Division tweaks #380
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Division tweaks #380
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Rebenchmarking this showed that perf changed for the worse only on really low end CPUs
These macros and functions are only in the public interface for testing purposes or because of `#[macro_export]` pollution
bjorn3
reviewed
Oct 3, 2020
| @@ -4,6 +4,7 @@ | |||
| // Compilers will insert the check for zero in cases where it is needed. | |||
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| /// Returns the number of leading binary zeros in `x`. | |||
| #[doc(hidden)] | |||
| pub fn usize_leading_zeros_default(x: usize) -> usize { | |||
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Can this be pub(crate) instead of#[doc(hidden)]?
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It is being used by the testcrate (the CI does not have a RISCV target at the moment, so we want to make sure that they both work)
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This slims down
asymmetric.rs, removes the old style signed division macro code, and constructs signed divisions independent of thespecialized_div_remmodule. I figured out that when this is done, LLVM autoinlines just how I want it (except that the code gen for RISCV is still horrendous, I guess myleading_zeroschanges still have not made it into nightly). The fact that I don't have to manage the signed divisions in thespecialized_div_remmodule will make it much easier to convert some macros to generics later. In another PR, I will fix problems I have with the division testing code and improve the edge cases that it covers.