What does it mean "ppc backend doesn't support sibcalls" ?

[Felix Shvaiger]

Hi, All.
Excuse me for probably very stupid question, but anyway...
I sent report about sibling and tail recursive calls to GNATS (7005)
and got an answer:
> x86 silliness fixed for 3.2.
> ppc backend doesn't support sibcalls
Could somebody please explain me what does it mean
"ppc backend doesn't support sibcalls".
Does it mean "this optimization is not applicable for this architecture" ?
Why ? As far as know PPC assembly and ABI/EABI this optimization
is perfectly applicable. Am I overlooking something ?
Does it mean "GCC code generator module for PPC is not ready for
this optimization" ? Can it be fixed ? When ?
Does it mean something else ?

Thanks.
==============
Felix Shvaiger
fshvaige@cisco.com