Index: include/llvm/IR/Value.h
===================================================================
--- include/llvm/IR/Value.h
+++ include/llvm/IR/Value.h
@@ -481,6 +481,16 @@
     return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
   }
 
+  /// \brief Strip off pointer casts and all-zero GEPs without stripping
+  /// @llvm.noalias intrinsics.
+  ///
+  /// Returns the original uncasted value.  If this is called on a non-pointer
+  /// value, it returns 'this'.
+  Value *stripPointerCastsExceptNoAlias();
+  const Value *stripPointerCastsExceptNoAlias() const {
+    return const_cast<Value*>(this)->stripPointerCastsExceptNoAlias();
+  }
+
   /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
   ///
   /// Stores the resulting constant offset stripped into the APInt provided.
Index: lib/IR/Value.cpp
===================================================================
--- lib/IR/Value.cpp
+++ lib/IR/Value.cpp
@@ -429,7 +429,7 @@
 };
 
 template <PointerStripKind StripKind>
-static Value *stripPointerCastsAndOffsets(Value *V) {
+static Value *stripPointerCastsAndOffsets(Value *V, bool StripNoAlias = true) {
   if (!V->getType()->isPointerTy())
     return V;
 
@@ -466,8 +466,14 @@
     } else {
       if (auto CS = CallSite(V))
         if (Value *RV = CS.getReturnedArgOperand()) {
-          V = RV;
-          continue;
+          bool IsNoAlias = false;
+          if (auto *I = dyn_cast<IntrinsicInst>(V))
+            IsNoAlias = I->getIntrinsicID() == Intrinsic::noalias;
+
+          if (StripNoAlias || !IsNoAlias) {
+            V = RV;
+            continue;
+          }
         }
 
       return V;
@@ -487,6 +493,10 @@
   return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
 }
 
+Value *Value::stripPointerCastsExceptNoAlias() {
+  return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this, false);
+}
+
 Value *Value::stripInBoundsConstantOffsets() {
   return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
 }
Index: lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- lib/Transforms/InstCombine/InstructionCombining.cpp
+++ lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1655,7 +1655,7 @@
   }
 
   // Handle gep(bitcast x) and gep(gep x, 0, 0, 0).
-  Value *StrippedPtr = PtrOp->stripPointerCasts();
+  Value *StrippedPtr = PtrOp->stripPointerCastsExceptNoAlias();
   PointerType *StrippedPtrTy = dyn_cast<PointerType>(StrippedPtr->getType());
 
   // We do not handle pointer-vector geps here.
Index: test/Transforms/InstCombine/noalias.ll
===================================================================
--- /dev/null
+++ test/Transforms/InstCombine/noalias.ll
@@ -0,0 +1,24 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+@g = global i32* null
+
+define i32 @test1(i32* %q, i32* %p, i1 %b) {
+  %pa = tail call i32* @llvm.noalias.p0i32(i32* %p, metadata !0)
+  %tmp2 = getelementptr inbounds i32, i32* %pa, i64 2
+  %val = load i32, i32* %tmp2, align 4
+  store i32 0, i32* %pa, align 4
+  store i32* %q, i32** @g, align 8
+  ret i32 %val
+
+; CHECK-LABEL: @test1
+; CHECK: call i32* @llvm.noalias.p0i32
+; CHECK: getelementptr inbounds i32, i32* %pa, i64 2
+; CHECK: ret i32
+}
+
+declare i32* @llvm.noalias.p0i32(i32*, metadata) nounwind
+
+!0 = !{!0, !"some domain"}
+!1 = !{!1, !0, !"some scope"}