[Mlir-commits] [mlir] [MLIR][LivenessAnalysis] Treat a public function as an external (PR #160648)

[xin liu]

================
@@ -503,12 +504,18 @@ AbstractSparseBackwardDataFlowAnalysis::visitOperation(Operation *op) {
       // If the call invokes an external function (or a function treated as
       // external due to config), defer to the corresponding extension hook.
       // By default, it just does `visitCallOperand` for all operands.
+      //
+      // If callable is a public function, treat it as an external function.
+      // Transforms like RemoveDeadValues cannot change the arguments or returns
+      // of it.
----------------
navyxliu wrote:

Sorry, but I still don't think the message is accurate. it's not "callers we can't visit". It's the other way around. 

If a callee is public, we can't change its function signature. 
if we delete d, we need to change the function signature, or figure out how to replace d with something cheaper than that. 

```
public void foo(%unused : i32) 

void bar() {
int d = computation();
foo(d);
}
```

Could you take a look my new message? 

https://github.com/llvm/llvm-project/pull/160648