[Libomptarget][NFC] Use C++ style attributes instead

Summary:
This patch changes no functionality and simply switches to using the C++
styled attributes. These tend to be shorter and have better IDE /
completion support as they are in the actual language.

Author: jhuber6

openmp/libomptarget/DeviceRTL/include/State.h

@@ -176,7 +176,7 @@ inline uint32_t &lookupImpl(uint32_t state::ICVStateTy::*Var,
   return TeamState.ICVState.*Var;
 }
 
-__attribute__((always_inline, flatten)) inline uint32_t &
+[[gnu::always_inline, gnu::flatten]] inline uint32_t &
 lookup32(ValueKind Kind, bool IsReadonly, IdentTy *Ident, bool ForceTeamState) {
   switch (Kind) {
   case state::VK_NThreads:
@@ -218,7 +218,7 @@ lookup32(ValueKind Kind, bool IsReadonly, IdentTy *Ident, bool ForceTeamState) {
   __builtin_unreachable();
 }
 
-__attribute__((always_inline, flatten)) inline void *&
+[[gnu::always_inline, gnu::flatten]] inline void *&
 lookupPtr(ValueKind Kind, bool IsReadonly, bool ForceTeamState) {
   switch (Kind) {
   case state::VK_ParallelRegionFn:
@@ -232,47 +232,45 @@ lookupPtr(ValueKind Kind, bool IsReadonly, bool ForceTeamState) {
 /// A class without actual state used to provide a nice interface to lookup and
 /// update ICV values we can declare in global scope.
 template <typename Ty, ValueKind Kind> struct Value {
-  __attribute__((flatten, always_inline)) operator Ty() {
+  [[gnu::flatten, gnu::always_inline]] operator Ty() {
     return lookup(/* IsReadonly */ true, /* IdentTy */ nullptr,
                   /* ForceTeamState */ false);
   }
 
-  __attribute__((flatten, always_inline)) Value &operator=(const Ty &Other) {
+  [[gnu::flatten, gnu::always_inline]] Value &operator=(const Ty &Other) {
     set(Other, /* IdentTy */ nullptr);
     return *this;
   }
 
-  __attribute__((flatten, always_inline)) Value &operator++() {
+  [[gnu::flatten, gnu::always_inline]] Value &operator++() {
     inc(1, /* IdentTy */ nullptr);
     return *this;
   }
 
-  __attribute__((flatten, always_inline)) Value &operator--() {
+  [[gnu::flatten, gnu::always_inline]] Value &operator--() {
     inc(-1, /* IdentTy */ nullptr);
     return *this;
   }
 
-  __attribute__((flatten, always_inline)) void
+  [[gnu::flatten, gnu::always_inline]] void
   assert_eq(const Ty &V, IdentTy *Ident = nullptr,
             bool ForceTeamState = false) {
     ASSERT(lookup(/* IsReadonly */ true, Ident, ForceTeamState) == V, nullptr);
   }
 
 private:
-  __attribute__((flatten, always_inline)) Ty &
+  [[gnu::flatten, gnu::always_inline]] Ty &
   lookup(bool IsReadonly, IdentTy *Ident, bool ForceTeamState) {
     Ty &t = lookup32(Kind, IsReadonly, Ident, ForceTeamState);
     return t;
   }
 
-  __attribute__((flatten, always_inline)) Ty &inc(int UpdateVal,
-                                                  IdentTy *Ident) {
+  [[gnu::flatten, gnu::always_inline]] Ty &inc(int UpdateVal, IdentTy *Ident) {
     return (lookup(/* IsReadonly */ false, Ident, /* ForceTeamState */ false) +=
             UpdateVal);
   }
 
-  __attribute__((flatten, always_inline)) Ty &set(Ty UpdateVal,
-                                                  IdentTy *Ident) {
+  [[gnu::flatten, gnu::always_inline]] Ty &set(Ty UpdateVal, IdentTy *Ident) {
     return (lookup(/* IsReadonly */ false, Ident, /* ForceTeamState */ false) =
                 UpdateVal);
   }
@@ -284,12 +282,12 @@ template <typename Ty, ValueKind Kind> struct Value {
 /// a nice interface to lookup and update ICV values
 /// we can declare in global scope.
 template <typename Ty, ValueKind Kind> struct PtrValue {
-  __attribute__((flatten, always_inline)) operator Ty() {
+  [[gnu::flatten, gnu::always_inline]] operator Ty() {
     return lookup(/* IsReadonly */ true, /* IdentTy */ nullptr,
                   /* ForceTeamState */ false);
   }
 
