diff --git a/llvm/lib/Transforms/Scalar/MergeICmps.cpp b/llvm/lib/Transforms/Scalar/MergeICmps.cpp
--- a/llvm/lib/Transforms/Scalar/MergeICmps.cpp
+++ b/llvm/lib/Transforms/Scalar/MergeICmps.cpp
@@ -145,6 +145,10 @@
     return {};
   }
   Value *const Addr = LoadI->getOperand(0);
+  if (Addr->getType()->getPointerAddressSpace() != 0) {
+    LLVM_DEBUG(dbgs() << "from non-zero AddressSpace\n");
+    return {};
+  }
   auto *const GEP = dyn_cast<GetElementPtrInst>(Addr);
   if (!GEP)
     return {};
diff --git a/llvm/test/Transforms/MergeICmps/X86/addressspaces.ll b/llvm/test/Transforms/MergeICmps/X86/addressspaces.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/MergeICmps/X86/addressspaces.ll
@@ -0,0 +1,94 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -S -mergeicmps -verify-dom-info | FileCheck %s
+target triple = "x86_64"
+
+; First check that we try to from a memcmp.
+define void @form_memcmp([2 x i64]* dereferenceable(16) %a, [2 x i64]* dereferenceable(16) %b) {
+; CHECK-LABEL: @form_memcmp(
+; CHECK-NEXT:  bb0:
+; CHECK-NEXT:    [[PTR_A0:%.*]] = getelementptr inbounds [2 x i64], [2 x i64]* [[A:%.*]], i64 0, i64 0
+; CHECK-NEXT:    [[PTR_A1:%.*]] = getelementptr inbounds [2 x i64], [2 x i64]* [[A]], i64 0, i64 1
+; CHECK-NEXT:    [[PTR_B0:%.*]] = getelementptr inbounds [2 x i64], [2 x i64]* [[B:%.*]], i64 0, i64 0
+; CHECK-NEXT:    [[PTR_B1:%.*]] = getelementptr inbounds [2 x i64], [2 x i64]* [[B]], i64 0, i64 1
+; CHECK-NEXT:    br label %"bb1+bb2"
+; CHECK:       "bb1+bb2":
+; CHECK-NEXT:    [[TMP0:%.*]] = getelementptr inbounds [2 x i64], [2 x i64]* [[A]], i64 0, i64 0
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr inbounds [2 x i64], [2 x i64]* [[B]], i64 0, i64 0
+; CHECK-NEXT:    [[CSTR:%.*]] = bitcast i64* [[TMP0]] to i8*
+; CHECK-NEXT:    [[CSTR1:%.*]] = bitcast i64* [[TMP1]] to i8*
+; CHECK-NEXT:    [[MEMCMP:%.*]] = call i32 @memcmp(i8* [[CSTR]], i8* [[CSTR1]], i64 16)
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[MEMCMP]], 0
+; CHECK-NEXT:    br label [[BB3:%.*]]
+; CHECK:       bb3:
+; CHECK-NEXT:    ret void
+;
+bb0:
+  %ptr_a0 = getelementptr inbounds [2 x i64], [2 x i64]* %a, i64 0, i64 0
+  %ptr_a1 = getelementptr inbounds [2 x i64], [2 x i64]* %a, i64 0, i64 1
+  %ptr_b0 = getelementptr inbounds [2 x i64], [2 x i64]* %b, i64 0, i64 0
+  %ptr_b1 = getelementptr inbounds [2 x i64], [2 x i64]* %b, i64 0, i64 1
+  br label %bb1
+
+bb1:                                              ; preds = %bb0
+  %a0 = load i64, i64* %ptr_a0
+  %b0 = load i64, i64* %ptr_b0
+  %cond0 = icmp eq i64 %a0, %b0
+  br i1 %cond0, label %bb2, label %bb3
+
+bb2:                                              ; preds = %bb1
