Remove m_obj from c_Continuation

m_obj in c_Continuation is redundant. It is only used at the time
Continuation is created. First, it is set in init() call. Few
instructions later, it is read so that $this in the Continuation's
ActRec can be populated.

Kill it.

hphp/runtime/ext/ext_continuation.cpp

@@ -46,10 +46,10 @@ static StaticString s___cont__("__cont__");
 
 c_Continuation::c_Continuation(Class* cb) :
     ExtObjectData(cb),
+    m_origFunc(nullptr),
     m_index(-1LL),
     m_value(Variant::NullInit()),
     m_received(Variant::NullInit()),
-    m_origFunc(nullptr),
     m_label(0) {
   o_subclassData.u16 = 0;
 }

hphp/runtime/ext/ext_continuation.h

@@ -46,17 +46,9 @@ class c_Continuation : public ExtObjectData {
 
 public:
   void init(const Func* origFunc,
-            ObjectData* thisPtr,
             ArrayData* args) noexcept {
     m_origFunc = const_cast<Func*>(origFunc);
     assert(m_origFunc);
-
-    if (thisPtr != nullptr) {
-      m_obj = thisPtr;
-    } else {
-      assert(m_obj.isNull());
-    }
-
     m_args = args;
   }
 
@@ -128,13 +120,11 @@ public:
   }
 
 public:
-  Object m_obj;
+  Func *m_origFunc;
   Array m_args;
   int64_t m_index;
   Variant m_value;
   Variant m_received;
-  Func *m_origFunc;
-
   int32_t m_label;
   int m_localsOffset;
   ActRec* m_arPtr;

hphp/runtime/vm/bytecode.cpp

@@ -7038,7 +7038,7 @@ VMExecutionContext::createContinuationHelper(const Func* origFunc,
   );
   cont->incRefCount();
   cont->setNoDestruct();
-  cont->init(origFunc, thisPtr, args);
+  cont->init(origFunc, args);
 
   // The ActRec corresponding to the generator body lives as long as the object
   // does. We set it up once, here, and then just change FP to point to it when
@@ -7151,10 +7151,10 @@ VMExecutionContext::fillContinuationVars(ActRec* fp,
   // If $this is used as a local inside the body and is not provided
   // by our containing environment, just prefill it here instead of
   // using InitThisLoc inside the body
-  if (!skipThis && cont->m_obj.get()) {
+  if (!skipThis && fp->hasThis()) {
     Id id = genFunc->lookupVarId(thisStr);
     if (id != kInvalidId) {
-      tvAsVariant(&cont->locals()[nLocals - id - 1]) = cont->m_obj;
+      tvAsVariant(&cont->locals()[nLocals - id - 1]) = fp->getThis();
     }
   }
   return cont;

hphp/runtime/vm/jit/codegen.cpp

@@ -5080,17 +5080,14 @@ void CodeGenerator::cgInterpOneCF(IRInstruction* inst) {
 }
 
 void CodeGenerator::cgFillContThis(IRInstruction* inst) {
-  SSATmp* cont = inst->src(0);
+  auto thisObj = m_regs[inst->src(0)].reg();
   auto baseReg = m_regs[inst->src(1)].reg();
   int64_t offset = inst->src(2)->getValInt();
-  auto scratch = m_rScratch;
-  auto contReg = m_regs[cont].reg();
 
-  m_as.loadq(contReg[CONTOFF(m_obj)], scratch);
-  m_as.testq(scratch, scratch);
+  m_as.testq(thisObj, thisObj);
   ifThen(m_as, CC_NZ, [&] {
-    m_as.addl(1, scratch[FAST_REFCOUNT_OFFSET]);
-    m_as.storeq(scratch, baseReg[offset + TVOFF(m_data)]);
+    m_as.addl(1, thisObj[FAST_REFCOUNT_OFFSET]);
+    m_as.storeq(thisObj, baseReg[offset + TVOFF(m_data)]);
     emitStoreTVType(m_as, KindOfObject, baseReg[offset + TVOFF(m_type)]);
   });
 }

hphp/runtime/vm/jit/hhbctranslator.cpp

@@ -1046,7 +1046,7 @@ void HhbcTranslator::emitCreateCont(bool getArgs,
     }
     if (fillThis) {
       assert(thisId != kInvalidId);
-      gen(FillContThis, cont, locals,
+      gen(FillContThis, gen(LdThis, m_tb->fp()), locals,
                 cns(cellsToBytes(genLocals - thisId - 1)));
     }
   } else {