When shrinking semispace don't relink pages if semispace is not committed

src/spaces.cc

Index: src/spaces.cc
diff --git a/src/spaces.cc b/src/spaces.cc
index 84b0f1bcb49c8191521ad1497aa2d3e67aac8ea3..b82d06c49f21f8d34f4c3a8ae93858cb85cfc1a8 100644
--- a/src/spaces.cc
+++ b/src/spaces.cc
@@ -1263,11 +1263,16 @@ bool SemiSpace::ShrinkTo(int new_capacity) {
   Address old_start = space_end - capacity_;
   size_t delta = capacity_ - new_capacity;
   ASSERT(IsAligned(delta, OS::AllocateAlignment()));
-  if (!heap()->isolate()->memory_allocator()->UncommitBlock(old_start, delta)) {
+  if (is_committed() &&
+      !heap()->isolate()->memory_allocator()->UncommitBlock(old_start, delta)) {
     return false;
   }
   capacity_ = new_capacity;
 
+  if (!is_committed()) {

[Michael Starzinger, 2012/01/04 14:38:28]

Can we invert the condition and place the block below inside the if statement? I
like that better than early returns.

[Sven Panne, 2012/01/04 14:46:54]

Drive-by comment: I *do* like guard clauses, they can make the normal control
flow much clearer.
(http://martinfowler.com/refactoring/catalog/replaceNestedConditionalWithGuard...)

Just my 2c... :-)

+    return true;
+  }
+
   int pages_after = capacity_ / Page::kPageSize;
   NewSpacePage* new_last_page =
       NewSpacePage::FromAddress(space_end - pages_after * Page::kPageSize);