Rework GCF_DONT_BLOCK to be cx->gcDontBlock, assert it's set, set before entering trace and clear on exit.

js/src/jsbuiltins.cpp

@@ -90,8 +90,7 @@ js_BoxDouble(JSContext* cx, jsdouble d)
     jsint i;
     if (JSDOUBLE_IS_INT(d, i))
         return INT_TO_JSVAL(i);
-    if (!cx->doubleFreeList) /* we must be certain the GC won't kick in */
-        return JSVAL_ERROR_COOKIE;
+    JS_ASSERT(cx->gcDontBlock);
     jsval v; /* not rooted but ok here because we know GC won't run */
     if (!js_NewDoubleInRootedValue(cx, d, &v))
         return JSVAL_ERROR_COOKIE;
@@ -103,8 +102,7 @@ js_BoxInt32(JSContext* cx, jsint i)
 {
     if (JS_LIKELY(INT_FITS_IN_JSVAL(i)))
         return INT_TO_JSVAL(i);
-    if (!cx->doubleFreeList) /* we must be certain the GC won't kick in */
-        return JSVAL_ERROR_COOKIE;
+    JS_ASSERT(cx->gcDontBlock);
     jsval v; /* not rooted but ok here because we know GC won't run */
     jsdouble d = (jsdouble)i;
     if (!js_NewDoubleInRootedValue(cx, d, &v))
@@ -209,6 +207,7 @@ JSString* FASTCALL
 js_String_p_substring(JSContext* cx, JSString* str, jsint begin, jsint end)
 {
     JS_ASSERT(end >= begin);
+    JS_ASSERT(cx->gcDontBlock);
     return js_NewDependentString(cx, str, (size_t)begin, (size_t)(end - begin));
 }
 
@@ -217,6 +216,7 @@ js_String_p_substring_1(JSContext* cx, JSString* str, jsint begin)
 {
     jsint end = JSSTRING_LENGTH(str);
     JS_ASSERT(end >= begin);
+    JS_ASSERT(cx->gcDontBlock);
     return js_NewDependentString(cx, str, (size_t)begin, (size_t)(end - begin));
 }
 
@@ -225,15 +225,14 @@ js_String_getelem(JSContext* cx, JSString* str, jsint i)
 {
     if ((size_t)i >= JSSTRING_LENGTH(str))
         return NULL;
-    /* XXX check for string freelist space */
     return js_GetUnitString(cx, str, (size_t)i);
 }
 
 JSString* FASTCALL
 js_String_fromCharCode(JSContext* cx, jsint i)
 {
+    JS_ASSERT(cx->gcDontBlock);
     jschar c = (jschar)i;
-    /* XXX check for string freelist space */
     if (c < UNIT_STRING_LIMIT)
         return js_GetUnitStringForChar(cx, c);
     return js_NewStringCopyN(cx, &c, 1);
@@ -342,7 +341,8 @@ js_FastNewObject(JSContext* cx, JSObject* ctor)
     JSFunction* fun = GET_FUNCTION_PRIVATE(cx, ctor);
     JSClass* clasp = FUN_INTERPRETED(fun) ? &js_ObjectClass : fun->u.n.clasp;
 
-    JSObject* obj = (JSObject*) js_NewGCThing(cx, GCF_DONT_BLOCK | GCX_OBJECT, sizeof(JSObject));
+    JS_ASSERT(cx->gcDontBlock);
+    JSObject* obj = (JSObject*) js_NewGCThing(cx, GCX_OBJECT, sizeof(JSObject));
     if (!obj)
         return NULL;
 

js/src/jscntxt.h

@@ -705,11 +705,17 @@ struct JSContext {
      * property values associated with this context's global object.
      */
     uint8               xmlSettingFlags;
-    uint8               padding;
 #else
-    uint16              padding;
+    uint8               padding;
 #endif
 
+    /*
+     * Flag to prevent last-ditch garbage collection when up against runtime
+     * memory limits. This also suppresses calls to JS_ReportOutOfMemory when
+     * failing due to runtime limits.
+     */
+    JSPackedBool        gcDontBlock;
+
     /* Runtime version control identifier. */
     uint16              version;
 

js/src/jsgc.cpp

@@ -1749,7 +1749,7 @@ js_NewGCThing(JSContext *cx, uintN flags, size_t nbytes)
 
     arenaList = &rt->gcArenaList[flindex];
     for (;;) {
-        if (doGC && !(flags & GCF_DONT_BLOCK)) {
+        if (doGC && !cx->gcDontBlock) {
             /*
              * Keep rt->gcLock across the call into js_GC so we don't starve
              * and lose to racing threads who deplete the heap just after
@@ -1809,7 +1809,7 @@ js_NewGCThing(JSContext *cx, uintN flags, size_t nbytes)
         } else {
             a = NewGCArena(rt);
             if (!a) {
-                if (doGC || (flags & GCF_DONT_BLOCK))
+                if (doGC || cx->gcDontBlock)
                     goto fail;
                 doGC = JS_TRUE;
                 continue;
@@ -1912,7 +1912,7 @@ fail:
         JS_UNLOCK_GC(rt);
 #endif
     METER(astats->fail++);
-    if (!(flags & GCF_DONT_BLOCK))
+    if (!cx->gcDontBlock)
         JS_ReportOutOfMemory(cx);
     return NULL;
 }

js/src/jsgc.h

@@ -93,13 +93,6 @@ JS_STATIC_ASSERT(GCX_NTYPES <= GCX_LIMIT);
 #define GCF_LOCKSHIFT   (GCX_LIMIT_LOG2 + 2)   /* lock bit shift */
 #define GCF_LOCK        JS_BIT(GCF_LOCKSHIFT)   /* lock request bit in API */
 
-/*
- * Pseudo-flag, not stored but passed into js_NewGCThing, to prevent last-ditch
- * collection when up against runtime memory limits. This also suppresses calls
- * to JS_ReportOutOfMemory when failing due to runtime limits.
- */
-#define GCF_DONT_BLOCK  0x100
-
 /*
  * Get the type of the external string or -1 if the string was not created
  * with JS_NewExternalString.

js/src/jstracer.cpp

@@ -1651,7 +1651,10 @@ js_ExecuteTree(JSContext* cx, Fragment* f, uintN& inlineCallCount)
     uint64 start = rdtsc();
 #endif
 
+    JS_ASSERT(!cx->gcDontBlock);
+    cx->gcDontBlock = JS_TRUE;
     GuardRecord* lr = u.func(&state, NULL);
+    cx->gcDontBlock = JS_FALSE;
 
     for (int32 i = 0; i < lr->calldepth; i++)
         js_SynthesizeFrame(cx, callstack[i]);