diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index f208bb72e2e..22f0486e8a2 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -790,6 +790,17 @@ void computeKnownBits(Value *V, APInt &KnownZero, APInt &KnownOne,
     return;
   }
 
+  // A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has
+  // the bits of its aliasee.
+  if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
+    if (GA->mayBeOverridden()) {
+      KnownZero.clearAllBits(); KnownOne.clearAllBits();
+    } else {
+      computeKnownBits(GA->getAliasee(), KnownZero, KnownOne, TD, Depth+1, Q);
+    }
+    return;
+  }
+
   // The address of an aligned GlobalValue has trailing zeros.
   if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
     unsigned Align = GV->getAlignment();
@@ -815,16 +826,6 @@ void computeKnownBits(Value *V, APInt &KnownZero, APInt &KnownOne,
     KnownOne.clearAllBits();
     return;
   }
-  // A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has
-  // the bits of its aliasee.
-  if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
-    if (GA->mayBeOverridden()) {
-      KnownZero.clearAllBits(); KnownOne.clearAllBits();
-    } else {
-      computeKnownBits(GA->getAliasee(), KnownZero, KnownOne, TD, Depth+1, Q);
-    }
-    return;
-  }
 
   if (Argument *A = dyn_cast<Argument>(V)) {
     unsigned Align = A->getType()->isPointerTy() ? A->getParamAlignment() : 0;
diff --git a/test/Transforms/InstCombine/constant-fold-alias.ll b/test/Transforms/InstCombine/constant-fold-alias.ll
new file mode 100644
index 00000000000..13da0f44524
--- /dev/null
+++ b/test/Transforms/InstCombine/constant-fold-alias.ll
@@ -0,0 +1,40 @@
+; RUN: opt -S < %s -instcombine | FileCheck %s
+
+target datalayout = "e-p1:16:16-p2:32:32-p3:64:64"
+
+@G1 = global i32 42, align 1
+@G2 = global i32 42
+@G3 = global [4 x i8] zeroinitializer, align 1
+
+@A1 = alias bitcast (i8* getelementptr inbounds ([4 x i8]* @G3, i32 0, i32 2) to i32*)
+@A2 = alias inttoptr (i64 and (i64 ptrtoint (i8* getelementptr inbounds ([4 x i8]* @G3, i32 0, i32 3) to i64), i64 -4) to i32*)
+
+define i64 @f1() {
+; This cannot be constant folded because G1 is underaligned.
+; CHECK-LABEL: @f1(
+; CHECK: ret i64 and
+  ret i64 and (i64 ptrtoint (i32* @G1 to i64), i64 1)
+}
+
+define i64 @f2() {
+; The preferred alignment for G2 allows this one to foled to zero.
+; CHECK-LABEL: @f2(
+; CHECK: ret i64 0
+  ret i64 and (i64 ptrtoint (i32* @G2 to i64), i64 1)
+}
+
+define i64 @g1() {
+; This cannot be constant folded because A1 aliases G3 which is underalaigned.
+; CHECK-LABEL: @g1(
+; CHECK: ret i64 and
+  ret i64 and (i64 ptrtoint (i32* @A1 to i64), i64 1)
+}
+
+define i64 @g2() {
+; While A2 also aliases G3 which is underaligned, the math of A2 forces a
+; certain alignment allowing this to fold to zero.
+; CHECK-LABEL: @g2(
+; CHECK: ret i64 0
+  ret i64 and (i64 ptrtoint (i32* @A2 to i64), i64 1)
+}
+