From eca847549619229b31b4cf47898fb975df6d3546 Mon Sep 17 00:00:00 2001
From: William Moses <gh@wsmoses.com>
Date: Thu, 14 Sep 2023 09:46:39 -0500
Subject: [PATCH] Fix error when returning undef from function (#1054)

---
 src/compiler.jl          |  2 ++
 src/compiler/optimize.jl | 20 +++++++++++++++-----
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/compiler.jl b/src/compiler.jl
index a777010921..2a926b965b 100644
--- a/src/compiler.jl
+++ b/src/compiler.jl
@@ -149,6 +149,7 @@ const nofreefns = Set{String}((
     "jl_box_uint64", "jl_box_uint32",
     "ijl_box_uint64", "ijl_box_uint32",
     "ijl_box_char", "jl_box_char",
+    "ijl_subtype",
     "jl_subtype", "julia.get_pgcstack", "jl_in_threaded_region",
     "jl_object_id_", "jl_object_id", "ijl_object_id_", "ijl_object_id",
     "jl_breakpoint",
@@ -214,6 +215,7 @@ const inactivefns = Set{String}((
     "jl_box_uint64", "jl_box_uint32",
     "ijl_box_uint64", "ijl_box_uint32",
     "ijl_box_char", "jl_box_char",
+    "ijl_subtype",
     "jl_subtype", "julia.get_pgcstack", "jl_in_threaded_region",
     "jl_object_id_", "jl_object_id", "ijl_object_id_", "ijl_object_id",
     "jl_breakpoint",
diff --git a/src/compiler/optimize.jl b/src/compiler/optimize.jl
index 01c1c4b952..4f496c019d 100644
--- a/src/compiler/optimize.jl
+++ b/src/compiler/optimize.jl
@@ -400,8 +400,8 @@ function fix_decayaddr!(mod::LLVM.Module)
                     end
                 end
                 if !sret
-                    @safe_show f
-                    @safe_show inst, st, fop
+                    println(string(f))
+                    @show inst, st, fop
                     flush(stdout)
                 end
                 
@@ -661,10 +661,8 @@ function propagate_returned!(mod::LLVM.Module)
                     push!(toremove, i-1)
                 end
             end
-            if argn === nothing && length(toremove) == 0
-                continue
-            end
             illegalUse = !(linkage(fn) == LLVM.API.LLVMInternalLinkage || linkage(fn) == LLVM.API.LLVMPrivateLinkage)
+            hasAnyUse = false
             for u in LLVM.uses(fn)
                 un = LLVM.user(u)
                 if !isa(un, LLVM.CallInst)
@@ -694,8 +692,20 @@ function propagate_returned!(mod::LLVM.Module)
                         push!(next, LLVM.name(LLVM.parent(LLVM.parent(un))))
                         LLVM.replace_uses!(un, ops[argn])
                     end
+                else
+                    for u in LLVM.uses(un)
+                        hasAnyUse = true
+                        break
+                    end
                 end
             end
+            #if the function return has no users whatsoever, remove it
+            if argn === nothing && !hasAnyUse && LLVM.return_type(LLVM.function_type(fn)) != LLVM.VoidType()
+                argn = -1
+            end
+            if argn === nothing && length(toremove) == 0
+                continue
+            end
             if !illegalUse
                 push!(tofinalize, (fn, argn === nothing, toremove))
             end