From 88cf1d87c60e963cbf4990d9fcefd9ea23880b62 Mon Sep 17 00:00:00 2001
From: Andreas Gal <gal@mozilla.com>
Date: Tue, 14 Jul 2009 17:03:20 -0700
Subject: [PATCH] Avoid integer math for GC trigger factor calculation in
 allocation path, take 2 (503463, r=dmandelin).

---
 js/src/jsapi.cpp |  2 +-
 js/src/jscntxt.h | 12 ++++++++----
 js/src/jsgc.cpp  | 27 +++++++++++++++++++++++----
 3 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index 312b416c7ef..13085424304 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -2585,7 +2585,7 @@ 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;
     }
 }
diff --git a/js/src/jscntxt.h b/js/src/jscntxt.h
index 9f7c9183bff..0f8b5d8ce50 100644
--- a/js/src/jscntxt.h
+++ b/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. */
diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
index c262021f540..d33259635eb 100644
--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -1308,13 +1308,13 @@ 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;
@@ -1800,6 +1800,25 @@ 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;
+    uint64 triggerBytes = uint64(lastBytes) * uint64(gcTriggerFactor / 100);
+    if (triggerBytes != size_t(triggerBytes))
+        triggerBytes = size_t(-1);
+    gcTriggerBytes = size_t(triggerBytes);
+}
+
 static JS_INLINE bool
 IsGCThresholdReached(JSRuntime *rt)
 {
@@ -1814,7 +1833,7 @@ 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 *
@@ -3846,7 +3865,7 @@ out:
         goto restart;
     }
 
-    rt->gcLastBytes = rt->gcBytes;
+    rt->setGCLastBytes(rt->gcBytes);
   done_running:
     rt->gcLevel = 0;
     rt->gcRunning = JS_FALSE;