Index: lib/Analysis/ValueTracking.cpp
===================================================================
--- lib/Analysis/ValueTracking.cpp
+++ lib/Analysis/ValueTracking.cpp
@@ -793,22 +793,11 @@
     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();
+  if (GlobalObject *GO = dyn_cast<GlobalObject>(V)) {
+    unsigned Align = GO->getAlignment();
     if (Align == 0 && TD) {
-      if (GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
+      if (GlobalVariable *GVar = dyn_cast<GlobalVariable>(GO)) {
         Type *ObjectType = GVar->getType()->getElementType();
         if (ObjectType->isSized()) {
           // If the object is defined in the current Module, we'll be giving
@@ -855,6 +844,17 @@
   if (Depth == MaxDepth)
     return;  // Limit search depth.
 
+  // 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;
+  }
+
   // Check whether a nearby assume intrinsic can determine some known bits.
   computeKnownBitsFromAssume(V, KnownZero, KnownOne, TD, Depth, Q);
 
Index: test/Transforms/InstCombine/alias-recursion.ll
===================================================================
--- test/Transforms/InstCombine/alias-recursion.ll
+++ test/Transforms/InstCombine/alias-recursion.ll
@@ -0,0 +1,45 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+%rtti.CompleteObjectLocator = type { i32, i32, i32, i32, i32, i32 }
+%rtti.TypeDescriptor = type { i8**, i8*, [8 x i8] }
+%rtti.ClassHierarchyDescriptor = type { i32, i32, i32, i32 }
+%rtti.BaseClassDescriptor = type { i32, i32, i32, i32, i32, i32, i32 }
+%class.A = type { i32 (...)** }
+
+@0 = private unnamed_addr constant [2 x i8*] [i8* bitcast (%rtti.CompleteObjectLocator* @"\01??_R4A@@6B@" to i8*), i8* bitcast (i32 (%class.A*)* @"\01?virt@A@@UEAAHXZ" to i8*)]
+@"\01??_R4A@@6B@" = linkonce_odr constant %rtti.CompleteObjectLocator { i32 1, i32 0, i32 0, i32 trunc (i64 sub nuw nsw (i64 ptrtoint (%rtti.TypeDescriptor* @"\01??_R0?AVA@@@8" to i64), i64 ptrtoint (i8* @__ImageBase to i64)) to i32), i32 trunc (i64 sub nuw nsw (i64 ptrtoint (%rtti.ClassHierarchyDescriptor* @"\01??_R3A@@8" to i64), i64 ptrtoint (i8* @__ImageBase to i64)) to i32), i32 trunc (i64 sub nuw nsw (i64 ptrtoint (%rtti.CompleteObjectLocator* @"\01??_R4A@@6B@" to i64), i64 ptrtoint (i8* @__ImageBase to i64)) to i32) }
+@"\01??_7type_info@@6B@" = external constant i8*
+@"\01??_R0?AVA@@@8" = linkonce_odr global %rtti.TypeDescriptor { i8** @"\01??_7type_info@@6B@", i8* null, [8 x i8] c".?AVA@@\00" }
+@__ImageBase = external constant i8
+@"\01??_R3A@@8" = linkonce_odr constant %rtti.ClassHierarchyDescriptor { i32 0, i32 0, i32 1, i32 trunc (i64 sub nuw nsw (i64 ptrtoint ([2 x i32]* @"\01??_R2A@@8" to i64), i64 ptrtoint (i8* @__ImageBase to i64)) to i32) }
+@"\01??_R2A@@8" = linkonce_odr constant [2 x i32] [i32 trunc (i64 sub nuw nsw (i64 ptrtoint (%rtti.BaseClassDescriptor* @"\01??_R1A@?0A@EA@A@@8" to i64), i64 ptrtoint (i8* @__ImageBase to i64)) to i32), i32 0]
+@"\01??_R1A@?0A@EA@A@@8" = linkonce_odr constant %rtti.BaseClassDescriptor { i32 trunc (i64 sub nuw nsw (i64 ptrtoint (%rtti.TypeDescriptor* @"\01??_R0?AVA@@@8" to i64), i64 ptrtoint (i8* @__ImageBase to i64)) to i32), i32 0, i32 0, i32 -1, i32 0, i32 64, i32 trunc (i64 sub nuw nsw (i64 ptrtoint (%rtti.ClassHierarchyDescriptor* @"\01??_R3A@@8" to i64), i64 ptrtoint (i8* @__ImageBase to i64)) to i32) }
+@"\01??_7A@@6B@" = unnamed_addr alias getelementptr inbounds ([2 x i8*]* @0, i32 0, i32 1)
+
+define void @test() {
+; CHECK-LABEL: test
+entry:
+  br i1 undef, label %for.body.lr.ph, label %for.end
+
+for.body.lr.ph:                                   ; preds = %entry
+  br label %for.body
+
+for.body:                                         ; preds = %for.body.for.body_crit_edge, %for.body.lr.ph
+  %vtable = phi i32 (%class.A*)** [ bitcast (i8** @"\01??_7A@@6B@" to i32 (%class.A*)**), %for.body.lr.ph ], [ null, %for.body.for.body_crit_edge ]
+  %0 = load i32 (%class.A*)** %vtable, align 8
+  %call2 = tail call i32 %0(%class.A* undef)
+  br i1 undef, label %for.body.for.body_crit_edge, label %for.end
+
+for.body.for.body_crit_edge:                      ; preds = %for.body
+  br label %for.body
+
+for.end:                                          ; preds = %for.body, %entry
+  ret void
+}
+
+declare i32 @"\01?virt@A@@UEAAHXZ"(%class.A*) unnamed_addr align 2
+
+