Auto merge of rust-lang#88839 - nbdd0121:alignof, r=nagisa

Introduce NullOp::AlignOf

This PR introduces `Rvalue::NullaryOp(NullOp::AlignOf, ty)`, which will be lowered from `align_of`, similar to `size_of` lowering to `Rvalue::NullaryOp(NullOp::SizeOf, ty)`.

The changes are originally part of rust-lang#88700 but since it's not dependent on other changes and could have performance impact on its own, it's separated into its own PR.

Author: bors

src/base.rs

@@ -726,15 +726,20 @@ fn codegen_stmt<'tcx>(
                     let ptr = fx.bcx.inst_results(call)[0];
                     lval.write_cvalue(fx, CValue::by_val(ptr, box_layout));
                 }
-                Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
+                Rvalue::NullaryOp(null_op, ty) => {
                     assert!(
                         lval.layout()
                             .ty
                             .is_sized(fx.tcx.at(stmt.source_info.span), ParamEnv::reveal_all())
                     );
-                    let ty_size = fx.layout_of(fx.monomorphize(ty)).size.bytes();
+                    let layout = fx.layout_of(fx.monomorphize(ty));
+                    let val = match null_op {
+                        NullOp::SizeOf => layout.size.bytes(),
+                        NullOp::AlignOf => layout.align.abi.bytes(),
+                        NullOp::Box => unreachable!(),
+                    };
                     let val =
-                        CValue::const_val(fx, fx.layout_of(fx.tcx.types.usize), ty_size.into());
+                        CValue::const_val(fx, fx.layout_of(fx.tcx.types.usize), val.into());
                     lval.write_cvalue(fx, val);
                 }
                 Rvalue::Aggregate(ref kind, ref operands) => match kind.as_ref() {

src/intrinsics/mod.rs

@@ -823,7 +823,7 @@ pub(crate) fn codegen_intrinsic_call<'tcx>(
             dest.write_cvalue(fx, val);
         };
 
-        pref_align_of | min_align_of | needs_drop | type_id | type_name | variant_count, () {
+        pref_align_of | needs_drop | type_id | type_name | variant_count, () {
             let const_val =
                 fx.tcx.const_eval_instance(ParamEnv::reveal_all(), instance, None).unwrap();
             let val = crate::constant::codegen_const_value(