Index: llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
===================================================================
--- llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
+++ llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
@@ -1643,10 +1643,12 @@
   // instead of a select to synthesize the desired value.
   bool IsOneZero = false;
   bool EmitOneOrZero = true;
-  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)){
+  auto *CI = dyn_cast<ConstantInt>(OtherVal);
+  if (CI && CI->getValue().getActiveBits() <= 64) {
     IsOneZero = InitVal->isNullValue() && CI->isOne();
 
-    if (ConstantInt *CIInit = dyn_cast<ConstantInt>(GV->getInitializer())){
+    auto *CIInit = dyn_cast<ConstantInt>(GV->getInitializer());
+    if (CIInit && CIInit->getValue().getActiveBits() <= 64) {
       uint64_t ValInit = CIInit->getZExtValue();
       uint64_t ValOther = CI->getZExtValue();
       uint64_t ValMinus = ValOther - ValInit;
Index: llvm/trunk/test/Transforms/GlobalOpt/large-int-crash.ll
===================================================================
--- llvm/trunk/test/Transforms/GlobalOpt/large-int-crash.ll
+++ llvm/trunk/test/Transforms/GlobalOpt/large-int-crash.ll
@@ -0,0 +1,23 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -globalopt -S | FileCheck %s
+
+@X = internal global i128 0
+
+define void @foo() {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:    [[T0_B:%.*]] = load i1, i1* @X
+; CHECK-NEXT:    [[T0:%.*]] = select i1 [[T0_B]], i128 18446744073709551616, i128 0
+; CHECK-NEXT:    ret void
+;
+  %t0 = load i128, i128* @X, align 8
+  ret void
+}
+
+define void @store() {
+; CHECK-LABEL: @store(
+; CHECK-NEXT:    store i1 true, i1* @X
+; CHECK-NEXT:    ret void
+;
+  store i128 18446744073709551616, i128* @X, align 8
+  ret void
+}