tail call (LLVM-266)

[yamt]

there is a todo comment about tail call optimization:

llvm-project/llvm/lib/Target/Xtensa/XtensaISelLowering.cpp

Lines 1039 to 1040 in 6ef2689

	// TODO: Support tail call optimization.
	IsTailCall = false;

do you have any plans or ideas about implementation?
i understand that it isn't straightforward with the windowed abi.

[yamt]

the current code just ignores the musttail attribute.
it should bail out at least.

void
f(void)
{
        void g(void);
        __attribute__((musttail)) return g();
}

[yamt]

the current code just ignores the musttail attribute. it should bail out at least.

void
f(void)
{
        void g(void);
        __attribute__((musttail)) return g();
}

#73

[andreisfr]

Hi @yamt ! Thank you for comment, we have a plans about "tail call" implementation.

[yamt]

Hi @yamt ! Thank you for comment, we have a plans about "tail call" implementation.

are you implying a general implementation is possible? how? just curious.

when caller and callee happen to have the same frame size, maybe you can make it jump into callee+3.
otherwise, i'm not sure how it can be done.

[ProfFan]

Hello @andreisfr do you know what is the status for tail call?