Revision: 25194
Author:   [email protected]
Date:     Thu Nov  6 13:11:53 2014 UTC
Log: Revert "Remove workaround for successors on end block from scheduler."

[email protected]

Review URL: https://codereview.chromium.org/705043002
https://code.google.com/p/v8/source/detail?r=25194

Modified:
 /branches/bleeding_edge/src/compiler/scheduler.cc
 /branches/bleeding_edge/test/cctest/compiler/test-scheduler.cc

=======================================
--- /branches/bleeding_edge/src/compiler/scheduler.cc Thu Nov 6 12:30:47 2014 UTC +++ /branches/bleeding_edge/src/compiler/scheduler.cc Thu Nov 6 13:11:53 2014 UTC
@@ -527,6 +527,7 @@
         schedule_(schedule),
         order_(NULL),
         loops_(zone),
+        beyond_end_(NULL),
         backedges_(1, zone),
         stack_(zone),
         previous_block_count_(0) {}
@@ -534,9 +535,9 @@
// Computes the special reverse-post-order for the main control flow graph, // that is for the graph spanned between the schedule's start and end blocks.
   void ComputeSpecialRPO() {
-    DCHECK(schedule_->end()->SuccessorCount() == 0);
     DCHECK_EQ(NULL, order_);  // Main order does not exist yet.
-    ComputeAndInsertSpecialRPO(schedule_->start(), schedule_->end());
+    // TODO(mstarzinger): Should use Schedule::end() after tests are fixed.
+    ComputeAndInsertSpecialRPO(schedule_->start(), NULL);
   }

// Computes the special reverse-post-order for a partial control flow graph,
@@ -569,9 +570,7 @@
       l->block->set_rpo_number(number++);
       schedule_->rpo_order()->push_back(l->block);
     }
-    if (schedule_->end()->rpo_number() < 0) {
-      schedule_->end()->set_rpo_number(number);
-    }
+    BeyondEndSentinel()->set_rpo_number(number);
   }

   // Print and verify the special reverse-post-order.
@@ -655,6 +654,17 @@
   static bool HasLoopNumber(BasicBlock* block) {
     return block->ao_number() >= 0;
   }
+
+ // TODO(mstarzinger): We only need this special sentinel because some tests + // use the schedule's end block in actual control flow (e.g. with end having + // successors). Once this has been cleaned up we can use the end block here.
+  BasicBlock* BeyondEndSentinel() {
+    if (beyond_end_ == NULL) {
+      BasicBlock::Id id = BasicBlock::Id::FromInt(-1);
+ beyond_end_ = new (schedule_->zone()) BasicBlock(schedule_->zone(), id);
+    }
+    return beyond_end_;
+  }

// Compute special RPO for the control flow graph between {entry} and {end},
   // mutating any existing order so that the result is still valid.
@@ -838,7 +848,7 @@
         ++loop_depth;
         current_loop = &loops_[GetLoopNumber(current)];
         BlockList* end = current_loop->end;
-        current->set_loop_end(end == NULL ? schedule_->end() : end->block);
+ current->set_loop_end(end == NULL ? BeyondEndSentinel() : end->block);
         current_header = current_loop->header;
         Trace("B%d is a loop header, increment loop depth to %d\n",
               current->id().ToInt(), loop_depth);
@@ -1008,6 +1018,7 @@
   Schedule* schedule_;
   BlockList* order_;
   ZoneVector<LoopInfo> loops_;
+  BasicBlock* beyond_end_;
   ZoneList<Backedge> backedges_;
   ZoneVector<SpecialRPOStackFrame> stack_;
   size_t previous_block_count_;
=======================================
--- /branches/bleeding_edge/test/cctest/compiler/test-scheduler.cc Thu Nov 6 12:30:47 2014 UTC +++ /branches/bleeding_edge/test/cctest/compiler/test-scheduler.cc Thu Nov 6 13:11:53 2014 UTC
@@ -200,13 +200,12 @@
 TEST(RPOEntryLoop) {
   HandleAndZoneScope scope;
   Schedule schedule(scope.main_zone());
-  BasicBlock* body = schedule.NewBasicBlock();
-  schedule.AddSuccessorForTesting(schedule.start(), body);
-  schedule.AddSuccessorForTesting(body, schedule.start());
+  schedule.AddSuccessorForTesting(schedule.start(), schedule.end());
+  schedule.AddSuccessorForTesting(schedule.end(), schedule.start());
   ZonePool zone_pool(scope.main_isolate());
BasicBlockVector* order = Scheduler::ComputeSpecialRPO(&zone_pool, &schedule);
   CheckRPONumbers(order, 2, true);
-  BasicBlock* loop[] = {schedule.start(), body};
+  BasicBlock* loop[] = {schedule.start(), schedule.end()};
   CheckLoop(order, loop, 2);
 }

@@ -654,7 +653,7 @@
   BasicBlock* A = schedule.start();
   BasicBlock* B = schedule.NewBasicBlock();
   BasicBlock* C = schedule.NewBasicBlock();
-  BasicBlock* D = schedule.NewBasicBlock();
+  BasicBlock* D = schedule.end();
   BasicBlock* E = schedule.NewBasicBlock();

   schedule.AddSuccessorForTesting(A, B);

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