https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90706
--- Comment #2 from Berni <bseifert at gmx dot at> --- (In reply to Georg-Johann Lay from comment #1) > (In reply to Berni from comment #0) > > pushing r0 does not make sense at all since it is by definition a temporary > > register that can freely be modified. Maybe it's just pushed to make room > > for the stack operations? > > Yes. > > The code from v8 is already suboptimal: It's nonsense to load R28 with 0x1 > just to survive a function call. Better use a call-used register and load it > after the function call to where the return value is computed. Then there > would be no need to push/pop R28. > > Does -fno-caller-saves improve v9 code? > > This is definitely not a target issue. It's likely a register-allocation > problem. And the v8 problem is because some (tree) passes move setters away > from their consumers. With option -fno-caller-saves there is no change in v9 code!
