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Optimize integral pattern matching #65089

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merged 5 commits into from
Oct 6, 2019
Merged

Optimize integral pattern matching #65089

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9a1a3b9
Combine two `match` arms in `specialize()`.
nnethercote Oct 4, 2019
62ea39a
Inline and remove `constructor_intersects_pattern()`.
nnethercote Oct 4, 2019
a69e0e0
Rearrange `IntRange::from_{ctor,pat}()`.
nnethercote Oct 4, 2019
5515a97
Introduce a special case in `IntRange::from_const`.
nnethercote Oct 4, 2019
2a3a544
Replace `flat_map()` with `filter_map()` in `is_useful_specialized()`.
nnethercote Oct 4, 2019
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11 changes: 8 additions & 3 deletions src/librustc/mir/interpret/value.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -343,14 +343,19 @@ impl<'tcx, Tag> Scalar<Tag> {
}
}

#[inline(always)]
pub fn check_raw(data: u128, size: u8, target_size: Size) {
assert_eq!(target_size.bytes(), size as u64);
assert_ne!(size, 0, "you should never look at the bits of a ZST");
Scalar::check_data(data, size);
}

/// Do not call this method! Use either `assert_bits` or `force_bits`.
#[inline]
pub fn to_bits(self, target_size: Size) -> InterpResult<'tcx, u128> {
match self {
Scalar::Raw { data, size } => {
assert_eq!(target_size.bytes(), size as u64);
assert_ne!(size, 0, "you should never look at the bits of a ZST");
Scalar::check_data(data, size);
Self::check_raw(data, size, target_size);
Ok(data)
}
Scalar::Ptr(_) => throw_unsup!(ReadPointerAsBytes),
Expand Down
18 changes: 2 additions & 16 deletions src/librustc/ty/sty.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ use rustc_macros::HashStable;
use crate::ty::subst::{InternalSubsts, Subst, SubstsRef, GenericArg, GenericArgKind};
use crate::ty::{self, AdtDef, Discr, DefIdTree, TypeFlags, Ty, TyCtxt, TypeFoldable};
use crate::ty::{List, TyS, ParamEnvAnd, ParamEnv};
use crate::ty::layout::{Size, Integer, IntegerExt, VariantIdx};
use crate::ty::layout::VariantIdx;
use crate::util::captures::Captures;
use crate::mir::interpret::{Scalar, GlobalId};

Expand All @@ -24,7 +24,6 @@ use std::marker::PhantomData;
use std::ops::Range;
use rustc_target::spec::abi;
use syntax::ast::{self, Ident};
use syntax::attr::{SignedInt, UnsignedInt};
use syntax::symbol::{kw, InternedString};

use self::InferTy::*;
Expand Down Expand Up @@ -2299,20 +2298,7 @@ impl<'tcx> Const<'tcx> {
ty: Ty<'tcx>,
) -> Option<u128> {
assert_eq!(self.ty, ty);
// This is purely an optimization -- layout_of is a pretty expensive operation,
// but if we can determine the size without calling it, we don't need all that complexity
// (hashing, caching, etc.). As such, try to skip it.
let size = match ty.kind {
ty::Bool => Size::from_bytes(1),
ty::Char => Size::from_bytes(4),
ty::Int(ity) => {
Integer::from_attr(&tcx, SignedInt(ity)).size()
}
ty::Uint(uty) => {
Integer::from_attr(&tcx, UnsignedInt(uty)).size()
}
_ => tcx.layout_of(param_env.with_reveal_all().and(ty)).ok()?.size,
};
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@RalfJung RalfJung Oct 12, 2019 •
edited
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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

let size = tcx.layout_of(param_env.with_reveal_all().and(ty)).ok()?.size;
// if `ty` does not depend on generic parameters, use an empty param_env
self.eval(tcx, param_env).val.try_to_bits(size)
}
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