Auto merge of #55665 - eddyb:by-ref-layout-of, r=oli-obk

rustc_target: pass contexts by reference, not value.

`LayoutOf` now takes `&self` instead of `self`, and so does every method generic over a context that implements `LayoutOf` and/or other traits, like `HasDataLayout`, `HasTyCtxt`, etc.

Originally using by-value `Copy` types was relevant because `TyCtxt` was one of those types, but now `TyCtxt::layout_of` is separate from `LayoutOf`, and `TyCtxt` is not an often used layout context.

Passing these context by reference is a lot nicer for miri, which has `self: &mut EvalContext`, and needed `f(&self)` (that is, creating `&&mut EvalContext` references) for layout purposes.
Now, the `&mut EvalContext` can be passed to a function expecting `&C`, directly.

This should help with #54012 / #55627 (to not need `where &'a T::Cx: LayoutOf` bounds).

r? @nikomatsakis or @oli-obk or @nagisa cc @sunfishcode

Author: bors

Diff for: src/librustc/lint/context.rs

@@ -783,11 +783,11 @@ impl<'a, 'tcx> LateContext<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> LayoutOf for &'a LateContext<'a, 'tcx> {
+impl<'a, 'tcx> LayoutOf for LateContext<'a, 'tcx> {
     type Ty = Ty<'tcx>;
     type TyLayout = Result<TyLayout<'tcx>, LayoutError<'tcx>>;
 
-    fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout {
+    fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyLayout {
         self.tcx.layout_of(self.param_env.and(ty))
     }
 }

Diff for: src/librustc/middle/intrinsicck.rs

@@ -84,7 +84,7 @@ impl<'a, 'tcx> ExprVisitor<'a, 'tcx> {
             // `Option<typeof(function)>` to present a clearer error.
             let from = unpack_option_like(self.tcx.global_tcx(), from);
             if let (&ty::FnDef(..), SizeSkeleton::Known(size_to)) = (&from.sty, sk_to) {
-                if size_to == Pointer.size(self.tcx) {
+                if size_to == Pointer.size(&self.tcx) {
                     struct_span_err!(self.tcx.sess, span, E0591,
                                      "can't transmute zero-sized type")
                         .note(&format!("source type: {}", from))

Diff for: src/librustc/mir/interpret/mod.rs

@@ -86,18 +86,18 @@ pub trait PointerArithmetic: layout::HasDataLayout {
     // These are not supposed to be overridden.
 
     #[inline(always)]
-    fn pointer_size(self) -> Size {
+    fn pointer_size(&self) -> Size {
         self.data_layout().pointer_size
     }
 
     //// Trunace the given value to the pointer size; also return whether there was an overflow
-    fn truncate_to_ptr(self, val: u128) -> (u64, bool) {
+    fn truncate_to_ptr(&self, val: u128) -> (u64, bool) {
         let max_ptr_plus_1 = 1u128 << self.pointer_size().bits();
         ((val % max_ptr_plus_1) as u64, val >= max_ptr_plus_1)
     }
 
     // Overflow checking only works properly on the range from -u64 to +u64.
-    fn overflowing_signed_offset(self, val: u64, i: i128) -> (u64, bool) {
+    fn overflowing_signed_offset(&self, val: u64, i: i128) -> (u64, bool) {
         // FIXME: is it possible to over/underflow here?
         if i < 0 {
             // trickery to ensure that i64::min_value() works fine
@@ -109,23 +109,23 @@ pub trait PointerArithmetic: layout::HasDataLayout {
         }
     }
 
-    fn overflowing_offset(self, val: u64, i: u64) -> (u64, bool) {
+    fn overflowing_offset(&self, val: u64, i: u64) -> (u64, bool) {
         let (res, over1) = val.overflowing_add(i);
         let (res, over2) = self.truncate_to_ptr(res as u128);
         (res, over1 || over2)
     }
 
-    fn signed_offset<'tcx>(self, val: u64, i: i64) -> EvalResult<'tcx, u64> {
+    fn signed_offset<'tcx>(&self, val: u64, i: i64) -> EvalResult<'tcx, u64> {
         let (res, over) = self.overflowing_signed_offset(val, i as i128);
         if over { err!(Overflow(mir::BinOp::Add)) } else { Ok(res) }
     }
 
