P0595R1 - is_constant_evaluated

	P0595R1 - is_constant_evaluated
cp/
	* cp-tree.h (enum cp_built_in_function): New.
	(maybe_constant_init): Add pretend_const_required argument.
	* typeck2.c (store_init_value): Pass true as new argument to
	maybe_constant_init.
	* constexpr.c (constexpr_fn_retval): Check also DECL_BUILT_IN_CLASS
	for BUILT_IN_UNREACHABLE.
	(struct constexpr_ctx): Add pretend_const_required field.
	(cxx_eval_builtin_function_call): Use DECL_IS_BUILTIN_CONSTANT_P
	macro.  Handle CP_BUILT_IN_IS_CONSTANT_EVALUATED.  Check also
	DECL_BUILT_IN_CLASS for BUILT_IN_UNREACHABLE.
	(cxx_eval_outermost_constant_expr): Add pretend_const_required
	argument, initialize pretend_const_required field in ctx.  If the
	result is TREE_CONSTANT and non_constant_p, retry with
	pretend_const_required false if it was true.
	(is_sub_constant_expr): Initialize pretend_const_required_field in
	ctx.
	(cxx_constant_value): Pass true as pretend_const_required to
	cxx_eval_outermost_constant_expr.
	(maybe_constant_value): Pass false as pretend_const_required to
	cxx_eval_outermost_constant_expr.
	(fold_non_dependent_expr): Likewise.
	(maybe_constant_init_1): Add pretend_const_required argument, pass it
	down to cxx_eval_outermost_constant_expr.  Pass !allow_non_constant
	instead of false as strict to cxx_eval_outermost_constant_expr.
	(maybe_constant_init): Add pretend_const_required argument, pass it
	down to maybe_constant_init_1.
	(cxx_constant_init): Pass true as pretend_const_required to
	maybe_constant_init_1.
	* cp-gimplify.c (cp_gimplify_expr): Handle CALL_EXPRs to
	CP_BUILT_IN_IS_CONSTANT_EVALUATED.
	(cp_fold): Don't fold CP_BUILT_IN_IS_CONSTANT_EVALUATED calls.
	* decl.c: Include langhooks.h.
	(cxx_init_decl_processing): Register __builtin_is_constant_evaluated
	built-in.
	* tree.c (builtin_valid_in_constant_expr_p): Return true for
	CP_BUILT_IN_IS_CONSTANT_EVALUATED.
	* pt.c (declare_integer_pack): Initialize DECL_FUNCTION_CODE.
testsuite/
	* g++.dg/cpp2a/is-constant-evaluated1.C: New test.

From-SVN: r263392

1 files changed, 16 insertions, 0 deletions

diff --git a/gcc/cp/cp-gimplify.c b/gcc/cp/cp-gimplify.c
index 28802b5..7db4acc 100644
--- a/gcc/cp/cp-gimplify.c
+++ b/gcc/cp/cp-gimplify.c
@@ -793,6 +793,15 @@ cp_gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
 		ret = GS_ERROR;
 	    }
 	}
+      if (ret != GS_ERROR)
+	{
+	  tree decl = cp_get_callee_fndecl_nofold (*expr_p);
+	  if (decl
+	      && DECL_BUILT_IN_CLASS (decl) == BUILT_IN_FRONTEND
+	      && ((int) DECL_FUNCTION_CODE (decl)
+		  == CP_BUILT_IN_IS_CONSTANT_EVALUATED))
+	    *expr_p = boolean_false_node;
+	}
       break;
 
     case RETURN_EXPR:
@@ -2483,6 +2492,13 @@ cp_fold (tree x)
 	    && DECL_DECLARED_CONSTEXPR_P (current_function_decl))
 	  nw = 1;
 
+	/* Defer folding __builtin_is_constant_evaluated.  */
+	if (callee
+	    && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_FRONTEND
+	    && ((int) DECL_FUNCTION_CODE (callee)
+		== CP_BUILT_IN_IS_CONSTANT_EVALUATED))
+	  break;
+
 	x = copy_node (x);
 
 	m = call_expr_nargs (x);