Introduce a special case in `IntRange::from_const`.

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%.

0 files changed, 0 insertions, 0 deletions