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[SYCL] float atomic_ref performance fix #2714

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Merged
merged 3 commits into from
Nov 6, 2020
Merged

[SYCL] float atomic_ref performance fix #2714

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[SYCL] float atomic_ref performance fix
cperkinsintel Oct 31, 2020
82fc74b
changes requested by reviewers. Performance improvement measured ove…
cperkinsintel Nov 3, 2020
1a40779
updated comment
cperkinsintel Nov 4, 2020
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7 changes: 5 additions & 2 deletions sycl/include/CL/sycl/ONEAPI/atomic_ref.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -454,9 +454,11 @@ class atomic_ref_impl<
T fetch_add(T operand, memory_order order = default_read_modify_write_order,
memory_scope scope = default_scope) const noexcept {
auto load_order = detail::getLoadOrder(order);
T expected = load(load_order, scope);
T expected;
T desired;
do {
expected =
load(load_order, scope); // performs better with load in CAS loop.
desired = expected + operand;
} while (!compare_exchange_weak(expected, desired, order, scope));
return expected;
Expand Down Expand Up @@ -563,9 +565,10 @@ class atomic_ref_impl<T *, DefaultOrder, DefaultScope, AddressSpace>
memory_scope scope = default_scope) const noexcept {
// TODO: Find a way to avoid compare_exchange here
auto load_order = detail::getLoadOrder(order);
T *expected = load(load_order, scope);
T *expected;
T *desired;
do {
expected = load(load_order, scope);
desired = expected + operand;
} while (!compare_exchange_weak(expected, desired, order, scope));
return expected;
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3 changes: 1 addition & 2 deletions sycl/include/CL/sycl/atomic.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -237,8 +237,7 @@ class atomic {
Ptr);
cl_int TmpVal = __spirv_AtomicLoad(
TmpPtr, SpirvScope, detail::getSPIRVMemorySemanticsMask(Order));
cl_float ResVal;
detail::memcpy(&ResVal, &TmpVal, sizeof(TmpVal));
cl_float ResVal = detail::bit_cast<cl_float>(TmpVal);
return ResVal;
}
#else
Expand Down