[llvm] r312648 - Fix PR33878: BasicAA incorrectly assumes different address spaces don't alias

[Nuno Lopes via llvm-commits]

Author: nlopes
Date: Wed Sep  6 09:55:31 2017
New Revision: 312648

URL: http://llvm.org/viewvc/llvm-project?rev=312648&view=rev
Log:
Fix PR33878: BasicAA incorrectly assumes different address spaces don't alias
Remove code that assumed that a nullptr of address space != 0 couldnt alias with a non-null pointer. This is incorrect, since nothing can be concluded about a null pointer in an address space != 0.
This code was written before address spaces were introduced

Differential Revision: https://reviews.llvm.org/D37518

Modified:
    llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp

Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=312648&r1=312647&r2=312648&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Wed Sep  6 09:55:31 2017
@@ -1590,11 +1590,6 @@ AliasResult BasicAAResult::aliasCheck(co
         (isa<Argument>(O2) && isIdentifiedFunctionLocal(O1)))
       return NoAlias;
 
-    // Most objects can't alias null.
-    if ((isa<ConstantPointerNull>(O2) && isKnownNonNull(O1)) ||
-        (isa<ConstantPointerNull>(O1) && isKnownNonNull(O2)))
-      return NoAlias;
-
     // If one pointer is the result of a call/invoke or load and the other is a
     // non-escaping local object within the same function, then we know the
     // object couldn't escape to a point where the call could return it.