From 289f860fe62423a66e43989688e1d24bcdb25b5e Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@acm.org>
Date: Wed, 1 Jun 2022 04:52:21 -0700
Subject: [PATCH] c++: Static init guard generation
The guard generation for a static var init was overly verbose. We can
use a bit of RAII and avoid some rechecking. Also in the !cxa_atexit
case, the only difference is whether can become whether to use
post-inc or pre-dec.
gcc/cp/
* decl2.cc (fix_temporary_vars_context_r): Use data argument
for new context.
(one_static_initialization_or_destruction): Adjust tree walk
call. Refactor guard generation.
---
gcc/cp/decl2.cc | 111 ++++++++++++++++++------------------------------
1 file changed, 42 insertions(+), 69 deletions(-)
@@ -4085,34 +4085,25 @@ get_priority_info (int priority)
|| DECL_ONE_ONLY (decl) \
|| DECL_WEAK (decl)))
-/* Called from one_static_initialization_or_destruction(),
- via walk_tree.
- Walks the initializer list of a global variable and looks for
+/* Walks the initializer list of a global variable and looks for
temporary variables (DECL_NAME() == NULL and DECL_ARTIFICIAL != 0)
- and that have their DECL_CONTEXT() == NULL.
- For each such temporary variable, set their DECL_CONTEXT() to
- the current function. This is necessary because otherwise
- some optimizers (enabled by -O2 -fprofile-arcs) might crash
- when trying to refer to a temporary variable that does not have
- it's DECL_CONTECT() properly set. */
+ and that have their DECL_CONTEXT() == NULL. For each such
+ temporary variable, set their DECL_CONTEXT() to CTX -- the
+ initializing function. This is necessary because otherwise some
+ optimizers (enabled by -O2 -fprofile-arcs) might crash when trying
+ to refer to a temporary variable that does not have its
+ DECL_CONTEXT() properly set. */
+
static tree
fix_temporary_vars_context_r (tree *node,
int * /*unused*/,
- void * /*unused1*/)
+ void *ctx)
{
- gcc_assert (current_function_decl);
-
if (TREE_CODE (*node) == BIND_EXPR)
- {
- tree var;
-
- for (var = BIND_EXPR_VARS (*node); var; var = DECL_CHAIN (var))
- if (VAR_P (var)
- && !DECL_NAME (var)
- && DECL_ARTIFICIAL (var)
- && !DECL_CONTEXT (var))
- DECL_CONTEXT (var) = current_function_decl;
- }
+ for (tree var = BIND_EXPR_VARS (*node); var; var = DECL_CHAIN (var))
+ if (VAR_P (var) && !DECL_NAME (var)
+ && DECL_ARTIFICIAL (var) && !DECL_CONTEXT (var))
+ DECL_CONTEXT (var) = tree (ctx);
return NULL_TREE;
}
@@ -4124,9 +4115,6 @@ fix_temporary_vars_context_r (tree *node,
static void
one_static_initialization_or_destruction (bool initp, tree decl, tree init)
{
- tree guard_if_stmt = NULL_TREE;
- tree guard;
-
/* If we are supposed to destruct and there's a trivial destructor,
nothing has to be done. */
if (!initp
@@ -4150,7 +4138,7 @@ one_static_initialization_or_destruction (bool initp, tree decl, tree init)
of the temporaries are set to the current function decl. */
cp_walk_tree_without_duplicates (&init,
fix_temporary_vars_context_r,
- NULL);
+ current_function_decl);
/* Because of:
@@ -4171,62 +4159,50 @@ one_static_initialization_or_destruction (bool initp, tree decl, tree init)
}
/* Assume we don't need a guard. */
- guard = NULL_TREE;
+ tree guard_if_stmt = NULL_TREE;
+
/* We need a guard if this is an object with external linkage that
might be initialized in more than one place. (For example, a
static data member of a template, when the data member requires
construction.) */
if (NEEDS_GUARD_P (decl))
{
+ tree guard = get_guard (decl);
tree guard_cond;
- guard = get_guard (decl);
-
- /* When using __cxa_atexit, we just check the GUARD as we would
- for a local static. */
if (flag_use_cxa_atexit)
{
- /* When using __cxa_atexit, we never try to destroy
+ /* When using __cxa_atexit, we just check the GUARD as we
+ would for a local static. We never try to destroy
anything from a static destructor. */
gcc_assert (initp);
guard_cond = get_guard_cond (guard, false);
}
- /* If we don't have __cxa_atexit, then we will be running
- destructors from .fini sections, or their equivalents. So,
- we need to know how many times we've tried to initialize this
- object. We do initializations only if the GUARD is zero,
- i.e., if we are the first to initialize the variable. We do
- destructions only if the GUARD is one, i.e., if we are the
- last to destroy the variable. */
- else if (initp)
- guard_cond
- = cp_build_binary_op (input_location,
- EQ_EXPR,
- cp_build_unary_op (PREINCREMENT_EXPR,
- guard,
- /*noconvert=*/true,
- tf_warning_or_error),
- integer_one_node,
- tf_warning_or_error);
else
- guard_cond
- = cp_build_binary_op (input_location,
- EQ_EXPR,
- cp_build_unary_op (PREDECREMENT_EXPR,
- guard,
- /*noconvert=*/true,
- tf_warning_or_error),
- integer_zero_node,
- tf_warning_or_error);
+ {
+ /* If we don't have __cxa_atexit, then we will be running
+ destructors from .fini sections, or their equivalents.
+ So, we need to know how many times we've tried to
+ initialize this object. We do initializations only if
+ the GUARD was or becomes zero (initp vs !initp
+ respectively). */
+ guard_cond = cp_build_unary_op (initp ? POSTINCREMENT_EXPR
+ : PREDECREMENT_EXPR,
+ guard,
+ /*noconvert=*/true,
+ tf_warning_or_error);
+ guard_cond = cp_build_binary_op (input_location, EQ_EXPR, guard_cond,
+ integer_zero_node,
+ tf_warning_or_error);
+ }
guard_if_stmt = begin_if_stmt ();
finish_if_stmt_cond (guard_cond, guard_if_stmt);
- }
- /* If we're using __cxa_atexit, we have not already set the GUARD,
- so we must do so now. */
- if (guard && initp && flag_use_cxa_atexit)
- finish_expr_stmt (set_guard (guard));
+ if (flag_use_cxa_atexit)
+ /* Set the GUARD now. */
+ finish_expr_stmt (set_guard (guard));
+ }
/* Perform the initialization or destruction. */
if (initp)
@@ -4235,11 +4211,8 @@ one_static_initialization_or_destruction (bool initp, tree decl, tree init)
{
finish_expr_stmt (init);
if (sanitize_flags_p (SANITIZE_ADDRESS, decl))
- {
- varpool_node *vnode = varpool_node::get (decl);
- if (vnode)
- vnode->dynamically_initialized = 1;
- }
+ if (varpool_node *vnode = varpool_node::get (decl))
+ vnode->dynamically_initialized = 1;
}
/* If we're using __cxa_atexit, register a function that calls the
@@ -4251,7 +4224,7 @@ one_static_initialization_or_destruction (bool initp, tree decl, tree init)
finish_expr_stmt (build_cleanup (decl));
/* Finish the guard if-stmt, if necessary. */
- if (guard)
+ if (guard_if_stmt)
{
finish_then_clause (guard_if_stmt);
finish_if_stmt (guard_if_stmt);
--
2.30.2