[OpenMP][Clang] Parsing/Sema support for need_device_ptr(fb_nullify/fb_preserve). (#168905)

This patch adds parsing, semantic handling, and diagnostics for the
`OpenMP 6.1 fb_nullify` and` fb_preserve` fallback modifiers used with
the `need_device_ptr` map modifier.

Author: zahiraam

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -1724,6 +1724,10 @@ def warn_omp_invalid_attribute_for_ompx_attributes : Warning<"'ompx_attribute' c
   "%0 is ignored">, InGroup<OpenMPExtensions>;
 def err_omp_duplicate_modifier : Error<"duplicate modifier '%0' in '%1' clause">;
 def err_omp_expected_modifier : Error<"expected modifier in '%0' clause">;
+def err_omp_unknown_need_device_ptr_kind
+    : Error<
+        "invalid argument for 'need_device_ptr' kind in 'adjust_args' clause; "
+        "expected 'fp_nullify' or 'fb_preserve'">;
 
 // Pragma loop support.
 def err_pragma_loop_missing_argument : Error<

clang/include/clang/Basic/OpenMPKinds.def

@@ -107,6 +107,9 @@
 #ifndef OPENMP_THREADSET_KIND
 #define OPENMP_THREADSET_KIND(Name)
 #endif
+#ifndef OPENMP_NEED_DEVICE_PTR_KIND
+#define OPENMP_NEED_DEVICE_PTR_KIND(Name)
+#endif
 
 // Static attributes for 'schedule' clause.
 OPENMP_SCHEDULE_KIND(static)
@@ -274,6 +277,10 @@ OPENMP_DOACROSS_MODIFIER(source_omp_cur_iteration)
 OPENMP_THREADSET_KIND(omp_pool)
 OPENMP_THREADSET_KIND(omp_team)
 
+// OpenMP 6.1 modifiers for 'adjust_args' clause.
+OPENMP_NEED_DEVICE_PTR_KIND(fb_nullify)
+OPENMP_NEED_DEVICE_PTR_KIND(fb_preserve)
+
 #undef OPENMP_NUMTASKS_MODIFIER
 #undef OPENMP_NUMTHREADS_MODIFIER
 #undef OPENMP_DYN_GROUPPRIVATE_MODIFIER
@@ -306,3 +313,4 @@ OPENMP_THREADSET_KIND(omp_team)
 #undef OPENMP_DOACROSS_MODIFIER
 #undef OPENMP_ALLOCATE_MODIFIER
 #undef OPENMP_THREADSET_KIND
+#undef OPENMP_NEED_DEVICE_PTR_KIND

clang/include/clang/Basic/OpenMPKinds.h

@@ -211,6 +211,13 @@ enum OpenMPAdjustArgsOpKind {
   OMPC_ADJUST_ARGS_unknown,
 };
 
+/// OpenMP 6.1 need_device modifier
+enum OpenMPNeedDevicePtrModifier {
+#define OPENMP_NEED_DEVICE_PTR_KIND(Name) OMPC_NEED_DEVICE_PTR_##Name,
+#include "clang/Basic/OpenMPKinds.def"
+  OMPC_NEED_DEVICE_PTR_unknown,
+};
+
 /// OpenMP bindings for the 'bind' clause.
 enum OpenMPBindClauseKind {
 #define OPENMP_BIND_KIND(Name) OMPC_BIND_##Name,

clang/include/clang/Sema/SemaOpenMP.h

@@ -1174,6 +1174,8 @@ class SemaOpenMP : public SemaBase {
     int ExtraModifier = -1; ///< Additional modifier for linear, map, depend or
                             ///< lastprivate clause.
     int OriginalSharingModifier = 0; // Default is shared
+    int NeedDevicePtrModifier = 0;
+    SourceLocation NeedDevicePtrModifierLoc;
     SmallVector<OpenMPMapModifierKind, NumberOfOMPMapClauseModifiers>
         MapTypeModifiers;
     SmallVector<SourceLocation, NumberOfOMPMapClauseModifiers>