-  __attribute__((flatten, always_inline)) PtrValue &operator=(const Ty Other) {
+  [[gnu::flatten, gnu::always_inline]] PtrValue &operator=(const Ty Other) {
     set(Other);
     return *this;
   }

openmp/libomptarget/DeviceRTL/include/Synchronization.h

@@ -115,7 +115,7 @@ void threads(atomic::OrderingTy Ordering);
 /// (hence all threads in the block are "aligned"). Also perform a fence before
 /// and after the barrier according to \p Ordering. Note that the
 /// fence might be part of the barrier if the target offers this.
-__attribute__((noinline)) void threadsAligned(atomic::OrderingTy Ordering);
+[[gnu::noinline]] void threadsAligned(atomic::OrderingTy Ordering);
 
 #pragma omp end assumes
 ///}

openmp/libomptarget/DeviceRTL/include/Utils.h

@@ -83,7 +83,7 @@ template <typename DstTy, typename SrcTy> inline DstTy convertViaPun(SrcTy V) {
 }
 
 /// A  pointer variable that has by design an `undef` value. Use with care.
-__attribute__((loader_uninitialized)) static void *const UndefPtr;
+[[clang::loader_uninitialized]] static void *const UndefPtr;
 
 #define OMP_LIKELY(EXPR) __builtin_expect((bool)(EXPR), true)
 #define OMP_UNLIKELY(EXPR) __builtin_expect((bool)(EXPR), false)

openmp/libomptarget/DeviceRTL/src/Configuration.cpp

@@ -27,8 +27,9 @@ using namespace ompx;
 
 // This variable should be visibile to the plugin so we override the default
 // hidden visibility.
-DeviceEnvironmentTy CONSTANT(__omp_rtl_device_environment)
-    __attribute__((used, retain, weak, visibility("protected")));
+[[gnu::used, gnu::retain, gnu::weak,
+  gnu::visibility("protected")]] DeviceEnvironmentTy
+    CONSTANT(__omp_rtl_device_environment);
 
 uint32_t config::getDebugKind() {
   return __omp_rtl_debug_kind & __omp_rtl_device_environment.DebugKind;

openmp/libomptarget/DeviceRTL/src/Mapping.cpp

@@ -345,7 +345,7 @@ uint32_t mapping::getNumberOfProcessorElements() {
 
 // TODO: This is a workaround for initialization coming from kernels outside of
 //       the TU. We will need to solve this more correctly in the future.
-int __attribute__((weak)) SHARED(IsSPMDMode);
+[[gnu::weak]] int SHARED(IsSPMDMode);
 
 void mapping::init(bool IsSPMD) {
   if (mapping::isInitialThreadInLevel0(IsSPMD))
@@ -358,15 +358,15 @@ bool mapping::isGenericMode() { return !isSPMDMode(); }
 ///}
 
 extern "C" {
-__attribute__((noinline)) uint32_t __kmpc_get_hardware_thread_id_in_block() {
+[[gnu::noinline]] uint32_t __kmpc_get_hardware_thread_id_in_block() {
   return mapping::getThreadIdInBlock();
 }
 
-__attribute__((noinline)) uint32_t __kmpc_get_hardware_num_threads_in_block() {
+[[gnu::noinline]] uint32_t __kmpc_get_hardware_num_threads_in_block() {
   return impl::getNumberOfThreadsInBlock(mapping::DIM_X);
 }
 
-__attribute__((noinline)) uint32_t __kmpc_get_warp_size() {
+[[gnu::noinline]] uint32_t __kmpc_get_warp_size() {
   return impl::getWarpSize();
 }
 }

openmp/libomptarget/DeviceRTL/src/Parallelism.cpp

@@ -68,10 +68,9 @@ uint32_t determineNumberOfThreads(int32_t NumThreadsClause) {
 }
 
 // Invoke an outlined parallel function unwrapping arguments (up to 32).
-__attribute__((always_inline)) void invokeMicrotask(int32_t global_tid,
-                                                    int32_t bound_tid, void *fn,
-                                                    void **args,
-                                                    int64_t nargs) {
+[[clang::always_inline]] void invokeMicrotask(int32_t global_tid,
+                                              int32_t bound_tid, void *fn,
+                                              void **args, int64_t nargs) {
   switch (nargs) {
 #include "generated_microtask_cases.gen"
   default:
@@ -84,7 +83,7 @@ __attribute__((always_inline)) void invokeMicrotask(int32_t global_tid,
 
 extern "C" {
 
-__attribute__((always_inline)) void
+[[clang::always_inline]] void
 __kmpc_parallel_51(IdentTy *ident, int32_t, int32_t if_expr,
                    int32_t num_threads, int proc_bind, void *fn,
                    void *wrapper_fn, void **args, int64_t nargs) {
@@ -262,8 +261,7 @@ __kmpc_parallel_51(IdentTy *ident, int32_t, int32_t if_expr,
     __kmpc_end_sharing_variables();
 }
 
