Code that directly uses _Decimal* types on architectures not
supporting DFP is properly diagnosed ("error: decimal floating-point
not supported for this target"), via a call to
targetm.decimal_float_supported_p, if the _Decimal32, _Decimal64 or
_Decimal128 keywords are used to access it. Use via mode attributes
is also diagnosed ("unable to emulate 'SD'"); so is use of the
FLOAT_CONST_DECIMAL64 pragma. However, it is possible to access those
types via typeof applied to constants or built-in functions without
such an error. I expect that there are ways to get an ICE from this;
certainly it uses a completely undefined ABI.
This patch arranges for the types not to exist in the compiler at all
when DFP is not supported. As is done with unsupported _FloatN /
_FloatNx types, the global tree nodes are left as NULL_TREE, and the
built-in function machinery is made to use error_mark_node for them in
that case in builtin-types.def, so that the built-in functions are
unavailable. Code handling constants is adjusted to give an error,
and other code that might not work with the global tree nodes being
NULL_TREE is also updated.
Bootstrapped with no regressions for x86_64-pc-linux-gnu. Also tested
with no regressions for cross to aarch64-linux-gnu, as a configuration
without DFP support.
PR c/91985
gcc:
* builtin-types.def (BT_DFLOAT32, BT_DFLOAT64, BT_DFLOAT128)
(BT_DFLOAT32_PTR, BT_DFLOAT64_PTR, BT_DFLOAT128_PTR): Define to
error_mark_node if corresponding global tree node is NULL.
* tree.c (build_common_tree_nodes): Do not initialize
dfloat32_type_node, dfloat64_type_node or dfloat128_type_node if
decimal floating-point not supported.
gcc/c:
* c-decl.c (finish_declspecs): Use int instead of decimal
floating-point types if decimal floating-point not supported.
gcc/c-family:
* c-common.c (c_common_type_for_mode): Handle decimal
floating-point types being NULL_TREE.
* c-format.c (get_format_for_type_1): Handle specified types being
NULL_TREE.
* c-lex.c (interpret_float): Give an error for decimal
floating-point constants when decimal floating-point not
supported.
gcc/lto:
* lto-lang.c (lto_type_for_mode): Handle decimal floating-point
types being NULL_TREE.
gcc/testsuite:
* gcc.dg/c2x-no-dfp-1.c, gcc.dg/gnu2x-builtins-no-dfp-1.c: New
tests.
* gcc.dg/fltconst-pedantic-dfp.c: Expect errors when decimal
floating-point not supported.
From-SVN: r278684
