[Bug middle-end/122871] [13/14/15/16 Regression] de-optimized synthesis of long long shift and add

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122871

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note shift by over half for the double register is always just one shift in one
register. (Assuming left shift or logical right shift; arthemic (signed) left
shift is 2 shifts, one to splat the sign bit for the upper half, and then shift
for the lower half).