Add loop printing to block comments.

runtime/vm/flow_graph_compiler.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_XXX.
 
 #include "vm/flow_graph_compiler.h"
 
+#include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/deopt_instructions.h"
 #include "vm/exceptions.h"
 #include "vm/flow_graph_allocator.h"
 #include "vm/il_printer.h"
 #include "vm/intrinsifier.h"
 #include "vm/locations.h"
 #include "vm/longjump.h"
@@ skipping 287 matching lines @@
   const Script& s = Script::Handle(function.script());
   intptr_t line_nr;
   intptr_t column_nr;
   s.GetTokenLocation(instr->token_pos(), &line_nr, &column_nr);
   const String& line = String::Handle(s.GetLine(line_nr));
   assembler()->Comment("Line %" Pd " in '%s':\n           %s",
       line_nr, function.ToFullyQualifiedCString(), line.ToCString());
 }
 
 
+static void LoopInfoComment(
+    Assembler* assembler,
+    const BlockEntryInstr& block,
+    const ZoneGrowableArray<BlockEntryInstr*>& loop_headers) {
+  if (Assembler::EmittingComments()) {
+    for (intptr_t loop_id = 0; loop_id < loop_headers.length(); ++loop_id) {
+      for (BitVector::Iterator loop_it(loop_headers[loop_id]->loop_info());
+           !loop_it.Done();
+           loop_it.Advance()) {
+        if (loop_it.Current() == block.preorder_number()) {
+           assembler->Comment("  Loop %" Pd "", loop_id);
+        }
+      }
+    }
+  }
+}
+
+
 void FlowGraphCompiler::VisitBlocks() {
   CompactBlocks();
+  const ZoneGrowableArray<BlockEntryInstr*>* loop_headers = NULL;
+  if (Assembler::EmittingComments()) {
+    // 'loop_headers' were cleared, recompute.
+    loop_headers = flow_graph().ComputeLoops();
+    ASSERT(loop_headers != NULL);
+  }
 
   for (intptr_t i = 0; i < block_order().length(); ++i) {
     // Compile the block entry.
     BlockEntryInstr* entry = block_order()[i];
     assembler()->Comment("B%" Pd "", entry->block_id());
     set_current_block(entry);
 
     if (WasCompacted(entry)) {
       continue;
     }
 
+    LoopInfoComment(assembler(), *entry, *loop_headers);
+
     entry->EmitNativeCode(this);
     // Compile all successors until an exit, branch, or a block entry.
     for (ForwardInstructionIterator it(entry); !it.Done(); it.Advance()) {
       Instruction* instr = it.Current();
       if (FLAG_code_comments ||
           FLAG_disassemble ||
           FLAG_disassemble_optimized) {
         if (FLAG_source_lines) {
           EmitSourceLine(instr);
         }
@@ skipping 1057 matching lines @@
   }
   const ICData& ic_data = ICData::ZoneHandle(isolate(), ICData::New(
       parsed_function().function(), String::Handle(isolate(), target.name()),
       arguments_descriptor, deopt_id, num_args_tested));
   ic_data.AddTarget(target);
   (*deopt_id_to_ic_data_)[deopt_id] = &ic_data;
   return &ic_data;
 }
 
 }  // namespace dart