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Optimize integral pattern matching #65089
This reduces the number of call sites for `constructor_intersects_pattern()` from two to one, which the next commit will take advantage of.
This commit moves a lot of code around but doesn't change functionality at all. The main goal was for `from_pat()` to no longer call `from_ctor()`. The increase in inlining resulted in less function call overhead, for a 3% instruction count win on `unicode_normalization-check-clean`.
The `if let Some(val) = value.try_eval_bits(...)` branch in `from_const()` is very hot for the `unicode_normalization` benchmark. This commit introduces a special-case alternative for scalars that avoids `try_eval_bits()` and all the functions it calls (`Const::eval()`, `ConstValue::try_to_bits()`, `ConstValue::try_to_scalar()`, and `Scalar::to_bits()`), instead extracting the result immediately. The type and value checking done by `Scalar::to_bits()` is replicated by moving it into a new function `Scalar::check_raw()` and using that new function in the special case. PR #64673 introduced some special-case handling of scalar types in `Const::try_eval_bits()`. This handling is now moved out of that function into the new `IntRange::integral_size_and_signed_bias` function. This commit reduces the instruction count for `unicode_normalization-check-clean` by about 10%.
bors merged commit
Oct 6, 2019
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