Index: priv/guest_x86_defs.h
===================================================================
--- priv/guest_x86_defs.h	(revision 1965)
+++ priv/guest_x86_defs.h	(working copy)
@@ -164,6 +164,8 @@
 extern void x86g_dirtyhelper_OUT ( UInt portno, UInt data, 
                                    UInt sz/*1,2 or 4*/ );
 
+void x86g_dirtyhelper_SxDT ( void* address, ULong op /* 0 or 1 */ );
+
 extern VexEmWarn
             x86g_dirtyhelper_FXRSTOR ( VexGuestX86State*, HWord );
 
Index: priv/guest_amd64_helpers.c
===================================================================
--- priv/guest_amd64_helpers.c	(revision 1965)
+++ priv/guest_amd64_helpers.c	(working copy)
@@ -2229,6 +2229,28 @@
 #  endif
 }
 
+/* CALLED FROM GENERATED CODE */
+/* DIRTY HELPER (non-referentially-transparent) */
+/* Horrible hack.  On non-amd64 platforms, do nothing. */
+/* op = 0: call the native SGDT instruction.
+   op = 1: call the native SIDT instruction.
+*/
+void amd64g_dirtyhelper_SxDT ( void *address, ULong op ) {
+#  if defined(__x86_64__)
+  switch (op) {
+    case 0:
+       __asm__ __volatile__("sgdt %0" : "=m" (*address));
+       break;
+    case 1:
+       __asm__ __volatile__("sidt %0" : "=m" (*address));
+       break;
+    default:
+       break;
+  }
+#  else
+   /* do nothing */
+#  endif
+}
 
 /*---------------------------------------------------------------*/
 /*--- Helpers for MMX/SSE/SSE2.                               ---*/
Index: priv/guest_amd64_toIR.c
===================================================================
--- priv/guest_amd64_toIR.c	(revision 1965)
+++ priv/guest_amd64_toIR.c	(working copy)
@@ -16752,6 +16752,36 @@
          DIP("{f}emms\n");
          break;
 
+      /* =-=-=-=-=-=-=-=-=- SGDT and SIDT =-=-=-=-=-=-=-=-=-=-= */
+      case 0x01: /* 0F 01 /0 -- SGDT */
+                 /* 0F 01 /1 -- SIDT */
+
+         modrm = getUChar(delta);
+         addr = disAMode ( &alen, vbi, pfx, delta, dis_buf, 0 );
+         delta += alen;
+         if (epartIsReg(modrm)) goto decode_failure;
+         if (gregLO3ofRM(modrm) != 0 && gregLO3ofRM(modrm) != 1)
+            goto decode_failure;
+         switch (gregLO3ofRM(modrm)) {
+            case 0: DIP("sgdt %p\n", addr); break;
+            case 1: DIP("sidt %p\n", addr); break;
+            default: vassert(0); /*NOTREACHED*/
+         }
+
+         IRDirty* d = unsafeIRDirty_0_N (
+                          0/*regparms*/,
+                          "amd64g_dirtyhelper_SxDT",
+                          &amd64g_dirtyhelper_SxDT,
+                          mkIRExprVec_2( mkexpr(addr),
+                                         mkU64(gregLO3ofRM(modrm)) )
+                      );
+         /* declare we're writing memory */
+         d->mFx   = Ifx_Write;
+         d->mAddr = mkexpr(addr);
+         d->mSize = 6;
+         stmt( IRStmt_Dirty(d) );
+         break;
+
       /* =-=-=-=-=-=-=-=-=- unimp2 =-=-=-=-=-=-=-=-=-=-= */
 
       default:
Index: priv/guest_amd64_defs.h
===================================================================
--- priv/guest_amd64_defs.h	(revision 1965)
+++ priv/guest_amd64_defs.h	(working copy)
@@ -164,6 +164,7 @@
 extern void  amd64g_dirtyhelper_OUT ( ULong portno, ULong data, 
                                       ULong sz/*1,2 or 4*/ );
 
+void amd64g_dirtyhelper_SxDT ( void* address, ULong op /* 0 or 1 */ );
 //extern void  amd64g_dirtyhelper_CPUID_sse0 ( VexGuestAMD64State* );
 //extern void  amd64g_dirtyhelper_CPUID_sse1 ( VexGuestAMD64State* );
 //extern void  amd64g_dirtyhelper_CPUID_sse2 ( VexGuestAMD64State* );
Index: priv/guest_x86_helpers.c
===================================================================
--- priv/guest_x86_helpers.c	(revision 1965)
+++ priv/guest_x86_helpers.c	(working copy)
@@ -2364,6 +2364,28 @@
 #  endif
 }
 
+/* CALLED FROM GENERATED CODE */
+/* DIRTY HELPER (non-referentially-transparent) */
+/* Horrible hack.  On non-x86 platforms, do nothing. */
+/* op = 0: call the native SGDT instruction.
+   op = 1: call the native SIDT instruction.
+*/
+void x86g_dirtyhelper_SxDT ( void *address, ULong op ) {
+#  if defined(__i386__)
+  switch (op) {
+    case 0:
+       __asm__ __volatile__("sgdt %0" : "=m" (*address));
+       break;
+    case 1:
+       __asm__ __volatile__("sidt %0" : "=m" (*address));
+       break;
+    default:
+       break;
+  }
+#  else
+   /* do nothing */
+#  endif
+}
 
 /*---------------------------------------------------------------*/
 /*--- Helpers for MMX/SSE/SSE2.                               ---*/
Index: priv/guest_x86_toIR.c
===================================================================
--- priv/guest_x86_toIR.c	(revision 1965)
+++ priv/guest_x86_toIR.c	(working copy)
@@ -14777,6 +14777,36 @@
          DIP("emms\n");
          break;
 
+      /* =-=-=-=-=-=-=-=-=- SGDT and SIDT =-=-=-=-=-=-=-=-=-=-= */
+      case 0x01: /* 0F 01 /0 -- SGDT */
+                 /* 0F 01 /1 -- SIDT */
+
+         modrm = getUChar(delta);
+         addr = disAMode ( &alen, sorb, delta, dis_buf );
+         delta += alen;
+         if (epartIsReg(modrm)) goto decode_failure;
+         if (gregOfRM(modrm) != 0 && gregOfRM(modrm) != 1)
+            goto decode_failure;
+         switch (gregOfRM(modrm)) {
+            case 0: DIP("sgdt %p\n", addr); break;
+            case 1: DIP("sidt %p\n", addr); break;
+            default: vassert(0); /*NOTREACHED*/
+         }
+
+         IRDirty* d = unsafeIRDirty_0_N (
+                          0/*regparms*/,
+                          "x86g_dirtyhelper_SxDT",
+                          &x86g_dirtyhelper_SxDT,
+                          mkIRExprVec_2( mkexpr(addr),
+                                         mkU64(gregOfRM(modrm)) )
+                      );
+         /* declare we're writing memory */
+         d->mFx   = Ifx_Write;
+         d->mAddr = mkexpr(addr);
+         d->mSize = 6;
+         stmt( IRStmt_Dirty(d) );
+         break;
+
       /* =-=-=-=-=-=-=-=-=- unimp2 =-=-=-=-=-=-=-=-=-=-= */
 
       default: