x86: Fix post-call NOP check access outside code blob

Change-Id: I5f5fd681ba699f96859180d984841dd6df8524b5

Author: ruben-arm

src/hotspot/cpu/x86/c1_LIRAssembler_x86.hpp

@@ -48,7 +48,7 @@
   enum {
     _call_stub_size = 28,
     _exception_handler_size = DEBUG_ONLY(1*K) NOT_DEBUG(175),
-    _deopt_handler_size = 10
+    _deopt_handler_size = 7
   };
 
 public:

src/hotspot/cpu/x86/nativeInst_x86.hpp

@@ -73,6 +73,7 @@ class NativeInstruction {
   s_char sbyte_at(int offset) const    { return *(s_char*) addr_at(offset); }
   u_char ubyte_at(int offset) const    { return *(u_char*) addr_at(offset); }
 
+  jshort short_at(int offset) const    { return *(jshort*) addr_at(offset); }
   jint int_at(int offset) const         { return *(jint*) addr_at(offset); }
 
   intptr_t ptr_at(int offset) const    { return *(intptr_t*) addr_at(offset); }
@@ -581,7 +582,7 @@ class NativePostCallNop: public NativeInstruction {
     displacement_offset = 4
   };
 
-  bool check() const { return int_at(0) == 0x841f0f; }
+  bool check() const { return short_at(0) == 0x1f0f && short_at(2) == 0x0084; }
   bool decode(int32_t& oopmap_slot, int32_t& cb_offset) const {
     int32_t data = int_at(displacement_offset);
     if (data == 0) {

src/hotspot/cpu/x86/x86.ad

@@ -2771,7 +2771,7 @@ class HandlerImpl {
 
   static uint size_deopt_handler() {
     // one call and one jmp.
-    return 10;
+    return 7;
   }
 };