DPCT1089

Intel® DPC++ Compatibility Tool Developer Guide and Reference

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ID 768918

Date 12/16/2022

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Public

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DPCT1089

Message

The value of the sub-group size attribute argument <argument name> cannot be evaluated by the Intel(R) DPC++ Compatibility Tool. Replace "dpct_placeholder" with an integral constant expression.

Detailed Help

The argument to the attribute must be an integral constant expression. This warning is emitted when the Intel® DPC++ Compatibility Tool cannot evaluate the value of the sub-group size argument as an integral constant expression. Check if the sub-group size attribute argument can be replaced by an integral constant expression, and if not, redesign the code logic.

For example, this original code:

// original code

_global_ void kernel(int WarpSize) {   int Input, Output, Lane;   ...   Output = __shfl(Input, Lane, WarpSize); }
...
if(condition)
{   kernel<<<GirdSize, BlockSize>>>(16); }
else
{   kernel<<<GirdSize, BlockSize>>>(32); }

results in the following migrated DPC++ code:

// migrated DPC++ code

void kernel(int WarpSize, sycl::nd_item<3> item_ct1)
{   int Input, Output, Lane;   ...   Output = Item_ct1.get_sub_group().shuffle(Input, Lane); }
...
if(condition) {
/* DPCT1089 */
q_ct1.parallel_for(
    sycl::nd_range<3>(GridSize * BlockSize, BlockSize),
    [=](sycl::nd_item<3> item_ct1) [[intel::reqd_sub_group_size(dpct_placeholder)]] {       kernel(16, item_ct1); });
} else {
/* DPCT1089 */
q_ct1.parallel_for(
    sycl::nd_range<3>(GridSize * BlockSize, BlockSize),
    [=](sycl::nd_item<3> item_ct1) [[intel::reqd_sub_group_size(dpct_placeholder)]] {       kernel(32, item_ct1); }

which is manually adjusted to:

// fixed DPC++ code

void kernel(int WarpSize, sycl::nd_item<3> item_ct1) {   int Input, Output, Lane;   ...   Output = Item_ct1.get_sub_group().shuffle(Input, Lane); }
...
if(condition) {
/* DPCT1089 */
q_ct1.parallel_for(
    sycl::nd_range<3>(GridSize * BlockSize, BlockSize),
    [=](sycl::nd_item<3> item_ct1) [[intel::reqd_sub_group_size(16)]]
{       kernel(16, item_ct1); }
);
} else {
/* DPCT1089 */
q_ct1.parallel_for(
    sycl::nd_range<3>(GridSize * BlockSize, BlockSize),
    [=](sycl::nd_item<3> item_ct1) [[intel::reqd_sub_group_size(32)]]
{       kernel(32, item_ct1); }

Suggestions to Fix

Code requires manual fix. Replace “dpct_placeholder” with an integral constant expression.

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Intel® DPC++ Compatibility Tool Developer Guide and Reference

DPCT1089

Message

Detailed Help

Suggestions to Fix