diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index cfe5cf003664d2062503770b49248d2f28f44e0e..385bfcd72db4103aaaa47f3673a041befb5dde33 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,37 @@
+2020-05-21 Patrick Palka <ppalka@redhat.com>
+
+ PR c++/94038
+ * constexpr.c (constexpr_ctx::uid_sensitive): Remove field.
+ (uid_sensitive_constexpr_evaluation_value): Define.
+ (uid_sensitive_constexpr_evaluation_true_counter): Define.
+ (uid_sensitive_constexpr_evaluation_p): Define.
+ (uid_sensitive_constexpr_evaluation_sentinel): Define its
+ constructor.
+ (uid_sensitive_constexpr_evaluation_checker): Define its
+ constructor and its evaluation_restricted_p method.
+ (get_fundef_copy): Remove 'ctx' parameter. Use u_s_c_e_p
+ instead of constexpr_ctx::uid_sensitive.
+ (cxx_eval_call_expression): Use u_s_c_e_p instead, and test it
+ last. Adjust call to get_fundef_copy.
+ (instantiate_cx_fn_r): Test u_s_c_e_p so that we increment the
+ counter if necessary.
+ (cxx_eval_outermost_constant_expr): Remove 'uid_sensitive'
+ parameter. Adjust function body accordingly.
+ (maybe_constant_value): Remove 'uid_sensitive' parameter and
+ adjust function body accordingly. Set up a
+ uid_sensitive_constexpr_evaluation_checker, and use it to
+ conditionally update the cv_cache.
+ * cp-gimplify.c (cp_fold): Set up a
+ uid_sensitive_constexpr_evaluation_checker, and use it to
+ conditionally update the fold_cache.
+ * cp-tree.h (maybe_constant_value): Update declaration.
+ (struct uid_sensitive_constexpr_evaluation_sentinel): Define.
+ (struct sensitive_constexpr_evaluation_checker): Define.
+ * expr.c (fold_for_warn): Set up a
+ uid_sensitive_constexpr_evaluation_sentinel before calling
+ the folding subroutines. Drop all but the first argument to
+ maybe_constant_value.
+
2020-05-20 Marek Polacek <polacek@redhat.com>
DR 2237
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 04faabc02583328caa944ccd495c5998c6f58533..c1ab9288f72eeb55d15df2dfde9b40007a377cf9 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1089,11 +1089,67 @@ struct constexpr_ctx {
bool strict;
/* Whether __builtin_is_constant_evaluated () should be true. */
bool manifestly_const_eval;
- /* Whether we want to avoid doing anything that will cause extra DECL_UID
- generation. */
- bool uid_sensitive;
};
+/* This internal flag controls whether we should avoid doing anything during
+ constexpr evaluation that would cause extra DECL_UID generation, such as
+ template instantiation and function body copying. */
+
+static bool uid_sensitive_constexpr_evaluation_value;
+
+/* An internal counter that keeps track of the number of times
+ uid_sensitive_constexpr_evaluation_p returned true. */
+
+static unsigned uid_sensitive_constexpr_evaluation_true_counter;
+
+/* The accessor for uid_sensitive_constexpr_evaluation_value which also
+ increments the corresponding counter. */
+
+static bool
+uid_sensitive_constexpr_evaluation_p ()
+{
+ if (uid_sensitive_constexpr_evaluation_value)
+ {
+ ++uid_sensitive_constexpr_evaluation_true_counter;
+ return true;
+ }
+ else
+ return false;
+}
+
+/* The default constructor for uid_sensitive_constexpr_evaluation_sentinel
+ enables the internal flag for uid_sensitive_constexpr_evaluation_p
+ during the lifetime of the sentinel object. Upon its destruction, the
+ previous value of uid_sensitive_constexpr_evaluation_p is restored. */
+
+uid_sensitive_constexpr_evaluation_sentinel
+::uid_sensitive_constexpr_evaluation_sentinel ()
+ : ovr (uid_sensitive_constexpr_evaluation_value, true)
+{
+}
+
+/* The default constructor for uid_sensitive_constexpr_evaluation_checker
+ records the current number of times that uid_sensitive_constexpr_evaluation_p
+ has been called and returned true. */
+
+uid_sensitive_constexpr_evaluation_checker
+::uid_sensitive_constexpr_evaluation_checker ()
+ : saved_counter (uid_sensitive_constexpr_evaluation_true_counter)
+{
+}
+
+/* Returns true iff uid_sensitive_constexpr_evaluation_p is true, and
+ some constexpr evaluation was restricted due to u_s_c_e_p being called
+ and returning true during the lifetime of this checker object. */
+
+bool
+uid_sensitive_constexpr_evaluation_checker::evaluation_restricted_p () const
+{
+ return (uid_sensitive_constexpr_evaluation_value
