diff --git a/src/backend/iasm.h b/src/backend/iasm.h
index 03c2c98521ba..7587070129cd 100644
--- a/src/backend/iasm.h
+++ b/src/backend/iasm.h
@@ -21,6 +21,7 @@
 
 // This is for when the reg field of modregrm specifies which instruction it is
 #define NUM_MASK        0x7
+#define NUM_MASKR       0x8		// REX extension bit
 #define _0      (0x0 | _modrm)          // insure that some _modrm bit is set
 #define _1      0x1                     // with _0
 #define _2      0x2
@@ -67,6 +68,7 @@
 #define _modall         0xb000  // Instruction modifies all register values
 #define _modsiax        0xc000  // Instruction modifies AX and SI
 #define _modsinot1      0xd000  // Instruction modifies SI and not first param
+#define _modcxr11       0xe000  // Instruction modifies CX and R11
 
 /////////////////////////////////////////////////
 // Operand flags - usOp1, usOp2, usOp3
diff --git a/src/backend/ptrntab.c b/src/backend/ptrntab.c
index dcbe4546f78e..3ac018fd656a 100644
--- a/src/backend/ptrntab.c
+++ b/src/backend/ptrntab.c
@@ -556,8 +556,10 @@ PTRNTAB2  aptb2LDS[] = /* LDS */ {
 PTRNTAB2  aptb2LEA[] = /* LEA */ {
         { 0x8d, _r|_16_bit,             _r16,   _m8 | _m16 | _m32 | _m48 },
         { 0x8d, _r|_32_bit,             _r32,   _m8 | _m16 | _m32 | _m48 },
+        { 0x8d, _r|_64_bit,             _r64,   _m8 | _m16 | _m32 | _m48 | _m64 },
         { 0x8d, _r|_16_bit,             _r16,   _rel16 },
         { 0x8d, _r|_32_bit,             _r32,   _rel32 },
+        { 0x8d, _r|_64_bit,             _r64,   _rel32 },
         { ASM_END, 0, 0, 0 }
 };
 PTRNTAB2  aptb2LES[] = /* LES */ {
@@ -1471,6 +1473,14 @@ PTRNTAB0 aptb0PAUSE[] =  /* PAUSE */ {
 };
 #endif
 
+PTRNTAB0 aptb0SYSCALL[] =  /* SYSCALL */ {
+        { 0x0f05, _modcxr11 }
+};
+
+PTRNTAB0 aptb0SYSRET[] =  /* SYSRET */ {
+        { 0x0f07, 0 }
+};
+
 PTRNTAB0 aptb0SYSENTER[] =  /* SYSENTER */ {
         { 0x0f34, 0 }
 };
@@ -3122,8 +3132,10 @@ getsec
         X("subps",      2,              (P) aptb2SUBPS ) \
         X("subsd",      2,              (P) aptb2SUBSD ) \
         X("subss",      2,              (P) aptb2SUBSS ) \
+        X("syscall",    0,              aptb0SYSCALL ) \
         X("sysenter",   0,              aptb0SYSENTER ) \
         X("sysexit",    0,              aptb0SYSEXIT ) \
+        X("sysret",     0,              aptb0SYSRET ) \
         X("test",       2,              (P) aptb2TEST ) \
         X("ucomisd",    2,              (P) aptb2UCOMISD ) \
         X("ucomiss",    2,              (P) aptb2UCOMISS ) \
diff --git a/src/iasm.c b/src/iasm.c
index eba2a89bfd0b..7e3e35dff3ca 100644
--- a/src/iasm.c
+++ b/src/iasm.c
@@ -2361,6 +2361,8 @@ STATIC void asm_make_modrm_byte(
     if (aopty == _reg || amod == _rspecial) {
             mrmb.modregrm.mod = 0x3;
             mrmb.modregrm.rm |= popnd->base->val;
+            if ( popnd->base->val & NUM_MASKR )
+                pc->Irex |= REX_B;
     }
     else if (amod == _addr16 || (amod == _flbl && I16))
     {   unsigned rm;
@@ -2578,6 +2580,8 @@ STATIC void asm_make_modrm_byte(
          ASM_GET_amod(popnd2->usFlags) == _rspecial))
     {
             mrmb.modregrm.reg =  popnd2->base->val;
+            if ( popnd2->base->val & NUM_MASKR )
+                pc->Irex |= REX_R;
     }
 #ifdef DEBUG
     puchOpcode[ (*pusIdx)++ ] = mrmb.uchOpcode;
@@ -2691,6 +2695,9 @@ STATIC regm_t asm_modify_regs(PTRNTAB ptb, OPND *popnd1, OPND *popnd2)
         usRet |= mSI;
         popnd1 = NULL;
         break;
+    case _modcxr11:
+        usRet |= (mCX | mR11);
+        break;
     }
     if (popnd1 && ASM_GET_aopty(popnd1->usFlags) == _reg)
     {
@@ -4050,6 +4057,7 @@ STATIC OPND *asm_primary_exp()
             case TOKthis:
                 strcpy(tok.TKid,cpp_name_this);
 #endif
+            case TOKthis:
             case TOKidentifier:
             case_ident:
                 o1 = opnd_calloc();