[PATCH] D35633: [ThinLTO] Add FunctionAttr NoRecurse and ReadAttr propagation to ThinLTO

[Charles Saternos via Phabricator via llvm-commits]

ncharlie added inline comments.


================
Comment at: lib/Transforms/IPO/FunctionImport.cpp:445
+              if (!S->fflags().NoRecurse ||
+                  S->getOriginalName() == F->getOriginalName())
+                return false;
----------------
mehdi_amini wrote:
> Not sure why the second condition is needed?
I copied that out of the original FunctionAttrs pass to prevent the function from being marked NoRecurse if it calls itself (http://llvm-cs.pcc.me.uk/lib/Transforms/IPO/FunctionAttrs.cpp#1068).


================
Comment at: lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp:443
+      FS->updateCallGraphEdgeMAK(P.first->getGUID(), P.second);
+    }
+  }
----------------
mehdi_amini wrote:
> Why do we need to mark the edges?
I was planning on using that to propagate read attrs up to the caller. For instance:

```
void x(int *k) { // can't mark readonly since k could be global
  *k++;
}

void j() {
  int i = 5;
  x(&i); // since i is local memory, we can mark j as readnone
}
```

I'm currently working on implementing this - when I finish I'll update the patch.


https://reviews.llvm.org/D35633