Rollup merge of rust-lang#115240 - RalfJung:llvm-no-type, r=bjorn3

codegen_llvm/llvm_type: avoid matching on the Rust type

This `match` is highly suspicious. Looking at `scalar_llvm_type_at` I think it makes no difference. But if it were to make a difference that would be a huge problem, since it doesn't look through `repr(transparent)`!

Cc `@eddyb` `@bjorn3`

src/abi.rs

@@ -125,8 +125,8 @@ impl<'gcc, 'tcx> FnAbiGccExt<'gcc, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                 PassMode::Ignore => continue,
                 PassMode::Direct(_) => arg.layout.immediate_gcc_type(cx),
                 PassMode::Pair(..) => {
-                    argument_tys.push(arg.layout.scalar_pair_element_gcc_type(cx, 0, true));
-                    argument_tys.push(arg.layout.scalar_pair_element_gcc_type(cx, 1, true));
+                    argument_tys.push(arg.layout.scalar_pair_element_gcc_type(cx, 0));
+                    argument_tys.push(arg.layout.scalar_pair_element_gcc_type(cx, 1));
                     continue;
                 }
                 PassMode::Indirect { extra_attrs: Some(_), .. } => {

src/builder.rs

@@ -821,7 +821,7 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
 
                 let mut load = |i, scalar: &abi::Scalar, align| {
                     let llptr = self.struct_gep(pair_type, place.llval, i as u64);
-                    let llty = place.layout.scalar_pair_element_gcc_type(self, i, false);
+                    let llty = place.layout.scalar_pair_element_gcc_type(self, i);
                     let load = self.load(llty, llptr, align);
                     scalar_load_metadata(self, load, scalar);
                     if scalar.is_bool() { self.trunc(load, self.type_i1()) } else { load }

src/type_of.rs

@@ -4,7 +4,7 @@ use gccjit::{Struct, Type};
 use crate::rustc_codegen_ssa::traits::{BaseTypeMethods, DerivedTypeMethods, LayoutTypeMethods};
 use rustc_middle::bug;
 use rustc_middle::ty::{self, Ty, TypeVisitableExt};
-use rustc_middle::ty::layout::{FnAbiOf, LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_target::abi::{self, Abi, Align, F32, F64, FieldsShape, Int, Integer, Pointer, PointeeInfo, Size, TyAbiInterface, Variants};
 use rustc_target::abi::call::{CastTarget, FnAbi, Reg};
@@ -74,8 +74,8 @@ fn uncached_gcc_type<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, layout: TyAndLayout
         Abi::ScalarPair(..) => {
             return cx.type_struct(
                 &[
-                    layout.scalar_pair_element_gcc_type(cx, 0, false),
-                    layout.scalar_pair_element_gcc_type(cx, 1, false),
+                    layout.scalar_pair_element_gcc_type(cx, 0),
+                    layout.scalar_pair_element_gcc_type(cx, 1),
                 ],
                 false,
             );
@@ -150,7 +150,7 @@ pub trait LayoutGccExt<'tcx> {
     fn gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>) -> Type<'gcc>;
     fn immediate_gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>) -> Type<'gcc>;
     fn scalar_gcc_type_at<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, scalar: &abi::Scalar, offset: Size) -> Type<'gcc>;
-    fn scalar_pair_element_gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, index: usize, immediate: bool) -> Type<'gcc>;
+    fn scalar_pair_element_gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, index: usize) -> Type<'gcc>;
     fn gcc_field_index(&self, index: usize) -> u64;
     fn pointee_info_at<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, offset: Size) -> Option<PointeeInfo>;
 }
@@ -182,23 +182,16 @@ impl<'tcx> LayoutGccExt<'tcx> for TyAndLayout<'tcx> {
     /// of that field's type - this is useful for taking the address of
     /// that field and ensuring the struct has the right alignment.
     fn gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>) -> Type<'gcc> {
+        // This must produce the same result for `repr(transparent)` wrappers as for the inner type!
+        // In other words, this should generally not look at the type at all, but only at the
+        // layout.
         if let Abi::Scalar(ref scalar) = self.abi {
             // Use a different cache for scalars because pointers to DSTs
             // can be either fat or thin (data pointers of fat pointers).
             if let Some(&ty) = cx.scalar_types.borrow().get(&self.ty) {
                 return ty;
             }
-            let ty =
-                match *self.ty.kind() {
-                    ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
-                        cx.type_ptr_to(cx.layout_of(ty).gcc_type(cx))
-                    }
-                    ty::Adt(def, _) if def.is_box() => {
-                        cx.type_ptr_to(cx.layout_of(self.ty.boxed_ty()).gcc_type(cx))
-                    }
-                    ty::FnPtr(sig) => cx.fn_ptr_backend_type(&cx.fn_abi_of_fn_ptr(sig, ty::List::empty())),
-                    _ => self.scalar_gcc_type_at(cx, scalar, Size::ZERO),
-                };
+            let ty = self.scalar_gcc_type_at(cx, scalar, Size::ZERO);
             cx.scalar_types.borrow_mut().insert(self.ty, ty);
             return ty;
         }
@@ -272,23 +265,10 @@ impl<'tcx> LayoutGccExt<'tcx> for TyAndLayout<'tcx> {
         }
     }
 
-    fn scalar_pair_element_gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, index: usize, immediate: bool) -> Type<'gcc> {
-        // TODO(antoyo): remove llvm hack:
-        // HACK(eddyb) special-case fat pointers until LLVM removes
-        // pointee types, to avoid bitcasting every `OperandRef::deref`.
-        match self.ty.kind() {
-            ty::Ref(..) | ty::RawPtr(_) => {
-                return self.field(cx, index).gcc_type(cx);
-            }
-            // only wide pointer boxes are handled as pointers
-            // thin pointer boxes with scalar allocators are handled by the general logic below
-            ty::Adt(def, args) if def.is_box() && cx.layout_of(args.type_at(1)).is_zst() => {
-                let ptr_ty = Ty::new_mut_ptr(cx.tcx,self.ty.boxed_ty());
-                return cx.layout_of(ptr_ty).scalar_pair_element_gcc_type(cx, index, immediate);
-            }
-            _ => {}
-        }
-
+    fn scalar_pair_element_gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, index: usize) -> Type<'gcc> {
+        // This must produce the same result for `repr(transparent)` wrappers as for the inner type!
+        // In other words, this should generally not look at the type at all, but only at the
+        // layout.
         let (a, b) = match self.abi {
             Abi::ScalarPair(ref a, ref b) => (a, b),
             _ => bug!("TyAndLayout::scalar_pair_element_llty({:?}): not applicable", self),
@@ -367,8 +347,8 @@ impl<'gcc, 'tcx> LayoutTypeMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         layout.gcc_field_index(index)
     }
 
-    fn scalar_pair_element_backend_type(&self, layout: TyAndLayout<'tcx>, index: usize, immediate: bool) -> Type<'gcc> {
-        layout.scalar_pair_element_gcc_type(self, index, immediate)
+    fn scalar_pair_element_backend_type(&self, layout: TyAndLayout<'tcx>, index: usize, _immediate: bool) -> Type<'gcc> {
+        layout.scalar_pair_element_gcc_type(self, index)
     }
 
     fn cast_backend_type(&self, ty: &CastTarget) -> Type<'gcc> {