[gcc/devel/omp/gcc-11] Allow static constexpr fields in mappable types for C++

[Kwok Yeung <kcy@gcc.gnu.org>]

https://gcc.gnu.org/g:90aea329baced1dc0d2a806b274eb43562e9df2a

commit 90aea329baced1dc0d2a806b274eb43562e9df2a
Author: Chung-Lin Tang <cltang@codesourcery.com>
Date:   Wed Mar 3 22:39:10 2021 +0800

    Allow static constexpr fields in mappable types for C++
    
    This patch is a merge of:
    https://gcc.gnu.org/legacy-ml/gcc-patches/2020-01/msg01246.html
    
    Static members in general disqualify a C++ class from being target mappable,
    but static constexprs are inline optimized away, so should not interfere.
    
    OpenMP 5.0 in general lifts the static member limitation, so this
    patch will probably further adjusted later.
    
    2021-03-03  Chung-Lin Tang  <cltang@codesourcery.com>
    
    gcc/cp/ChangeLog:
    
            * decl2.c (cp_omp_mappable_type_1): Allow fields with
            DECL_DECLARED_CONSTEXPR_P to be mapped.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/goacc/static-constexpr-1.C: New test.
            * g++.dg/gomp/static-constexpr-1.C: New test.

Diff:
---
 gcc/cp/decl2.c                                  |  5 ++++-
 gcc/testsuite/g++.dg/goacc/static-constexpr-1.C | 17 +++++++++++++++++
 gcc/testsuite/g++.dg/gomp/static-constexpr-1.C  | 17 +++++++++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index a82960fb39c..d47dbd2192d 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -1461,7 +1461,10 @@ cp_omp_mappable_type_1 (tree type, bool notes)
     {
       tree field;
       for (field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
-	if (VAR_P (field))
+	if (VAR_P (field)
+	    /* Fields that are 'static constexpr' can be folded away at compile
+	       time, thus does not interfere with mapping.  */
+	    && !DECL_DECLARED_CONSTEXPR_P (field))
 	  {
 	    if (notes)
 	      inform (DECL_SOURCE_LOCATION (field),
diff --git a/gcc/testsuite/g++.dg/goacc/static-constexpr-1.C b/gcc/testsuite/g++.dg/goacc/static-constexpr-1.C
new file mode 100644
index 00000000000..edf5f1a7628
--- /dev/null
+++ b/gcc/testsuite/g++.dg/goacc/static-constexpr-1.C
@@ -0,0 +1,17 @@
+// { dg-do compile }
+// { dg-require-effective-target c++11 }
+
+/* Test that static constexpr members do not interfere with offloading.  */
+struct rec
+{
+  static constexpr int x = 1;
+  int y, z;
+};
+
+void foo (rec& r)
+{
+  #pragma acc parallel copy(r)
+  {
+    r.y = r.y = r.x;
+  }
+}
diff --git a/gcc/testsuite/g++.dg/gomp/static-constexpr-1.C b/gcc/testsuite/g++.dg/gomp/static-constexpr-1.C
new file mode 100644
index 00000000000..39eee92dddd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/gomp/static-constexpr-1.C
@@ -0,0 +1,17 @@
+// { dg-do compile }
+// { dg-require-effective-target c++11 }
+
+/* Test that static constexpr members do not interfere with offloading.  */
+struct rec
+{
+  static constexpr int x = 1;
+  int y, z;
+};
+
+void foo (rec& r)
+{
+  #pragma omp target map(r)
+  {
+    r.y = r.y = r.x;
+  }
+}