bjoernager/rust
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use ptradd for vtable indexing

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Like field offsets, these are always constant.
This commit is contained in:
Erik Desjardins 2024-03-10 22:38:53 -04:00
parent 76ee6fc926
commit a7cd803d02
4 changed files with 104 additions and 17 deletions
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13
compiler/rustc_codegen_ssa/src/base.rs
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@ -165,14 +165,11 @@ pub fn unsized_info<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
cx.tcx().vtable_trait_upcasting_coercion_new_vptr_slot((source, target));
if let Some(entry_idx) = vptr_entry_idx {
let ptr_ty = cx.type_ptr();
let ptr_align = cx.tcx().data_layout.pointer_align.abi;
let gep = bx.inbounds_gep(
ptr_ty,
old_info,
&[bx.const_usize(u64::try_from(entry_idx).unwrap())],
);
let new_vptr = bx.load(ptr_ty, gep, ptr_align);
let ptr_size = bx.data_layout().pointer_size;
let ptr_align = bx.data_layout().pointer_align.abi;
let vtable_byte_offset = u64::try_from(entry_idx).unwrap() * ptr_size.bytes();
let gep = bx.inbounds_ptradd(old_info, bx.const_usize(vtable_byte_offset));
let new_vptr = bx.load(bx.type_ptr(), gep, ptr_align);
bx.nonnull_metadata(new_vptr);
// VTable loads are invariant.
bx.set_invariant_load(new_vptr);