[OpenMP] Remove noinline attributes in the device runtime

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.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D130368

Author: jhuber6

llvm/lib/Transforms/IPO/OpenMPOpt.cpp

@@ -499,18 +499,6 @@ struct OMPInformationCache : public InformationCache {
   }
 #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.
   }
 

llvm/test/Transforms/OpenMP/remove_noinline_attributes.ll

@@ -29,15 +29,13 @@ 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
 ///}

openmp/libomptarget/DeviceRTL/include/Synchronization.h

@@ -289,17 +289,17 @@ 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();
 }

openmp/libomptarget/DeviceRTL/src/Mapping.cpp

@@ -243,8 +243,7 @@ void __kmpc_parallel_51(IdentTy *ident, int32_t, int32_t if_expr,
     __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;
@@ -259,7 +258,7 @@ __kmpc_kernel_parallel(ParallelRegionFnTy *WorkFn) {
   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.

openmp/libomptarget/DeviceRTL/src/Parallelism.cpp

@@ -393,12 +393,12 @@ 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");
 }

openmp/libomptarget/DeviceRTL/src/State.cpp

@@ -358,14 +358,12 @@ void __kmpc_barrier(IdentTy *Loc, int32_t 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();
 }