-    fn offset<'tcx>(self, val: u64, i: u64) -> EvalResult<'tcx, u64> {
+    fn offset<'tcx>(&self, val: u64, i: u64) -> EvalResult<'tcx, u64> {
         let (res, over) = self.overflowing_offset(val, i);
         if over { err!(Overflow(mir::BinOp::Add)) } else { Ok(res) }
     }
 
-    fn wrapping_signed_offset(self, val: u64, i: i64) -> u64 {
+    fn wrapping_signed_offset(&self, val: u64, i: i64) -> u64 {
         self.overflowing_signed_offset(val, i as i128).0
     }
 }
@@ -176,33 +176,33 @@ impl<'tcx, Tag> Pointer<Tag> {
         Pointer { alloc_id, offset, tag }
     }
 
-    pub fn wrapping_signed_offset(self, i: i64, cx: impl HasDataLayout) -> Self {
+    pub fn wrapping_signed_offset(self, i: i64, cx: &impl HasDataLayout) -> Self {
         Pointer::new_with_tag(
             self.alloc_id,
             Size::from_bytes(cx.data_layout().wrapping_signed_offset(self.offset.bytes(), i)),
             self.tag,
         )
     }
 
-    pub fn overflowing_signed_offset(self, i: i128, cx: impl HasDataLayout) -> (Self, bool) {
+    pub fn overflowing_signed_offset(self, i: i128, cx: &impl HasDataLayout) -> (Self, bool) {
         let (res, over) = cx.data_layout().overflowing_signed_offset(self.offset.bytes(), i);
         (Pointer::new_with_tag(self.alloc_id, Size::from_bytes(res), self.tag), over)
     }
 
-    pub fn signed_offset(self, i: i64, cx: impl HasDataLayout) -> EvalResult<'tcx, Self> {
+    pub fn signed_offset(self, i: i64, cx: &impl HasDataLayout) -> EvalResult<'tcx, Self> {
         Ok(Pointer::new_with_tag(
             self.alloc_id,
             Size::from_bytes(cx.data_layout().signed_offset(self.offset.bytes(), i)?),
             self.tag,
         ))
     }
 
-    pub fn overflowing_offset(self, i: Size, cx: impl HasDataLayout) -> (Self, bool) {
+    pub fn overflowing_offset(self, i: Size, cx: &impl HasDataLayout) -> (Self, bool) {
         let (res, over) = cx.data_layout().overflowing_offset(self.offset.bytes(), i.bytes());
         (Pointer::new_with_tag(self.alloc_id, Size::from_bytes(res), self.tag), over)
     }
 
-    pub fn offset(self, i: Size, cx: impl HasDataLayout) -> EvalResult<'tcx, Self> {
+    pub fn offset(self, i: Size, cx: &impl HasDataLayout) -> EvalResult<'tcx, Self> {
         Ok(Pointer::new_with_tag(
             self.alloc_id,
             Size::from_bytes(cx.data_layout().offset(self.offset.bytes(), i.bytes())?),

Diff for: src/librustc/mir/interpret/value.rs

@@ -65,7 +65,7 @@ impl<'tcx> ConstValue<'tcx> {
     pub fn new_slice(
         val: Scalar,
         len: u64,
-        cx: impl HasDataLayout
+        cx: &impl HasDataLayout
     ) -> Self {
         ConstValue::ScalarPair(val, Scalar::Bits {
             bits: len as u128,
@@ -121,7 +121,7 @@ impl<'tcx, Tag> Scalar<Tag> {
     }
 
     #[inline]
-    pub fn ptr_null(cx: impl HasDataLayout) -> Self {
+    pub fn ptr_null(cx: &impl HasDataLayout) -> Self {
         Scalar::Bits {
             bits: 0,
             size: cx.data_layout().pointer_size.bytes() as u8,
@@ -134,52 +134,52 @@ impl<'tcx, Tag> Scalar<Tag> {
     }
 
