pub fn inverse_ballot(value: u64) -> bool🔬This is a nightly-only experimental API. (
stdarch_amdgpu #149988)Available on AMD GPU only.
Expand description
Indexes into the value with the current lane id and returns for each lane
if the corresponding bit is set.
While ballot converts a bool to a mask, inverse_ballot converts a mask back to a bool.
This means inverse_ballot(ballot(b)) == b.
The inverse of ballot(inverse_ballot(value)) ~= value is not always true as inactive lanes are set to zero by ballot.
This intrinsic does not behave like a normal function call; it is a “convergent” operation and as such has non-standard control-flow effects which need special treatment by the language. Rust currently does not properly support convergent operations. This operation is hence provided on a best-effort basis. Using it may result in incorrect code under some circumstances.