1 files changed, 31 insertions, 6 deletions

diff --git a/deps/v8/src/codegen/signature.h b/deps/v8/src/codegen/signature.h
index 38f79d4629..5a17688a54 100644
--- a/deps/v8/src/codegen/signature.h
+++ b/deps/v8/src/codegen/signature.h
@@ -66,11 +66,22 @@ class Signature : public ZoneObject {
     Builder(Zone* zone, size_t return_count, size_t parameter_count)
         : return_count_(return_count),
           parameter_count_(parameter_count),
-          zone_(zone),
           rcursor_(0),
-          pcursor_(0),
-          buffer_(zone->NewArray<T>(
-              static_cast<int>(return_count + parameter_count))) {}
+          pcursor_(0) {
+      // Allocate memory for the signature plus the array backing the
+      // signature.
+      constexpr size_t padding = sizeof(Signature<T>) % alignof(T);
+      using AllocationTypeTag = Signature<T>::Builder;
+      const size_t allocated_bytes =
+          sizeof(Signature<T>) + padding +
+          sizeof(T) * (return_count + parameter_count);
+      void* memory = zone->Allocate<AllocationTypeTag>(allocated_bytes);
+      uint8_t* rep_buffer =
+          reinterpret_cast<uint8_t*>(memory) + sizeof(Signature<T>) + padding;
+      DCHECK(IsAligned(reinterpret_cast<uintptr_t>(rep_buffer), alignof(T)));
+      buffer_ = reinterpret_cast<T*>(rep_buffer);
+      sig_ = new (memory) Signature<T>{return_count, parameter_count, buffer_};
+    }
 
     const size_t return_count_;
     const size_t parameter_count_;
@@ -91,16 +102,30 @@ class Signature : public ZoneObject {
       pcursor_ = std::max(pcursor_, index + 1);
     }
 
+    Signature<T>* Get() const {
+      DCHECK_EQ(rcursor_, return_count_);
+      DCHECK_EQ(pcursor_, parameter_count_);
+      DCHECK_NOT_NULL(sig_);
+      return sig_;
+    }
+
+    // TODO(clemensb): Remove {Build()}, replace all callers by {Get()}.
     Signature<T>* Build() {
+      // {Build} is the old API, and should be replaced by {Get}.
+      // {Build} did previously return a freshly allocated pointer, so make sure
+      // that we do not call it twice by clearing the {sig_} field.
+      DCHECK_NOT_NULL(sig_);
       DCHECK_EQ(rcursor_, return_count_);
       DCHECK_EQ(pcursor_, parameter_count_);
-      return zone_->New<Signature<T>>(return_count_, parameter_count_, buffer_);
+      Signature<T>* sig = sig_;
+      sig_ = nullptr;
+      return sig;
     }
 
    private:
-    Zone* zone_;
     size_t rcursor_;
     size_t pcursor_;
+    Signature<T>* sig_;
     T* buffer_;
   };