diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index b744537aeb474..31546e628b226 100755
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1495,22 +1495,22 @@ Constant *llvm::ConstantFoldCastOperand(unsigned Opcode, Constant *C,
   default:
     llvm_unreachable("Missing case");
   case Instruction::PtrToAddr:
-    // TODO: Add some of the ptrtoint folds here as well.
-    break;
   case Instruction::PtrToInt:
     if (auto *CE = dyn_cast<ConstantExpr>(C)) {
       Constant *FoldedValue = nullptr;
-      // If the input is a inttoptr, eliminate the pair.  This requires knowing
+      // If the input is an inttoptr, eliminate the pair.  This requires knowing
       // the width of a pointer, so it can't be done in ConstantExpr::getCast.
       if (CE->getOpcode() == Instruction::IntToPtr) {
-        // zext/trunc the inttoptr to pointer size.
-        FoldedValue = ConstantFoldIntegerCast(CE->getOperand(0),
-                                              DL.getIntPtrType(CE->getType()),
+        // zext/trunc the inttoptr to pointer/address size.
+        Type *MidTy = Opcode == Instruction::PtrToInt
+                          ? DL.getAddressType(CE->getType())
+                          : DL.getIntPtrType(CE->getType());
+        FoldedValue = ConstantFoldIntegerCast(CE->getOperand(0), MidTy,
                                               /*IsSigned=*/false, DL);
       } else if (auto *GEP = dyn_cast<GEPOperator>(CE)) {
         // If we have GEP, we can perform the following folds:
-        // (ptrtoint (gep null, x)) -> x
-        // (ptrtoint (gep (gep null, x), y) -> x + y, etc.
+        // (ptrtoint/ptrtoaddr (gep null, x)) -> x
+        // (ptrtoint/ptrtoaddr (gep (gep null, x), y) -> x + y, etc.
         unsigned BitWidth = DL.getIndexTypeSizeInBits(GEP->getType());
         APInt BaseOffset(BitWidth, 0);
         auto *Base = cast<Constant>(GEP->stripAndAccumulateConstantOffsets(
@@ -1518,7 +1518,8 @@ Constant *llvm::ConstantFoldCastOperand(unsigned Opcode, Constant *C,
         if (Base->isNullValue()) {
           FoldedValue = ConstantInt::get(CE->getContext(), BaseOffset);
         } else {
-          // ptrtoint (gep i8, Ptr, (sub 0, V)) -> sub (ptrtoint Ptr), V
+          // ptrtoint/ptrtoaddr (gep i8, Ptr, (sub 0, V))
+          //   -> sub (ptrtoint/ptrtoaddr Ptr), V
           if (GEP->getNumIndices() == 1 &&
               GEP->getSourceElementType()->isIntegerTy(8)) {
             auto *Ptr = cast<Constant>(GEP->getPointerOperand());
@@ -1528,12 +1529,13 @@ Constant *llvm::ConstantFoldCastOperand(unsigned Opcode, Constant *C,
                 Sub->getOpcode() == Instruction::Sub &&
                 Sub->getOperand(0)->isNullValue())
               FoldedValue = ConstantExpr::getSub(
-                  ConstantExpr::getPtrToInt(Ptr, IntIdxTy), Sub->getOperand(1));
+                  ConstantExpr::getCast(Opcode, Ptr, IntIdxTy),
+                  Sub->getOperand(1));
           }
         }
       }
       if (FoldedValue) {
-        // Do a zext or trunc to get to the ptrtoint dest size.
+        // Do a zext or trunc to get to the ptrtoint/ptrtoaddr dest size.
         return ConstantFoldIntegerCast(FoldedValue, DestTy, /*IsSigned=*/false,
                                        DL);
       }
diff --git a/llvm/test/Transforms/InstCombine/ptrtoaddr.ll b/llvm/test/Transforms/InstCombine/ptrtoaddr.ll
index 61b13312521d2..f76a1399f8f2a 100644
--- a/llvm/test/Transforms/InstCombine/ptrtoaddr.ll
+++ b/llvm/test/Transforms/InstCombine/ptrtoaddr.ll
@@ -1,6 +1,14 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
 ; RUN: opt < %s -passes=instcombine -S | FileCheck %s
-target datalayout = "p1:64:64:64:32"
+
+; The ptrtoaddr folds are also valid for pointers that have external state.
+target datalayout = "pe1:64:64:64:32"
+
+@g = external global i8
+@g2 = external global i8
+
+@g.as1 = external addrspace(1) global i8
+@g2.as1 = external addrspace(1) global i8
 
