Index: lib/Analysis/MemoryBuiltins.cpp
===================================================================
--- lib/Analysis/MemoryBuiltins.cpp
+++ lib/Analysis/MemoryBuiltins.cpp
@@ -392,7 +392,7 @@
   IntTyBits = DL.getPointerTypeSizeInBits(V->getType());
   Zero = APInt::getNullValue(IntTyBits);
 
-  V = V->stripPointerCasts();
+  V = V->stripPointerCasts(/*LookThroughNoAlias*/true);
   if (Instruction *I = dyn_cast<Instruction>(V)) {
     // If we have already seen this instruction, bail out. Cycles can happen in
     // unreachable code after constant propagation.
@@ -612,7 +612,7 @@
     return std::make_pair(ConstantInt::get(Context, Const.first),
                           ConstantInt::get(Context, Const.second));
 
-  V = V->stripPointerCasts();
+  V = V->stripPointerCasts(/*LookThroughNoAlias*/true);
 
   // check cache
   CacheMapTy::iterator CacheIt = CacheMap.find(V);
Index: test/Analysis/BasicAA/global-size.ll
===================================================================
--- test/Analysis/BasicAA/global-size.ll
+++ test/Analysis/BasicAA/global-size.ll
@@ -16,6 +16,17 @@
 ; CHECK: ret i16 0
 }
 
+; CHECK-LABEL: @test1a(
+define i16 @test1a(i32* %P) {
+        %b = call i16* @llvm.noalias.p0i16(i16* @B, metadata !1)
+        %X = load i16, i16* %b
+        store i32 7, i32* %P
+        %Y = load i16, i16* %b
+        %Z = sub i16 %Y, %X
+        ret i16 %Z
+; CHECK: ret i16 0
+}
+
 @B_as1 = addrspace(1) global i16 8
 
 define i16 @test1_as1(i32 addrspace(1)* %P) {
@@ -50,3 +61,8 @@
 ; CHECK: ret i8 %C
 }
 
+declare i16* @llvm.noalias.p0i16(i16*, metadata) nounwind
+
+!0 = !{!0, !"some domain"}
+!1 = !{!1, !0, !"some scope"}
+