[turbofan] Always align loop headers at 16-byte boundaries.

src/compiler/code-generator.cc

 // Copyright 2013 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/compiler/code-generator.h"
 
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/pipeline.h"
 
@@ skipping 39 matching lines @@
   // Architecture-specific, linkage-specific prologue.
   info->set_prologue_offset(masm()->pc_offset());
   AssemblePrologue();
 
   // Assemble all non-deferred blocks, followed by deferred ones.
   for (int deferred = 0; deferred < 2; ++deferred) {
     for (auto const block : code()->instruction_blocks()) {
       if (block->IsDeferred() == (deferred == 0)) {
         continue;
       }
+      // Align loop headers on 16-byte boundaries.
+      if (block->IsLoopHeader()) masm()->Align(16);
       // Bind a label for a block.
       current_block_ = block->rpo_number();
       if (FLAG_code_comments) {
         // TODO(titzer): these code comments are a giant memory leak.
         Vector<char> buffer = Vector<char>::New(32);
         SNPrintF(buffer, "-- B%d start --", block->id().ToInt());
         masm()->RecordComment(buffer.start());
       }
       masm()->bind(GetLabel(current_block_));
       for (int i = block->code_start(); i < block->code_end(); ++i) {
@@ skipping 506 matching lines @@
     : masm_(gen->masm()), next_(gen->ools_) {
   gen->ools_ = this;
 }
 
 
 OutOfLineCode::~OutOfLineCode() {}
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8