A custom ref counter for wqfor.hh

920a2be3 · Silas Boyd-Wickizer · 67827161 · 920a2be3
--- a/include/wqfor.hh
+++ b/include/wqfor.hh
+struct forframe
+{
+  forframe(int v) : v_(v) {}
+  int inc() { return __sync_add_and_fetch(&v_, 1); }
+  int dec() { return __sync_sub_and_fetch(&v_, 1); }
+  bool zero() volatile { return v_ == 0; };
+  volatile int v_;
+};
+
 template <typename IT, typename BODY>
 struct forwork : public work {
-  typedef std::atomic<int> forframe;
-
  forwork(IT &it, bool (*cond)(IT &it), BODY &body, forframe &frame) 
    : it_(it), cond_(cond), body_(body), frame_(frame) {}

@@ -10,11 +17,11 @@ struct forwork : public work {
    ++it_;
    if (cond_(it_)) {
      forwork<IT, BODY> *w = new forwork<IT, BODY>(it_, cond_, body_, frame_);
-      ++frame_;
+      frame_.inc();
      wq_push(w);    
    }
    body_(v);
-    --frame_;
+    frame_.dec();
    delete this;
  }

@@ -37,7 +44,7 @@ template <typename IT, typename BODY>
 static inline void
 wq_for(IT &init, bool (*cond)(IT &it), BODY body)
 {
-  typename forwork<IT, BODY>::forframe frame(0);
+  forframe frame(0);

  // XXX(sbw) should be able to coarsen loop

@@ -45,11 +52,11 @@ wq_for(IT &init, bool (*cond)(IT &it), BODY body)
  ++init;
  if (cond(init)) {
    forwork<IT, BODY> *w = new forwork<IT, BODY>(init, cond, body, frame);
-    ++frame;
+    frame.inc();
    wq_push(w);
  }
  body(v);

-  while (frame != 0)
+  while (!frame.zero())
    wq_trywork();
 }