False positive on cpp:S1238

[IRC (Ian R. Campbell)]

• Operating system: Win 10-64
• IDE name and flavor/env: VS 2022 17.7.0
• Version: 7.0.0.74072

And a thorough description of the problem / question:

Consider the following method:

inline __m256 __vectorcall Poly2Y_8f(const __m256 x, const __m256 a, const __m256 b, const __m256 c) noexcept(true)
{
return mm256_fmadd_ps(
mm256_fmadd_ps(a, x, b),
x,
c);
}

cpp:S1238 suggests that the arguments be passed by reference. However, these are passed by registers and should not be passed by reference.

[pdschbrt (Philipp Dominik Schubert)]

Hi Ian,

Thanks for reporting this false positive. Passing “large” values by reference (to const) indeed does not hold for these wide registers.

I created a ticket to exempt these special types from this rule. Feel free to track progress at [CPP-4607] - Jira.

Best,
Philipp