Swift triggers an assert in the copy elision code now. We believe this to be cause by i1 parameters. I was able to craft a small reproducer:

target triple = "x86_64-apple-macosx"

@g = common global i8* null, align 8

define void @foo(i32 %a0, i32 %a1, i32 %a2, i32 %a3, i32 %a4, i32 %a5, i1 %a6) {
  %tmp = alloca i1, align 4
  store i1 %a6, i1* %tmp, align 4
  %ptr = bitcast i1* %tmp to i8*
  store i8* %ptr, i8** @g, align 8
  ret void
}