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 --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index a82960fb39c031760b244799526f9174bf00ba81..d47dbd2192d52d8f091e772686f35c2db76599d3 100644 (file)
--- 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 (file)
index 0000000..edf5f1a
--- /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 (file)
index 0000000..39eee92
--- /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;
+  }
+}