Index: include/llvm/IR/Value.h
===================================================================
--- include/llvm/IR/Value.h
+++ include/llvm/IR/Value.h
@@ -509,6 +509,17 @@
                          static_cast<const Value *>(this)->stripPointerCasts());
   }
 
+  /// \brief Strip off pointer casts (except addrspacecast), all-zero GEPs,
+  /// and aliases.
+  ///
+  /// Returns the original uncasted value or addrspacecast (if present).
+  /// If this is called on a non-pointer value, it returns 'this'.
+  const Value *stripPointerCastsKeepAddrSpaceCast() const;
+  Value *stripPointerCastsKeepAddrSpaceCast() {
+    return const_cast<Value *>(
+      static_cast<const Value *>(this)->stripPointerCastsKeepAddrSpaceCast());
+  }
+
   /// \brief Strip off pointer casts, all-zero GEPs, aliases and barriers.
   ///
   /// Returns the original uncasted value.  If this is called on a non-pointer
Index: lib/IR/Value.cpp
===================================================================
--- lib/IR/Value.cpp
+++ lib/IR/Value.cpp
@@ -490,6 +490,7 @@
 enum PointerStripKind {
   PSK_ZeroIndices,
   PSK_ZeroIndicesAndAliases,
+  PSK_ZeroIndicesAndAliasesKeepAddrSpaceCast,
   PSK_ZeroIndicesAndAliasesAndBarriers,
   PSK_InBoundsConstantIndices,
   PSK_InBounds
@@ -509,6 +510,7 @@
     if (auto *GEP = dyn_cast<GEPOperator>(V)) {
       switch (StripKind) {
       case PSK_ZeroIndicesAndAliases:
+      case PSK_ZeroIndicesAndAliasesKeepAddrSpaceCast:
       case PSK_ZeroIndicesAndAliasesAndBarriers:
       case PSK_ZeroIndices:
         if (!GEP->hasAllZeroIndices())
@@ -525,7 +527,8 @@
       }
       V = GEP->getPointerOperand();
     } else if (Operator::getOpcode(V) == Instruction::BitCast ||
-               Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
+               (StripKind != PSK_ZeroIndicesAndAliasesKeepAddrSpaceCast &&
+                Operator::getOpcode(V) == Instruction::AddrSpaceCast)) {
       V = cast<Operator>(V)->getOperand(0);
     } else if (auto *GA = dyn_cast<GlobalAlias>(V)) {
       if (StripKind == PSK_ZeroIndices || GA->isInterposable())
@@ -559,6 +562,11 @@
   return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
 }
 
+const Value *Value::stripPointerCastsKeepAddrSpaceCast() const {
+  return stripPointerCastsAndOffsets<
+    PSK_ZeroIndicesAndAliasesKeepAddrSpaceCast>(this);
+}
+
 const Value *Value::stripPointerCastsNoFollowAliases() const {
   return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
 }
Index: lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- lib/Transforms/InstCombine/InstructionCombining.cpp
+++ lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -135,6 +135,10 @@
 static cl::opt<unsigned> ShouldLowerDbgDeclare("instcombine-lower-dbg-declare",
                                                cl::Hidden, cl::init(true));
 
+static cl::opt<bool>
+NoAddrSpaceCastFolding("instcombine-no-addrspacecast-folding",
+                       cl::desc("Do not fold addrspacecast into GEP."));
+
 Value *InstCombiner::EmitGEPOffset(User *GEP) {
   return llvm::EmitGEPOffset(&Builder, DL, GEP);
 }
@@ -1771,7 +1775,11 @@
     return nullptr;
 
   // Handle gep(bitcast x) and gep(gep x, 0, 0, 0).
-  Value *StrippedPtr = PtrOp->stripPointerCasts();
+  Value *StrippedPtr;
+  if (NoAddrSpaceCastFolding)
+    StrippedPtr = PtrOp->stripPointerCastsKeepAddrSpaceCast();
+  else
+    StrippedPtr = PtrOp->stripPointerCasts();
   PointerType *StrippedPtrTy = cast<PointerType>(StrippedPtr->getType());
 
   if (StrippedPtr != PtrOp) {
Index: test/Transforms/InstCombine/cast-no-addrspacecast-folding.ll
===================================================================
--- /dev/null
+++ test/Transforms/InstCombine/cast-no-addrspacecast-folding.ll
@@ -0,0 +1,16 @@
+; RUN: opt < %s -instcombine -instcombine-no-addrspacecast-folding=true -S | FileCheck %s
+target datalayout = "E-p:64:64:64-p1:32:32:32-p2:64:64:64-p3:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128-n8:16:32:64"
+
+define double @test80_addrspacecast(double addrspace(1)* %p, i32 %i) {
+; CHECK-LABEL: @test80_addrspacecast(
+; CHECK-NEXT:    [[Q:%.*]] = addrspacecast double addrspace(1)* %p to double addrspace(2)*
+; CHECK-NEXT:    [[S:%.*]] = sext i32 %i to i64
+; CHECK-NEXT:    [[PP:%.*]] = getelementptr double, double addrspace(2)* [[Q]], i64 [[S]]
+; CHECK-NEXT:    [[L:%.*]] = load double, double addrspace(2)* [[PP]], align 8
+; CHECK-NEXT:    ret double [[L]]
+;
+  %q = addrspacecast double addrspace(1)* %p to double addrspace(2)*
+  %pp = getelementptr double, double addrspace(2)* %q, i32 %i
+  %l = load double, double addrspace(2)* %pp
+  ret double %l
+}