[OpenMP] Utilize the "non-uniform-workgroup" to simplify DeviceRTL

OpenMP offloading always uses uniform workgroups, see
https://reviews.llvm.org/D135374. The runtime doesn't need to handle
non-uniform workgroups at all either.

Differential Revision: https://reviews.llvm.org/D135444

Author: jdoerfert

openmp/libomptarget/DeviceRTL/src/Mapping.cpp

@@ -26,9 +26,6 @@ namespace impl {
 
 // Forward declarations defined to be defined for AMDGCN and NVPTX.
 const llvm::omp::GV &getGridValue();
-uint32_t getGridDim(uint32_t n, uint16_t d);
-uint32_t getWorkgroupDim(uint32_t group_id, uint32_t grid_size,
-                         uint16_t group_size);
 uint32_t getNumHardwareThreadsInBlock();
 LaneMaskTy activemask();
 LaneMaskTy lanemaskLT();
@@ -50,21 +47,8 @@ const llvm::omp::GV &getGridValue() {
   return llvm::omp::getAMDGPUGridValues<__AMDGCN_WAVEFRONT_SIZE>();
 }
 
-uint32_t getGridDim(uint32_t n, uint16_t d) {
-  uint32_t q = n / d;
-  return q + (n > q * d);
-}
-
-uint32_t getWorkgroupDim(uint32_t group_id, uint32_t grid_size,
-                         uint16_t group_size) {
-  uint32_t r = grid_size - group_id * group_size;
-  return (r < group_size) ? r : group_size;
-}
-
 uint32_t getNumHardwareThreadsInBlock() {
-  return getWorkgroupDim(__builtin_amdgcn_workgroup_id_x(),
-                         __builtin_amdgcn_grid_size_x(),
-                         __builtin_amdgcn_workgroup_size_x());
+  return __builtin_amdgcn_workgroup_size_x();
 }
 
 LaneMaskTy activemask() { return __builtin_amdgcn_read_exec(); }
@@ -95,10 +79,7 @@ uint32_t getKernelSize() { return __builtin_amdgcn_grid_size_x(); }
 
 uint32_t getBlockId() { return __builtin_amdgcn_workgroup_id_x(); }
 
-uint32_t getNumberOfBlocks() {
-  return getGridDim(__builtin_amdgcn_grid_size_x(),
-                    __builtin_amdgcn_workgroup_size_x());
-}
+uint32_t getNumberOfBlocks() { return __builtin_amdgcn_grid_size_x(); }
 
 uint32_t getWarpId() {
   return impl::getThreadIdInBlock() / mapping::getWarpSize();
@@ -228,8 +209,8 @@ uint32_t mapping::getThreadIdInBlock() {
 uint32_t mapping::getWarpSize() { return impl::getWarpSize(); }
 
 uint32_t mapping::getBlockSize(bool IsSPMD) {
-  uint32_t BlockSize = mapping::getNumberOfProcessorElements() -
-                       (!IsSPMD * impl::getWarpSize());
+  uint32_t BlockSize =
+      mapping::getNumberOfProcessorElements() - (!IsSPMD * impl::getWarpSize());
   return BlockSize;
 }
 uint32_t mapping::getBlockSize() {