-__attribute__((noinline)) bool
-__kmpc_kernel_parallel(ParallelRegionFnTy *WorkFn) {
+[[clang::noinline]] bool __kmpc_kernel_parallel(ParallelRegionFnTy *WorkFn) {
   // Work function and arguments for L1 parallel region.
   *WorkFn = state::ParallelRegionFn;
 
@@ -277,7 +275,7 @@ __kmpc_kernel_parallel(ParallelRegionFnTy *WorkFn) {
   return ThreadIsActive;
 }
 
-__attribute__((noinline)) void __kmpc_kernel_end_parallel() {
+[[clang::noinline]] void __kmpc_kernel_end_parallel() {
   // In case we have modified an ICV for this thread before a ThreadState was
   // created. We drop it now to not contaminate the next parallel region.
   ASSERT(!mapping::isSPMDMode(), nullptr);

openmp/libomptarget/DeviceRTL/src/State.cpp

@@ -31,7 +31,7 @@ using namespace ompx;
 constexpr const uint32_t Alignment = 16;
 
 /// External symbol to access dynamic shared memory.
-extern unsigned char DynamicSharedBuffer[] __attribute__((aligned(Alignment)));
+[[gnu::aligned(Alignment)]] extern unsigned char DynamicSharedBuffer[];
 #pragma omp allocate(DynamicSharedBuffer) allocator(omp_pteam_mem_alloc)
 
 /// The kernel environment passed to the init method by the compiler.
@@ -105,10 +105,8 @@ struct SharedMemorySmartStackTy {
   }
 
   /// The actual storage, shared among all warps.
-  unsigned char Data[state::SharedScratchpadSize]
-      __attribute__((aligned(Alignment)));
-  unsigned char Usage[mapping::MaxThreadsPerTeam]
-      __attribute__((aligned(Alignment)));
+  [[gnu::aligned(Alignment)]] unsigned char Data[state::SharedScratchpadSize];
+  [[gnu::aligned(Alignment)]] unsigned char Usage[mapping::MaxThreadsPerTeam];
 };
 
 static_assert(state::SharedScratchpadSize / mapping::MaxThreadsPerTeam <= 256,
@@ -423,11 +421,11 @@ int omp_get_initial_device(void) { return -1; }
 }
 
 extern "C" {
-__attribute__((noinline)) void *__kmpc_alloc_shared(uint64_t Bytes) {
+[[clang::noinline]] void *__kmpc_alloc_shared(uint64_t Bytes) {
   return memory::allocShared(Bytes, "Frontend alloc shared");
 }
 
-__attribute__((noinline)) void __kmpc_free_shared(void *Ptr, uint64_t Bytes) {
+[[clang::noinline]] void __kmpc_free_shared(void *Ptr, uint64_t Bytes) {
   memory::freeShared(Ptr, Bytes, "Frontend free shared");
 }
 

openmp/libomptarget/DeviceRTL/src/Synchronization.cpp

@@ -523,13 +523,12 @@ void __kmpc_barrier(IdentTy *Loc, int32_t TId) {
   impl::namedBarrier();
 }
 
-__attribute__((noinline)) void __kmpc_barrier_simple_spmd(IdentTy *Loc,
-                                                          int32_t TId) {
+[[clang::noinline]] void __kmpc_barrier_simple_spmd(IdentTy *Loc, int32_t TId) {
   synchronize::threadsAligned(atomic::OrderingTy::seq_cst);
 }
 
-__attribute__((noinline)) void __kmpc_barrier_simple_generic(IdentTy *Loc,
-                                                             int32_t TId) {
+[[clang::noinline]] void __kmpc_barrier_simple_generic(IdentTy *Loc,
+                                                       int32_t TId) {
   synchronize::threads(atomic::OrderingTy::seq_cst);
 }
 

openmp/libomptarget/DeviceRTL/src/Utils.cpp

@@ -19,7 +19,7 @@
 
 using namespace ompx;
 
-extern "C" __attribute__((weak)) int IsSPMDMode;
+extern "C" [[gnu::weak]] int IsSPMDMode;
 
 namespace impl {