DPCT1108

Intel® DPC++ Compatibility Tool Developer Guide and Reference

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ID 768918

Date 3/22/2024

Version

Public

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DPCT1108

Message

<original API> was migrated with the experimental feature <feature name> which may not be supported by all compilers or runtimes. You may need to adjust the code.

Detailed Help

To support better migration, Intel® DPC++ Compatibility Tool provides the -use-experimental-features option to apply experimental features during migration. <feature name> may not be supported by all SYCL compilers or runtimes. If the target SYCL compiler and runtime does not support <feature name>, you need to adjust the code and not use <feature name>.

Suggestions to Fix

For example, this original CUDA* code:

__global__ void kernel() {
  int lane_id = threadIdx.x % 32;
  int foo = 0, result = 0;
  int mask = 0xf;
  if (lane_id == 0) {
    result = 10;
  }
  if (lane_id & mask) {
    foo = __shfl_sync(mask, result, 0);
  }
}

results in the following migrated SYCL code:

void kernel(const sycl::nd_item<3> &item_ct1) {
  int lane_id = item_ct1.get_local_id(2) % 32;
  int foo = 0, result = 0;
  int mask = 0xf;
  if (lane_id == 0) {
    result = 10;
  }
  if (lane_id & mask) {
    /*
    DPCT1108:0: '__shfl_sync' was migrated with the experimental feature masked
    sub_group function which may not be supported by all compilers or runtimes.
    You may need to adjust the code.
    */
    foo = dpct::experimental::select_from_sub_group(
        mask, item_ct1.get_sub_group(), result, 0);
  }
}

which is rewritten to:

void kernel(const sycl::nd_item<3> &item_ct1) {
  int lane_id = item_ct1.get_local_id(2) % 32;
  int foo = 0, result = 0;
  int mask = 0xf;
  if (lane_id == 0) {
    result = 10;
  }
  // If not use experimental feature masked sub-group function
  int foo_tmp = dpct::select_from_sub_group(item_ct1.get_sub_group(), result, 0);
  if (lane_id & mask) {
    foo = foo_tmp;
  }
}

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Intel® DPC++ Compatibility Tool Developer Guide and Reference

DPCT1108

Message

Detailed Help

Suggestions to Fix