[parisc-linux] HPUX syscall ABI?

[Philipp Rumpf]

> For those interested; Linux syscalls now take the syscall number in r20,
> take arguments in r26-r21, zero r1, r19-r26, r29 and r31 on exit, preserve
> r3-r18, r27(dp) and r30(sp), clobber r2 and return the result in r28.

sounds rather strange but as long as gcc takes it as inline assembly ...

> ObRant: Why on earth define a register to be caller-saves but not allow it
> to contain an argument?  Why force it onto the stack?

An ABI that would specify too many argument registers would force the caller
to load them before the call and the callee to save them again because both
would need the additional argument registers.