[Feature Request] Some way to guarantee using caller stack frame

I've been working on creating a programming language with the LLVM backed, and think it would be really interesting if something like the pseudo code below was possible.

```c
[use-caller-stack-frame]
char* temp_error_message(const char* msg){
char error_message[2048];
snprintf(error_message, 2048, "Error: %s", msg);
return error_message;
}

int main(){
char* msg = "This is an error message";
char* error_message = temp_error_message(msg); // valid becuase of [use-parent-stack-frame]
printf("%s\n", error_message);
return 0;
}
```

The issue provides only a C-like pseudocode example involving temp_error_message and main; it names no LLVM files, tests, or implementation entry point. Start by determining which LLVM subsystem would own a caller-stack-frame guarantee and what constraints would define completion, then document the design before attempting implementation.

Written by the indexing model from the issue text.