Remove useless interpreting flag from execution context

We were maintaining a flag that said if we were interpreting on the EC. It was only used in the implementation of hphp_break(), for pretty minimal benefit. I yanked it… it seems fine to me to throw the switch exception if someone steps out of the hard break even if we're already interpreting.

Also yank out a vestige of the previous stepping and breakpoint logic from the dispatch loop I noticed today. I'd previously missed it, but I made a change a while ago to put the state of the last location filter into the hands of the flow control commands. This was unnecessary and should have been removed then.

hphp/runtime/base/execution_context.cpp

@@ -79,8 +79,7 @@ VMExecutionContext::VMExecutionContext() :
     m_preg_recursion_limit(RuntimeOption::PregRecursionLimit),
     m_lambdaCounter(0), m_nesting(0),
     m_breakPointFilter(nullptr), m_lastLocFilter(nullptr),
-    m_interpreting(false), m_dbgNoBreak(false),
-    m_coverPrevLine(-1), m_coverPrevUnit(nullptr),
+    m_dbgNoBreak(false), m_coverPrevLine(-1), m_coverPrevUnit(nullptr),
     m_executingSetprofileCallback(false) {
 
   // Make sure any fields accessed from the TC are within a byte of

hphp/runtime/base/execution_context.h

@@ -668,7 +668,6 @@ public:
   Array getLocalDefinedVariables(int frame);
   HPHP::PCFilter* m_breakPointFilter;
   HPHP::PCFilter* m_lastLocFilter;
-  bool m_interpreting;
   bool m_dbgNoBreak;
   bool doFCall(HPHP::ActRec* ar, PC& pc);
   bool doFCallArray(PC& pc);

hphp/runtime/ext/ext_debugger.cpp

@@ -76,8 +76,7 @@ void f_hphpd_break(bool condition /* = true */) {
   }
   CallerFrame cf;
   Debugger::InterruptVMHook(HardBreakPoint);
-  if (RuntimeOption::EvalJit && !g_vmContext->m_interpreting &&
-      DEBUGGER_FORCE_INTR) {
+  if (RuntimeOption::EvalJit && DEBUGGER_FORCE_INTR) {
     TRACE(5, "switch mode\n");
     throw VMSwitchModeBuiltin();
   }

hphp/runtime/vm/bytecode.cpp

@@ -7134,8 +7134,6 @@ inline void VMExecutionContext::dispatchImpl(int numInstrs) {
       ONTRACE(1,                                                        \
               Trace::trace("dispatch: Halt ExecutionContext::dispatch(%p)\n", \
                            m_fp));                                      \
-      delete g_vmContext->m_lastLocFilter;                              \
-      g_vmContext->m_lastLocFilter = nullptr;                              \
       return;                                                           \
     }                                                                   \
     Op op = (Op)*pc;                                                    \
@@ -7179,21 +7177,7 @@ inline void VMExecutionContext::dispatchImpl(int numInstrs) {
 #undef DISPATCH
 }
 
-class InterpretingFlagGuard {
-private:
-  bool m_oldFlag;
-public:
-  InterpretingFlagGuard() {
-    m_oldFlag = g_vmContext->m_interpreting;
-    g_vmContext->m_interpreting = true;
-  }
-  ~InterpretingFlagGuard() {
-    g_vmContext->m_interpreting = m_oldFlag;
-  }
-};
-
 void VMExecutionContext::dispatch() {
-  InterpretingFlagGuard ifg;
   if (shouldProfile()) {
     dispatchImpl<Profile>(0);
   } else {
@@ -7202,7 +7186,6 @@ void VMExecutionContext::dispatch() {
 }
 
 void VMExecutionContext::dispatchN(int numInstrs) {
-  InterpretingFlagGuard ifg;
   dispatchImpl<LimitInstrs | BreakOnCtlFlow>(numInstrs);
   // We are about to go back to Jit, check whether we should
   // stick with interpreter
@@ -7212,7 +7195,6 @@ void VMExecutionContext::dispatchN(int numInstrs) {
 }
 
 void VMExecutionContext::dispatchBB() {
-  InterpretingFlagGuard ifg;
   dispatchImpl<BreakOnCtlFlow>(0);
   // We are about to go back to Jit, check whether we should
   // stick with interpreter