Bug 772722 - Remove superfluous usage of Atomics in SpiderMonkey; r=luke

None of the current usages of ATOMIC_INC/DEC are useful now that we do not allow
multi-threaded runtimes. This also removes a pre-mature optimization that
happened to be using the atomics. I measured it as saving strictly < 3us on old
hardware.

js/src/builtin/TestingFunctions.cpp

@@ -464,7 +464,7 @@ static unsigned finalizeCount = 0;
 static void
 finalize_counter_finalize(JSFreeOp *fop, JSObject *obj)
 {
-    JS_ATOMIC_INCREMENT(&finalizeCount);
+    ++finalizeCount;
 }
 
 static JSClass FinalizeCounterClass = {

js/src/jsapi.cpp

@@ -4564,14 +4564,14 @@ JS_CheckAccess(JSContext *cx, JSObject *obj, jsid id_, JSAccessMode mode,
 JS_PUBLIC_API(void)
 JS_HoldPrincipals(JSPrincipals *principals)
 {
-    JS_ATOMIC_INCREMENT(&principals->refcount);
+    ++principals->refcount;
 }
 
 JS_PUBLIC_API(void)
 JS_DropPrincipals(JSRuntime *rt, JSPrincipals *principals)
 {
-    int rc = JS_ATOMIC_DECREMENT(&principals->refcount);
-    if (rc == 0)
+    JS_AbortIfWrongThread(rt);
+    if (--principals->refcount == 0)
         rt->destroyPrincipals(principals);
 }
 

js/src/jscntxt.cpp

@@ -125,11 +125,7 @@ JSRuntime::sizeOfExplicitNonHeap()
 void
 JSRuntime::triggerOperationCallback()
 {
-    /*
-     * Use JS_ATOMIC_SET in the hope that it ensures the write will become
-     * immediately visible to other processors polling the flag.
-     */
-    JS_ATOMIC_SET(&interrupt, 1);
+    interrupt = 1;
 }
 
 void
@@ -438,8 +434,9 @@ js_ReportOutOfMemory(JSContext *cx)
     }
 
     if (onError) {
-        AutoAtomicIncrement incr(&cx->runtime->inOOMReport);
+        ++cx->runtime->inOOMReport;
         onError(cx, msg, &report);
+        --cx->runtime->inOOMReport;
     }
 }
 
@@ -911,7 +908,7 @@ js_InvokeOperationCallback(JSContext *cx)
      * thread is racing us here we will accumulate another callback request
      * which will be serviced at the next opportunity.
      */
-    JS_ATOMIC_SET(&rt->interrupt, 0);
+    rt->interrupt = 0;
 
     if (rt->gcIsNeeded)
         GCSlice(rt, GC_NORMAL, rt->gcTriggerReason);

js/src/jscntxt.h

@@ -758,7 +758,7 @@ struct JSRuntime : js::RuntimeFriendFields
      * and for each JSObject::remove method call that frees a slot in the given
      * object. See js_NativeGet and js_NativeSet in jsobj.cpp.
      */
-    int32_t             propertyRemovals;
+    uint32_t            propertyRemovals;
 
     /* Number localization, used by jsnum.c */
     const char          *thousandsSeparator;

js/src/jslock.h

@@ -10,49 +10,17 @@
 
 #ifdef JS_THREADSAFE
 
-# include "pratom.h"
 # include "prlock.h"
 # include "prcvar.h"
 # include "prthread.h"
 # include "prinit.h"
 
-# define JS_ATOMIC_INCREMENT(p)      PR_ATOMIC_INCREMENT((PRInt32 *)(p))
-# define JS_ATOMIC_DECREMENT(p)      PR_ATOMIC_DECREMENT((PRInt32 *)(p))
-# define JS_ATOMIC_ADD(p,v)          PR_ATOMIC_ADD((PRInt32 *)(p), (PRInt32)(v))
-# define JS_ATOMIC_SET(p,v)          PR_ATOMIC_SET((PRInt32 *)(p), (PRInt32)(v))
-
 #else  /* JS_THREADSAFE */
 
 typedef struct PRThread PRThread;
 typedef struct PRCondVar PRCondVar;
 typedef struct PRLock PRLock;
 
-# define JS_ATOMIC_INCREMENT(p)      (++*(p))
-# define JS_ATOMIC_DECREMENT(p)      (--*(p))
-# define JS_ATOMIC_ADD(p,v)          (*(p) += (v))
-# define JS_ATOMIC_SET(p,v)          (*(p) = (v))
-
 #endif /* JS_THREADSAFE */
 
