[PATCH] D27855: [InstCombine] try to extend nonnull-ness of arguments from a callsite back to its parent function

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


================
Comment at: lib/Transforms/InstCombine/InstCombineCalls.cpp:2799
+  Instruction *Call = CS.getInstruction();
+  auto CallDominatesOtherUsesOfValue = [&Call, &DT](Value *V) {
+    for (User *U : V->users())
----------------
I don't think this check is sufficient; consider something like this:

```
void g(int* NONNULL notnull_ptr);
void f(int *ptr, bool ptr_is_nonnull) {
  if (ptr_is_nonnull) g(ptr);
}
```

I think your check marks the "ptr" argument to f() as nonnull.  This deduction gets propagated out to callers of f(), which then assume the pointer isn't null.


https://reviews.llvm.org/D27855