For example, we seek to eliminate the gc frame from this function, as
observed here:

```julia
julia> code_llvm((BitSet,), raw=true) do x; r = x.bits; GC.safepoint(); @inbounds r[1]; end
; Function Signature: var"#3"(Base.BitSet)
;  @ REPL[1]:1 within `#3`
define swiftcc i64 @"julia_#3_494"(ptr nonnull swiftself %pgcstack, ptr noundef nonnull align 8 dereferenceable(16) %"x::BitSet") #0 !dbg !5 {
top:
  call void @llvm.dbg.declare(metadata ptr %"x::BitSet", metadata !21, metadata !DIExpression()), !dbg !22
  %ptls_field = getelementptr inbounds ptr, ptr %pgcstack, i64 2
  %ptls_load = load ptr, ptr %ptls_field, align 8, !tbaa !23
  %0 = getelementptr inbounds ptr, ptr %ptls_load, i64 2
  %safepoint = load ptr, ptr %0, align 8, !tbaa !27
  fence syncscope("singlethread") seq_cst
  %1 = load volatile i64, ptr %safepoint, align 8, !dbg !22
  fence syncscope("singlethread") seq_cst
; ┌ @ Base.jl:49 within `getproperty`
   %"x::BitSet.bits" = load atomic ptr, ptr %"x::BitSet" unordered, align 8, !dbg !29, !tbaa !27, !alias.scope !33, !noalias !36, !nonnull !11, !dereferenceable !41, !align !42
; └
; ┌ @ gcutils.jl:253 within `safepoint`
   %ptls_load4 = load ptr, ptr %ptls_field, align 8, !dbg !43, !tbaa !23
   %2 = getelementptr inbounds ptr, ptr %ptls_load4, i64 2, !dbg !43
   %safepoint5 = load ptr, ptr %2, align 8, !dbg !43, !tbaa !27
   fence syncscope("singlethread") seq_cst, !dbg !43
   %3 = load volatile i64, ptr %safepoint5, align 8, !dbg !43
   fence syncscope("singlethread") seq_cst, !dbg !43
; └
; ┌ @ essentials.jl:892 within `getindex`
   %4 = load ptr, ptr %"x::BitSet.bits", align 8, !dbg !46, !tbaa !49, !alias.scope !52, !noalias !53
   %5 = load i64, ptr %4, align 8, !dbg !46, !tbaa !54, !alias.scope !57, !noalias !58
   ret i64 %5, !dbg !46
; └
}
```