================
@@ -12658,10 +12658,10 @@ This instruction requires several arguments:
the return value of the callee is returned to the caller's caller, even
if a void return type is in use.
- Both markers imply that the callee does not access allocas from the caller.
- The ``tail`` marker additionally implies that the callee does not access
- varargs from the caller. Calls marked ``musttail`` must obey the following
- additional rules:
+ Both markers imply that the callee does not access allocas or ``byval``
+ arguments from the caller. The ``tail`` marker additionally implies that the
----------------
rnk wrote:
I think you want to say that this case is not supported:
```
struct ByVal { int large[5]; };
void f(ByVal*);
void g(ByVal o) {
[[clang::musttail]] f(&o);
}
```
The LangRef needs to permit *forwarding* cases like this, though:
```
struct ByVal { int large[5]; };
void f(ByVal a, ByVal b);
void g(ByVal a, ByVal b) {
[[clang::musttail]] f(b, a);
}
```
We can make this work by copying the arguments out and back in before tearing
down the call frame.
Can you please clarify?
https://github.com/llvm/llvm-project/pull/109943
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