 define i32 @ptrtoaddr_inttoptr_arg(i32 %a) {
 ; CHECK-LABEL: define i32 @ptrtoaddr_inttoptr_arg(
@@ -24,14 +32,14 @@ define i32 @ptrtoaddr_inttoptr() {
 
 define i32 @ptrtoaddr_inttoptr_diff_size1() {
 ; CHECK-LABEL: define i32 @ptrtoaddr_inttoptr_diff_size1() {
-; CHECK-NEXT:    ret i32 ptrtoaddr (ptr addrspace(1) inttoptr (i64 -1 to ptr addrspace(1)) to i32)
+; CHECK-NEXT:    ret i32 -1
 ;
   ret i32 ptrtoaddr (ptr addrspace(1) inttoptr (i64 -1 to ptr addrspace(1)) to i32)
 }
 
 define i32 @ptrtoaddr_inttoptr_diff_size2() {
 ; CHECK-LABEL: define i32 @ptrtoaddr_inttoptr_diff_size2() {
-; CHECK-NEXT:    ret i32 ptrtoaddr (ptr addrspace(1) inttoptr (i16 -1 to ptr addrspace(1)) to i32)
+; CHECK-NEXT:    ret i32 65535
 ;
   ret i32 ptrtoaddr (ptr addrspace(1) inttoptr (i16 -1 to ptr addrspace(1)) to i32)
 }
@@ -52,14 +60,42 @@ define i64 @ptr2addr2_inttoptr_noas2() {
 
 define i64 @ptrtoaddr_inttoptr_noas_diff_size1() {
 ; CHECK-LABEL: define i64 @ptrtoaddr_inttoptr_noas_diff_size1() {
-; CHECK-NEXT:    ret i64 ptrtoaddr (ptr inttoptr (i32 -1 to ptr) to i64)
+; CHECK-NEXT:    ret i64 4294967295
 ;
   ret i64 ptrtoaddr (ptr inttoptr (i32 -1 to ptr) to i64)
 }
 
 define i64 @ptrtoaddr_inttoptr_noas_diff_size2() {
 ; CHECK-LABEL: define i64 @ptrtoaddr_inttoptr_noas_diff_size2() {
-; CHECK-NEXT:    ret i64 ptrtoaddr (ptr inttoptr (i128 -1 to ptr) to i64)
+; CHECK-NEXT:    ret i64 -1
 ;
   ret i64 ptrtoaddr (ptr inttoptr (i128 -1 to ptr) to i64)
 }
+
+define i64 @ptrtoaddr_gep_null() {
+; CHECK-LABEL: define i64 @ptrtoaddr_gep_null() {
+; CHECK-NEXT:    ret i64 42
+;
+  ret i64 ptrtoaddr (ptr getelementptr (i8, ptr null, i64 42) to i64)
+}
+
+define i32 @ptrtoaddr_gep_null_addrsize() {
+; CHECK-LABEL: define i32 @ptrtoaddr_gep_null_addrsize() {
+; CHECK-NEXT:    ret i32 42
+;
+  ret i32 ptrtoaddr (ptr addrspace(1) getelementptr (i8, ptr addrspace(1) null, i32 42) to i32)
+}
+
+define i64 @ptrtoaddr_gep_sub() {
+; CHECK-LABEL: define i64 @ptrtoaddr_gep_sub() {
+; CHECK-NEXT:    ret i64 sub (i64 ptrtoaddr (ptr @g to i64), i64 ptrtoaddr (ptr @g2 to i64))
+;
+  ret i64 ptrtoaddr (ptr getelementptr (i8, ptr @g, i64 sub (i64 0, i64 ptrtoaddr (ptr @g2 to i64))) to i64)
+}
+
+define i32 @ptrtoaddr_gep_sub_addrsize() {
+; CHECK-LABEL: define i32 @ptrtoaddr_gep_sub_addrsize() {
+; CHECK-NEXT:    ret i32 sub (i32 ptrtoaddr (ptr addrspace(1) @g.as1 to i32), i32 ptrtoaddr (ptr addrspace(1) @g2.as1 to i32))
+;
+  ret i32 ptrtoaddr (ptr addrspace(1) getelementptr (i8, ptr addrspace(1) @g.as1, i32 sub (i32 0, i32 ptrtoaddr (ptr addrspace(1) @g2.as1 to i32))) to i32)
+}