[SYCL][libdevice] return qNaN for (float/double)sNaN to bfloat16 conversion - #23084
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[SYCL][libdevice] return qNaN for (float/double)sNaN to bfloat16 conversion#23084Maetveis wants to merge 1 commit into
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…ersion intel#22114 introduced a fix to return NaN for some specific float or double sNaN bit patterns when converting to bfloat16. Together with that change it also changed the behavior and added a test specifically for the case of converting sNaN to bfloat16. The new behaviour in that PR is to return sNaN for all sNaN inputs. This is not the correct behaviour, IEEE 754 specifies conversions should signal and then return a quiet NaN. We do not implement raising exceptions in the device library, so we cannot signal, but we should still return a quiet NaN for all sNaN inputs. The new behaviour matches the host conversion (from glibc/compiler-rt), see this example on compiler explorer: https://godbolt.org/z/E7ezaPxEd (assisted by Claude Opus 5 <noreply@anthropic.com>).
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#22114 introduced a fix to return NaN for some specific float or double sNaN bit patterns when converting to bfloat16.
Together with that change it also changed the behavior and added a test specifically for the case of converting sNaN to bfloat16. The new behaviour in that PR is to return sNaN for all sNaN inputs.
This is not the correct behaviour, IEEE 754 specifies conversions should signal and then return a quiet NaN. We do not implement raising exceptions in the device library, so we cannot signal, but we should still return a quiet NaN for all sNaN inputs.
The new behaviour matches the host conversion (from glibc/compiler-rt), see this example on compiler explorer: https://godbolt.org/z/E7ezaPxEd (assisted by Claude Opus 5 noreply@anthropic.com).