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<div>typedef struct vtable_t {<br>
int (*pf4)(int a, int b, int c, int d);<br>
int (*pf5)(int a, int b, int c, int d, int e);<br>
} vtable_t;</div>
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<div>int f1(int (*pf4)(int a, int b, int c, int d))<br>
{<br>
return pf4(1, 2, 3, 4);<br>
}</div>
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<div>int f2(vtable_t *vt)<br>
{<br>
return vt->pf4(1, 2, 3, 4);<br>
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<div>}</div>
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<div>gcc and clang will not tailcall these on arm with -O3.</div>
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<div>int f3(int (*pf5)(int a, int b, int c, int d, int e))<br>
{<br>
return pf5(1, 2, 3, 4, 5);<br>
}</div>
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<div>int f4(vtable_t *vt)<br>
{<br>
return vt->pf5(1, 2, 3, 4, 5);<br>
}</div>
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Could you not allocate an extra word on the stack,<br>
in the first position, store the return address there, and pop<br>
it to pc (or ip and then move to pc) after restoring nonvolatiles and lr?</div>
<div>Is that not describable in unwind data?</div>
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<div>I only tested Debian's 3.3 so far but I'll try to try 6.0.</div>
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<p style="margin-top:0;margin-bottom:0">I ask because I'm working on tailcalls in another project.</p>
<p style="margin-top:0;margin-bottom:0">I figured I'd look at gcc/clang output for hints here.</p>
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<p style="margin-top:0;margin-bottom:0">I understand there can be multiple exits of a function -- tailcalls of varying signatures and non-tailcalls.<br>
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<p style="margin-top:0;margin-bottom:0">I don't think that breaks the idea.</p>
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<p style="margin-top:0;margin-bottom:0">Thank you,</p>
<p style="margin-top:0;margin-bottom:0"> - Jay</p>
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