+ && saved_counter != uid_sensitive_constexpr_evaluation_true_counter);
+}
+
+
/* A table of all constexpr calls that have been evaluated by the
compiler in this translation unit. */
@@ -1156,7 +1212,7 @@ static GTY(()) hash_map<tree, tree> *fundef_copies_table;
is parms, TYPE is result. */
static tree
-get_fundef_copy (const constexpr_ctx *ctx, constexpr_fundef *fundef)
+get_fundef_copy (constexpr_fundef *fundef)
{
tree copy;
bool existed;
@@ -1173,7 +1229,7 @@ get_fundef_copy (const constexpr_ctx *ctx, constexpr_fundef *fundef)
}
else if (*slot == NULL_TREE)
{
- if (ctx->uid_sensitive)
+ if (uid_sensitive_constexpr_evaluation_p ())
return NULL_TREE;
/* We've already used the function itself, so make a copy. */
@@ -2292,8 +2348,8 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
/* We can't defer instantiating the function any longer. */
if (!DECL_INITIAL (fun)
- && !ctx->uid_sensitive
- && DECL_TEMPLOID_INSTANTIATION (fun))
+ && DECL_TEMPLOID_INSTANTIATION (fun)
+ && !uid_sensitive_constexpr_evaluation_p ())
{
location_t save_loc = input_location;
input_location = loc;
@@ -2454,7 +2510,7 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
gcc_assert (at_eof >= 2 && ctx->quiet);
*non_constant_p = true;
}
- else if (tree copy = get_fundef_copy (ctx, new_call.fundef))
+ else if (tree copy = get_fundef_copy (new_call.fundef))
{
tree body, parms, res;
releasing_vec ctors;
@@ -6485,7 +6541,8 @@ instantiate_cx_fn_r (tree *tp, int *walk_subtrees, void */*data*/)
&& DECL_DECLARED_CONSTEXPR_P (*tp)
&& !DECL_INITIAL (*tp)
&& !trivial_fn_p (*tp)
- && DECL_TEMPLOID_INSTANTIATION (*tp))
+ && DECL_TEMPLOID_INSTANTIATION (*tp)
+ && !uid_sensitive_constexpr_evaluation_p ())
{
++function_depth;
instantiate_decl (*tp, /*defer_ok*/false, /*expl_inst*/false);
@@ -6552,8 +6609,7 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
bool strict = true,
bool manifestly_const_eval = false,
bool constexpr_dtor = false,
- tree object = NULL_TREE,
- bool uid_sensitive = false)
+ tree object = NULL_TREE)
{
auto_timevar time (TV_CONSTEXPR);
@@ -6569,8 +6625,7 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
constexpr_global_ctx global_ctx;
constexpr_ctx ctx = { &global_ctx, NULL, NULL, NULL, NULL, NULL, NULL,
allow_non_constant, strict,
- manifestly_const_eval || !allow_non_constant,
- uid_sensitive };
+ manifestly_const_eval || !allow_non_constant };
tree type = initialized_type (t);
tree r = t;
@@ -6660,8 +6715,7 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
auto_vec<tree, 16> cleanups;
global_ctx.cleanups = &cleanups;
- if (!uid_sensitive)
- instantiate_constexpr_fns (r);
+ instantiate_constexpr_fns (r);
r = cxx_eval_constant_expression (&ctx, r,
false, &non_constant_p, &overflow_p);
@@ -6909,14 +6963,12 @@ fold_simple (tree t)
Otherwise, if T does not have TREE_CONSTANT set, returns T.
Otherwise, returns a version of T without TREE_CONSTANT.
MANIFESTLY_CONST_EVAL is true if T is manifestly const-evaluated
- as per P0595. UID_SENSITIVE is true if we can't do anything that
- would affect DECL_UID ordering. */
+ as per P0595. */
static GTY((deletable)) hash_map<tree, tree> *cv_cache;
tree
-maybe_constant_value (tree t, tree decl, bool manifestly_const_eval,
- bool uid_sensitive)
+maybe_constant_value (tree t, tree decl, bool manifestly_const_eval)
{
tree r;
@@ -6934,8 +6986,7 @@ maybe_constant_value (tree t, tree decl, bool manifestly_const_eval,
return t;
if (manifestly_const_eval)
- return cxx_eval_outermost_constant_expr (t, true, true, true, false,
- decl, uid_sensitive);
+ return cxx_eval_outermost_constant_expr (t, true, true, true, false, decl);
if (cv_cache == NULL)
cv_cache = hash_map<tree, tree>::create_ggc (101);
@@ -6950,14 +7001,15 @@ maybe_constant_value (tree t, tree decl, bool manifestly_const_eval,
return r;
}
- r = cxx_eval_outermost_constant_expr (t, true, true, false, false,
- decl, uid_sensitive);
+ uid_sensitive_constexpr_evaluation_checker c;
+ r = cxx_eval_outermost_constant_expr (t, true, true, false, false, decl);
gcc_checking_assert (r == t
|| CONVERT_EXPR_P (t)
|| TREE_CODE (t) == VIEW_CONVERT_EXPR
|| (TREE_CONSTANT (t) && !TREE_CONSTANT (r))
|| !cp_tree_equal (r, t));
- cv_cache->put (t, r);
+ if (!c.evaluation_restricted_p ())
+ cv_cache->put (t, r);
