 
> _Float16 and decltype(0.0bf16) types are on x86 supported only with
> -msse2.  On x86_64 that is the default, but on ia32 it is not.
> We should still emit fundamental type tinfo for those types in
> libsupc++.a/libstdc++.*, regardless of whether libsupc++/libstdc++
> is compiled with -msse2 or not, as user programs can be compiled
> with different ISA flags from libsupc++/libstdc++ and if they
> are compiled with -msse2 and use std::float16_t or std::bfloat16_t
> and need RTTI for it, it should work out of the box.  Furthermore,
> libstdc++ ABI on ia32 shouldn't depend on whether the library
> is compiled with -mno-sse or -msse2.
> 
> Unfortunately, just hacking up libsupc++ Makefile/configure so that
> a single source is compiled with -msse2 isn't appropriate, because
> that TU emits also code and the code should be able to run on CPUs
> which libstdc++ supports.  We could add [[gnu::attribute ("no-sse2")]]
> there perhaps conditionally, but it all gets quite ugly.
> 
> The following patch instead adds a target hook which allows the backend
> to temporarily tweak registered types such that emit_support_tinfos
> emits whatever is needed.

Why handle these types differently from the DFP handling at the end of 
emit_support_tinfos?

> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
> 
> 2023-02-23  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR target/108883
> 	* hooks.h (hook_void_bool): Declare.
> 	* hooks.cc (hook_void_bool): New function.
> 	* target.def (emit_support_tinfos): New target hook.
> 	* doc/tm.texi.in (emit_support_tinfos): Document it.
> 	* doc/tm.texi: Regenerated.
> 	* config/i386/i386.cc (ix86_emit_support_tinfos): New function.
> 	(TARGET_EMIT_SUPPORT_TINFOS): Redefine.
> 
> 	* rtti.cc (emit_support_tinfos): Call targetm.emit_support_tinfos
> 	before and after emit_support_tinfo_1 calls.
> 
> --- gcc/hooks.h.jj	2023-01-02 09:32:29.418183667 +0100
> +++ gcc/hooks.h	2023-02-22 12:34:32.144973558 +0100
> @@ -77,6 +77,7 @@ extern bool hook_bool_wint_wint_uint_boo
>   						unsigned int, bool);
>   
>   extern void hook_void_void (void);
> +extern void hook_void_bool (bool);
>   extern void hook_void_constcharptr (const char *);
>   extern void hook_void_rtx_insn_int (rtx_insn *, int);
>   extern void hook_void_FILEptr_constcharptr (FILE *, const char *);
> --- gcc/hooks.cc.jj	2023-01-02 09:32:49.675890970 +0100
> +++ gcc/hooks.cc	2023-02-22 12:36:46.241035355 +0100
> @@ -271,6 +271,11 @@ hook_hwi_void_0 (void)
>   }
>   
>   void
> +hook_void_bool (bool)
> +{
> +}
> +
> +void
>   hook_void_tree (tree)
>   {
>   }
> --- gcc/target.def.jj	2023-01-04 10:45:50.117881714 +0100
> +++ gcc/target.def	2023-02-22 12:33:39.715731356 +0100
> @@ -2606,6 +2606,20 @@ types.",
>    const char *, (const_tree type),
>    hook_constcharptr_const_tree_null)
>   
> +/* Temporarily add conditional target specific types for the purpose of
> +   emitting C++ fundamental type tinfos.  */
> +DEFHOOK
> +(emit_support_tinfos,
> + "If your target defines any fundamental types which depend on ISA flags,\n\
> +they might need C++ tinfo symbols in libsupc++/libstdc++ regardless of\n\
> +ISA flags the library is compiled with.\n\
> +The hook is called with @var{add} @code{true} at the start of C++ FE\n\
> +@code{emit_support_tinfos} and with @var{add} @code{false} at the end of it\n\
> +and can temporarily create fundamental types that are not supposed to be\n\
> +otherwise created due to the ISA options.",
> + void, (bool add),
> + hook_void_bool)
> +
>   /* Make any adjustments to libfunc names needed for this target.  */
>   DEFHOOK
>   (init_libfuncs,
> --- gcc/doc/tm.texi.in.jj	2023-01-16 11:52:16.124733460 +0100
> +++ gcc/doc/tm.texi.in	2023-02-22 12:46:37.951482849 +0100
> @@ -1286,6 +1286,8 @@ pattern needs to support both a 32- and
>   
>   @hook TARGET_MANGLE_TYPE
>   
> +@hook TARGET_EMIT_SUPPORT_TINFOS
> +
>   @node Type Layout
>   @section Layout of Source Language Data Types
>   
> --- gcc/doc/tm.texi.jj	2023-01-16 11:52:16.123733475 +0100
> +++ gcc/doc/tm.texi	2023-02-22 12:46:41.741428081 +0100
> @@ -1525,6 +1525,16 @@ appropriate for a target that does not d
>   types.
>   @end deftypefn
>   
> +@deftypefn {Target Hook} void TARGET_EMIT_SUPPORT_TINFOS (bool @var{add})
> +If your target defines any fundamental types which depend on ISA flags,
> +they might need C++ tinfo symbols in libsupc++/libstdc++ regardless of
> +ISA flags the library is compiled with.
> +The hook is called with @var{add} @code{true} at the start of C++ FE
> +@code{emit_support_tinfos} and with @var{add} @code{false} at the end of it
> +and can temporarily create fundamental types that are not supposed to be
> +otherwise created due to the ISA options.
> +@end deftypefn
> +
>   @node Type Layout
>   @section Layout of Source Language Data Types
>   
> --- gcc/config/i386/i386.cc.jj	2023-02-16 10:13:23.701210667 +0100
> +++ gcc/config/i386/i386.cc	2023-02-22 12:59:55.110960505 +0100
> @@ -22775,6 +22775,30 @@ ix86_mangle_type (const_tree type)
>       }
>   }
>   
> +/* Temporarily tweak the set of fundamental types for C++
> +   emit_support_tinfos purposes.  */
> +
> +static void
> +ix86_emit_support_tinfos (bool add)
> +{
> +  extern tree ix86_float16_type_node;
> +  extern tree ix86_bf16_type_node;
> +
> +  if (TARGET_SSE2)
> +    return;
> +  if (add)
> +    {
> +      gcc_checking_assert (!float16_type_node && !bfloat16_type_node);
> +      float16_type_node = ix86_float16_type_node;
> +      bfloat16_type_node = ix86_bf16_type_node;
> +    }
> +  else
> +    {
> +      float16_type_node = NULL_TREE;
> +      bfloat16_type_node = NULL_TREE;
> +    }
> +}
> +
>   static GTY(()) tree ix86_tls_stack_chk_guard_decl;
>   
>   static tree
> @@ -24954,6 +24978,9 @@ ix86_libgcc_floating_mode_supported_p
>   #undef TARGET_MANGLE_TYPE
>   #define TARGET_MANGLE_TYPE ix86_mangle_type
>   
> +#undef TARGET_EMIT_SUPPORT_TINFOS
> +#define TARGET_EMIT_SUPPORT_TINFOS ix86_emit_support_tinfos
> +
>   #undef TARGET_STACK_PROTECT_GUARD
>   #define TARGET_STACK_PROTECT_GUARD ix86_stack_protect_guard
>   
> --- gcc/cp/rtti.cc.jj	2023-01-16 11:52:16.090733961 +0100
> +++ gcc/cp/rtti.cc	2023-02-22 12:40:10.078089124 +0100
> @@ -1623,6 +1623,9 @@ emit_support_tinfos (void)
>     if (!dtor || DECL_EXTERNAL (dtor))
>       return;
>   
> +  /* Tell target code that support tinfos are about to be emitted.  */
> +  targetm.emit_support_tinfos (true);
> +
>     /* All these are really builtins.  So set the location.  */
>     location_t saved_loc = input_location;
>     input_location = BUILTINS_LOCATION;
> @@ -1652,6 +1655,9 @@ emit_support_tinfos (void)
>         emit_support_tinfo_1 (fallback_dfloat128_type);
>       }
>     input_location = saved_loc;
> +
> +  /* Tell target code that support tinfos have been emitted.  */
> +  targetm.emit_support_tinfos (false);
>   }
>   
>   /* Finish a type info decl. DECL_PTR is a pointer to an unemitted
> 
> 	Jakub
>