# \#calling-convention **URL:** https://discuss.ocaml.org/tag/calling-convention/589.md [Latest](https://discuss.ocaml.org/latest.md) · [Categories](https://discuss.ocaml.org/categories.md) · [Tags](https://discuss.ocaml.org/tags.md) --- ## [When are floating-point registers used in OCaml?](https://discuss.ocaml.org/t/when-are-floating-point-registers-used-in-ocaml/11978)
**Author:** [@otini](https://discuss.ocaml.org/u/otini)\ **Replies:** 3\ **Last updated:** [April 19, 2023, 9:07am UTC](https://discuss.ocaml.org/t/when-are-floating-point-registers-used-in-ocaml/11978 "2023-04-19T09:07:37Z")
I was wondering when OCaml, on x86\_64, uses floating-point registers xmm0-15? I know they can be used when passing unboxed floats to and from C functions. Are they also used in other cases? Does it depend on flambda bein…