re PR c++/88446 (__builtin_is_constant_evaluated rejects some converted constant...

	PR c++/88446
	* cp-tree.h (maybe_constant_value): Add manifestly_const_eval
	argument.
	* constexpr.c (struct constexpr_call): Rename pretend_const_required
	member to manifestly_const_eval.
	(struct constexpr_ctx): Likewise.
	(constexpr_call_hasher::equal): Adjust users.
	(cxx_eval_builtin_function_call): Likewise.  Formatting fix.
	(cxx_eval_call_expression): Adjust users.
	(cxx_eval_outermost_constant_expr, maybe_constant_init_1,
	maybe_constant_init): Rename pretend_const_required argument to
	manifestly_const_eval, adjust function comments.
	(maybe_constant_value): Add manifestly_const_eval argument.  If true,
	don't cache and call cxx_eval_outermost_constant_expr with true as
	manifestly_const_eval.
	* decl.c (compute_array_index_type_loc): Call maybe_constant_value
	with true as manifestly_const_eval.

	* g++.dg/cpp2a/is-constant-evaluated3.C: New test.

From-SVN: r267047

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 0347daa2bd3d51e6e58c9cc9263b14a31300ad3e..2c1f39288c43bd288009f0e5c9a0b2117bcdc320 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,23 @@
 2018-12-12  Jakub Jelinek  <jakub@redhat.com>
 
+       PR c++/88446
+       * cp-tree.h (maybe_constant_value): Add manifestly_const_eval
+       argument.
+       * constexpr.c (struct constexpr_call): Rename pretend_const_required
+       member to manifestly_const_eval.
+       (struct constexpr_ctx): Likewise.
+       (constexpr_call_hasher::equal): Adjust users.
+       (cxx_eval_builtin_function_call): Likewise.  Formatting fix.
+       (cxx_eval_call_expression): Adjust users.
+       (cxx_eval_outermost_constant_expr, maybe_constant_init_1,
+       maybe_constant_init): Rename pretend_const_required argument to
+       manifestly_const_eval, adjust function comments.
+       (maybe_constant_value): Add manifestly_const_eval argument.  If true,
+       don't cache and call cxx_eval_outermost_constant_expr with true as
+       manifestly_const_eval.
+       * decl.c (compute_array_index_type_loc): Call maybe_constant_value
+       with true as manifestly_const_eval.
+
        PR c++/88449
        * constexpr.c (struct constexpr_call): Add pretend_const_required
        member.

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 81ce4cdbe756d24ffb466c8ed6a86196bf14a6e5..f8049468c2233fee1f98e64c1c7e9d9b6cb84627 100644 (file)
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -977,7 +977,7 @@ struct GTY((for_user)) constexpr_call {
      recalculate it when expanding the hash table.  */
   hashval_t hash;
   /* Whether __builtin_is_constant_evaluated() should evaluate to true.  */
-  bool pretend_const_required;
+  bool manifestly_const_eval;
 };
 
 struct constexpr_call_hasher : ggc_ptr_hash<constexpr_call>
@@ -1025,7 +1025,7 @@ struct constexpr_ctx {
      trying harder to get a constant value.  */
   bool strict;
   /* Whether __builtin_is_constant_evaluated () should be true.  */
-  bool pretend_const_required;
+  bool manifestly_const_eval;
 };
 
 /* A table of all constexpr calls that have been evaluated by the
@@ -1057,7 +1057,7 @@ constexpr_call_hasher::equal (constexpr_call *lhs, constexpr_call *rhs)
     return true;
   if (lhs->hash != rhs->hash)
     return false;
-  if (lhs->pretend_const_required != rhs->pretend_const_required)
+  if (lhs->manifestly_const_eval != rhs->manifestly_const_eval)
     return false;
   if (!constexpr_fundef_hasher::equal (lhs->fundef, rhs->fundef))
     return false;
@@ -1206,11 +1206,11 @@ cxx_eval_builtin_function_call (const constexpr_ctx *ctx, tree t, tree fun,
     }
 
