--- a/src/hotspot/share/c1/c1_Instruction.hpp	Mon May 21 21:27:12 2018 -0700
+++ b/src/hotspot/share/c1/c1_Instruction.hpp	Tue May 22 09:04:15 2018 +0200
@@ -2122,11 +2122,11 @@
   // creation
   TableSwitch(Value tag, BlockList* sux, int lo_key, ValueStack* state_before, bool is_safepoint)
     : Switch(tag, sux, state_before, is_safepoint)
-  , _lo_key(lo_key) {}
+  , _lo_key(lo_key) { assert(_lo_key <= hi_key(), "integer overflow"); }
 
   // accessors
   int lo_key() const                             { return _lo_key; }
-  int hi_key() const                             { return _lo_key + length() - 1; }
+  int hi_key() const                             { return _lo_key + (length() - 1); }
 };
 
 

--- a/src/hotspot/share/c1/c1_LIRGenerator.cpp	Mon May 21 21:27:12 2018 -0700
+++ b/src/hotspot/share/c1/c1_LIRGenerator.cpp	Tue May 22 09:04:15 2018 +0200
@@ -2304,8 +2304,8 @@
   move_to_phi(x->state());
 
   int lo_key = x->lo_key();
-  int hi_key = x->hi_key();
   int len = x->length();
+  assert(lo_key <= (lo_key + (len - 1)), "integer overflow");
   LIR_Opr value = tag.result();
 
   if (compilation()->env()->comp_level() == CompLevel_full_profile && UseSwitchProfiling) {