     #[inline]
-    pub fn ptr_signed_offset(self, i: i64, cx: impl HasDataLayout) -> EvalResult<'tcx, Self> {
-        let layout = cx.data_layout();
+    pub fn ptr_signed_offset(self, i: i64, cx: &impl HasDataLayout) -> EvalResult<'tcx, Self> {
+        let dl = cx.data_layout();
         match self {
             Scalar::Bits { bits, size } => {
-                assert_eq!(size as u64, layout.pointer_size.bytes());
+                assert_eq!(size as u64, dl.pointer_size.bytes());
                 Ok(Scalar::Bits {
-                    bits: layout.signed_offset(bits as u64, i)? as u128,
+                    bits: dl.signed_offset(bits as u64, i)? as u128,
                     size,
                 })
             }
-            Scalar::Ptr(ptr) => ptr.signed_offset(i, layout).map(Scalar::Ptr),
+            Scalar::Ptr(ptr) => ptr.signed_offset(i, dl).map(Scalar::Ptr),
         }
     }
 
     #[inline]
-    pub fn ptr_offset(self, i: Size, cx: impl HasDataLayout) -> EvalResult<'tcx, Self> {
-        let layout = cx.data_layout();
+    pub fn ptr_offset(self, i: Size, cx: &impl HasDataLayout) -> EvalResult<'tcx, Self> {
+        let dl = cx.data_layout();
         match self {
             Scalar::Bits { bits, size } => {
-                assert_eq!(size as u64, layout.pointer_size.bytes());
+                assert_eq!(size as u64, dl.pointer_size.bytes());
                 Ok(Scalar::Bits {
-                    bits: layout.offset(bits as u64, i.bytes())? as u128,
+                    bits: dl.offset(bits as u64, i.bytes())? as u128,
                     size,
                 })
             }
-            Scalar::Ptr(ptr) => ptr.offset(i, layout).map(Scalar::Ptr),
+            Scalar::Ptr(ptr) => ptr.offset(i, dl).map(Scalar::Ptr),
         }
     }
 
     #[inline]
-    pub fn ptr_wrapping_signed_offset(self, i: i64, cx: impl HasDataLayout) -> Self {
-        let layout = cx.data_layout();
+    pub fn ptr_wrapping_signed_offset(self, i: i64, cx: &impl HasDataLayout) -> Self {
+        let dl = cx.data_layout();
         match self {
             Scalar::Bits { bits, size } => {
-                assert_eq!(size as u64, layout.pointer_size.bytes());
+                assert_eq!(size as u64, dl.pointer_size.bytes());
                 Scalar::Bits {
-                    bits: layout.wrapping_signed_offset(bits as u64, i) as u128,
+                    bits: dl.wrapping_signed_offset(bits as u64, i) as u128,
                     size,
                 }
             }
-            Scalar::Ptr(ptr) => Scalar::Ptr(ptr.wrapping_signed_offset(i, layout)),
+            Scalar::Ptr(ptr) => Scalar::Ptr(ptr.wrapping_signed_offset(i, dl)),
         }
     }
 
     #[inline]
-    pub fn is_null_ptr(self, cx: impl HasDataLayout) -> bool {
+    pub fn is_null_ptr(self, cx: &impl HasDataLayout) -> bool {
         match self {
             Scalar::Bits { bits, size } => {
                 assert_eq!(size as u64, cx.data_layout().pointer_size.bytes());
@@ -301,7 +301,7 @@ impl<'tcx, Tag> Scalar<Tag> {
         Ok(b as u64)
     }
 
-    pub fn to_usize(self, cx: impl HasDataLayout) -> EvalResult<'static, u64> {
+    pub fn to_usize(self, cx: &impl HasDataLayout) -> EvalResult<'static, u64> {
         let b = self.to_bits(cx.data_layout().pointer_size)?;
         assert_eq!(b as u64 as u128, b);
         Ok(b as u64)
@@ -331,7 +331,7 @@ impl<'tcx, Tag> Scalar<Tag> {
         Ok(b as i64)
     }
 
-    pub fn to_isize(self, cx: impl HasDataLayout) -> EvalResult<'static, i64> {
+    pub fn to_isize(self, cx: &impl HasDataLayout) -> EvalResult<'static, i64> {
         let b = self.to_bits(cx.data_layout().pointer_size)?;
         let b = sign_extend(b, cx.data_layout().pointer_size) as i128;
         assert_eq!(b as i64 as i128, b);

