[OpenMP] Remove noinline attributes in the device runtime

[jhuber6]

Summary

We previously used the noinline attributes to specify some defintions
which should be kept alive in the runtime. These were then stripped
immediately in the OpenMPOpt module pass. However, Since the changes in
D130298, we not explicitly state which functions will have external
visiblity in the bitcode library. Additionally the OpenMPOpt module pass
should run before the inliner pass, so this shouldn't make a difference
in whether or not the functions will be alive for the initial pass of
OpenMPOpt. This should simplify the interface, and additionally save
time spend on scanning funciton names for noinline.

[jdoerfert]

Assuming this works properly now, LGTM.

llvm/lib/Transforms/IPO/OpenMPOpt.cpp

if (declMatchesRTFTypes(F, OMPBuilder._ReturnType, ArgsTypes)) {           \
           dbgs() << TAG << "-> got " << NumUses << " uses in "                 \
                  << RFI.getNumFunctionsWithUses()                              \
                  << " different functions.\n";                                 \
       });                                                                      \
     }                                                                          \
   }
 #include "llvm/Frontend/OpenMP/OMPKinds.def"
 
-    // Remove the `noinline` attribute from `__kmpc`, `_OMP::` and `omp_`
-    // functions, except if `optnone` is present.
-    if (isOpenMPDevice(M)) {
-      for (Function &F : M) {
-        for (StringRef Prefix : {"__kmpc", "_ZN4_OMP", "omp_"})
-          if (F.hasFnAttribute(Attribute::NoInline) &&
-              F.getName().startswith(Prefix) &&
-              !F.hasFnAttribute(Attribute::OptimizeNone))
-            F.removeFnAttr(Attribute::NoInline);
-      }
-    }
-
     // TODO: We should attach the attributes defined in OMPKinds.def.
   }
 
   /// Collection of known kernels (\see Kernel) in the module.
   KernelSet &Kernels;
 
   /// Collection of known OpenMP runtime functions..
   DenseSet<const Function *> RTLFunctions;

llvm/test/Transforms/OpenMP/remove_noinline_attributes.ll

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-attributes
-; RUN: opt < %s -S -openmp-opt-cgscc        | FileCheck %s
-; RUN: opt < %s -S -passes=openmp-opt-cgscc | FileCheck %s
-
-declare void @unknown()
-
-; __kmpc functions
-define void @__kmpc_noinline() noinline nounwind {
-; CHECK: Function Attrs: nounwind
-; CHECK-LABEL: @__kmpc_noinline(
-; CHECK-NEXT:    call void @unknown()
-; CHECK-NEXT:    ret void
-;
-  call void @unknown()
-  ret void
-}
-; omp_X functions
-define void @omp_noinline() noinline nounwind {
-; CHECK: Function Attrs: nounwind
-; CHECK-LABEL: @omp_noinline(
-; CHECK-NEXT:    call void @unknown()
-; CHECK-NEXT:    ret void
-;
-  call void @unknown()
-  ret void
-}
-; _OMP namespace
-define void @_ZN4_OMP_noinline() noinline nounwind {
-; CHECK: Function Attrs: nounwind
-; CHECK-LABEL: @_ZN4_OMP_noinline(
-; CHECK-NEXT:    call void @unknown()
-; CHECK-NEXT:    ret void
-;
-  call void @unknown()
-  ret void
-}
-
-; Negative tests:
-
-define void @__kmpc_noinline_optnone() noinline optnone nounwind {
-; CHECK: Function Attrs: noinline nounwind optnone
-; CHECK-LABEL: @__kmpc_noinline_optnone(
-; CHECK-NEXT:    call void @unknown()
-; CHECK-NEXT:    ret void
-;
-  call void @unknown()
-  ret void
-}
-define void @omp_noinline_optnone() noinline optnone nounwind {
-; CHECK: Function Attrs: noinline nounwind optnone
-; CHECK-LABEL: @omp_noinline_optnone(
-; CHECK-NEXT:    call void @unknown()
-; CHECK-NEXT:    ret void
-;
-  call void @unknown()
-  ret void
-}
-; _OMP namespace
-define void @_ZN4_OMP_noinline_optnone() noinline optnone nounwind {
-; CHECK: Function Attrs: noinline nounwind optnone
-; CHECK-LABEL: @_ZN4_OMP_noinline_optnone(
-; CHECK-NEXT:    call void @unknown()
-; CHECK-NEXT:    ret void
-;
-  call void @unknown()
-  ret void
-}
-define void @a___kmpc_noinline() noinline nounwind {
-; CHECK: Function Attrs: noinline nounwind
-; CHECK-LABEL: @a___kmpc_noinline(
-; CHECK-NEXT:    call void @unknown()
-; CHECK-NEXT:    ret void
-;
-  call void @unknown()
-  ret void
-}
-define void @a_omp_noinline() noinline nounwind {
-; CHECK: Function Attrs: noinline nounwind
-; CHECK-LABEL: @a_omp_noinline(
-; CHECK-NEXT:    call void @unknown()
-; CHECK-NEXT:    ret void
-;
-  call void @unknown()
-  ret void
-}
-define void @a__ZN4_OMP_noinline() noinline nounwind {
-; CHECK: Function Attrs: noinline nounwind
-; CHECK-LABEL: @a__ZN4_OMP_noinline(
-; CHECK-NEXT:    call void @unknown()
-; CHECK-NEXT:    ret void
-;
-  call void @unknown()
-  ret void
-}
-
-!llvm.module.flags = !{!0, !1}
-
-!0 = !{i32 7, !"openmp", i32 50}
-!1 = !{i32 7, !"openmp-device", i32 50}

openmp/libomptarget/DeviceRTL/include/Synchronization.h

 /// Synchronize all threads in a warp identified by \p Mask.
 void warp(LaneMaskTy Mask);
 
