Optimize integral pattern matching #65089
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This reduces the number of call sites for `constructor_intersects_pattern()` from two to one, which the next commit will take advantage of.
This is a 2% instruction count win on `unicode_normalization-check-clean`.
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 rust-lang#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%.
`filter_map()` is less general, but more efficient, and has the same effect in this case. This commit reduces the instruction count for `unicode_normalization-check-clean` by about 2%.
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fbstj
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Oct 4, 2019
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Changes look good to me; they're all just shuffling code around so we can probably land this without additional review, but cc @oli-obk
oli-obk
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Oct 4, 2019
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r? @varkor |
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oops; r? @Mark-Simulacrum but cc @varkor :) |
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@bors r+ rollup=never since perf |
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📌 Commit 2a3a544 has been approved by |
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Oct 6, 2019
…, r=Mark-Simulacrum Optimize integral pattern matching Various improvements to integral pattern matching. Together they reduce instruction counts for `unicode_normalization-check-clean` by about 16%. r? @Mark-Simulacrum
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☀️ Test successful - checks-azure |
RalfJung
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Oct 12, 2019
| Integer::from_attr(&tcx, UnsignedInt(uty)).size() | ||
| } | ||
| _ => tcx.layout_of(param_env.with_reveal_all().and(ty)).ok()?.size, | ||
| }; |
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A quick grep shows a few more sites that call layout_of just to get the size or alignment (and there's likely more but split across multiple lines). So it might still be worth having size_and_align_of(Ty<'tcx>) somewhere with an optimization like this -- maybe?
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yea, this could just be a method on TyCtxt
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Oct 18, 2019
This reverses changes from rust-lang#65089, but I need this temporarily for rebase to be tractable.
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Various improvements to integral pattern matching. Together they reduce instruction counts for
unicode_normalization-check-cleanby about 16%.r? @Mark-Simulacrum