Tested x86_64-pc-linux-gnu, OK for trunk?
-- 8< --
While working on PR119162 it occurred to me that it would be simpler to
detect the problem of a value referring to a heap allocation if we stopped
setting TREE_STATIC on them so they naturally are not considered to have a
constant address. With that change we no longer need to specifically avoid
caching a value that refers to a deleted pointer.
But with this change maybe_nonzero_address is not sure whether the variable
could have address zero. I don't understand why it returns 1 only for
variables in the current function, rather than all non-symtab decls; an auto
variable from some other function also won't have address zero. Maybe this
made more sense when it was in tree_single_nonzero_warnv_p before r7-5868?
But assuming there is some reason for the current behavior, this patch only
changes the handling of non-symtab decls when folding_cxx_constexpr.
PR c++/119162
gcc/cp/ChangeLog:
* constexpr.cc (find_deleted_heap_var): Remove.
(cxx_eval_call_expression): Don't call it. Don't set TREE_STATIC on
heap vars.
(cxx_eval_outermost_constant_expr): Don't mess with varpool.
gcc/ChangeLog:
* fold-const.cc (maybe_nonzero_address): Return 1 for non-symtab
vars if folding_cxx_constexpr.
---
gcc/cp/constexpr.cc | 29 -----------------------------
gcc/fold-const.cc | 25 ++++++++++++++++---------
2 files changed, 16 insertions(+), 38 deletions(-)
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 8a11e6265f2..5b7b70f7e65 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -1550,7 +1550,6 @@ static tree cxx_eval_bare_aggregate (const constexpr_ctx
*, tree,
static tree cxx_fold_indirect_ref (const constexpr_ctx *, location_t, tree,
tree,
bool * = NULL);
static tree find_heap_var_refs (tree *, int *, void *);
-static tree find_deleted_heap_var (tree *, int *, void *);
/* Attempt to evaluate T which represents a call to a builtin function.
We assume here that all builtin functions evaluate to scalar types
@@ -2975,14 +2974,6 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree
t,
: heap_uninit_identifier,
type);
DECL_ARTIFICIAL (var) = 1;
- TREE_STATIC (var) = 1;
- // Temporarily register the artificial var in varpool,
- // so that comparisons of its address against NULL are folded
- // through nonzero_address even with
- // -fno-delete-null-pointer-checks or that comparison of
- // addresses of different heap artificial vars is folded too.
- // See PR98988 and PR99031.
- varpool_node::finalize_decl (var);
ctx->global->heap_vars.safe_push (var);
ctx->global->put_value (var, NULL_TREE);
return fold_convert (ptr_type_node, build_address (var));
@@ -3454,11 +3445,6 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree
t,
cacheable = false;
break;
}
- /* And don't cache a ref to a deleted heap variable (119162). */
- if (cacheable
- && (cp_walk_tree_without_duplicates
- (&result, find_deleted_heap_var, NULL)))
- cacheable = false;
}
/* Rewrite all occurrences of the function's RESULT_DECL with the
@@ -9025,20 +9011,6 @@ find_heap_var_refs (tree *tp, int *walk_subtrees, void
*/*data*/)
return NULL_TREE;
}
-/* Look for deleted heap variables in the expression *TP. */
-
-static tree
-find_deleted_heap_var (tree *tp, int *walk_subtrees, void */*data*/)
-{
- if (VAR_P (*tp)
- && DECL_NAME (*tp) == heap_deleted_identifier)
- return *tp;
-
- if (TYPE_P (*tp))
- *walk_subtrees = 0;
- return NULL_TREE;
-}
-
/* Find immediate function decls in *TP if any. */
static tree
@@ -9275,7 +9247,6 @@ cxx_eval_outermost_constant_expr (tree t, bool
allow_non_constant,
r = t;
non_constant_p = true;
}
- varpool_node::get (heap_var)->remove ();
}
}
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index c9471ea44b0..35fcf5087fb 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -9917,22 +9917,29 @@ pointer_may_wrap_p (tree base, tree offset, poly_int64
bitpos)
static int
maybe_nonzero_address (tree decl)
{
+ if (!DECL_P (decl))
+ return -1;
+
/* Normally, don't do anything for variables and functions before symtab is
built; it is quite possible that DECL will be declared weak later.
But if folding_initializer, we need a constant answer now, so create
the symtab entry and prevent later weak declaration. */
- if (DECL_P (decl) && decl_in_symtab_p (decl))
- if (struct symtab_node *symbol
- = (folding_initializer
- ? symtab_node::get_create (decl)
- : symtab_node::get (decl)))
- return symbol->nonzero_address ();
+ if (decl_in_symtab_p (decl))
+ {
+ if (struct symtab_node *symbol
+ = (folding_initializer
+ ? symtab_node::get_create (decl)
+ : symtab_node::get (decl)))
+ return symbol->nonzero_address ();
+ }
+ else if (folding_cxx_constexpr)
+ /* Anything that doesn't go in the symtab has non-zero address. */
+ return 1;
/* Function local objects are never NULL. */
- if (DECL_P (decl)
- && (DECL_CONTEXT (decl)
+ if (DECL_CONTEXT (decl)
&& TREE_CODE (DECL_CONTEXT (decl)) == FUNCTION_DECL
- && auto_var_in_fn_p (decl, DECL_CONTEXT (decl))))
+ && auto_var_in_fn_p (decl, DECL_CONTEXT (decl)))
return 1;
return -1;
base-commit: 9ac98b5742ebce41d7da9fda10852a0bc958f1cb
--
2.49.0
