Empty loops need to check surprise flags

We didnt count a brach to itself as a backward branch.
Also, there seemed to be a signed vs unsigned issue with IterBreak.

hphp/runtime/vm/bytecode.cpp

@@ -3948,7 +3948,7 @@ inline void OPTBLD_INLINE VMExecutionContext::iopFatal(PC& pc) {
 }
 
 inline void OPTBLD_INLINE VMExecutionContext::jmpSurpriseCheck(Offset offset) {
-  if (offset < 0 && UNLIKELY(Transl::TargetCache::loadConditionFlags())) {
+  if (offset <= 0 && UNLIKELY(Transl::TargetCache::loadConditionFlags())) {
     EventHook::CheckSurprise();
   }
 }

hphp/runtime/vm/jit/hhbc-translator.cpp

@@ -1107,7 +1107,7 @@ void HhbcTranslator::emitIterBreak(const ImmVector& iv,
                                     uint32_t         offset,
                                     bool             breakTracelet,
                                     bool             noSurprise) {
-  bool backward = (offset - (int32_t)bcOff()) < 0;
+  bool backward = offset <= bcOff();
   if (backward && !noSurprise) {
     gen(ExitWhenSurprised, getExitSlowTrace());
   }
@@ -1615,7 +1615,7 @@ void HhbcTranslator::emitJmp(int32_t offset,
                              bool  breakTracelet,
                              bool  noSurprise) {
   // If surprise flags are set, exit trace and handle surprise
-  bool backward = (offset - (int32_t)bcOff()) < 0;
+  bool backward = (uint32_t)offset <= bcOff();
   if (backward && !noSurprise) {
     gen(ExitWhenSurprised, getExitSlowTrace());
   }