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67683048be
Our implementation of the indexed version of SVE SDOT/UDOT/USDOT got the calculation of the inner loop terminator wrong. Although we correctly account for the element size when we calculate the terminator for the first iteration: intptr_t segend = MIN(16 / sizeof(TYPED), opr_sz_n); we don't do that when we move it forward after the first inner loop completes. The intention is that we process the vector in 128-bit segments, which for a 64-bit element size should mean (1, 2), (3, 4), (5, 6), etc. This bug meant that we would iterate (1, 2), (3, 4, 5, 6), (7, 8, 9, 10) etc and apply the wrong indexed element to some of the operations, and also index off the end of the vector. You don't see this bug if the vector length is small enough that we don't need to iterate the outer loop, i.e. if it is only 128 bits, or if it is the 64-bit special case from AA32/AA64 AdvSIMD. If the vector length is 256 bits then we calculate the right results for the elements in the vector but do index off the end of the vector. Vector lengths greater than 256 bits see wrong answers. The instructions that produce 32-bit results behave correctly. Fix the recalculation of 'segend' for subsequent iterations, and restore a version of the comment that was lost in the refactor of commit |
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