add intrinsic to access vtable size and align

4 files changed, 32 insertions, 0 deletions

diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 9f364749287..01e276ac902 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -363,6 +363,20 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                 return;
             }
 
+            sym::vtable_size | sym::vtable_align => {
+                let ptr = args[0].immediate();
+                let layout = self.layout_of(self.tcx.types.usize);
+                let type_ = self.backend_type(layout);
+                let offset = match name {
+                    sym::vtable_size => 1,
+                    sym::vtable_align => 2,
+                    _ => bug!(),
+                };
+                let offset = self.const_int(type_, offset);
+                let vtable_field_ptr = self.inbounds_gep(type_, ptr, &[offset]);
+                self.load(type_, vtable_field_ptr, layout.align.abi)
+            }
+
             _ if name.as_str().starts_with("simd_") => {
                 match generic_simd_intrinsic(self, name, callee_ty, args, ret_ty, llret_ty, span) {
                     Ok(llval) => llval,
diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics.rs b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
index 0f6eb2ecaa3..025f8647c95 100644
--- a/compiler/rustc_const_eval/src/interpret/intrinsics.rs
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
@@ -492,6 +492,18 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let result = self.raw_eq_intrinsic(&args[0], &args[1])?;
                 self.write_scalar(result, dest)?;
             }
+
+            sym::vtable_size => {
+                let ptr = self.read_pointer(&args[0])?;
+                let (size, _align) = self.get_vtable_size_and_align(ptr)?;
+                self.write_scalar(Scalar::from_machine_usize(size.bytes(), self), dest)?;
+            }
+            sym::vtable_align => {
+                let ptr = self.read_pointer(&args[0])?;
+                let (_size, align) = self.get_vtable_size_and_align(ptr)?;
+                self.write_scalar(Scalar::from_machine_usize(align.bytes(), self), dest)?;
+            }
+
             _ => return Ok(false),
         }
 
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index ec1d2c39b80..a207927c9d2 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1564,6 +1564,8 @@ symbols! {
         volatile_store,
         vreg,
         vreg_low16,
+        vtable_align,
+        vtable_size,
         warn,
         wasm_abi,
         wasm_import_module,
diff --git a/compiler/rustc_typeck/src/check/intrinsic.rs b/compiler/rustc_typeck/src/check/intrinsic.rs
index 7fe710cf8f4..3f2a0da8d65 100644
--- a/compiler/rustc_typeck/src/check/intrinsic.rs
+++ b/compiler/rustc_typeck/src/check/intrinsic.rs
@@ -400,6 +400,10 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
 
             sym::const_eval_select => (4, vec![param(0), param(1), param(2)], param(3)),
 
+            sym::vtable_size | sym::vtable_align => {
+                (0, vec![tcx.mk_imm_ptr(tcx.mk_unit())], tcx.types.usize)
+            }
+
             other => {
                 tcx.sess.emit_err(UnrecognizedIntrinsicFunction { span: it.span, name: other });
                 return;