codegen: move undef freeze before promotion point (#55428)

Fixes #55396

Author: vtjnash

src/cgutils.cpp

@@ -3947,8 +3947,6 @@ static jl_cgval_t emit_new_struct(jl_codectx_t &ctx, jl_value_t *ty, size_t narg
             else {
                 strct = emit_static_alloca(ctx, lt);
                 setName(ctx.emission_context, strct, arg_typename);
-                if (nargs < nf)
-                    promotion_point = ctx.builder.CreateStore(ctx.builder.CreateFreeze(UndefValue::get(lt)), strct);
                 if (tracked.count)
                     undef_derived_strct(ctx, strct, sty, ctx.tbaa().tbaa_stack);
             }
@@ -4104,6 +4102,14 @@ static jl_cgval_t emit_new_struct(jl_codectx_t &ctx, jl_value_t *ty, size_t narg
                     }
                 }
             }
+            if (promotion_point && nargs < nf) {
+                assert(!init_as_value);
+                IRBuilderBase::InsertPoint savedIP = ctx.builder.saveIP();
+                ctx.builder.SetInsertPoint(promotion_point);
+                promotion_point = cast<FreezeInst>(ctx.builder.CreateFreeze(UndefValue::get(lt)));
+                ctx.builder.CreateStore(promotion_point, strct);
+                ctx.builder.restoreIP(savedIP);
+            }
             if (type_is_ghost(lt))
                 return mark_julia_const(ctx, sty->instance);
             else if (init_as_value)

test/compiler/codegen.jl

@@ -956,3 +956,13 @@ function foonopreds()
     pkgid.uuid !== nothing ? pkgid.uuid : false
 end
 @test foonopreds() !== nothing
+
+# issue 55396
+struct Incomplete55396
+  x::Tuple{Int}
+  y::Int
+  @noinline Incomplete55396(x::Int) = new((x,))
+end
+let x = Incomplete55396(55396)
+    @test x.x === (55396,)
+end