Fix ref generator parameters

Alias manager does not know whether generator parameters are passed by
reference. This didn't matter, because every generator had at least one
function call (hphp_continuation_done()) that pretty much disabled unused
variable elimination.

This diff fixes that, lets us get rid of artificial function calls in
generators and will allow later improvements in alias manager.

hphp/compiler/analysis/symbol_table.h

@@ -116,6 +116,7 @@ public:
   bool isReferenced() const { return !m_flags.m_notReferenced; }
   bool isHidden() const { return m_flags.m_hidden; }
   bool isGeneratorParameter() const { return m_flags.m_generatorParameter; }
+  bool isRefGeneratorParameter() const { return m_flags.m_refGeneratorParameter; }
   bool isClosureVar() const { return m_flags.m_closureVar; }
   bool isRefClosureVar() const { return m_flags.m_refClosureVar; }
   bool isPassClosureVar() const { return m_flags.m_passClosureVar; }
@@ -142,6 +143,7 @@ public:
   void setReferenced() { m_flags.m_notReferenced = false; }
   void setHidden() { m_flags.m_hidden = true; }
   void setGeneratorParameter() { m_flags.m_generatorParameter = true; }
+  void setRefGeneratorParameter() { m_flags.m_refGeneratorParameter = true; }
   void setClosureVar() { m_flags.m_closureVar = true; }
   void setRefClosureVar() { m_flags.m_refClosureVar = true; }
   void setPassClosureVar() { m_flags.m_passClosureVar = true; }
@@ -222,6 +224,7 @@ private:
       unsigned m_notReferenced : 1;
       unsigned m_hidden : 1;
       unsigned m_generatorParameter : 1;
+      unsigned m_refGeneratorParameter : 1;
       unsigned m_closureVar : 1;
       unsigned m_refClosureVar : 1;
       unsigned m_passClosureVar : 1;

hphp/compiler/analysis/variable_table.cpp

@@ -567,6 +567,10 @@ void VariableTable::clearUsed() {
     } else {
       sym.second.setReferenced();
     }
+
+    if (sym.second.isRefGeneratorParameter()) {
+      sym.second.setReferenced();
+    }
   }
 }
 

hphp/compiler/statement/method_statement.cpp

@@ -390,6 +390,10 @@ void MethodStatement::analyzeProgram(AnalysisResultPtr ar) {
           Symbol *gp = variables->addDeclaredSymbol(
             param->getName(), ConstructPtr());
           gp->setGeneratorParameter();
+          if (param->isRef()) {
+            gp->setRefGeneratorParameter();
+            gp->setReferenced();
+          }
         }
       }
 
@@ -400,6 +404,10 @@ void MethodStatement::analyzeProgram(AnalysisResultPtr ar) {
             Symbol *gp = variables->addDeclaredSymbol(
               param->getName(), ConstructPtr());
             gp->setGeneratorParameter();
+            if (param->isRef()) {
+              gp->setRefGeneratorParameter();
+              gp->setReferenced();
+            }
           }
         }
       }