 /// Synchronize all threads in a block.
 void threads();
 
 /// Synchronizing threads is allowed even if they all hit different instances of
 /// `synchronize::threads()`. However, `synchronize::threadsAligned()` is more
-/// restrictive in that it requires all threads to hit the same instance. The
-/// noinline is removed by the openmp-opt pass and helps to preserve the
-/// information till then.
+/// restrictive in that it requires all threads to hit the same instance.
 ///{
 #pragma omp begin assumes ext_aligned_barrier
 
 /// Synchronize all threads in a block, they are are reaching the same
 /// instruction (hence all threads in the block are "aligned").
-__attribute__((noinline)) void threadsAligned();
+void threadsAligned();
 
 #pragma omp end assumes
 ///}
 
 } // namespace synchronize
 
 namespace fence {
 

openmp/libomptarget/DeviceRTL/src/Mapping.cpp

 }
 
 bool mapping::isSPMDMode() { return IsSPMDMode; }
 
 bool mapping::isGenericMode() { return !isSPMDMode(); }
 ///}
 
 extern "C" {
-__attribute__((noinline)) uint32_t __kmpc_get_hardware_thread_id_in_block() {
+uint32_t __kmpc_get_hardware_thread_id_in_block() {
   FunctionTracingRAII();
   return mapping::getThreadIdInBlock();
 }
 
-__attribute__((noinline)) uint32_t __kmpc_get_hardware_num_threads_in_block() {
+uint32_t __kmpc_get_hardware_num_threads_in_block() {
   FunctionTracingRAII();
   return impl::getNumHardwareThreadsInBlock();
 }
 
-__attribute__((noinline)) uint32_t __kmpc_get_warp_size() {
+uint32_t __kmpc_get_warp_size() {
   FunctionTracingRAII();
   return impl::getWarpSize();
 }
 }
 #pragma omp end declare target

openmp/libomptarget/DeviceRTL/src/Parallelism.cpp

if (nargs) {
     // Master waits for workers to signal.
     synchronize::threads();
   }
 
   if (nargs)
     __kmpc_end_sharing_variables();
 }
 
-__attribute__((noinline)) bool
-__kmpc_kernel_parallel(ParallelRegionFnTy *WorkFn) {
+bool __kmpc_kernel_parallel(ParallelRegionFnTy *WorkFn) {
   FunctionTracingRAII();
   // Work function and arguments for L1 parallel region.
   *WorkFn = state::ParallelRegionFn;
 
   // If this is the termination signal from the master, quit early.
   if (!*WorkFn)
     return false;
 
   // Set to true for workers participating in the parallel region.
   uint32_t TId = mapping::getThreadIdInBlock();
   bool ThreadIsActive = TId < state::ParallelTeamSize;
   return ThreadIsActive;
 }
 
-__attribute__((noinline)) void __kmpc_kernel_end_parallel() {
+void __kmpc_kernel_end_parallel() {
   FunctionTracingRAII();
   // 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());
   uint32_t TId = mapping::getThreadIdInBlock();
   state::resetStateForThread(TId);
   ASSERT(!mapping::isSPMDMode());
 }

openmp/libomptarget/DeviceRTL/src/State.cpp

 int omp_get_num_teams(void) { return mapping::getNumberOfBlocks(); }
 
 int omp_get_team_num() { return mapping::getBlockId(); }
 
 int omp_get_initial_device(void) { return -1; }
 }
 
 extern "C" {
-__attribute__((noinline)) void *__kmpc_alloc_shared(uint64_t Bytes) {
+void *__kmpc_alloc_shared(uint64_t Bytes) {
   FunctionTracingRAII();
   return memory::allocShared(Bytes, "Frontend alloc shared");
 }
 
-__attribute__((noinline)) void __kmpc_free_shared(void *Ptr, uint64_t Bytes) {
+void __kmpc_free_shared(void *Ptr, uint64_t Bytes) {
   FunctionTracingRAII();
   memory::freeShared(Ptr, Bytes, "Frontend free shared");
 }
 
 void *__kmpc_get_dynamic_shared() { return memory::getDynamicBuffer(); }
 
 void *llvm_omp_target_dynamic_shared_alloc() {
   return __kmpc_get_dynamic_shared();

openmp/libomptarget/DeviceRTL/src/Synchronization.cpp

if (mapping::isMainThreadInGenericMode())
     return __kmpc_flush(Loc);
 
   if (mapping::isSPMDMode())
     return __kmpc_barrier_simple_spmd(Loc, TId);
 
   impl::namedBarrier();
 }
 
-__attribute__((noinline)) void __kmpc_barrier_simple_spmd(IdentTy *Loc,
-                                                          int32_t TId) {
+void __kmpc_barrier_simple_spmd(IdentTy *Loc, int32_t TId) {
   FunctionTracingRAII();
   synchronize::threadsAligned();
 }
 
-__attribute__((noinline)) void __kmpc_barrier_simple_generic(IdentTy *Loc,
-                                                             int32_t TId) {
+void __kmpc_barrier_simple_generic(IdentTy *Loc, int32_t TId) {
   FunctionTracingRAII();
   synchronize::threads();
 }
 
 int32_t __kmpc_master(IdentTy *Loc, int32_t TId) {
   FunctionTracingRAII();
   return omp_get_team_num() == 0;
 }