diff options
| -rw-r--r-- | src/librustc_middle/lib.rs | 1 | ||||
| -rw-r--r-- | src/librustc_middle/ty/layout.rs | 26 | ||||
| -rw-r--r-- | src/test/ui/print_type_sizes/niche-filling.stdout | 6 | ||||
| -rw-r--r-- | src/test/ui/type-sizes.rs | 25 |
4 files changed, 7 insertions, 51 deletions
diff --git a/src/librustc_middle/lib.rs b/src/librustc_middle/lib.rs index a68301385b7..b7dccb8d8ce 100644 --- a/src/librustc_middle/lib.rs +++ b/src/librustc_middle/lib.rs @@ -27,7 +27,6 @@ #![feature(bool_to_option)] #![feature(box_patterns)] #![feature(box_syntax)] -#![feature(cmp_min_max_by)] #![feature(const_fn)] #![feature(const_panic)] #![feature(const_fn_transmute)] diff --git a/src/librustc_middle/ty/layout.rs b/src/librustc_middle/ty/layout.rs index dc775b15927..215f44819b5 100644 --- a/src/librustc_middle/ty/layout.rs +++ b/src/librustc_middle/ty/layout.rs @@ -876,8 +876,6 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> { .iter_enumerated() .all(|(i, v)| v.discr == ty::VariantDiscr::Relative(i.as_u32())); - let mut niche_filling_layout = None; - // Niche-filling enum optimization. if !def.repr.inhibit_enum_layout_opt() && no_explicit_discriminants { let mut dataful_variant = None; @@ -974,7 +972,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> { let largest_niche = Niche::from_scalar(dl, offset, niche_scalar.clone()); - niche_filling_layout = Some(Layout { + return Ok(tcx.intern_layout(Layout { variants: Variants::Multiple { tag: niche_scalar, tag_encoding: TagEncoding::Niche { @@ -993,7 +991,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> { largest_niche, size, align, - }); + })); } } } @@ -1216,7 +1214,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> { let largest_niche = Niche::from_scalar(dl, Size::ZERO, tag.clone()); - let tagged_layout = Layout { + tcx.intern_layout(Layout { variants: Variants::Multiple { tag, tag_encoding: TagEncoding::Direct, @@ -1231,23 +1229,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> { abi, align, size, - }; - - let best_layout = match (tagged_layout, niche_filling_layout) { - (tagged_layout, Some(niche_filling_layout)) => { - // Pick the smaller layout; otherwise, - // pick the layout with the larger niche; otherwise, - // pick tagged as it has simpler codegen. - cmp::min_by_key(tagged_layout, niche_filling_layout, |layout| { - let niche_size = - layout.largest_niche.as_ref().map_or(0, |n| n.available(dl)); - (layout.size, cmp::Reverse(niche_size)) - }) - } - (tagged_layout, None) => tagged_layout, - }; - - tcx.intern_layout(best_layout) + }) } // Types with no meaningful known layout. diff --git a/src/test/ui/print_type_sizes/niche-filling.stdout b/src/test/ui/print_type_sizes/niche-filling.stdout index 1894cd218ee..301edc0d086 100644 --- a/src/test/ui/print_type_sizes/niche-filling.stdout +++ b/src/test/ui/print_type_sizes/niche-filling.stdout @@ -8,12 +8,12 @@ print-type-size variant `Some`: 12 bytes print-type-size field `.0`: 12 bytes print-type-size variant `None`: 0 bytes print-type-size type: `EmbeddedDiscr`: 8 bytes, alignment: 4 bytes -print-type-size discriminant: 1 bytes print-type-size variant `Record`: 7 bytes -print-type-size field `.pre`: 1 bytes -print-type-size field `.post`: 2 bytes print-type-size field `.val`: 4 bytes +print-type-size field `.post`: 2 bytes +print-type-size field `.pre`: 1 bytes print-type-size variant `None`: 0 bytes +print-type-size end padding: 1 bytes print-type-size type: `MyOption<Union1<std::num::NonZeroU32>>`: 8 bytes, alignment: 4 bytes print-type-size discriminant: 4 bytes print-type-size variant `Some`: 4 bytes diff --git a/src/test/ui/type-sizes.rs b/src/test/ui/type-sizes.rs index 73a11a5e743..6a3f3c98f12 100644 --- a/src/test/ui/type-sizes.rs +++ b/src/test/ui/type-sizes.rs @@ -5,7 +5,6 @@ #![feature(never_type)] use std::mem::size_of; -use std::num::NonZeroU8; struct t {a: u8, b: i8} struct u {a: u8, b: i8, c: u8} @@ -103,23 +102,6 @@ enum Option2<A, B> { None } -// Two layouts are considered for `CanBeNicheFilledButShouldnt`: -// Niche-filling: -// { u32 (4 bytes), NonZeroU8 + tag in niche (1 byte), padding (3 bytes) } -// Tagged: -// { tag (1 byte), NonZeroU8 (1 byte), padding (2 bytes), u32 (4 bytes) } -// Both are the same size (due to padding), -// but the tagged layout is better as the tag creates a niche with 254 invalid values, -// allowing types like `Option<Option<CanBeNicheFilledButShouldnt>>` to fit into 8 bytes. -pub enum CanBeNicheFilledButShouldnt { - A(NonZeroU8, u32), - B -} -pub enum AlwaysTaggedBecauseItHasNoNiche { - A(u8, u32), - B -} - pub fn main() { assert_eq!(size_of::<u8>(), 1 as usize); assert_eq!(size_of::<u32>(), 4 as usize); @@ -163,11 +145,4 @@ pub fn main() { assert_eq!(size_of::<Option<Option<(&(), bool)>>>(), size_of::<(bool, &())>()); assert_eq!(size_of::<Option<Option2<bool, &()>>>(), size_of::<(bool, &())>()); assert_eq!(size_of::<Option<Option2<&(), bool>>>(), size_of::<(bool, &())>()); - - assert_eq!(size_of::<CanBeNicheFilledButShouldnt>(), 8); - assert_eq!(size_of::<Option<CanBeNicheFilledButShouldnt>>(), 8); - assert_eq!(size_of::<Option<Option<CanBeNicheFilledButShouldnt>>>(), 8); - assert_eq!(size_of::<AlwaysTaggedBecauseItHasNoNiche>(), 8); - assert_eq!(size_of::<Option<AlwaysTaggedBecauseItHasNoNiche>>(), 8); - assert_eq!(size_of::<Option<Option<AlwaysTaggedBecauseItHasNoNiche>>>(), 8); } |