Merge commit '15c8d31392b9fbab3b3368b67acc4bbe5983115a' into cranelift-rebase

[rust.git] / src / unsize.rs

diff --git a/src/unsize.rs b/src/unsize.rs
index 962fcaf48efc3e6833649ef72409c8ff1dc6eaa9..042583cd5720fa07b7cac71d3928a302f7d3be0b 100644 (file)
--- a/src/unsize.rs
+++ b/src/unsize.rs
@@ -1,3 +1,7 @@
+//! Codegen of the [`PointerCast::Unsize`] operation.
+//!
+//! [`PointerCast::Unsize`]: `rustc_middle::ty::adjustment::PointerCast::Unsize`
+
 use crate::prelude::*;
 
 // Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/base.rs#L159-L307
@@ -9,19 +13,18 @@
 /// in an upcast, where the new vtable for an object will be derived
 /// from the old one.
 pub(crate) fn unsized_info<'tcx>(
-    fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
+    fx: &mut FunctionCx<'_, '_, 'tcx>,
     source: Ty<'tcx>,
     target: Ty<'tcx>,
     old_info: Option<Value>,
 ) -> Value {
     let (source, target) =
-        fx.tcx
-            .struct_lockstep_tails_erasing_lifetimes(source, target, ParamEnv::reveal_all());
+        fx.tcx.struct_lockstep_tails_erasing_lifetimes(source, target, ParamEnv::reveal_all());
     match (&source.kind(), &target.kind()) {
-        (&ty::Array(_, len), &ty::Slice(_)) => fx.bcx.ins().iconst(
-            fx.pointer_type,
-            len.eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64,
-        ),
+        (&ty::Array(_, len), &ty::Slice(_)) => fx
+            .bcx
+            .ins()
+            .iconst(fx.pointer_type, len.eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64),
         (&ty::Dynamic(..), &ty::Dynamic(..)) => {
             // For now, upcasts are limited to changes in marker
             // traits, and hence never actually require an actual
@@ -31,17 +34,13 @@ pub(crate) fn unsized_info<'tcx>(
         (_, &ty::Dynamic(ref data, ..)) => {
             crate::vtable::get_vtable(fx, fx.layout_of(source), data.principal())
         }
-        _ => bug!(
-            "unsized_info: invalid unsizing {:?} -> {:?}",
-            source,
-            target
-        ),
+        _ => bug!("unsized_info: invalid unsizing {:?} -> {:?}", source, target),
     }
 }
 
 /// Coerce `src` to `dst_ty`. `src_ty` must be a thin pointer.
 fn unsize_thin_ptr<'tcx>(
-    fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
+    fx: &mut FunctionCx<'_, '_, 'tcx>,
     src: Value,
     src_layout: TyAndLayout<'tcx>,
     dst_layout: TyAndLayout<'tcx>,
@@ -85,24 +84,22 @@ fn unsize_thin_ptr<'tcx>(
 /// Coerce `src`, which is a reference to a value of type `src_ty`,
 /// to a value of type `dst_ty` and store the result in `dst`
 pub(crate) fn coerce_unsized_into<'tcx>(
-    fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
+    fx: &mut FunctionCx<'_, '_, 'tcx>,
     src: CValue<'tcx>,
     dst: CPlace<'tcx>,
 ) {
     let src_ty = src.layout().ty;
     let dst_ty = dst.layout().ty;
     let mut coerce_ptr = || {
-        let (base, info) = if fx
-            .layout_of(src.layout().ty.builtin_deref(true).unwrap().ty)
-            .is_unsized()
-        {
-            // fat-ptr to fat-ptr unsize preserves the vtable
-            // i.e., &'a fmt::Debug+Send => &'a fmt::Debug
-            src.load_scalar_pair(fx)
-        } else {
-            let base = src.load_scalar(fx);
-            unsize_thin_ptr(fx, base, src.layout(), dst.layout())
-        };
+        let (base, info) =
+            if fx.layout_of(src.layout().ty.builtin_deref(true).unwrap().ty).is_unsized() {
+                // fat-ptr to fat-ptr unsize preserves the vtable
+                // i.e., &'a fmt::Debug+Send => &'a fmt::Debug
+                src.load_scalar_pair(fx)
+            } else {
+                let base = src.load_scalar(fx);
+                unsize_thin_ptr(fx, base, src.layout(), dst.layout())
+            };
         dst.write_cvalue(fx, CValue::by_val_pair(base, info, dst.layout()));
     };
     match (&src_ty.kind(), &dst_ty.kind()) {
@@ -127,39 +124,26 @@ pub(crate) fn coerce_unsized_into<'tcx>(
                 }
             }
         }
-        _ => bug!(
-            "coerce_unsized_into: invalid coercion {:?} -> {:?}",
-            src_ty,
-            dst_ty
-        ),
+        _ => bug!("coerce_unsized_into: invalid coercion {:?} -> {:?}", src_ty, dst_ty),
     }
 }
 
 // Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/glue.rs
 
 pub(crate) fn size_and_align_of_dst<'tcx>(
-    fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
+    fx: &mut FunctionCx<'_, '_, 'tcx>,
     layout: TyAndLayout<'tcx>,
     info: Value,
 ) -> (Value, Value) {
     if !layout.is_unsized() {
-        let size = fx
-            .bcx
-            .ins()
-            .iconst(fx.pointer_type, layout.size.bytes() as i64);
-        let align = fx
-            .bcx
-            .ins()
-            .iconst(fx.pointer_type, layout.align.abi.bytes() as i64);
+        let size = fx.bcx.ins().iconst(fx.pointer_type, layout.size.bytes() as i64);
+        let align = fx.bcx.ins().iconst(fx.pointer_type, layout.align.abi.bytes() as i64);
         return (size, align);
     }
     match layout.ty.kind() {
         ty::Dynamic(..) => {
             // load size/align from vtable
-            (
-                crate::vtable::size_of_obj(fx, info),
-                crate::vtable::min_align_of_obj(fx, info),
-            )
+            (crate::vtable::size_of_obj(fx, info), crate::vtable::min_align_of_obj(fx, info))
         }
         ty::Slice(_) | ty::Str => {
             let unit = layout.field(fx, 0);
@@ -167,9 +151,7 @@ pub(crate) fn size_and_align_of_dst<'tcx>(
             // times the unit size.
             (
                 fx.bcx.ins().imul_imm(info, unit.size.bytes() as i64),
-                fx.bcx
-                    .ins()
-                    .iconst(fx.pointer_type, unit.align.abi.bytes() as i64),
+                fx.bcx.ins().iconst(fx.pointer_type, unit.align.abi.bytes() as i64),
             )
         }
         _ => {
@@ -207,10 +189,7 @@ pub(crate) fn size_and_align_of_dst<'tcx>(
 
             // Choose max of two known alignments (combined value must
             // be aligned according to more restrictive of the two).
-            let cmp = fx
-                .bcx
-                .ins()
-                .icmp(IntCC::UnsignedGreaterThan, sized_align, unsized_align);
+            let cmp = fx.bcx.ins().icmp(IntCC::UnsignedGreaterThan, sized_align, unsized_align);
             let align = fx.bcx.ins().select(cmp, sized_align, unsized_align);
 
             // Issue #27023: must add any necessary padding to `size`