[PATCH] D13358: InstCombine: Fold comparisons between unguessable allocas and other pointers

[Hans Wennborg via llvm-commits]

hans added inline comments.

================
Comment at: lib/Transforms/InstCombine/InstCombineCompares.cpp:780
@@ +779,3 @@
+      // Storing *to* the pointer is fine, but storing the pointer escapes it.
+      if (SI->getValueOperand() == U->get())
+        return nullptr;
----------------
majnemer wrote:
> Is this sufficient?  What if `getValueOperand` is not `U->get()` but, say, a bitcast of `U->get()` ?
I think so. Such a bitcast would show up as a use of our value, so we'd track it and see if it ends up getting stored.

================
Comment at: lib/Transforms/InstCombine/InstCombineCompares.cpp:792-793
@@ +791,4 @@
+        case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
+        case Intrinsic::memcpy: case Intrinsic::memmove: case Intrinsic::memset:
+          continue;
+        default:
----------------
majnemer wrote:
> Can't `memcpy` escape the value just like a `StoreInst` would?
It's not possible to memcpy the value directly. The value would have to be stored in an object, and then that could be memcpy'd. But we'd notice the value escaping through the store.


http://reviews.llvm.org/D13358