[Bug rtl-optimization/61605] Potential optimization: Keep unclobbered argument registers live across function calls

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61605

--- Comment #7 from vries at gcc dot gnu.org ---
Created attachment 33619
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33619&action=edit
[2/2] Don't regard a copy with identical src and dest as killing dest

This patch adds handling of copies with identical source and destination
register in copyprop_hardreg_forward_1.

Using this patch series we get the desired code.