[OPENMP50]Do not mark the function as used if referenced only in declare

variant directive.

If the function is used only in declare variant directive as a variant
function, it should not be marked as used to prevent emission of the
target-specific functions. Build the reference in the unevaluated
context.

1 files changed, 6 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index e9456ebda58..71399ff3590 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -385,8 +385,13 @@ static void instantiateOMPDeclareVariantAttr(
   };
 
   ExprResult VariantFuncRef;
-  if (Expr *E = Attr.getVariantFuncRef())
+  if (Expr *E = Attr.getVariantFuncRef()) {
+    // Do not mark function as is used to prevent its emission if this is the
+    // only place where it is used.
+    EnterExpressionEvaluationContext Unevaluated(
+        S, Sema::ExpressionEvaluationContext::ConstantEvaluated);
     VariantFuncRef = Subst(E);
+  }
 
   // Check function/variant ref.
   Optional<std::pair<FunctionDecl *, Expr *>> DeclVarData =