From 72691483d9278c5753f986ea47480f2aca997b77 Mon Sep 17 00:00:00 2001
From: Ian Atol <ian.atol@juliacomputing.com>
Date: Mon, 11 Apr 2022 10:15:19 -0700
Subject: [PATCH] Fix 44921 by properly setting Vboxed field

---
 src/codegen.cpp          | 17 +++++++++--------
 test/compiler/codegen.jl | 17 +++++++++++++++++
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/src/codegen.cpp b/src/codegen.cpp
index 65bb19fc2f7bc..248216f475ee7 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -1864,14 +1864,15 @@ 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;
@@ -1884,12 +1885,12 @@ 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 {
diff --git a/test/compiler/codegen.jl b/test/compiler/codegen.jl
index d9f2bb1dbfcc0..9724091637f97 100644
--- a/test/compiler/codegen.jl
+++ b/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[]