Dfpir types #70127
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Dfpir types #70127
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…ng point types. This change adds basic type representation support for the decimal floating point types defined by ISO/IEC TS 18661-2 and adopted for C23. These types will also serve as the underlying native types for the library types defined by ISO/IEC TR 24733 and as implemented in libstdcxx. This change does not include representation support in LLVM IR, in debugging information, or in C++ mangling for the MS ABI; such support will be added in later patches.
Though the ISO/IEC TS 18661-2:2015 decimal floating-point (DFP) extension has been adopted for the upcoming C23 standard, it will remain necessary to be able to explicitly enable and disable support for the extension for the foreseeable future for use with previous C standards and with C++. This change adds a driver and cc1 option to enable language support. Since support for the feature is not yet complete, the option name explicitly reflects its status as experimental and only serves to enable testing at this point. No target considerations have been implemented yet. The option only serves to enable the _Decimal32, _Decimal64, and _Decimal128 keywords to be used as DFP type specifiers in C; these keywords are not enabled for C++ since, per ISO/IEC TR 24733:2011 and the gcc implementation, DFP support in C++ is provided via standard library types (that are expected to wrap a builtin type exposed by other means). The C23 standard specifies that the __STDC_IEC_60559_DFP__ macro be predefined when the DFP extensions are available. This change adds that macro with a placeholder value for use in testing.
…mal floating-point types. Current proposals for supporting decimal floating-point (DFP) types in C++, e.g., ISO/IEC TR 24733:2011, do not specify keywords to be used as type specifiers. Rather, DFP types are specified as standard library types that, in practice, wrap a builtin type that is not otherwise exposed with a simple name. Gcc enables builtin DFP types to be declared using the GNU mode attribute as follows: float __attribute__((mode(SD))) // _Decimal32 float __attribute__((mode(DD))) // _Decimal64 float __attribute__((mode(TD))) // _Decimal128 This change implements support for these additional machine modes. This change also extends several of the clang::Type AST node attributes to include DFP types in addition to other floating-point types. These extensions match extensions to terms of the same name made in C23. The directly affected predicates includes: Type::isRealFloatingType() Type::isFloatingType() Type::isRealType() Type::isArithmeticType() The following new predicate can be used to differentiate DFP types where needed. Type::isDecimalFloatingType() The existing DFP specifications, including C23, do not include support for complex DFP types. Gcc does not provide such support either. These changes follow that existing precedent and do not enable support for complex DFP types as well. However, vector types are allowed to have DFP types as their element type.
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