From 726bbd7afda4373e10b8ab1eac9dfb53c81c8755 Mon Sep 17 00:00:00 2001
From: Tim Besard <tim.besard@gmail.com>
Date: Thu, 24 Nov 2022 12:30:00 +0100
Subject: [PATCH] Fix regression in generic_bitcast with Union{} arguments.
 (#47605)

---
 src/intrinsics.cpp       | 7 ++++++-
 test/compiler/codegen.jl | 5 +++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/intrinsics.cpp b/src/intrinsics.cpp
index 7893a37664508..38d923cb5a99e 100644
--- a/src/intrinsics.cpp
+++ b/src/intrinsics.cpp
@@ -1134,7 +1134,12 @@ static jl_cgval_t emit_intrinsic(jl_codectx_t &ctx, intrinsic f, jl_value_t **ar
 
     jl_cgval_t *argv = (jl_cgval_t*)alloca(sizeof(jl_cgval_t) * nargs);
     for (size_t i = 0; i < nargs; ++i) {
-        argv[i] = emit_expr(ctx, args[i + 1]);
+        jl_cgval_t arg = emit_expr(ctx, args[i + 1]);
+        if (arg.typ == jl_bottom_type) {
+            // intrinsics generally don't handle buttom values, so bail out early
+            return jl_cgval_t();
+        }
+        argv[i] = arg;
     }
 
     // this forces everything to use runtime-intrinsics (e.g. for testing)
diff --git a/test/compiler/codegen.jl b/test/compiler/codegen.jl
index 4bc7eb8f6d856..11cbd21b793a1 100644
--- a/test/compiler/codegen.jl
+++ b/test/compiler/codegen.jl
@@ -785,3 +785,8 @@ f_isa_type(@nospecialize(x)) = isa(x, Type)
 # Issue #47247
 f47247(a::Ref{Int}, b::Nothing) = setfield!(a, :x, b)
 @test_throws TypeError f47247(Ref(5), nothing)
+
+@testset "regression in generic_bitcast: should support Union{} values" begin
+    f(x) = Core.bitcast(UInt64, x)
+    @test occursin("llvm.trap", get_llvm(f, Tuple{Union{}}))
+end