[Bug target/82618] Inefficient double-word subtration on x86_64

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82618

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Comment on attachment 42402
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42402
Prototype patch

Nice, thanks.