   /* For __builtin_is_constant_evaluated, defer it if not
-     ctx->pretend_const_required, otherwise fold it to true.  */
+     ctx->manifestly_const_eval, otherwise fold it to true.  */
   if (fndecl_built_in_p (fun, CP_BUILT_IN_IS_CONSTANT_EVALUATED,
-                      BUILT_IN_FRONTEND))
+                        BUILT_IN_FRONTEND))
     {
-      if (!ctx->pretend_const_required)
+      if (!ctx->manifestly_const_eval)
        {
          *non_constant_p = true;
          return t;
@@ -1508,7 +1508,7 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
   location_t loc = cp_expr_loc_or_loc (t, input_location);
   tree fun = get_function_named_in_call (t);
   constexpr_call new_call
-    = { NULL, NULL, NULL, 0, ctx->pretend_const_required };
+    = { NULL, NULL, NULL, 0, ctx->manifestly_const_eval };
   bool depth_ok;
 
   if (fun == NULL_TREE)
@@ -1684,7 +1684,7 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
       new_call.hash
        = iterative_hash_template_arg (new_call.bindings, new_call.hash);
       new_call.hash
-       = iterative_hash_object (ctx->pretend_const_required, new_call.hash);
+       = iterative_hash_object (ctx->manifestly_const_eval, new_call.hash);
 
       /* If we have seen this call before, we are done.  */
       maybe_initialize_constexpr_call_table ();
@@ -5022,13 +5022,13 @@ instantiate_constexpr_fns (tree t)
    STRICT has the same sense as for constant_value_1: true if we only allow
    conforming C++ constant expressions, or false if we want a constant value
    even if it doesn't conform.
-   PRETEND_CONST_REQUIRED is true if T is required to be const-evaluated as
+   MANIFESTLY_CONST_EVAL is true if T is manifestly const-evaluated as
    per P0595 even when ALLOW_NON_CONSTANT is true.  */
 
 static tree
 cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
                                  bool strict = true,
-                                 bool pretend_const_required = false,
+                                 bool manifestly_const_eval = false,
                                  tree object = NULL_TREE)
 {
   auto_timevar time (TV_CONSTEXPR);
@@ -5039,7 +5039,7 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
 
   constexpr_ctx ctx = { NULL, &map, NULL, NULL, NULL, NULL,
                        allow_non_constant, strict,
-                       pretend_const_required || !allow_non_constant };
+                       manifestly_const_eval || !allow_non_constant };
 
   tree type = initialized_type (t);
   tree r = t;
@@ -5131,7 +5131,7 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
       /* If __builtin_is_constant_evaluated () was evaluated to true
         and the result is not a valid constant expression, we need to
         punt.  */
-      if (pretend_const_required)
+      if (manifestly_const_eval)
        return cxx_eval_outermost_constant_expr (t, true, strict,
                                                 false, object);
       /* This isn't actually constant, so unset TREE_CONSTANT.
@@ -5274,12 +5274,14 @@ fold_simple (tree t)
 
 /* If T is a constant expression, returns its reduced value.
    Otherwise, if T does not have TREE_CONSTANT set, returns T.
-   Otherwise, returns a version of T without TREE_CONSTANT.  */
+   Otherwise, returns a version of T without TREE_CONSTANT.
+   MANIFESTLY_CONST_EVAL is true if T is manifestly const-evaluated
+   as per P0595.  */
 
 static GTY((deletable)) hash_map<tree, tree> *cv_cache;
 
 tree
-maybe_constant_value (tree t, tree decl)
+maybe_constant_value (tree t, tree decl, bool manifestly_const_eval)
 {
   tree r;
 
@@ -5296,6 +5298,9 @@ maybe_constant_value (tree t, tree decl)
     /* No caching or evaluation needed.  */
     return t;
 
+  if (manifestly_const_eval)
+    return cxx_eval_outermost_constant_expr (t, true, true, true, decl);
+
   if (cv_cache == NULL)
     cv_cache = hash_map<tree, tree>::create_ggc (101);
   if (tree *cached = cv_cache->get (t))
@@ -5399,12 +5404,12 @@ fold_non_dependent_expr (tree t,
 /* Like maybe_constant_value, but returns a CONSTRUCTOR directly, rather
    than wrapped in a TARGET_EXPR.
    ALLOW_NON_CONSTANT is false if T is required to be a constant expression.
-   PRETEND_CONST_REQUIRED is true if T is required to be const-evaluated as
+   MANIFESTLY_CONST_EVAL is true if T is manifestly const-evaluated as
    per P0595 even when ALLOW_NON_CONSTANT is true.  */
 
