[PATCH] D14228: [FunctionAttrs] Identify norecurse functions

[Manman Ren via llvm-commits]

manmanren added inline comments.

================
Comment at: lib/Transforms/IPO/FunctionAttrs.cpp:1832
@@ +1831,3 @@
+  // For a function not to recurse, it must be in its own SCC and must not
+  // call itself or be callable by external functions.
+  if (!SCC.isSingular())
----------------
joker.eph wrote:
> manmanren wrote:
> > This comment seems to be incorrect. Should it be "must not call itself or any function that may be recursive"?
> > 
> It can call a recursive function, as long at it is not involved in the recursion.
> 
> i.e. if:
>  a() calls b()
>  b() calls c()
>  c() calls b()
> 
> a is not recursive, but b() and c() are.
> 
> The issue with external function is that you don't know if they can call back into a() or one of its callers.
> Or did I misunderstand what you meant?
I was talking about what is actually implemented. But it is not the necessary condition.

 // For a function not to recurse, it must be in its own SCC and must not
  // call itself or any function that may be recursive.
is incorrect.

But this makes sense:
// We mark a function as norecurse if it is in its own SCC and it does not call itself
// or any function that may be recursive.



Repository:
  rL LLVM

http://reviews.llvm.org/D14228