[gcc/devel/omp/gcc-12] Allow static constexpr fields in mappable types for C++

[gcc/devel/omp/gcc-12] Allow static constexpr fields in mappable types for C++

[Kwok Yeung]

https://gcc.gnu.org/g:1f4ee53c2ea6ad4a91550d3e15f80cc7df24efa2

commit 1f4ee53c2ea6ad4a91550d3e15f80cc7df24efa2
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.cc (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/ChangeLog.omp                            |  5 +++++
 gcc/cp/decl2.cc                                 |  5 ++++-
 gcc/testsuite/ChangeLog.omp                     |  5 +++++
 gcc/testsuite/g++.dg/goacc/static-constexpr-1.C | 17 +++++++++++++++++
 gcc/testsuite/g++.dg/gomp/static-constexpr-1.C  | 17 +++++++++++++++++
 5 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/ChangeLog.omp b/gcc/cp/ChangeLog.omp
index f37510eb0fa..efda4eddf14 100644
--- a/gcc/cp/ChangeLog.omp
+++ b/gcc/cp/ChangeLog.omp
@@ -1,3 +1,8 @@
+2021-03-03  Chung-Lin Tang  <cltang@codesourcery.com>
+
+	* decl2.cc (cp_omp_mappable_type_1): Allow fields with
+	DECL_DECLARED_CONSTEXPR_P to be mapped.
+
 2021-02-02  Chung-Lin Tang  <cltang@codesourcery.com>
 
 	* parser.cc (cp_parser_simple_declaration): Set
diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index d2b29208ed5..d947c829756 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -1577,7 +1577,10 @@ 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/ChangeLog.omp b/gcc/testsuite/ChangeLog.omp
index fd15e7aa7fb..5365d8950cd 100644
--- a/gcc/testsuite/ChangeLog.omp
+++ b/gcc/testsuite/ChangeLog.omp
@@ -1,3 +1,8 @@
+2021-03-03  Chung-Lin Tang  <cltang@codesourcery.com>
+
+	* g++.dg/goacc/static-constexpr-1.C: New test.
+	* g++.dg/gomp/static-constexpr-1.C: New test.
+
 2021-02-02  Chung-Lin Tang  <cltang@codesourcery.com>
 
 	* c-c++-common/gomp/requires-4.c: Remove prune of "not supported yet".
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;
+  }
+}