[turbofan] move down parallel moves.

The regression the bug tracks (see the bug link) appears to
be due to identical gap moves in the predecessors of a block
not being moved to the common successor. This CR fixes one
reason that is happening.

BUG=chromium:549262
LOG=n

Review URL: https://codereview.chromium.org/1523393003

Cr-Commit-Position: refs/heads/master@{#32874}

src/compiler/move-optimizer.cc

@@ -91,11 +91,12 @@ MoveOptimizer::MoveOptimizer(Zone* local_zone, InstructionSequence* code)
 
 
 void MoveOptimizer::Run() {
-  for (auto* block : code()->instruction_blocks()) {
+  for (InstructionBlock* block : code()->instruction_blocks()) {
     CompressBlock(block);
   }
-  for (auto block : code()->instruction_blocks()) {
+  for (InstructionBlock* block : code()->instruction_blocks()) {
     if (block->PredecessorCount() <= 1) continue;
+    if (!block->IsDeferred()) {
       bool has_only_deferred = true;
       for (RpoNumber pred_id : block->predecessors()) {
         if (!code()->InstructionBlockAt(pred_id)->IsDeferred()) {
@@ -103,10 +104,12 @@ void MoveOptimizer::Run() {
           break;
         }
       }
-    // This would pull down common moves. If the moves occur in deferred blocks,
-    // and the closest common successor is not deferred, we lose the
-    // optimization of just spilling/filling in deferred blocks.
+      // This would pull down common moves. If the moves occur in deferred
+      // blocks, and the closest common successor is not deferred, we lose the
+      // optimization of just spilling/filling in deferred blocks, when the
+      // current block is not deferred.
       if (has_only_deferred) continue;
+    }
     OptimizeMerge(block);
   }
   for (auto gap : to_finalize_) {