[SYCL] Allow __spirv_ocl_printf vararg function (#909)

Vararg functions are generally not allowed in SYCL. However, printf is
a special case, because it can be mapped to a SPIR-V instruction, and
SPIR-V translator recognizes __spirv_ocl_printf function.

Signed-off-by: Andrew Savonichev <[email protected]>

Author: Andrew Savonichev

clang/lib/Sema/SemaSYCL.cpp

@@ -184,6 +184,19 @@ static bool IsSyclMathFunc(unsigned BuiltinID) {
   return true;
 }
 
+static bool isKnownGoodDecl(const Decl *D) {
+  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
+    const IdentifierInfo *II = FD->getIdentifier();
+    const DeclContext *DC = FD->getDeclContext();
+    if (II && II->isStr("__spirv_ocl_printf") &&
+        !FD->isDefined() &&
+        FD->getLanguageLinkage() == CXXLanguageLinkage &&
+        DC->getEnclosingNamespaceContext()->isTranslationUnit())
+      return true;
+  }
+  return false;
+}
+
 class MarkDeviceFunction : public RecursiveASTVisitor<MarkDeviceFunction> {
 public:
   MarkDeviceFunction(Sema &S)
@@ -312,8 +325,12 @@ class MarkDeviceFunction : public RecursiveASTVisitor<MarkDeviceFunction> {
   }
 
   bool VisitDeclRefExpr(DeclRefExpr *E) {
+    Decl* D = E->getDecl();
+    if (isKnownGoodDecl(D))
+      return true;
+
     CheckSYCLType(E->getType(), E->getSourceRange());
-    if (VarDecl *VD = dyn_cast<VarDecl>(E->getDecl())) {
+    if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
       bool IsConst = VD->getType().getNonReferenceType().isConstQualified();
       if (!IsConst && VD->isStaticDataMember())
         SemaRef.Diag(E->getExprLoc(), diag::err_sycl_restrict)

clang/test/SemaSYCL/sycl-varargs-cconv.cpp

@@ -1,4 +1,32 @@
 // RUN: %clang_cc1 -fsycl-is-device -verify -fsyntax-only -x c++ %s
+// RUN: %clang_cc1 -fsycl-is-device -verify -fsyntax-only -DPRINTF_INVALID_DEF -x c++ %s
+// RUN: %clang_cc1 -fsycl-is-device -verify -fsyntax-only -DPRINTF_INVALID_DECL -x c++ %s
+// RUN: %clang_cc1 -fsycl-is-device -verify -fsyntax-only -DPRINTF_VALID1 -x c++ %s
+// RUN: %clang_cc1 -fsycl-is-device -verify -fsyntax-only -DPRINTF_VALID2 -x c++ %s
+
+#if defined(PRINTF_INVALID_DECL)
+extern "C" int __spirv_ocl_printf(const char *__format, ...);
+namespace A {
+  int __spirv_ocl_printf(const char *__format, ...);
+}
+#elif defined(PRINTF_INVALID_DEF)
+int __spirv_ocl_printf(const char *__format, ...) {
+  return 42;
+}
+#elif defined(PRINTF_VALID1)
+class A {
+  friend int __spirv_ocl_printf(const char *__format, ...);
+};
+int __spirv_ocl_printf(const char *__format, ...);
+#elif defined(PRINTF_VALID2)
+extern "C" {
+  extern "C++" {
+    int __spirv_ocl_printf(const char *__format, ...);
+  }
+}
+#else
+int __spirv_ocl_printf(const char *__format, ...);
+#endif
 
 int __cdecl foo(int, ...); // expected-no-error
 
@@ -19,6 +47,19 @@ int main() {
   kernel_single_task<class fake_kernel>([]() { foo(6); });
   //expected-error@+1 {{SYCL kernel cannot call a variadic function}}
   kernel_single_task<class fake_kernel>([]() { bar(9.0); });
+
+#if defined(PRINTF_INVALID_DECL)
+  //expected-error@+1 {{SYCL kernel cannot call a variadic function}}
+  kernel_single_task<class fake_kernel>([]() { A::__spirv_ocl_printf("Hello world! %d%d\n", 4, 2); });
+  //expected-error@+1 {{SYCL kernel cannot call a variadic function}}
+  kernel_single_task<class fake_kernel>([]() { __spirv_ocl_printf("Hello world! %d%d\n", 4, 2); });
+#elif defined(PRINTF_INVALID_DEF)
+  //expected-error@+1 {{SYCL kernel cannot call a variadic function}}
+  kernel_single_task<class fake_kernel>([]() { __spirv_ocl_printf("Hello world! %d%d\n", 4, 2); });
+#else
+  kernel_single_task<class fake_kernel>([]() { __spirv_ocl_printf("Hello world! %d%d\n", 4, 2); });
+#endif
+
   bar();
   return 0;
 }