+  %a1 = load i64, i64* %ptr_a1
+  %b1 = load i64, i64* %ptr_b1
+  %cond1 = icmp eq i64 %a1, %b1
+  br label %bb3
+
+bb3:                                              ; preds = %bb2, %bb1
+  %necessary = phi i1 [ %cond1, %bb2 ], [ false, %bb1 ]
+  ret void
+}
+
+; We can't use memcmp between arbitrary addressesspaces
+define void @no_memcmp([2 x i64] addrspace(11)* dereferenceable(16) %a, [2 x i64] addrspace(11)* dereferenceable(16) %b) {
+; CHECK-LABEL: @no_memcmp(
+; CHECK-NEXT:  bb0:
+; CHECK-NEXT:    [[PTR_A0:%.*]] = getelementptr inbounds [2 x i64], [2 x i64] addrspace(11)* [[A:%.*]], i64 0, i64 0
+; CHECK-NEXT:    [[PTR_A1:%.*]] = getelementptr inbounds [2 x i64], [2 x i64] addrspace(11)* [[A]], i64 0, i64 1
+; CHECK-NEXT:    [[PTR_B0:%.*]] = getelementptr inbounds [2 x i64], [2 x i64] addrspace(11)* [[B:%.*]], i64 0, i64 0
+; CHECK-NEXT:    [[PTR_B1:%.*]] = getelementptr inbounds [2 x i64], [2 x i64] addrspace(11)* [[B]], i64 0, i64 1
+; CHECK-NEXT:    br label [[BB1:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[A0:%.*]] = load i64, i64 addrspace(11)* [[PTR_A0]], align 4
+; CHECK-NEXT:    [[B0:%.*]] = load i64, i64 addrspace(11)* [[PTR_B0]], align 4
+; CHECK-NEXT:    [[COND0:%.*]] = icmp eq i64 [[A0]], [[B0]]
+; CHECK-NEXT:    br i1 [[COND0]], label [[BB2:%.*]], label [[BB3:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[A1:%.*]] = load i64, i64 addrspace(11)* [[PTR_A1]], align 4
+; CHECK-NEXT:    [[B1:%.*]] = load i64, i64 addrspace(11)* [[PTR_B1]], align 4
+; CHECK-NEXT:    [[COND1:%.*]] = icmp eq i64 [[A1]], [[B1]]
+; CHECK-NEXT:    br label [[BB3]]
+; CHECK:       bb3:
+; CHECK-NEXT:    [[NECESSARY:%.*]] = phi i1 [ [[COND1]], [[BB2]] ], [ false, [[BB1]] ]
+; CHECK-NEXT:    ret void
+;
+bb0:
+  %ptr_a0 = getelementptr inbounds [2 x i64], [2 x i64] addrspace(11)* %a, i64 0, i64 0
+  %ptr_a1 = getelementptr inbounds [2 x i64], [2 x i64] addrspace(11)* %a, i64 0, i64 1
+  %ptr_b0 = getelementptr inbounds [2 x i64], [2 x i64] addrspace(11)* %b, i64 0, i64 0
+  %ptr_b1 = getelementptr inbounds [2 x i64], [2 x i64] addrspace(11)* %b, i64 0, i64 1
+  br label %bb1
+
+bb1:                                              ; preds = %bb0
+  %a0 = load i64, i64 addrspace(11)* %ptr_a0
+  %b0 = load i64, i64 addrspace(11)* %ptr_b0
+  %cond0 = icmp eq i64 %a0, %b0
+  br i1 %cond0, label %bb2, label %bb3
+
+bb2:                                              ; preds = %bb1
+  %a1 = load i64, i64 addrspace(11)* %ptr_a1
+  %b1 = load i64, i64 addrspace(11)* %ptr_b1
+  %cond1 = icmp eq i64 %a1, %b1
+  br label %bb3
+
+bb3:                                              ; preds = %bb2, %bb1
+  %necessary = phi i1 [ %cond1, %bb2 ], [ false, %bb1 ]
+  ret void
+}