[OpenMP] Do not propagate match extensions to nested contexts

If we have nested declare variant context, it doesn't make sense to
inherit the match extension from the parent. Instead, just skip it.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D95764

clang/include/clang/Basic/AttrDocs.td

@@ -4014,7 +4014,8 @@ 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
 selector is allowed to be in the OpenMP context, with ``any`` a single trait in
 both the selector and OpenMP context is sufficient. Only a single match
-extension trait is allowed per context selector.
+extension trait is allowed per context selector. Note that match extensions are
+not propagated to nested selectors like the standard defines it for other traits.
 The disable extensions remove default effects of the ``begin declare variant``
 applied to a definition. If ``disable_implicit_base`` is given, we will not
 introduce an implicit base function for a variant if no base function was

clang/lib/Parse/ParseOpenMP.cpp

@@ -21,6 +21,7 @@
 #include "clang/Parse/RAIIObjectsForParser.h"
 #include "clang/Sema/Scope.h"
 #include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/UniqueVector.h"
 #include "llvm/Frontend/OpenMP/OMPContext.h"
@@ -1463,7 +1464,29 @@ bool Parser::parseOMPDeclareVariantMatchClause(SourceLocation Loc,
   // TODO: Keep some source location in the TI to provide better diagnostics.
   // TODO: Perform some kind of equivalence check on the condition and score
   //       expressions.
-  for (const OMPTraitSet &ParentSet : ParentTI->Sets) {
+  auto StripImplementation = [](const OMPTraitSet &TSet) -> OMPTraitSet {
+    if (TSet.Kind != llvm::omp::TraitSet::implementation)
+      return TSet;
+    OMPTraitSet Set = TSet;
+    for (OMPTraitSelector &Selector : Set.Selectors) {
+      if (Selector.Kind != llvm::omp::TraitSelector::implementation_extension)
+        continue;
+      // Do not propagate match extensions to nested contexts.
+      llvm::erase_if(Selector.Properties, [](const OMPTraitProperty &Property) {
+        return (
+            Property.Kind ==
+                llvm::omp::TraitProperty::implementation_extension_match_any ||
+            Property.Kind ==
+                llvm::omp::TraitProperty::implementation_extension_match_all ||
+            Property.Kind ==
+                llvm::omp::TraitProperty::implementation_extension_match_none);
+      });
+      return Set;
+    }
+    return Set;
+  };
+  for (const OMPTraitSet &PSet : ParentTI->Sets) {
+    const OMPTraitSet ParentSet = StripImplementation(PSet);
     bool MergedSet = false;
     for (OMPTraitSet &Set : TI.Sets) {
       if (Set.Kind != ParentSet.Kind)

clang/test/OpenMP/begin_declare_variant_nested_propagation.c

@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -verify -fopenmp -x c -std=c99 -fms-extensions -Wno-pragma-pack %s
+// expected-no-diagnostics
+
+#pragma omp begin declare variant match(user={condition(1)}, device={kind(cpu)}, implementation={extension(match_any)})
+#pragma omp begin declare variant match(device = {kind(cpu, fpga)})
+ this is never reached
+#pragma omp end declare variant
+#pragma omp end declare variant
+
+#pragma omp begin declare variant match(user={condition(1)}, device={kind(cpu)}, implementation={extension(match_any)})
+#pragma omp begin declare variant match(device = {kind(cpu, fpga)}, implementation={vendor(llvm)})
+ this is never reached
+#pragma omp end declare variant
+#pragma omp end declare variant

llvm/lib/Frontend/OpenMP/OMPContext.cpp

@@ -168,8 +168,13 @@ static int isVariantApplicableInContextHelper(
     // For kind "any" a single match is enough but we ignore non-matched
     // properties.
     if (MK == MK_ANY) {
-      if (WasFound)
+      if (WasFound) {
+        LLVM_DEBUG(
+            dbgs() << "[" << DEBUG_TYPE << "] Property "
+                   << getOpenMPContextTraitPropertyName(Property, "")
+                   << " was in the OpenMP context and match kind is any.\n";);
         return true;
+      }
       return None;
     }