MAINT: restore auto-vectorization of inplace operations #8852
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juliantaylor
commented
Mar 27, 2017
| * unfortunately gcc 6/7 regressed and we need to give it additional hints to | ||
| * vectorize inplace operations (PR80198) | ||
| * must only be used after op1 == ip1 or ip2 has been checked | ||
| * TODO: using ivdep might allow other compilers to vectorize too |
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if someone cares about other compilers, you can likely use this type of pragma there too. Last I checked clang could not vectorize this code, with the pragma it might be able to but it needs testing.
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GCC 6/7 lost the ability to vectorize inplace operations with our current hinting. This causes inplace operations to become slower than out of place operations which is bad, especially as we automatically avoid temporaries now. This issue has been filed in GCC PR80198. Luckily gcc also has a no loop dependence pragma which we can use to enforce the vectorization in the inplace code path. In the inplace scalar path an extra code hint is sufficient.
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Thanks Julian. |
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GCC 6/7 lost the ability to vectorize inplace operations with our
current hinting. This causes inplace operations to become slower than
out of place operations which is bad, especially as we automatically
avoid temporaries now.
This issue has been filed in GCC PR80198.
Luckily gcc also has a no loop dependence pragma which we can use to
enforce the vectorization in the inplace code path.
In the inplace scalar path an extra code hint is sufficient.