Diff for: src/librustc/traits/error_reporting.rs

@@ -428,7 +428,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 ));
                 let tcx = self.tcx;
                 if let Some(len) = len.val.try_to_scalar().and_then(|scalar| {
-                    scalar.to_usize(tcx).ok()
+                    scalar.to_usize(&tcx).ok()
                 }) {
                     flags.push((
                         "_Self".to_owned(),

Diff for: src/librustc/ty/layout.rs

@@ -30,7 +30,7 @@ pub use rustc_target::abi::*;
 
 pub trait IntegerExt {
     fn to_ty<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, signed: bool) -> Ty<'tcx>;
-    fn from_attr<C: HasDataLayout>(cx: C, ity: attr::IntType) -> Integer;
+    fn from_attr<C: HasDataLayout>(cx: &C, ity: attr::IntType) -> Integer;
     fn repr_discr<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                             ty: Ty<'tcx>,
                             repr: &ReprOptions,
@@ -56,7 +56,7 @@ impl IntegerExt for Integer {
     }
 
     /// Get the Integer type from an attr::IntType.
-    fn from_attr<C: HasDataLayout>(cx: C, ity: attr::IntType) -> Integer {
+    fn from_attr<C: HasDataLayout>(cx: &C, ity: attr::IntType) -> Integer {
         let dl = cx.data_layout();
 
         match ity {
@@ -92,7 +92,7 @@ impl IntegerExt for Integer {
         let min_default = I8;
 
         if let Some(ity) = repr.int {
-            let discr = Integer::from_attr(tcx, ity);
+            let discr = Integer::from_attr(&tcx, ity);
             let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
             if discr < fit {
                 bug!("Integer::repr_discr: `#[repr]` hint too small for \
@@ -202,14 +202,13 @@ pub fn provide(providers: &mut ty::query::Providers<'_>) {
     };
 }
 
-#[derive(Copy, Clone)]
 pub struct LayoutCx<'tcx, C> {
     pub tcx: C,
     pub param_env: ty::ParamEnv<'tcx>
 }
 
 impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
-    fn layout_raw_uncached(self, ty: Ty<'tcx>)
+    fn layout_raw_uncached(&self, ty: Ty<'tcx>)
                            -> Result<&'tcx LayoutDetails, LayoutError<'tcx>> {
         let tcx = self.tcx;
         let param_env = self.param_env;
@@ -899,7 +898,7 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
 
                 let (mut min, mut max) = (i128::max_value(), i128::min_value());
                 let discr_type = def.repr.discr_type();
-                let bits = Integer::from_attr(tcx, discr_type).size().bits();
+                let bits = Integer::from_attr(self, discr_type).size().bits();
                 for (i, discr) in def.discriminants(tcx).enumerate() {
                     if variants[i].iter().any(|f| f.abi.is_uninhabited()) {
                         continue;
@@ -1141,7 +1140,7 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
     /// This is invoked by the `layout_raw` query to record the final
     /// layout of each type.
     #[inline]
-    fn record_layout_for_printing(self, layout: TyLayout<'tcx>) {
+    fn record_layout_for_printing(&self, layout: TyLayout<'tcx>) {
         // If we are running with `-Zprint-type-sizes`, record layouts for
         // dumping later. Ignore layouts that are done with non-empty
         // environments or non-monomorphic layouts, as the user only wants
@@ -1158,7 +1157,7 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
         self.record_layout_for_printing_outlined(layout)
     }
 
-    fn record_layout_for_printing_outlined(self, layout: TyLayout<'tcx>) {
+    fn record_layout_for_printing_outlined(&self, layout: TyLayout<'tcx>) {
         // (delay format until we actually need it)
         let record = |kind, packed, opt_discr_size, variants| {
             let type_desc = format!("{:?}", layout.ty);
@@ -1478,7 +1477,7 @@ impl<'a, 'tcx> LayoutOf for LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
 
     /// Computes the layout of a type. Note that this implicitly
     /// executes in "reveal all" mode.
-    fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout {
+    fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyLayout {
         let param_env = self.param_env.with_reveal_all();
         let ty = self.tcx.normalize_erasing_regions(param_env, ty);
         let details = self.tcx.layout_raw(param_env.and(ty))?;
@@ -1505,7 +1504,7 @@ impl<'a, 'tcx> LayoutOf for LayoutCx<'tcx, ty::query::TyCtxtAt<'a, 'tcx, 'tcx>>
 