-namespace js {
-
-class AutoAtomicIncrement
-{
-    int32_t *p;
-    JS_DECL_USE_GUARD_OBJECT_NOTIFIER
-
-  public:
-    AutoAtomicIncrement(int32_t *p JS_GUARD_OBJECT_NOTIFIER_PARAM)
-      : p(p) {
-        JS_GUARD_OBJECT_NOTIFIER_INIT;
-        JS_ATOMIC_INCREMENT(p);
-    }
-
-    ~AutoAtomicIncrement() {
-        JS_ATOMIC_DECREMENT(p);
-    }
-};
-
-}  /* namespace js */
-
 #endif /* jslock_h___ */

js/src/jsobj.cpp

@@ -4616,7 +4616,7 @@ js_NativeSet(JSContext *cx, Handle<JSObject*> obj, Handle<JSObject*> receiver,
 
     Rooted<Shape *> shapeRoot(cx, shape);
 
-    int32_t sample = cx->runtime->propertyRemovals;
+    uint32_t sample = cx->runtime->propertyRemovals;
     if (!shapeRoot->set(cx, obj, receiver, strict, vp))
         return false;
 

js/src/jsscope.cpp

@@ -748,7 +748,7 @@ JSObject::putProperty(JSContext *cx, jsid id_,
     if (hadSlot && !shape->hasSlot()) {
         if (oldSlot < self->slotSpan())
             self->freeSlot(cx, oldSlot);
-        JS_ATOMIC_INCREMENT(&cx->runtime->propertyRemovals);
+        ++cx->runtime->propertyRemovals;
     }
 
     self->checkShapeConsistency();
@@ -851,7 +851,7 @@ JSObject::removeProperty(JSContext *cx, jsid id_)
     /* If shape has a slot, free its slot number. */
     if (shape->hasSlot()) {
         self->freeSlot(cx, shape->slot());
-        JS_ATOMIC_INCREMENT(&cx->runtime->propertyRemovals);
+        ++cx->runtime->propertyRemovals;
     }
 
     /*
@@ -928,7 +928,7 @@ JSObject::clear(JSContext *cx)
 
     JS_ALWAYS_TRUE(setLastProperty(cx, shape));
 
-    JS_ATOMIC_INCREMENT(&cx->runtime->propertyRemovals);
+    ++cx->runtime->propertyRemovals;
     checkShapeConsistency();
 }
 

js/src/prmjtime.cpp

@@ -346,15 +346,9 @@ def PRMJ_Now():
 
 */
 
-// We parameterize the delay count just so that shell builds can
-// set it to 0 in order to get high-resolution benchmarking.
-// 10 seems to be the number of calls to load with a blank homepage.
-int CALIBRATION_DELAY_COUNT = 10;
-
 int64_t
 PRMJ_Now(void)
 {
-    static int nCalls = 0;
     long double lowresTime, highresTimerValue;
     FILETIME ft;
     LARGE_INTEGER now;
@@ -363,16 +357,6 @@ PRMJ_Now(void)
     int64_t returnedTime;
     long double cachedOffset = 0.0;
 
-    /* To avoid regressing startup time (where high resolution is likely
-       not needed), give the old behavior for the first few calls.
-       This does not appear to be needed on Vista as the timeBegin/timeEndPeriod
-       calls seem to immediately take effect. */
-    int thiscall = JS_ATOMIC_INCREMENT(&nCalls);
-    if (thiscall <= CALIBRATION_DELAY_COUNT) {
-        LowResTime(&ft);
-        return (FILETIME2INT64(ft)-win2un)/10L;
-    }
-
     /* For non threadsafe platforms, NowInit is not necessary */
 #ifdef JS_THREADSAFE
     PR_CallOnce(&calibrationOnce, NowInit);

js/src/shell/js.cpp

@@ -4853,13 +4853,6 @@ main(int argc, char **argv, char **envp)
     if (op.getBoolOption('U'))
         JS_SetCStringsAreUTF8();
 
-#ifdef XP_WIN
-    // Set the timer calibration delay count to 0 so we get high
-    // resolution right away, which we need for precise benchmarking.
-    extern int CALIBRATION_DELAY_COUNT;
-    CALIBRATION_DELAY_COUNT = 0;
-#endif
-
     /* Use the same parameters as the browser in xpcjsruntime.cpp. */
     rt = JS_NewRuntime(32L * 1024L * 1024L);
     if (!rt)