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

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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`
This commit is contained in:
Matthias Krüger 2023-08-28 19:53:55 +02:00 • committed by GitHub
commit a5b7504f41
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4 changed files with 25 additions and 67 deletions
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38
compiler/rustc_codegen_llvm/src/type_of.rs
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@ -3,7 +3,7 @@ use crate::context::TypeLowering;
use crate::type_::Type;
use rustc_codegen_ssa::traits::*;
use rustc_middle::bug;
use rustc_middle::ty::layout::{FnAbiOf, LayoutOf, TyAndLayout};
use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
use rustc_middle::ty::{self, Ty, TypeVisitableExt};
use rustc_target::abi::HasDataLayout;
@ -215,20 +215,16 @@ impl<'tcx> LayoutLlvmExt<'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 llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type {
// 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(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(&llty) = cx.scalar_lltypes.borrow().get(&self.ty) {
return llty;
}
let llty = match *self.ty.kind() {
ty::Ref(..) | ty::RawPtr(_) => cx.type_ptr(),
ty::Adt(def, _) if def.is_box() => cx.type_ptr(),
ty::FnPtr(sig) => {
cx.fn_ptr_backend_type(cx.fn_abi_of_fn_ptr(sig, ty::List::empty()))
}
_ => self.scalar_llvm_type_at(cx, scalar),
};
let llty = self.scalar_llvm_type_at(cx, scalar);
cx.scalar_lltypes.borrow_mut().insert(self.ty, llty);
return llty;
}
@ -303,27 +299,9 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
index: usize,
immediate: bool,
) -> &'a Type {
// 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).llvm_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_llvm_type(cx, index, immediate);
}
// `dyn* Trait` has the same ABI as `*mut dyn Trait`
ty::Dynamic(bounds, region, ty::DynStar) => {
let ptr_ty =
Ty::new_mut_ptr(cx.tcx, Ty::new_dynamic(cx.tcx, bounds, region, ty::Dyn));
return cx.layout_of(ptr_ty).scalar_pair_element_llvm_type(cx, index, immediate);
}
_ => {}
}
// 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 Abi::ScalarPair(a, b) = self.abi else {
bug!("TyAndLayout::scalar_pair_element_llty({:?}): not applicable", self);
};