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[SYCL] Return nullptr when allocation size is zero in usm allocator #12765

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merged 4 commits into from
Feb 21, 2024
Merged

[SYCL] Return nullptr when allocation size is zero in usm allocator #12765

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1b14c69
Return nullptr when allocation size is zero
uditagarwal97 Feb 20, 2024
454156b
Added test case
uditagarwal97 Feb 20, 2024
2145b66
Fix test case
uditagarwal97 Feb 20, 2024
7f1e0d3
Address reviews
uditagarwal97 Feb 21, 2024
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3 changes: 3 additions & 0 deletions sycl/include/sycl/usm/usm_allocator.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,9 @@ class usm_allocator {
T *allocate(size_t NumberOfElements, const detail::code_location CodeLoc =
detail::code_location::current()) {

if (!NumberOfElements)
return nullptr;

auto Result = reinterpret_cast<T *>(
aligned_alloc(getAlignment(), NumberOfElements * sizeof(value_type),
MDevice, MContext, AllocKind, MPropList, CodeLoc));
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31 changes: 31 additions & 0 deletions sycl/test-e2e/USM/usm_allocator_zero_allocation.cpp
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@@ -0,0 +1,31 @@
// RUN: %{build} -o %t.out
// RUN: %{run} %t.out

#include <sycl/sycl.hpp>

using namespace sycl;

template <usm::alloc alloc_kind> void test(queue &q) {
sycl::usm_allocator<int, alloc_kind> ua(q);
int *p = ua.allocate(0);

assert(!p && "Our implementation of usm_allocator is expected to return a "
"null pointer when allocation "
"size is zero.");
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I think this is fine, but another option is to simply remove the assert. From an API perspective, the important thing is that you can call allocate with a zero size and that you can then call deallocate on the returned pointer, all without any exception being raised. It's not important whether or not the returned pointer is null.

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ua.deallocate(p, 0);
}

int main() {
queue q;
auto dev = q.get_device();

if (dev.get_info<info::device::usm_host_allocations>()) {
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Why do we only test "host" here?

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I'm not sure how adding more allocation types will increase the test coverage of this change. Nevertheless, I've expanded the test to also check for zero-sized shared allocations. usm::alloc::device is not supported by usm_allocator so, I've skipped that.

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test<usm::alloc::host>(q);
}
if (dev.get_info<info::device::usm_shared_allocations>()) {
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test<usm::alloc::shared>(q);
}

return 0;
}
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