c++: Fix bogus warnings about ignored annotations [PR114691]

The middle-end warns about the ANNOTATE_EXPR added for while/for loops
if they declare a var inside of the loop condition.
This is because the assumption is that ANNOTATE_EXPR argument is used
immediately in a COND_EXPR (later GIMPLE_COND), but simplify_loop_decl_cond
wraps the ANNOTATE_EXPR inside of a TRUTH_NOT_EXPR, so it no longer
holds.

The following patch fixes that by adding the TRUTH_NOT_EXPR inside of the
ANNOTATE_EXPR argument if any.

2024-04-12  Jakub Jelinek  <jakub@redhat.com>

	PR c++/114691
	* semantics.cc (simplify_loop_decl_cond): Use cp_build_unary_op with
	TRUTH_NOT_EXPR on ANNOTATE_EXPR argument (if any) rather than
	ANNOTATE_EXPR itself.

	* g++.dg/ext/pr114691.C: New test.

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index abaa4a3ca5314812a161901090e6bdd0dc44d683..02c7c1bf5a419e16e6603eb2d4ceb5fbf1b8774f 100644 (file)
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -799,7 +799,11 @@ simplify_loop_decl_cond (tree *cond_p, tree body)
   *cond_p = boolean_true_node;
 
   if_stmt = begin_if_stmt ();
-  cond = cp_build_unary_op (TRUTH_NOT_EXPR, cond, false, tf_warning_or_error);
+  cond_p = &cond;
+  while (TREE_CODE (*cond_p) == ANNOTATE_EXPR)
+    cond_p = &TREE_OPERAND (*cond_p, 0);
+  *cond_p = cp_build_unary_op (TRUTH_NOT_EXPR, *cond_p, false,
+                              tf_warning_or_error);
   finish_if_stmt_cond (cond, if_stmt);
   finish_break_stmt ();
   finish_then_clause (if_stmt);

diff --git a/gcc/testsuite/g++.dg/ext/pr114691.C b/gcc/testsuite/g++.dg/ext/pr114691.C
new file mode 100644 (file)
index 0000000..f11731f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/pr114691.C
@@ -0,0 +1,22 @@
+// PR c++/114691
+// { dg-do compile }
+// { dg-options "-O2 -Wall" }
+
+void qux (int);
+int foo (int);
+
+void
+bar (int x)
+{
+  #pragma GCC novector
+  while (int y = foo (x))      // { dg-bogus "ignoring loop annotation" }
+    qux (y);
+}
+
+void
+baz (int x)
+{
+  #pragma GCC novector
+  for (; int y = foo (x); )    // { dg-bogus "ignoring loop annotation" }
+    qux (y);
+}