Fix 44921 by properly setting Vboxed field (#44942)

(cherry picked from commit 4c858f8)

Author: Ian Atol

src/codegen.cpp

@@ -1790,14 +1790,15 @@ static jl_cgval_t convert_julia_type_union(jl_codectx_t &ctx, const jl_cgval_t &
                 boxv = ctx.builder.CreateSelect(
                     ctx.builder.CreateAnd(wasboxed, isboxed), v.Vboxed, boxv);
             }
+            Value *slotv;
+            MDNode *tbaa;
             if (v.V == NULL) {
                 // v.V might be NULL if it was all ghost objects before
-                return jl_cgval_t(boxv, NULL, false, typ, new_tindex, ctx.tbaa());
+                slotv = NULL;
+                tbaa = ctx.tbaa().tbaa_const;
             }
             else {
                 Value *isboxv = ctx.builder.CreateIsNotNull(boxv);
-                Value *slotv;
-                MDNode *tbaa;
                 if (v.ispointer()) {
                     slotv = v.V;
                     tbaa = v.tbaa;
@@ -1810,12 +1811,12 @@ static jl_cgval_t convert_julia_type_union(jl_codectx_t &ctx, const jl_cgval_t &
                 slotv = ctx.builder.CreateSelect(isboxv,
                             decay_derived(ctx, boxv),
                             decay_derived(ctx, emit_bitcast(ctx, slotv, boxv->getType())));
-                jl_cgval_t newv = jl_cgval_t(slotv, NULL, false, typ, new_tindex, ctx.tbaa());
-                assert(boxv->getType() == ctx.types().T_prjlvalue);
-                newv.Vboxed = boxv;
-                newv.tbaa = tbaa;
-                return newv;
             }
+            jl_cgval_t newv = jl_cgval_t(slotv, NULL, false, typ, new_tindex, ctx.tbaa());
+            assert(boxv->getType() == ctx.types().T_prjlvalue);
+            newv.Vboxed = boxv;
+            newv.tbaa = tbaa;
+            return newv;
         }
     }
     else {

test/compiler/codegen.jl

@@ -702,6 +702,23 @@ function f42645()
 end
 @test ((f42645()::B42645).y::A42645{Int}).x
 
+struct A44921{T}
+    x::T
+end
+function f44921(a)
+    if a == :x
+        A44921(_f) # _f purposefully undefined
+    elseif a == :p
+        g44921(a)
+    end
+end
+function g44921(a)
+    if !@isdefined _f # just needs to be some non constprop-able condition
+        A44921(())
+    end
+end
+@test f44921(:p) isa A44921
+
 # issue #43123
 @noinline cmp43123(a::Some, b::Some) = something(a) === something(b)
 @noinline cmp43123(a, b) = a[] === b[]