Rollup merge of #102641 - eholk:dyn-star-box, r=compiler-errors

Support casting boxes to dyn*

Boxes have a pointer type at codegen time which LLVM does not allow to be transparently converted to an integer. Work around this by inserting a `ptrtoint` instruction if the argument is a pointer.

r? ``@compiler-errors``

Fixes #102427
This commit is contained in:
Yuki Okushi 2022-10-13 09:41:25 +09:00 committed by GitHub
commit 6755c2a89d
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2 changed files with 26 additions and 0 deletions

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@ -14,6 +14,7 @@ use rustc_middle::ty::cast::{CastTy, IntTy};
use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
use rustc_middle::ty::{self, adjustment::PointerCast, Instance, Ty, TyCtxt};
use rustc_span::source_map::{Span, DUMMY_SP};
use rustc_target::abi::Size;
impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
#[instrument(level = "trace", skip(self, bx))]
@ -285,6 +286,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
bug!("Only valid to do a DynStar cast into a DynStar type")
};
let vtable = get_vtable(bx.cx(), source.ty(self.mir, bx.tcx()), trait_ref);
let vtable = bx.pointercast(vtable, bx.cx().type_ptr_to(bx.cx().type_isize()));
// FIXME(dyn-star): this is probably not the best way to check if this is
// a pointer, and really we should ensure that the value is a suitable
// pointer earlier in the compilation process.
let data = match operand.layout.pointee_info_at(bx.cx(), Size::ZERO) {
Some(_) => bx.ptrtoint(data, bx.cx().type_isize()),
None => data,
};
OperandValue::Pair(data, vtable)
}
mir::CastKind::Pointer(

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@ -0,0 +1,17 @@
// run-pass
// compile-flags: -C opt-level=0
#![feature(dyn_star)]
#![allow(incomplete_features)]
use std::fmt::Display;
fn make_dyn_star() -> dyn* Display {
Box::new(42) as dyn* Display
}
fn main() {
let x = make_dyn_star();
println!("{x}");
}