[gcc r12-10523] c++: Fix bogus warnings about ignored annotations [PR114691]

[Jakub Jelinek]

https://gcc.gnu.org/g:e9b960edb01449786a29a8d196c476bfefc4f243

commit r12-10523-ge9b960edb01449786a29a8d196c476bfefc4f243
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Apr 12 20:53:10 2024 +0200

    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.
    
    (cherry picked from commit 91146346f57cc54dfeb2669347edd0eb3d13af7f)

Diff:
---
 gcc/cp/semantics.cc                 |  6 +++++-
 gcc/testsuite/g++.dg/ext/pr114691.C | 22 ++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index d4d1b01b91e..2d29b0ae1b5 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -800,7 +800,11 @@ 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
index 00000000000..bda8ff9b39f
--- /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 ivdep
+  while (int y = foo (x))	// { dg-bogus "ignoring loop annotation" }
+    qux (y);
+}
+
+void
+baz (int x)
+{
+  #pragma GCC ivdep
+  for (; int y = foo (x); )	// { dg-bogus "ignoring loop annotation" }
+    qux (y);
+}