From: Jakub Jelinek <jakub@redhat.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: richard.sandiford@arm.com, gcc-patches@gcc.gnu.org,
"Joseph S. Myers" <joseph@codesourcery.com>,
Richard Earnshaw <richard.earnshaw@arm.com>
Subject: Re: [PATCH] i386, rs6000, ia64, s390: Fix C++ ICEs with _Float64x or _Float128 [PR107080]
Date: Fri, 30 Sep 2022 17:31:26 +0200 [thread overview]
Message-ID: <YzcLzlu3Cq8bj4J2@tucnak> (raw)
In-Reply-To: <20220930150759.GH25951@gate.crashing.org>
On Fri, Sep 30, 2022 at 10:07:59AM -0500, Segher Boessenkool wrote:
> Hi!
>
> On Thu, Sep 29, 2022 at 12:01:43PM +0200, Jakub Jelinek via Gcc-patches wrote:
> > --- gcc/config/i386/i386.cc.jj 2022-09-29 09:13:25.713718513 +0200
> > +++ gcc/config/i386/i386.cc 2022-09-29 11:29:20.828358152 +0200
> > @@ -22725,6 +22725,9 @@ ix86_mangle_type (const_tree type)
> > && TREE_CODE (type) != INTEGER_TYPE && TREE_CODE (type) != REAL_TYPE)
> > return NULL;
> >
> > + if (type == float128_type_node || type == float64x_type_node)
> > + return NULL;
>
> Is float128_type_node always IEEE QP, never double-double? I couldn't
> find this documented anywhere. If this is not true, this part of the
> patch is incorrect.
It is always IEEE quad, if there is no IEEE quad support, it is NULL.
The C++ wording is:
"If the implementation supports an extended floating-point type whose
properties are specified by the ISO/IEC/IEEE 60559 floating-point
interchange format binary128, then the typedef-name std::float128_t is
defined in the header <stdfloat> and names such a type, the macro
__STDCPP_FLOAT128_T__ is defined, and the floating-point literal suffixes
f128 and F128 are supported."
and C:
Types designated:
_FloatN
where N is 16, 32, 64, or ≥128 and a multiple of 32; and, types designated
_DecimalN
where N ≥ 32 and a multiple of 32, are collectively called the interchange floating types. Each
interchange floating type has the IEC 60559 interchange format corresponding to its width (N) and
radix (2 for _FloatN, 10 for _DecimalN). Each interchange floating type is not compatible with any
other type."
So, _Float128 and std::float128_t which we use float128_type_node for
must be IEEE binary128, nothing else.
Internally, it is implemented by using targetm.floatn_mode hook to query
which mode if any is the IEEE one with corresponding width.
Jakub
next prev parent reply other threads:[~2022-09-30 15:32 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-29 10:01 Jakub Jelinek
2022-09-30 13:54 ` Jason Merrill
2022-09-30 17:13 ` [PATCH] arm, aarch64, csky: Fix C++ ICEs with _Float16 and __fp16 [PR107080] Jakub Jelinek
2022-09-30 17:38 ` Richard Sandiford
2022-09-30 17:49 ` Jakub Jelinek
2022-09-30 19:44 ` Jason Merrill
2022-09-30 15:07 ` [PATCH] i386, rs6000, ia64, s390: Fix C++ ICEs with _Float64x or _Float128 [PR107080] Segher Boessenkool
2022-09-30 15:31 ` Jakub Jelinek [this message]
2022-09-30 15:50 ` Segher Boessenkool
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