[zone] Simplify and inline Zone::New

This separates the fast-non-asan path from the asan path so it can be inlined.
Additionally avoid updating allocation_size_ on each Zone::New call.
Inlining Zone::New actually reduces binary size by 50kb...

Change-Id: Ie5d58638284e5a1a5e0198c24080b0f600d79092
Reviewed-on: https://chromium-review.googlesource.com/c/1288641Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56780}

src/zone/zone.cc

@@ -48,7 +48,7 @@ Zone::~Zone() {
   DCHECK_EQ(segment_bytes_allocated_, 0);
 }
 
-void* Zone::New(size_t size) {
+void* Zone::AsanNew(size_t size) {
   CHECK(!sealed_);
 
   // Round up the requested size to fit the alignment.
@@ -58,7 +58,7 @@ void* Zone::New(size_t size) {
   Address result = position_;
 
   const size_t size_with_redzone = size + kASanRedzoneBytes;
-  DCHECK(limit_ >= position_);
+  DCHECK_LE(position_, limit_);
   if (size_with_redzone > limit_ - position_) {
     result = NewExpand(size_with_redzone);
   } else {
@@ -72,7 +72,6 @@ void* Zone::New(size_t size) {
 
   // Check that the result has the proper alignment and return it.
   DCHECK(IsAligned(result, kAlignmentInBytes));
-  allocation_size_ += size;
   return reinterpret_cast<void*>(result);
 }
 
@@ -122,6 +121,8 @@ Address Zone::NewExpand(size_t size) {
   DCHECK_EQ(size, RoundDown(size, kAlignmentInBytes));
   DCHECK(limit_ - position_ < size);
 
+  // Commit the allocation_size_ of segment_head_ if any.
+  allocation_size_ = allocation_size();
   // Compute the new segment size. We use a 'high water mark'
   // strategy, where we increase the segment size every time we expand
   // except that we employ a maximum segment size when we delete. This

src/zone/zone.h

@@ -47,7 +47,21 @@ class V8_EXPORT_PRIVATE Zone final {
 
   // Allocate 'size' bytes of memory in the Zone; expands the Zone by
   // allocating new segments of memory on demand using malloc().
-  void* New(size_t size);
+  void* New(size_t size) {
+#ifdef V8_USE_ADDRESS_SANITIZER
+    return AsanNew(size);
+#else
+    size = RoundUp(size, kAlignmentInBytes);
+    Address result = position_;
+    if (V8_UNLIKELY(size > limit_ - position_)) {
+      result = NewExpand(size);
+    } else {
+      position_ += size;
+    }
+    return reinterpret_cast<void*>(result);
+#endif
+  }
+  void* AsanNew(size_t size);
 
   template <typename T>
   T* NewArray(size_t length) {
@@ -70,7 +84,10 @@ class V8_EXPORT_PRIVATE Zone final {
 
   const char* name() const { return name_; }
 
-  size_t allocation_size() const { return allocation_size_; }
+  size_t allocation_size() const {
+    size_t extra = segment_head_ ? position_ - segment_head_->start() : 0;
+    return allocation_size_ + extra;
+  }
 
   AccountingAllocator* allocator() const { return allocator_; }