clang/lib/Parse/ParseOpenMP.cpp

@@ -5010,6 +5010,37 @@ bool Parser::ParseOpenMPVarList(OpenMPDirectiveKind DKind,
       ConsumeToken();
       if (Tok.is(tok::colon))
         Data.ColonLoc = Tok.getLocation();
+      if (getLangOpts().OpenMP >= 61) {
+        // Handle the optional fallback argument for the need_device_ptr
+        // modifier.
+        if (Tok.is(tok::l_paren)) {
+          BalancedDelimiterTracker T(*this, tok::l_paren);
+          T.consumeOpen();
+          if (Tok.is(tok::identifier)) {
+            std::string Modifier = PP.getSpelling(Tok);
+            if (Modifier == "fb_nullify" || Modifier == "fb_preserve") {
+              Data.NeedDevicePtrModifier =
+                  Modifier == "fb_nullify" ? OMPC_NEED_DEVICE_PTR_fb_nullify
+                                           : OMPC_NEED_DEVICE_PTR_fb_preserve;
+            } else {
+              Diag(Tok, diag::err_omp_unknown_need_device_ptr_kind);
+              SkipUntil(tok::r_paren, tok::annot_pragma_openmp_end,
+                        StopBeforeMatch);
+              return false;
+            }
+            ConsumeToken();
+            if (Tok.is(tok::r_paren)) {
+              Data.NeedDevicePtrModifierLoc = Tok.getLocation();
+              ConsumeAnyToken();
+            } else {
+              Diag(Tok, diag::err_expected) << tok::r_paren;
+              SkipUntil(tok::r_paren, tok::annot_pragma_openmp_end,
+                        StopBeforeMatch);
+              return false;
+            }
+          }
+        }
+      }
       ExpectAndConsume(tok::colon, diag::warn_pragma_expected_colon,
                        "adjust-op");
     }

clang/test/OpenMP/need_device_ptr_kind_ast_print.cpp

@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 -verify -fopenmp -fopenmp-version=61 -ast-print %s \
+// RUN: | FileCheck %s
+
+// expected-no-diagnostics
+
+void __attribute__((noinline)) device_impl(int *xp, int *&xpref, int n) {}
+
+#pragma omp declare variant(device_impl) \
+  adjust_args(need_device_ptr(fb_nullify) : xp, xpref)
+void __attribute__((noinline)) host_entry_a(int *xp, int *&xpref, int n) {}
+
+#pragma omp declare variant(device_impl) \
+  adjust_args(need_device_ptr(fb_preserve) : xp, xpref)
+void __attribute__((noinline)) host_entry_b(int *xp, int *&xpref, int n) {}
+
+// CHECK-LABEL: int main()
+int main() {
+  int x;
+  int *xp = &x;
+
+  host_entry_a(xp, xp, 1);
+  host_entry_b(xp, xp, 1);
+  return 0;
+}

clang/test/OpenMP/need_device_ptr_kind_messages.cpp

@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -verify=omp61 -fopenmp -fopenmp-version=61 %s
+
+void __attribute__((noinline)) device_impl(int *xp, int *&xpref, int n) {}
+
+#pragma omp declare variant(device_impl) \
+    adjust_args(need_device_ptr(foo) : xp, xpref)   // omp61-error{{invalid argument for 'need_device_ptr' kind in 'adjust_args' clause; expected 'fp_nullify' or 'fb_preserve'}} // omp61-error{{expected 'match', 'adjust_args', or 'append_args' clause on 'omp declare variant' directive}}
+void __attribute__((noinline)) host_entry_a(int *xp, int *&xpref, int n) {}
+
+#pragma omp declare variant(device_impl) \
+  adjust_args(need_device_ptr(fb_nullify) : xp, xpref)
+void __attribute__((noinline)) host_entry_b(int *xp, int *&xpref, int n) {}
+
+#pragma omp declare variant(device_impl) \
+  adjust_args(need_device_ptr(fb_preserve) : xp, xpref)
+void __attribute__((noinline)) host_entry_c(int *xp, int *&xpref, int n) {}
+
+
+int main() {
+  int x;
+  int *xp = &x;
+
+  host_entry_a(xp, xp, 1);
+  host_entry_b(xp, xp, 1);
+  host_entry_c(xp, xp, 1);
+  return 0;
+}