Avoid integer math for GC trigger factor calculation in allocation path (503463, r=dmandelin).

js/src/jsapi.cpp

@@ -2583,7 +2583,7 @@ JS_SetGCParameter(JSRuntime *rt, JSGCParamKey key, uint32 value)
       default:
         JS_ASSERT(key == JSGC_TRIGGER_FACTOR);
         JS_ASSERT(value >= 100);
-        rt->gcTriggerFactor = value;
+        rt->SetGCTriggerFactor(value);
         return;
     }
 }

js/src/jscntxt.h

@@ -369,15 +369,16 @@ struct JSRuntime {
     JSDHashTable        gcRootsHash;
     JSDHashTable        *gcLocksHash;
     jsrefcount          gcKeepAtoms;
-    uint32              gcBytes;
-    uint32              gcLastBytes;
-    uint32              gcMaxBytes;
-    uint32              gcMaxMallocBytes;
+    size_t              gcBytes;
+    size_t              gcLastBytes;
+    size_t              gcMaxBytes;
+    size_t              gcMaxMallocBytes;
     uint32              gcEmptyArenaPoolLifespan;
     uint32              gcLevel;
     uint32              gcNumber;
     JSTracer            *gcMarkingTracer;
     uint32              gcTriggerFactor;
+    size_t              gcTriggerBytes;
     volatile JSBool     gcIsNeeded;
 
     /*
@@ -682,6 +683,9 @@ struct JSRuntime {
     JSFunctionMeter     functionMeter;
     char                lastScriptFilename[1024];
 #endif
+
+    void SetGCTriggerFactor(uint32 factor);
+    void SetGCLastBytes(size_t lastBytes);
 };
 
 /* Common macros to access thread-local caches in JSThread or JSRuntime. */

js/src/jsgc.cpp

@@ -1304,13 +1304,13 @@ js_InitGC(JSRuntime *rt, uint32 maxbytes)
      * By default the trigger factor gets maximum possible value. This
      * means that GC will not be triggered by growth of GC memory (gcBytes).
      */
-    rt->gcTriggerFactor = (uint32) -1;
+    rt->SetGCTriggerFactor((uint32) -1);
 
     /*
      * The assigned value prevents GC from running when GC memory is too low
      * (during JS engine start).
      */
-    rt->gcLastBytes = 8192;
+    rt->SetGCLastBytes(8192);
 
     METER(memset(&rt->gcStats, 0, sizeof rt->gcStats));
     return JS_TRUE;
@@ -1796,6 +1796,22 @@ EnsureLocalFreeList(JSContext *cx)
 
 #endif
 
+void
+JSRuntime::SetGCTriggerFactor(uint32 factor)
+{
+    JS_ASSERT(factor >= 100);
+
+    gcTriggerFactor = factor;
+    SetGCLastBytes(gcLastBytes);
+}
+
+void
+JSRuntime::SetGCLastBytes(size_t lastBytes)
+{
+    gcLastBytes = lastBytes;
+    gcTriggerBytes = lastBytes * gcTriggerFactor / 100;
+}
+
 static JS_INLINE bool
 IsGCThresholdReached(JSRuntime *rt)
 {
@@ -1810,7 +1826,7 @@ IsGCThresholdReached(JSRuntime *rt)
      * the gcBytes value is close to zero at the JS engine start.
      */
     return rt->gcMallocBytes >= rt->gcMaxMallocBytes ||
-           rt->gcBytes / rt->gcTriggerFactor >= rt->gcLastBytes / 100;
+           rt->gcBytes >= rt->gcTriggerBytes;
 }
 
 void *
@@ -3842,7 +3858,7 @@ out:
         goto restart;
     }
 
-    rt->gcLastBytes = rt->gcBytes;
+    rt->SetGCLastBytes(rt->gcBytes);
   done_running:
     rt->gcLevel = 0;
     rt->gcRunning = JS_FALSE;