On Fri, Sep 30, 2022 at 05:31:26PM +0200, Jakub Jelinek wrote: > On Fri, Sep 30, 2022 at 10:07:59AM -0500, Segher Boessenkool wrote: > > 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.
Great :-) > Internally, it is implemented by using targetm.floatn_mode hook to query > which mode if any is the IEEE one with corresponding width. tree.h says just /* Names for individual types (code should normally iterate over all such types; these are only for back-end use, or in contexts such as *.def where iteration is not possible). */ and there is nothing whatsoever in doc/. Looking at the current implementation never shows intent :-( Segher