return r;
}
diff --git a/gcc/cp/cp-gimplify.c b/gcc/cp/cp-gimplify.c
index ede98929179d29d0a3a6aa4f4a942865e098dc5d..2804958c2464667f288a044bd24ea38c41c36a1c 100644
--- a/gcc/cp/cp-gimplify.c
+++ b/gcc/cp/cp-gimplify.c
@@ -2447,6 +2447,8 @@ cp_fold (tree x)
if (tree *cached = fold_cache->get (x))
return *cached;
+ uid_sensitive_constexpr_evaluation_checker c;
+
code = TREE_CODE (x);
switch (code)
{
@@ -2929,10 +2931,13 @@ cp_fold (tree x)
return org_x;
}
- fold_cache->put (org_x, x);
- /* Prevent that we try to fold an already folded result again. */
- if (x != org_x)
- fold_cache->put (x, x);
+ if (!c.evaluation_restricted_p ())
+ {
+ fold_cache->put (org_x, x);
+ /* Prevent that we try to fold an already folded result again. */
+ if (x != org_x)
+ fold_cache->put (x, x);
+ }
return x;
}
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 27707abaadcbbc96620fbdbd083190c888ef977a..07c16144c988470468031aa21f63849267543890 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7950,7 +7950,7 @@ extern bool require_potential_rvalue_constant_expression (tree);
extern tree cxx_constant_value (tree, tree = NULL_TREE);
extern void cxx_constant_dtor (tree, tree);
extern tree cxx_constant_init (tree, tree = NULL_TREE);
-extern tree maybe_constant_value (tree, tree = NULL_TREE, bool = false, bool = false);
+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,
@@ -7969,6 +7969,27 @@ extern tree fold_sizeof_expr (tree);
extern void clear_cv_and_fold_caches (bool = true);
extern tree unshare_constructor (tree CXX_MEM_STAT_INFO);
+/* An RAII sentinel used to restrict constexpr evaluation so that it
+ doesn't do anything that causes extra DECL_UID generation. */
+
+struct uid_sensitive_constexpr_evaluation_sentinel
+{
+ temp_override<bool> ovr;
+ uid_sensitive_constexpr_evaluation_sentinel ();
+};
+
+/* Used to determine whether uid_sensitive_constexpr_evaluation_p was
+ called and returned true, indicating that we've restricted constexpr
+ evaluation in order to avoid UID generation. We use this to control
+ updates to the fold_cache and cv_cache. */
+
+struct uid_sensitive_constexpr_evaluation_checker
+{
+ const unsigned saved_counter;
+ uid_sensitive_constexpr_evaluation_checker ();
+ bool evaluation_restricted_p () const;
+};
+
/* In cp-ubsan.c */
extern void cp_ubsan_maybe_instrument_member_call (tree);
extern void cp_ubsan_instrument_member_accesses (tree *);
diff --git a/gcc/cp/expr.c b/gcc/cp/expr.c
index 9b535708c57257cb42f08aa1dba9acf5ec71e806..a6ab96af614edd6ecc0f12ef8ed92626520d1e54 100644
--- a/gcc/cp/expr.c
+++ b/gcc/cp/expr.c
@@ -399,6 +399,11 @@ fold_for_warn (tree x)
{
/* C++ implementation. */
+ /* Prevent warning-dependent constexpr evaluation from changing
+ DECL_UID (which breaks -fcompare-debug) and from instantiating
+ templates. */
+ uid_sensitive_constexpr_evaluation_sentinel s;
+
/* It's not generally safe to fully fold inside of a template, so
call fold_non_dependent_expr instead. */
if (processing_template_decl)
@@ -410,7 +415,7 @@ fold_for_warn (tree x)
return f;
}
else if (cxx_dialect >= cxx11)
- x = maybe_constant_value (x, NULL_TREE, false, true);
+ x = maybe_constant_value (x);
return c_fully_fold (x, /*for_init*/false, /*maybe_constp*/NULL);
}
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index bcac1c657f38b60650d04b511d594c71d68548b7..6de0c5e89235f54dbdfb9d0b939766b2a1132411 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-21 Patrick Palka <ppalka@redhat.com>
+
+ PR c++/94038
+ * g++.dg/warn/pr94038-2.C: New test.
+
2020-05-21 Martin Liska <mliska@suse.cz>
PR target/95229
diff --git a/gcc/testsuite/g++.dg/warn/pr94038-2.C b/gcc/testsuite/g++.dg/warn/pr94038-2.C
new file mode 100644
index 0000000000000000000000000000000000000000..a468cc055ebf6343a713f450a1eb81e7c8356c7e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/pr94038-2.C
@@ -0,0 +1,28 @@
+// PR c++/94038
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-O -Wall" }
+
+static constexpr int x = 0;
+
+template<typename T>
+constexpr const int&
+foo()
+{
+ static_assert(T(1) == 0, "");
+ return x;
+}
+
+template<typename T>
+constexpr const int&
+bar()
+{
+ return foo<T>();
+}
+
+constexpr int
+baz(int a)
+{
+ return a;
+}
+
+static_assert(decltype(baz(bar<int>())){} == 0, "");