Avoid integer overflow in volk_8ic_x2_multiply_conjugate_16ic corner case #701
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While looking for flaky tests with
ctest --repeat until-fail:<n>
, theqa_volk_8ic_x2_multiply_conjugate_16ic
test turned out to be flaky. Failures are rare, but can be induced with the following change to the test framework:The root cause is that the corner case
aVector[i] = -128-128j
,bVector[i] = -128-128j
produces an output of32768+0j
, and the real part is too large to fit in a signed 16-bit integer. The SIMD protokernels use saturation arithmetic (producing32767+0j
, while the generic protokernel (and tail processing in the other protokernels) overflows and produces-32768+0j
. To fix the problem, I've switched to saturation arithmetic everywhere, which seems more appropriate for a DSP context, and avoids Undefined Behaviour.Only the real part of the result needs to be clamped, because the imaginary part cannot overflow.