Block pretty printing (partial re-revert of 1177123002).

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"
 #include "src/snapshot/serialize.h"  // TODO(turbofan): RootIndexMap
@@ skipping 79 matching lines @@
       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(200);
-        SNPrintF(buffer, "-- B%d start%s%s%s%s --", block->rpo_number().ToInt(),
-                 block->IsDeferred() ? " (deferred)" : "",
-                 block->needs_frame() ? "" : " (no frame)",
-                 block->must_construct_frame() ? " (construct frame)" : "",
-                 block->must_deconstruct_frame() ? " (deconstruct frame)" : "");
-        masm()->RecordComment(buffer.start());
+        char* buffer_start = buffer.start();
+
+        int next = SNPrintF(
+            buffer, "-- B%d start%s%s%s%s", block->rpo_number().ToInt(),
+            block->IsDeferred() ? " (deferred)" : "",
+            block->needs_frame() ? "" : " (no frame)",
+            block->must_construct_frame() ? " (construct frame)" : "",
+            block->must_deconstruct_frame() ? " (deconstruct frame)" : "");
+
+        buffer = buffer.SubVector(next, buffer.length());
+
+        if (block->IsLoopHeader()) {
+          next =
+              SNPrintF(buffer, " (loop up to %d)", block->loop_end().ToInt());
+          buffer = buffer.SubVector(next, buffer.length());
+        }
+        if (block->loop_header().IsValid()) {
+          next =
+              SNPrintF(buffer, " (in loop %d)", block->loop_header().ToInt());
+          buffer = buffer.SubVector(next, buffer.length());
+        }
+        SNPrintF(buffer, " --");
+        masm()->RecordComment(buffer_start);
       }
       masm()->bind(GetLabel(current_block_));
       for (int i = block->code_start(); i < block->code_end(); ++i) {
         AssembleInstruction(code()->InstructionAt(i));
       }
     }
   }
 
   // Assemble all out-of-line code.
   if (ools_) {
@@ skipping 572 matching lines @@
     : masm_(gen->masm()), next_(gen->ools_) {
   gen->ools_ = this;
 }
 
 
 OutOfLineCode::~OutOfLineCode() {}
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8