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Add comments about address spaces

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Flakebi 2025-01-24 00:37:05 +01:00
parent 436e4fb647
commit b06e840d9e
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4 changed files with 26 additions and 1 deletions
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10
compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
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@ -1500,6 +1500,14 @@ fn build_vtable_type_di_node<'ll, 'tcx>(
.di_node
}
/// Get the global variable for the vtable.
///
/// When using global variables, we may have created an addrspacecast to get a pointer to the
/// default address space if global variables are created in a different address space.
/// For modifying the vtable, we need the real global variable. This function accepts either a
/// global variable (which is simply returned), or an addrspacecast constant expression.
/// If the given value is an addrspacecast, the cast is removed and the global variable behind
/// the cast is returned.
fn find_vtable_behind_cast<'ll>(vtable: &'ll Value) -> &'ll Value {
// The vtable is a global variable, which may be behind an addrspacecast.
unsafe {
@ -1532,6 +1540,7 @@ pub(crate) fn apply_vcall_visibility_metadata<'ll, 'tcx>(
let Some(trait_ref) = trait_ref else { return };
// Unwrap potential addrspacecast
let vtable = find_vtable_behind_cast(vtable);
let trait_ref_self = trait_ref.with_self_ty(cx.tcx, ty);
let trait_ref_self = cx.tcx.erase_regions(trait_ref_self);
@ -1606,6 +1615,7 @@ pub(crate) fn create_vtable_di_node<'ll, 'tcx>(
return;
}
// Unwrap potential addrspacecast
let vtable = find_vtable_behind_cast(vtable);
// When full debuginfo is enabled, we want to try and prevent vtables from being