Re: [PATCH] arm, aarch64, csky: Fix C++ ICEs with _Float16 and __fp16 [PR107080]

[Jason Merrill <jason@redhat.com>]

On 9/30/22 13:13, Jakub Jelinek wrote:
> On Fri, Sep 30, 2022 at 09:54:49AM -0400, Jason Merrill wrote:
>>> Note, there is one further problem on aarch64/arm, types with HFmode
>>> (_Float16 and __fp16) are there mangled as Dh (which is standard
>>> Itanium mangling:
>>>                    ::= Dh # IEEE 754r half-precision floating point (16 bits)
>>>                    ::= DF <number> _ # ISO/IEC TS 18661 binary floating point type _FloatN (N bits)
>>> so in theory is also ok, but DF16_ is more specific.  Should we just
>>> change Dh to DF16_ in those backends, or should __fp16 there be distinct
>>> type from _Float16 where __fp16 would mangle Dh and _Float16 DF16_ ?
>>
>> You argued for keeping __float128 separate from _Float128, does the same
>> argument not apply to this case?
> 
> Actually, they already were distinct types that just mangled the same.
> So the same issue that had to be solved on i?86, ia64 and rs6000 for
> _Float64x vs. long double is a problem on arm and aarch64 with _Float16
> vs. __fp16.
> The following patch fixes it.
> 
>>> And there is csky, which mangles __fp16 (but only if type's name is __fp16,
>>> not _Float16) as __fp16, that looks clearly invalid to me as it isn't
>>> valid in the mangling grammar.  So perhaps just nuke csky's mangle_type
>>> and have it mangled as DF16_ by the generic code?
> 
> And seems even on csky __fp16 is distinct type from _Float16 (which is a
> good thing for consistency, these 3 targets are the only ones that have
> __fp16 type), so instead the patch handles it the same as on arm/aarch64,
> Dh mangling for __fp16 and DF16_ for _Float16.
> 
> Tested with cross-compilers, ok for trunk?

OK.

> 2022-09-30  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c++/107080
> 	* config/arm/arm.cc (arm_mangle_type): Mangle just __fp16 as Dh
> 	and _Float16 as DF16_.
> 	* config/aarch64/aarch64.cc (aarch64_mangle_type): Likewise.
> 	* config/csky/csky.cc (csky_init_builtins): Fix a comment typo.
> 	(csky_mangle_type): Mangle __fp16 as Dh and _Float16 as DF16_
> 	rather than mangling __fp16 as __fp16.
> 
> 	* g++.target/arm/pr107080.C: New test.
> 	* g++.target/aarch64/pr107080.C: New test.
> 
> --- gcc/config/arm/arm.cc.jj	2022-09-29 18:11:28.746750048 +0200
> +++ gcc/config/arm/arm.cc	2022-09-30 19:01:48.774286551 +0200
> @@ -30359,6 +30359,8 @@ arm_mangle_type (const_tree type)
>     /* Half-precision floating point types.  */
>     if (TREE_CODE (type) == REAL_TYPE && TYPE_PRECISION (type) == 16)
>       {
> +      if (TYPE_MAIN_VARIANT (type) == float16_type_node)
> +	return NULL;
>         if (TYPE_MODE (type) == BFmode)
>   	return "u6__bf16";
>         else
> --- gcc/config/aarch64/aarch64.cc.jj	2022-09-29 18:11:34.806667210 +0200
> +++ gcc/config/aarch64/aarch64.cc	2022-09-30 19:02:02.079108171 +0200
> @@ -20664,6 +20664,8 @@ aarch64_mangle_type (const_tree type)
>     /* Half-precision floating point types.  */
>     if (TREE_CODE (type) == REAL_TYPE && TYPE_PRECISION (type) == 16)
>       {
> +      if (TYPE_MAIN_VARIANT (type) == float16_type_node)
> +	return NULL;
>         if (TYPE_MODE (type) == BFmode)
>   	return "u6__bf16";
>         else
> --- gcc/config/csky/csky.cc.jj	2022-09-08 13:01:19.239779562 +0200
> +++ gcc/config/csky/csky.cc	2022-09-30 19:06:09.126794587 +0200
> @@ -7300,7 +7300,7 @@ csky_init_cumulative_args (CUMULATIVE_AR
>   void
>   csky_init_builtins (void)
>   {
> -  /* Inint fp16.  */
> +  /* Init fp16.  */
>     static tree csky_floatHF_type_node = make_node (REAL_TYPE);
>     TYPE_PRECISION (csky_floatHF_type_node) = GET_MODE_PRECISION (HFmode);
>     layout_type (csky_floatHF_type_node);
> @@ -7313,10 +7313,10 @@ csky_init_builtins (void)
>   static const char *
>   csky_mangle_type (const_tree type)
>   {
> -  if (TYPE_NAME (type) && TREE_CODE (TYPE_NAME (type)) == TYPE_DECL
> -      && DECL_NAME (TYPE_NAME (type))
> -      && !strcmp (IDENTIFIER_POINTER (DECL_NAME (TYPE_NAME (type))), "__fp16"))
> -    return "__fp16";
> +  if (TREE_CODE (type) == REAL_TYPE
> +      && TYPE_PRECISION (type) == 16
> +      && TYPE_MAIN_VARIANT (type) != float16_type_node)
> +    return "Dh";
>   
>     /* Use the default mangling.  */
>     return NULL;
> --- gcc/testsuite/g++.target/arm/pr107080.C.jj	2022-09-30 18:56:08.885797047 +0200
> +++ gcc/testsuite/g++.target/arm/pr107080.C	2022-09-30 18:58:07.812221153 +0200
> @@ -0,0 +1,16 @@
> +// PR c++/107080
> +// { dg-do compile }
> +// { dg-options "-mfp16-format=ieee" }
> +
> +template <typename T, typename T1>
> +int
> +foo (T x, T1 y)
> +{
> +  return 3;
> +}
> +
> +int
> +main ()
> +{
> +  return (foo (0.0f16, 0.0f16) + foo (0.0f16, (__fp16) 0.0)) != 6;
> +}
> --- gcc/testsuite/g++.target/aarch64/pr107080.C.jj	2022-09-30 18:56:08.885797047 +0200
> +++ gcc/testsuite/g++.target/aarch64/pr107080.C	2022-09-30 18:56:04.805851530 +0200
> @@ -0,0 +1,16 @@
> +// PR c++/107080
> +// { dg-do compile }
> +// { dg-options "" }
> +
> +template <typename T, typename T1>
> +int
> +foo (T x, T1 y)
> +{
> +  return 3;
> +}
> +
> +int
> +main ()
> +{
> +  return (foo (0.0f16, 0.0f16) + foo (0.0f16, (__fp16) 0.0)) != 6;
> +}
> 
> 
> 	Jakub
>