Move isKnownNonNull out of AliasAnalysis.h and into ValueTracking.cpp since

it isn't really an AliasAnalysis concept, and ValueTracking has similar things
that it could plausibly share code with some day.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174027 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/ValueTracking.cpp

@@ -2014,3 +2014,19 @@ bool llvm::isSafeToSpeculativelyExecute(const Value *V,
     return false; // Misc instructions which have effects
   }
 }
+
+/// isKnownNonNull - Return true if we know that the specified value is never
+/// null.
+bool llvm::isKnownNonNull(const Value *V) {
+  // Alloca never returns null, malloc might.
+  if (isa<AllocaInst>(V)) return true;
+
+  // A byval argument is never null.
+  if (const Argument *A = dyn_cast<Argument>(V))
+    return A->hasByValAttr();
+
+  // Global values are not null unless extern weak.
+  if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
+    return !GV->hasExternalWeakLinkage();
+  return false;
+}