 static tree
 maybe_constant_init_1 (tree t, tree decl, bool allow_non_constant,
-                      bool pretend_const_required)
+                      bool manifestly_const_eval)
 {
   if (!t)
     return t;
@@ -5424,7 +5429,7 @@ maybe_constant_init_1 (tree t, tree decl, bool allow_non_constant,
   else
     t = cxx_eval_outermost_constant_expr (t, allow_non_constant,
                                          /*strict*/false,
-                                         pretend_const_required, decl);
+                                         manifestly_const_eval, decl);
   if (TREE_CODE (t) == TARGET_EXPR)
     {
       tree init = TARGET_EXPR_INITIAL (t);
@@ -5437,9 +5442,9 @@ maybe_constant_init_1 (tree t, tree decl, bool allow_non_constant,
 /* Wrapper for maybe_constant_init_1 which permits non constants.  */
 
 tree
-maybe_constant_init (tree t, tree decl, bool pretend_const_required)
+maybe_constant_init (tree t, tree decl, bool manifestly_const_eval)
 {
-  return maybe_constant_init_1 (t, decl, true, pretend_const_required);
+  return maybe_constant_init_1 (t, decl, true, manifestly_const_eval);
 }
 
 /* Wrapper for maybe_constant_init_1 which does not permit non constants.  */

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 3645965d7f348687b72cdf6b4181a9ab7ea12740..1d806b782bdcf0adf7b4120e451536de4ad444ea 100644 (file)
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7663,7 +7663,7 @@ extern bool require_rvalue_constant_expression (tree);
 extern bool require_potential_rvalue_constant_expression (tree);
 extern tree cxx_constant_value                 (tree, tree = NULL_TREE);
 extern tree cxx_constant_init                  (tree, tree = NULL_TREE);
-extern tree maybe_constant_value               (tree, tree = NULL_TREE);
+extern tree maybe_constant_value               (tree, tree = NULL_TREE, bool = false);
 extern tree maybe_constant_init                        (tree, tree = NULL_TREE, bool = false);
 extern tree fold_non_dependent_expr            (tree, tsubst_flags_t = tf_warning_or_error);
 extern tree fold_simple                                (tree);

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 3a53af4f8666178a4d019d5606801a02f6921490..9b0ea702ec46ad37f1ff170c23ec13037830b97e 100644 (file)
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -9646,7 +9646,11 @@ compute_array_index_type_loc (location_t name_loc, tree name, tree size,
        {
          size = instantiate_non_dependent_expr_sfinae (size, complain);
          size = build_converted_constant_expr (size_type_node, size, complain);
-         size = maybe_constant_value (size);
+         /* Pedantically a constant expression is required here and so
+            __builtin_is_constant_evaluated () should fold to true if it
+            is successfully folded into a constant.  */
+         size = maybe_constant_value (size, NULL_TREE,
+                                      /*manifestly_const_eval=*/true);
 
          if (!TREE_CONSTANT (size))
            size = osize;

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index aa11d0ecb2dbe81415c9f4eaa16271047f6ae956..9e851e4042a8f305ae3dd2a9e22eba7ffc93b30e 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2018-12-12  Jakub Jelinek  <jakub@redhat.com>
 
+       PR c++/88446
+       * g++.dg/cpp2a/is-constant-evaluated3.C: New test.
+
        PR c++/88449
        * g++.dg/cpp2a/is-constant-evaluated1.C: Change from dg-do compile
        to dg-do run.

diff --git a/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated3.C b/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated3.C
new file mode 100644 (file)
index 0000000..dd6104e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/is-constant-evaluated3.C
@@ -0,0 +1,26 @@
+// P0595R1
+// { dg-do run { target c++14 } }
+
+struct false_type { static constexpr bool value = false; };
+struct true_type { static constexpr bool value = true; };
+template<class T, class U>
+struct is_same : false_type {};
+template<class T>
+struct is_same<T, T> : true_type {};
+
+int a[__builtin_is_constant_evaluated () ? 1 : 2];
+int b[1];
+static_assert (is_same<decltype (a), decltype (b)>::value, "");
+
+int
+main ()
+{
+  int c[__builtin_is_constant_evaluated () ? 3 : 4];
+  int d[3];
+  static_assert (is_same<decltype (c), decltype (d)>::value, "");
+  int (*e)[7][9] = new int[__builtin_is_constant_evaluated () ? -1 : 5]
+                         [__builtin_is_constant_evaluated () ? 7 : 8]
+                         [__builtin_is_constant_evaluated () ? 9 : 10];
+  e[0][0][0] = 6;
+  delete[] e;
+}