[OpenMP] Add variant extension that applies to declarations

This patch adds a new extension to the `omp begin / end declare variant`
support that causes it to apply to function declarations as well. This
is explicitly not done in the standard, but can be useful in some
situations so we should provide it as an extension. This will allow us
to uniquely bind and overload existing definitions with a simple
declaration using variants.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D124624

diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index dbb7f69..4e4d871 100644 (file)
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -4330,6 +4330,7 @@ Clang provides the following context selector extensions, used via
     match_none
     disable_implicit_base
     allow_templates
+    bind_to_declaration
 
 The match extensions change when the *entire* context selector is considered a
 match for an OpenMP context. The default is ``all``, with ``none`` no trait in the
@@ -4345,8 +4346,9 @@ The allow extensions change when the ``begin declare variant`` effect is
 applied to a definition. If ``allow_templates`` is given, template function
 definitions are considered as specializations of existing or assumed template
 declarations with the same name. The template parameters for the base functions
-are used to instantiate the specialization.
-
+are used to instantiate the specialization. If ``bind_to_declartion`` is given,
+apply the same variant rules to function declarations. This allows the user to
+override declarations with only a function declaration.
   }];
 }
 

diff --git a/clang/lib/Parse/ParseOpenMP.cpp b/clang/lib/Parse/ParseOpenMP.cpp
index 7457886..de4a25c 100644 (file)
--- a/clang/lib/Parse/ParseOpenMP.cpp
+++ b/clang/lib/Parse/ParseOpenMP.cpp
@@ -960,6 +960,10 @@ static bool checkExtensionProperty(Parser &P, SourceLocation Loc,
       TraitProperty::implementation_extension_allow_templates)
     return true;
 
+  if (TIProperty.Kind ==
+      TraitProperty::implementation_extension_bind_to_declaration)
+    return true;
+
   auto IsMatchExtension = [](OMPTraitProperty &TP) {
     return (TP.Kind ==
                 llvm::omp::TraitProperty::implementation_extension_match_all ||

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 44f04d3..1139088 100644 (file)
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -5868,12 +5868,25 @@ void Sema::warnOnReservedIdentifier(const NamedDecl *D) {
 
 Decl *Sema::ActOnDeclarator(Scope *S, Declarator &D) {
   D.setFunctionDefinitionKind(FunctionDefinitionKind::Declaration);
+
+  // Check if we are in an `omp begin/end declare variant` scope. Handle this
+  // declaration only if the `bind_to_declaration` extension is set.
+  SmallVector<FunctionDecl *, 4> Bases;
+  if (LangOpts.OpenMP && isInOpenMPDeclareVariantScope())
+    if (getOMPTraitInfoForSurroundingScope()->isExtensionActive(llvm::omp::TraitProperty::
+              implementation_extension_bind_to_declaration))
+    ActOnStartOfFunctionDefinitionInOpenMPDeclareVariantScope(
+        S, D, MultiTemplateParamsArg(), Bases);
+
   Decl *Dcl = HandleDeclarator(S, D, MultiTemplateParamsArg());
 
   if (OriginalLexicalContext && OriginalLexicalContext->isObjCContainer() &&
       Dcl && Dcl->getDeclContext()->isFileContext())
     Dcl->setTopLevelDeclInObjCContainer();
 
+  if (!Bases.empty())
+    ActOnFinishedFunctionDefinitionInOpenMPDeclareVariantScope(Dcl, Bases);
+
   return Dcl;
 }
 

diff --git a/clang/test/OpenMP/declare_variant_bind_to_decl.cpp b/clang/test/OpenMP/declare_variant_bind_to_decl.cpp
new file mode 100644 (file)
index 0000000..dca18ab
--- /dev/null
+++ b/clang/test/OpenMP/declare_variant_bind_to_decl.cpp
@@ -0,0 +1,34 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --function-signature --include-generated-funcs
+// RUN: %clang_cc1 -verify -fopenmp -x c++ -triple powerpc64le-unknown-unknown -emit-llvm %s -o - | FileCheck %s
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+void foo() { }
+
+#pragma omp begin declare variant match( \
+    device = {arch(ppc64le, ppc64)},     \
+    implementation = {extension(match_any, bind_to_declaration)})
+
+void foo();
+
+#pragma omp end declare variant
+
+int main() {
+  foo();
+}
+
+#endif
+// CHECK-LABEL: define {{[^@]+}}@_Z3foov
+// CHECK-SAME: () #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    ret void
+//
+//
+// CHECK-LABEL: define {{[^@]+}}@main
+// CHECK-SAME: () #[[ATTR1:[0-9]+]] {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    call void @"_Z74foo$ompvariant$S2$s7$Pppc64le$Pppc64$S3$s9$Pmatch_any$Pbind_to_declarationv"()
+// CHECK-NEXT:    ret i32 0
+//

diff --git a/llvm/include/llvm/Frontend/OpenMP/OMPKinds.def b/llvm/include/llvm/Frontend/OpenMP/OMPKinds.def
index 0106fc4..14aa53a 100644 (file)
--- a/llvm/include/llvm/Frontend/OpenMP/OMPKinds.def
+++ b/llvm/include/llvm/Frontend/OpenMP/OMPKinds.def
@@ -1160,6 +1160,7 @@ __OMP_TRAIT_PROPERTY(implementation, extension, match_any)
 __OMP_TRAIT_PROPERTY(implementation, extension, match_none)
 __OMP_TRAIT_PROPERTY(implementation, extension, disable_implicit_base)
 __OMP_TRAIT_PROPERTY(implementation, extension, allow_templates)
+__OMP_TRAIT_PROPERTY(implementation, extension, bind_to_declaration)
 
 __OMP_TRAIT_SET(user)