From 827b5c21545aaa820403e9b5cced8c0181349ee2 Mon Sep 17 00:00:00 2001
From: Alexey Bataev <a.bataev@outlook.com>
Date: Thu, 3 Jun 2021 12:13:10 -0700
Subject: [PATCH] [OPENMP]Fix PR49790: Constexpr values not handled in `omp
 declare mapper` clause.

Patch allows using of constexpr vars evaluatable to constant calue to be
used in declare mapper construct.

Differential Revision: https://reviews.llvm.org/D103642
---
 clang/lib/Sema/SemaOpenMP.cpp                  | 9 +++++++--
 clang/test/OpenMP/declare_mapper_ast_print.cpp | 5 +++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 2fcc3fb4317e..514b3b9ed05f 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -19681,8 +19681,13 @@ Sema::ActOnOpenMPDeclareMapperDirectiveVarDecl(Scope *S, QualType MapperType,
 bool Sema::isOpenMPDeclareMapperVarDeclAllowed(const VarDecl *VD) const {
   assert(LangOpts.OpenMP && "Expected OpenMP mode.");
   const Expr *Ref = DSAStack->getDeclareMapperVarRef();
-  if (const auto *DRE = cast_or_null<DeclRefExpr>(Ref))
-    return VD->getCanonicalDecl() == DRE->getDecl()->getCanonicalDecl();
+  if (const auto *DRE = cast_or_null<DeclRefExpr>(Ref)) {
+    if (VD->getCanonicalDecl() == DRE->getDecl()->getCanonicalDecl())
+      return true;
+    if (VD->isUsableInConstantExpressions(Context))
+      return true;
+    return false;
+  }
   return true;
 }
 
diff --git a/clang/test/OpenMP/declare_mapper_ast_print.cpp b/clang/test/OpenMP/declare_mapper_ast_print.cpp
index 6462fa38d872..b9445ca35a0c 100644
--- a/clang/test/OpenMP/declare_mapper_ast_print.cpp
+++ b/clang/test/OpenMP/declare_mapper_ast_print.cpp
@@ -56,8 +56,9 @@ public:
 // CHECK: #pragma omp declare mapper (id : dat<double>::datin v) map(tofrom: v.in){{$}}
 // CHECK: };
 
-#pragma omp declare mapper(default : N1::vec kk) map(kk.len) map(kk.data[0:2])
-// CHECK: #pragma omp declare mapper (default : N1::vec kk) map(tofrom: kk.len) map(tofrom: kk.data[0:2]){{$}}
+constexpr int N = 2;
+#pragma omp declare mapper(default : N1::vec kk) map(kk.len) map(kk.data[0:N])
+// CHECK: #pragma omp declare mapper (default : N1::vec kk) map(tofrom: kk.len) map(tofrom: kk.data[0:N]){{$}}
 #pragma omp declare mapper(dat<double> d) map(to: d.d)
 // CHECK: #pragma omp declare mapper (default : dat<double> d) map(to: d.d){{$}}
 
-- 
2.34.1