Index: llvm/lib/Analysis/ConstantFolding.cpp
===================================================================
--- llvm/lib/Analysis/ConstantFolding.cpp
+++ llvm/lib/Analysis/ConstantFolding.cpp
@@ -429,18 +429,17 @@
     return true;
 
   if (auto *CI = dyn_cast<ConstantInt>(C)) {
-    if (CI->getBitWidth() > 64 ||
-        (CI->getBitWidth() & 7) != 0)
+    // TODO: Support non-byte-sized integers.
+    if ((CI->getBitWidth() & 7) != 0)
       return false;
-
-    uint64_t Val = CI->getZExtValue();
+    const APInt &Val = CI->getValue();
     unsigned IntBytes = unsigned(CI->getBitWidth()/8);
 
     for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) {
-      int n = ByteOffset;
+      unsigned n = ByteOffset;
       if (!DL.isLittleEndian())
         n = IntBytes - n - 1;
-      CurPtr[i] = (unsigned char)(Val >> (n * 8));
+      CurPtr[i] = Val.extractBits(8, n * 8).getZExtValue();
       ++ByteOffset;
     }
     return true;
Index: llvm/test/Transforms/InstSimplify/ConstProp/loads.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/ConstProp/loads.ll
+++ llvm/test/Transforms/InstSimplify/ConstProp/loads.ll
@@ -412,3 +412,22 @@
   %v = load i8, ptr @g_i1
   ret i8 %v
 }
+
+@global128 = internal constant i128 1125899906842625
+define i128 @load-128bit(){
+; CHECK-LABEL: @load-128bit(
+; CHECK-NEXT:    ret i128 1125899906842625
+;
+  %1 = load i128, ptr @global128, align 4
+  ret i128 %1
+}
+
+; TODO: Current ReadDataFromGlobal assumes only byte-sized integer
+define i43 @load-43bit(){
+; CHECK-LABEL: @load-43bit(
+; CHECK-NEXT:    [[TMP1:%.*]] = load i43, ptr @global128, align 4
+; CHECK-NEXT:    ret i43 [[TMP1]]
+;
+  %1 = load i43, ptr @global128, align 4
+  ret i43 %1
+}