Rollup merge of #114505 - ouz-a:cleanup_mir, r=RalfJung

Add documentation to has_deref

Documentation of `has_deref` needed some polish to be more clear about where it should be used and what's it's purpose.

cc https://github.com/rust-lang/rust/issues/114401

r? `@RalfJung`

compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -441,7 +441,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             LocalRef::Place(place) => place,
             LocalRef::UnsizedPlace(place) => bx.load_operand(place).deref(cx),
             LocalRef::Operand(..) => {
-                if place_ref.has_deref() {
+                if place_ref.is_indirect_first_projection() {
                     base = 1;
                     let cg_base = self.codegen_consume(
                         bx,