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 5343ea3b068ff39cdbbdd044e2328e5743d87c1d..872122fe83c0cafb7f12f468a0cea0ca98aceed1 100644 (file)
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -1460,7 +1460,10 @@ 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;
+  }
+}