[clang] 02d04d5 - [OPENMP50]Do not mark the function as used if referenced only in declare

[Alexey Bataev via cfe-commits]

Author: Alexey Bataev
Date: 2019-12-10T16:30:14-05:00
New Revision: 02d04d569edd39a17f27995565b7b65ac06afb35

URL: https://github.com/llvm/llvm-project/commit/02d04d569edd39a17f27995565b7b65ac06afb35
DIFF: https://github.com/llvm/llvm-project/commit/02d04d569edd39a17f27995565b7b65ac06afb35.diff

LOG: [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.

Added: 
    

Modified: 
    clang/lib/Parse/ParseOpenMP.cpp
    clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
    clang/test/OpenMP/declare_variant_mixed_codegen.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Parse/ParseOpenMP.cpp b/clang/lib/Parse/ParseOpenMP.cpp
index 89f7f909b379..442d2ce0e0f5 100644
--- a/clang/lib/Parse/ParseOpenMP.cpp
+++ b/clang/lib/Parse/ParseOpenMP.cpp
@@ -1078,9 +1078,16 @@ void Parser::ParseOMPDeclareVariantClauses(Parser::DeclGroupPtrTy Ptr,
   SourceLocation RLoc;
   // Parse with IsAddressOfOperand set to true to parse methods as DeclRefExprs
   // instead of MemberExprs.
-  ExprResult AssociatedFunction =
-      ParseOpenMPParensExpr(getOpenMPDirectiveName(OMPD_declare_variant), RLoc,
-                            /*IsAddressOfOperand=*/true);
+  ExprResult AssociatedFunction;
+  {
+    // Do not mark function as is used to prevent its emission if this is the
+    // only place where it is used.
+    EnterExpressionEvaluationContext Unevaluated(
+        Actions, Sema::ExpressionEvaluationContext::Unevaluated);
+    AssociatedFunction = ParseOpenMPParensExpr(
+        getOpenMPDirectiveName(OMPD_declare_variant), RLoc,
+        /*IsAddressOfOperand=*/true);
+  }
   if (!AssociatedFunction.isUsable()) {
     if (!Tok.is(tok::annot_pragma_openmp_end))
       while (!SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch))

diff  --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index e9456ebda581..71399ff35908 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 =

diff  --git a/clang/test/OpenMP/declare_variant_mixed_codegen.cpp b/clang/test/OpenMP/declare_variant_mixed_codegen.cpp
index dea42d1c2170..0c13f5f2f120 100644
--- a/clang/test/OpenMP/declare_variant_mixed_codegen.cpp
+++ b/clang/test/OpenMP/declare_variant_mixed_codegen.cpp
@@ -27,6 +27,7 @@
 // CHECK-DAG: ret i32 85
 // CHECK-DAG: ret i32 86
 // CHECK-DAG: ret i32 87
+// CHECK-DAG: ret i32 88
 // CHECK-NOT: ret i32 {{1|4|81|84}}
 
 #ifndef HEADER
@@ -45,8 +46,10 @@ int test();
 #pragma omp declare variant(test) match(implementation = {vendor(llvm)}, device={kind(cpu)})
 int call() { return 1; }
 
+static int stat_unused_no_emit() { return 1; }
 static int stat_unused_();
 #pragma omp declare variant(stat_unused_) match(implementation = {vendor(llvm)}, device={kind(cpu)})
+#pragma omp declare variant(stat_unused_no_emit) match(implementation = {vendor(xxx)}, device={kind(gpu)})
 static int stat_unused() { return 1; }
 
 static int stat_used_();
@@ -134,4 +137,12 @@ int fn_variant2() { return 1; }
 #pragma omp declare variant(fn_variant2) match(implementation = {vendor(llvm)}, device={kind(fpga)})
 int fn2() { return 87; }
 
+#pragma omp declare variant(stat_unused_no_emit) match(implementation = {vendor(xxx)}, device={kind(gpu)})
+template <typename T>
+static T stat_unused_T() { return 88; }
+
+int bazzzzzzzz() {
+  return stat_unused_T<int>();
+}
+
 #endif // HEADER