https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100974
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:117c64266405e244da4dae3ae7b60905af63b955 commit r12-1390-g117c64266405e244da4dae3ae7b60905af63b955 Author: Jakub Jelinek <ja...@redhat.com> Date: Fri Jun 11 15:50:34 2021 +0200 c++: Add C++23 consteval if support - P1938R3 [PR100974] The following patch implements consteval if support. There is a new IF_STMT_CONSTEVAL_P flag on IF_STMT and IF_COND is boolean_false_node to match the non-manifestly constant evaluation behavior, while constexpr evaluation special-cases it. Perhaps cleaner would be to set the condition to __builtin_is_constant_evaluated () call but we need the IF_STMT_CONSTEVAL_P flag anyway and the IL would be larger. And I'm not changing the libstdc++ side, where perhaps we could change std::is_constant_evaluated definition for #ifdef __cpp_if_consteval case to if consteval { return true; } else { return false; } but we need to keep it defined to __builtin_is_constant_evaluated () for C++20 or older. 2021-06-11 Jakub Jelinek <ja...@redhat.com> PR c++/100974 gcc/c-family/ * c-cppbuiltin.c (c_cpp_builtins): Predefine __cpp_if_consteval for -std=c++2b for P1938R3 consteval if support. gcc/cp/ * cp-tree.h (struct saved_scope): Add consteval_if_p member. Formatting fix for the discarded_stmt comment. (in_consteval_if_p, IF_STMT_CONSTEVAL_P): Define. * parser.c (cp_parser_lambda_expression): Temporarily disable in_consteval_if_p when parsing lambda body. (cp_parser_selection_statement): Parse consteval if. * decl.c (struct named_label_entry): Add in_consteval_if member. (level_for_consteval_if): New function. (poplevel_named_label_1, check_previous_goto_1, check_goto): Handle consteval if. * constexpr.c (cxx_eval_builtin_function_call): Clarify in comment why CP_BUILT_IN_IS_CONSTANT_EVALUATED needs to *non_constant_p for !ctx->manifestly_const_eval. (cxx_eval_conditional_expression): For IF_STMT_CONSTEVAL_P evaluate condition as if it was __builtin_is_constant_evaluated call. (potential_constant_expression_1): For IF_STMT_CONSTEVAL_P always recurse on both branches. * cp-gimplify.c (genericize_if_stmt): Genericize IF_STMT_CONSTEVAL_P as the else branch. * pt.c (tsubst_expr) <case IF_STMT>: Copy IF_STMT_CONSTEVAL_P. Temporarily set in_consteval_if_p when recursing on IF_STMT_CONSTEVAL_P then branch. (tsubst_lambda_expr): Temporarily disable in_consteval_if_p when instantiating lambda body. * call.c (immediate_invocation_p): Return false when in_consteval_if_p. gcc/testsuite/ * g++.dg/cpp23/consteval-if1.C: New test. * g++.dg/cpp23/consteval-if2.C: New test. * g++.dg/cpp23/consteval-if3.C: New test. * g++.dg/cpp23/consteval-if4.C: New test. * g++.dg/cpp23/consteval-if5.C: New test. * g++.dg/cpp23/consteval-if6.C: New test. * g++.dg/cpp23/consteval-if7.C: New test. * g++.dg/cpp23/consteval-if8.C: New test. * g++.dg/cpp23/consteval-if9.C: New test. * g++.dg/cpp23/consteval-if10.C: New test. * g++.dg/cpp23/feat-cxx2b.C: Add __cpp_if_consteval tests.
