We should never allocate a 0-sized buffer, so never grow from 0.

src/x64/assembler-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/macro-assembler.h"
 #include "src/serialize.h"
@@ skipping 313 matching lines @@
   bind_to(L, pc_offset());
 }
 
 
 void Assembler::GrowBuffer() {
   DCHECK(buffer_overflow());
   if (!own_buffer_) FATAL("external code buffer is too small");
 
   // Compute new buffer size.
   CodeDesc desc;  // the new buffer
-  if (buffer_size_ == 0) {
-    desc.buffer_size = kMinimalBufferSize;
-  } else {
-    desc.buffer_size = 2*buffer_size_;
-  }
+  desc.buffer_size = 2 * buffer_size_;
+
   // Some internal data structures overflow for very large buffers,
   // they must ensure that kMaximalBufferSize is not too large.
   if ((desc.buffer_size > kMaximalBufferSize) ||
       (desc.buffer_size > isolate()->heap()->MaxOldGenerationSize())) {
     V8::FatalProcessOutOfMemory("Assembler::GrowBuffer");
   }
 
   // Set up new buffer.
   desc.buffer = NewArray<byte>(desc.buffer_size);
   desc.instr_size = pc_offset();
@@ skipping 2640 matching lines @@
 
 
 bool RelocInfo::IsInConstantPool() {
   return false;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64