[array] Make array normalization independent of heap configuration.

The heuristic for deciding whether to normalize elements in a JSArray
should not depend on the current old generation size, for the sake of
predictability. This also wouldn't work when we start inlining this
into optimized code, where we'd bake in the max old generation size
value at the time of optimization.

Bug: v8:6399
Change-Id: Ie30d8855953b8fa97b86b18d9eac6e5de87e5aa9
Reviewed-on: https://chromium-review.googlesource.com/609013
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47272}

src/objects-inl.h

@@ -6058,13 +6058,7 @@ void JSArray::set_length(Smi* length) {
 
 
 bool JSArray::SetLengthWouldNormalize(Heap* heap, uint32_t new_length) {
-  // This constant is somewhat arbitrary. Any large enough value would work.
-  const uint32_t kMaxFastArrayLength = 32 * 1024 * 1024;
-  // If the new array won't fit in a some non-trivial fraction of the max old
-  // space size, then force it to go dictionary mode.
-  uint32_t heap_based_upper_bound =
-      static_cast<uint32_t>((heap->MaxOldGenerationSize() / kDoubleSize) / 4);
-  return new_length >= Min(kMaxFastArrayLength, heap_based_upper_bound);
+  return new_length > kMaxFastArrayLength;
 }
 
 

src/objects.h

@@ -6868,6 +6868,9 @@ class JSArray: public JSObject {
   // Max. number of elements being copied in Array builtins.
   static const int kMaxCopyElements = 100;
 
+  // This constant is somewhat arbitrary. Any large enough value would work.
+  static const uint32_t kMaxFastArrayLength = 32 * 1024 * 1024;
+
   static const int kInitialMaxFastElementArray =
       (kMaxRegularHeapObjectSize - FixedArray::kHeaderSize - kSize -
        AllocationMemento::kSize) /