bjoernager/rust
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Auto merge of #88337 - eddyb:field-failure-is-not-an-option, r=nagisa

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rustc_target: `TyAndLayout::field` should never error.

This refactor (making `TyAndLayout::field` return `TyAndLayout` without any `Result` around it) is based on a simple observation, regarding `TyAndLayout::field`:

If `cx.layout_of(ty)` succeeds (for some `cx` and `ty`), then `.field(cx, i)` on the resulting `TyAndLayout` should *always* succeed in computing `cx.layout_of(field_ty)` (where `field_ty` is the type of the `i`th field of `ty`).

The reason for this is that no matter which field is chosen, `cx.layout_of(field_ty)` *will have already been computed*, as part of computing `cx.layout_of(ty)`, as we cannot determine the layout of *any* type without considering the layouts of *all* of its fields.

And so it should be fine to turn any errors into ICEs, since they likely indicate a `cx` mismatch, or some other edge case that is due to a compiler bug (as opposed to ever being an user-facing error).

<hr/>

Each commit should probably be reviewed separately, though note that there's some `where` clauses (in `rustc_target::abi::call::*`) that change in most commits.

cc `@nagisa` `@oli-obk`
This commit is contained in:
bors 2021-08-29 22:54:26 +00:00
commit 9556d7a09a
32 changed files with 308 additions and 271 deletions
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2
compiler/rustc_codegen_llvm/src/builder.rs
View file

@ -88,7 +88,7 @@ impl HasTargetSpec for Builder<'_, '_, 'tcx> {
}
}
impl abi::LayoutOf for Builder<'_, '_, 'tcx> {
impl abi::LayoutOf<'tcx> for Builder<'_, '_, 'tcx> {
type Ty = Ty<'tcx>;
type TyAndLayout = TyAndLayout<'tcx>;

2
compiler/rustc_codegen_llvm/src/context.rs
View file

@ -835,7 +835,7 @@ impl ty::layout::HasTyCtxt<'tcx> for CodegenCx<'ll, 'tcx> {
}
}
impl LayoutOf for CodegenCx<'ll, 'tcx> {
impl LayoutOf<'tcx> for CodegenCx<'ll, 'tcx> {
type Ty = Ty<'tcx>;
type TyAndLayout = TyAndLayout<'tcx>;

7
compiler/rustc_codegen_llvm/src/type_of.rs
View file

@ -9,7 +9,7 @@ use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::{self, Ty, TypeFoldable};
use rustc_target::abi::{Abi, AddressSpace, Align, FieldsShape};
use rustc_target::abi::{Int, Pointer, F32, F64};
use rustc_target::abi::{LayoutOf, PointeeInfo, Scalar, Size, TyAndLayoutMethods, Variants};
use rustc_target::abi::{LayoutOf, PointeeInfo, Scalar, Size, TyAbiInterface, Variants};
use smallvec::{smallvec, SmallVec};
use tracing::debug;
@ -393,12 +393,15 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
}
}
// FIXME(eddyb) this having the same name as `TyAndLayout::pointee_info_at`
// (the inherent method, which is lacking this caching logic) can result in
// the uncached version being called - not wrong, but potentially inefficient.
fn pointee_info_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>, offset: Size) -> Option<PointeeInfo> {
if let Some(&pointee) = cx.pointee_infos.borrow().get(&(self.ty, offset)) {
return pointee;
}
let result = Ty::pointee_info_at(*self, cx, offset);
let result = Ty::ty_and_layout_pointee_info_at(*self, cx, offset);
cx.pointee_infos.borrow_mut().insert((self.ty, offset), result);
result