[heap] Introduce NewSpace::EvacuatePrologue

Calls to Flip and ResetLinearAllocationArea of SemiSpaceNewSpace are
(almost) always called together, and always at the start of evacuation.
Introducing NewSpace::EvacuatePrologue, allows removing these methods
from SemiSpaceNewSpace public interface and reduces future branches
between the semi space and paged new space cases.

Bug: v8:12612
Change-Id: Ic589a48c1e7751631603da757f4f5f7edb69e571
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3650599Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80561}

src/heap/heap.cc

@@ -65,6 +65,7 @@
 #include "src/heap/memory-chunk-layout.h"
 #include "src/heap/memory-measurement.h"
 #include "src/heap/memory-reducer.h"
+#include "src/heap/new-spaces.h"
 #include "src/heap/object-stats.h"
 #include "src/heap/objects-visiting-inl.h"
 #include "src/heap/objects-visiting.h"
@@ -2740,14 +2741,7 @@ void Heap::Scavenge() {
 
   SetGCState(SCAVENGE);
 
-  // Flip the semispaces.  After flipping, to space is empty, from space has
-  // live objects.
-  {
-    SemiSpaceNewSpace* semi_space_new_space =
-        SemiSpaceNewSpace::From(new_space());
-    semi_space_new_space->Flip();
-    semi_space_new_space->ResetLinearAllocationArea();
-  }
+  SemiSpaceNewSpace::From(new_space())->EvacuatePrologue();
 
   // We also flip the young generation large object space. All large objects
   // will be in the from space.

src/heap/mark-compact.cc

@@ -3591,8 +3591,7 @@ void MarkCompactCollector::EvacuatePrologue() {
          PageRange(new_space->first_allocatable_address(), new_space->top())) {
       new_space_evacuation_pages_.push_back(p);
     }
-    SemiSpaceNewSpace::From(new_space)->Flip();
-    new_space->ResetLinearAllocationArea();
+    new_space->EvacuatePrologue();
 
     DCHECK_EQ(new_space->Size(), 0);
   }
@@ -5683,8 +5682,7 @@ void MinorMarkCompactCollector::EvacuatePrologue() {
     new_space_evacuation_pages_.push_back(p);
   }
 
-  SemiSpaceNewSpace::From(new_space)->Flip();
-  new_space->ResetLinearAllocationArea();
+  new_space->EvacuatePrologue();
 
   heap()->new_lo_space()->Flip();
   heap()->new_lo_space()->ResetPendingObject();

src/heap/new-spaces.cc

@@ -601,8 +601,6 @@ SemiSpaceNewSpace::~SemiSpaceNewSpace() {
   from_space_.TearDown();
 }
 
-void SemiSpaceNewSpace::Flip() { SemiSpace::Swap(&from_space_, &to_space_); }
-
 void SemiSpaceNewSpace::Grow() {
   heap()->safepoint()->AssertActive();
   // Double the semispace size but only up to maximum capacity.
@@ -820,5 +818,12 @@ size_t SemiSpaceNewSpace::AllocatedSinceLastGC() const {
   return allocated;
 }
 
+void SemiSpaceNewSpace::EvacuatePrologue() {
+  // Flip the semispaces.  After flipping, to space is empty, from space has
+  // live objects.
+  SemiSpace::Swap(&from_space_, &to_space_);
+  ResetLinearAllocationArea();
+}
+
 }  // namespace internal
 }  // namespace v8

src/heap/new-spaces.h

@@ -306,10 +306,10 @@ class NewSpace : NON_EXPORTED_BASE(public SpaceWithLinearArea) {
 
   virtual Address first_allocatable_address() const = 0;
 
-  virtual void ResetLinearAllocationArea() = 0;
-
   virtual bool AddFreshPage() = 0;
 
+  virtual void EvacuatePrologue() = 0;
+
  protected:
   static const int kAllocationBufferParkingThreshold = 4 * KB;
 
@@ -343,9 +343,6 @@ class V8_EXPORT_PRIVATE SemiSpaceNewSpace final : public NewSpace {
 
   bool ContainsSlow(Address a) const final;
 
-  // Flip the pair of spaces.
-  void Flip();
-
   // Grow the capacity of the semispaces.  Assumes that they are not at
   // their maximum capacity.
   void Grow() final;
@@ -441,9 +438,6 @@ class V8_EXPORT_PRIVATE SemiSpaceNewSpace final : public NewSpace {
   // Set the age mark in the active semispace.
   void set_age_mark(Address mark) { to_space_.set_age_mark(mark); }
 
-  // Reset the allocation pointer to the beginning of the active semispace.
-  void ResetLinearAllocationArea() final;
-
   // When inline allocation stepping is active, either because of incremental
   // marking, idle scavenge, or allocation statistics gathering, we 'interrupt'
   // inline allocation every once in a while. This is done by setting
@@ -509,7 +503,12 @@ class V8_EXPORT_PRIVATE SemiSpaceNewSpace final : public NewSpace {
 
   bool ShouldBePromoted(Address address) const final;
 
+  void EvacuatePrologue() final;
+
  private:
+  // Reset the allocation pointer to the beginning of the active semispace.
+  void ResetLinearAllocationArea();
+
   // Update linear allocation area to match the current to-space page.
   void UpdateLinearAllocationArea(Address known_top = 0);
 

src/heap/promote-young-generation.cc

@@ -47,10 +47,10 @@ void PromoteYoungGenerationGC::EvacuateYoungGeneration() {
   }
 
   // Reset new space.
+  semi_space_new_space->EvacuatePrologue();
   if (!semi_space_new_space->Rebalance()) {
     V8::FatalProcessOutOfMemory(heap_->isolate(), "NewSpace::Rebalance", true);
   }
-  semi_space_new_space->ResetLinearAllocationArea();
   semi_space_new_space->set_age_mark(semi_space_new_space->top());
 
   for (auto it = heap_->new_lo_space()->begin();