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Auto merge of #89597 - michaelwoerister:improve-vtable-debuginfo, r=wesleywiser

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Create more accurate debuginfo for vtables.

Before this PR all vtables would have the same name (`"vtable"`) in debuginfo. Now they get an unambiguous name that identifies the implementing type and the trait that is being implemented.

This is only one of several possible improvements:
- This PR describes vtables as arrays of `*const u8` pointers. It would nice to describe them as structs where function pointer is represented by a field with a name indicative of the method it maps to. However, this requires coming up with a naming scheme that avoids clashes between methods with the same name (which is possible if the vtable contains multiple traits).
- The PR does not update the debuginfo we generate for the vtable-pointer field in a fat `dyn` pointer. Right now there does not seem to be an easy way of getting ahold of a vtable-layout without also knowing the concrete self-type of a trait object.

r? `@wesleywiser`
This commit is contained in:
bors 2021-10-11 04:31:47 +00:00
commit 9a757817c3
8 changed files with 163 additions and 62 deletions
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2
compiler/rustc_codegen_ssa/src/meth.rs
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@ -78,7 +78,7 @@ pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
let align = cx.data_layout().pointer_align.abi;
let vtable = cx.static_addr_of(vtable_const, align, Some("vtable"));
cx.create_vtable_metadata(ty, vtable);
cx.create_vtable_metadata(ty, trait_ref, vtable);
cx.vtables().borrow_mut().insert((ty, trait_ref), vtable);
vtable
}