Suggested fix:
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diff --git a/src/hotspot/cpu/x86/register_x86.hpp b/src/hotspot/cpu/x86/register_x86.hpp
index 0c4004d..1461742 100644
--- a/src/hotspot/cpu/x86/register_x86.hpp
+++ b/src/hotspot/cpu/x86/register_x86.hpp
@@ -50,7 +50,7 @@ class RegisterImpl: public AbstractRegisterImpl {
 #else
     number_of_registers = 16,
     number_of_byte_registers = 16,
- max_slots_per_register = 1
+ max_slots_per_register = 2
 #endif // AMD64
   };
 
@@ -256,10 +256,7 @@ class ConcreteRegisterImpl : public AbstractRegisterImpl {
   // There is no requirement that any ordering here matches any ordering c2 gives
   // it's optoregs.
 
- number_of_registers = RegisterImpl::number_of_registers +
-#ifdef AMD64
- RegisterImpl::number_of_registers + // "H" half of a 64bit register
-#endif // AMD64
+ number_of_registers = RegisterImpl::number_of_registers * RegisterImpl::max_slots_per_register +
       2 * FloatRegisterImpl::number_of_registers +
       XMMRegisterImpl::max_slots_per_register * XMMRegisterImpl::number_of_registers +
       KRegisterImpl::number_of_registers + // mask registers
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