     /// Computes the layout of a type. Note that this implicitly
     /// executes in "reveal all" mode.
-    fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout {
+    fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyLayout {
         let param_env = self.param_env.with_reveal_all();
         let ty = self.tcx.normalize_erasing_regions(param_env, ty);
         let details = self.tcx.layout_raw(param_env.and(ty))?;
@@ -1563,7 +1562,7 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
     where C: LayoutOf<Ty = Ty<'tcx>> + HasTyCtxt<'tcx>,
           C::TyLayout: MaybeResult<TyLayout<'tcx>>
 {
-    fn for_variant(this: TyLayout<'tcx>, cx: C, variant_index: usize) -> TyLayout<'tcx> {
+    fn for_variant(this: TyLayout<'tcx>, cx: &C, variant_index: usize) -> TyLayout<'tcx> {
         let details = match this.variants {
             Variants::Single { index } if index == variant_index => this.details,
 
@@ -1602,7 +1601,7 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
         }
     }
 
-    fn field(this: TyLayout<'tcx>, cx: C, i: usize) -> C::TyLayout {
+    fn field(this: TyLayout<'tcx>, cx: &C, i: usize) -> C::TyLayout {
         let tcx = cx.tcx();
         cx.layout_of(match this.ty.sty {
             ty::Bool |
@@ -1699,7 +1698,7 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
                     Variants::Tagged { tag: ref discr, .. } |
                     Variants::NicheFilling { niche: ref discr, .. } => {
                         assert_eq!(i, 0);
-                        let layout = LayoutDetails::scalar(tcx, discr.clone());
+                        let layout = LayoutDetails::scalar(cx, discr.clone());
                         return MaybeResult::from_ok(TyLayout {
                             details: tcx.intern_layout(layout),
                             ty: discr.value.to_ty(tcx)
@@ -1725,7 +1724,7 @@ struct Niche {
 impl Niche {
     fn reserve<'a, 'tcx>(
         &self,
-        cx: LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>>,
+        cx: &LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>>,
         count: u128,
     ) -> Option<(u128, Scalar)> {
         if count > self.available {
@@ -1745,7 +1744,7 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
     /// Find the offset of a niche leaf field, starting from
     /// the given type and recursing through aggregates.
     // FIXME(eddyb) traverse already optimized enums.
-    fn find_niche(self, layout: TyLayout<'tcx>) -> Result<Option<Niche>, LayoutError<'tcx>> {
+    fn find_niche(&self, layout: TyLayout<'tcx>) -> Result<Option<Niche>, LayoutError<'tcx>> {
         let scalar_niche = |scalar: &Scalar, offset| {
             let Scalar { value, valid_range: ref v } = *scalar;
 

Diff for: src/librustc/ty/util.rs

@@ -43,7 +43,7 @@ impl<'tcx> fmt::Display for Discr<'tcx> {
         match self.ty.sty {
             ty::Int(ity) => {
                 let bits = ty::tls::with(|tcx| {
-                    Integer::from_attr(tcx, SignedInt(ity)).size().bits()
+                    Integer::from_attr(&tcx, SignedInt(ity)).size().bits()
                 });
                 let x = self.val as i128;
                 // sign extend the raw representation to be an i128
@@ -62,8 +62,8 @@ impl<'tcx> Discr<'tcx> {
     }
     pub fn checked_add<'a, 'gcx>(self, tcx: TyCtxt<'a, 'gcx, 'tcx>, n: u128) -> (Self, bool) {
         let (int, signed) = match self.ty.sty {
-            Int(ity) => (Integer::from_attr(tcx, SignedInt(ity)), true),
-            Uint(uty) => (Integer::from_attr(tcx, UnsignedInt(uty)), false),
+            Int(ity) => (Integer::from_attr(&tcx, SignedInt(ity)), true),
+            Uint(uty) => (Integer::from_attr(&tcx, UnsignedInt(uty)), false),
             _ => bug!("non integer discriminant"),
         };