BUG, SIMD: Fix 64-bit/8-bit integer division by a scalar #20153
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The multiplier factor that used for integer division wasn't correctly calculated due inaccurate implementation of the emulated version of intrinsic `_udiv128`.
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I don't think it matters, we will just delete it later. A test might be nice, but I can add it also. Thanks for taking such a quick look Sayed! |
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@seiko2plus Could you add a test for this? |
…several data ranges
Same as 64-bit divistion, except quad wide divison leads to inaccurate multiplier in certain cases when the log2 of the divisor overflow to zero.
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Thanks Sayed |
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This pull request fixes two bugs:
64-bit integer division by a scalar for both unsigned and signed division,
which was discovered by BUG: Bad SIMD integer
//on windows in numpy 1.21.2 #20025.It's only limited to old versions of msvc <= 2017, due to inaccurate
implementation of the emulated version for intrinsic
_udiv128,which leads to producing an inaccurate multiplier.
8-bit unsigned integer division, similar to the above except it is not limited to a certain compiler
and the inaccurate multiplier was caused due to wrong casting leads to perform quad division.
it can be triggered if the ceil(log2(divisor)) == 8.
closes #20025, #20168