[clang] add __has_extension(gnu_asm_goto_with_outputs_full)

Also move the line about __has_extension(gnu_asm_goto_with_outputs) so
that it is more generally about asm goto, not the paragraph on symbolic
references.

Reviewed By: efriedma, void

Differential Revision: https://reviews.llvm.org/D143205

clang/docs/LanguageExtensions.rst

@@ -1591,6 +1591,12 @@ ASM Goto with Output Constraints
 Outputs may be used along any branches from the ``asm goto`` whether the
 branches are taken or not.
 
+Query for this feature with ``__has_extension(gnu_asm_goto_with_outputs)``.
+
+Prior to clang-16, the output may only be used safely when the indirect
+branches are not taken.  Query for this difference with
+``__has_extension(gnu_asm_goto_with_outputs_full)``.
+
 When using tied-outputs (i.e. outputs that are inputs and outputs, not just
 outputs) with the `+r` constraint, there is a hidden input that's created
 before the label, so numeric references to operands must account for that.
@@ -1618,8 +1624,6 @@ references can be used instead of numeric references.
       return -1;
   }
 
-Query for this feature with ``__has_extension(gnu_asm_goto_with_outputs)``.
-
 Objective-C Features
 ====================
 

clang/include/clang/Basic/Features.def

@@ -268,6 +268,7 @@ EXTENSION(pragma_clang_attribute_external_declaration, true)
 EXTENSION(statement_attributes_with_gnu_syntax, true)
 EXTENSION(gnu_asm, LangOpts.GNUAsm)
 EXTENSION(gnu_asm_goto_with_outputs, LangOpts.GNUAsm)
+EXTENSION(gnu_asm_goto_with_outputs_full, LangOpts.GNUAsm)
 EXTENSION(matrix_types, LangOpts.MatrixTypes)
 EXTENSION(matrix_types_scalar_division, true)
 EXTENSION(cxx_attributes_on_using_declarations, LangOpts.CPlusPlus11)

clang/test/Parser/asm-goto.c

@@ -7,6 +7,9 @@
 #if !__has_extension(gnu_asm_goto_with_outputs)
 #error Extension 'gnu_asm_goto_with_outputs' should be available by default
 #endif
+#if !__has_extension(gnu_asm_goto_with_outputs_full)
+#error Extension 'gnu_asm_goto_with_outputs_full' should be available by default
+#endif
 
 int a, b, c, d, e, f, g, h, i, j, k, l;