[Bug middle-end/90773] Improve piecewise operation

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90773

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> ---
Created attachment 46476
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46476&action=edit
I am testing this patch.