[PATCH] D18634: Don't IPO over functions that can be de-refined

[Sanjoy Das via llvm-commits]

sanjoy added inline comments.

================
Comment at: include/llvm/IR/GlobalValue.h:300
@@ -263,1 +299,3 @@
+  }
+
   bool hasExternalLinkage() const { return isExternalLinkage(getLinkage()); }
----------------
joker.eph wrote:
> Isn't it what `isStrongDefinitionForLinker()` would return?
> 
> I don't see why we need a new predicate? (there are probably already too many...)
> Isn't it what isStrongDefinitionForLinker() would return?

Yes, except that `isStrongDefinitionForLinker` returns `false` for
declarations as well.  But most places where I check `mayBeDerefined`
I also check for `isDeclaration`, so that's not really a problem.

> I don't see why we need a new predicate? (there are probably already too many...)

I was trying to have a distinction between the linkage type, and the
IPO restriction it implies.  So, for instance, if we later add a new
function attribute that allows for the same replacement semantics (or
extract out the optimization restrictions into a function attribute,
and have the linkage type be solely about the linker), then we'd know
what places to update.


Having said that, I don't have a strong opinion one way or the other,
so if the consensus is that it is better to use
`isStrongDefinitionForLinker`, then I'll change the patch to do that.


http://reviews.llvm.org/D18634